otany bay project forking paper no.4 natural water quality€¦ · one of the objects of the botany...

Natural water quality

HANCOCK TD189.5 . A82 B6 B64 no. 4

TD189.5.A82B6B64 no.4.

A . N . U . L I B R A R Y

otany Bay Project forking paper no.4

This book was published by ANU Press between 1965–1991.

This republication is part of the digitisation project being carried out by Scholarly Information Services/Library and ANU Press.

This project aims to make past scholarly works published by The Australian National University available to

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Botany Bay working paper no. 4 (Completed July 1978)

Natural water qualityMerike Johnson

Botany Bay Project Canberra 1978

First published in Australia 1978

Printed in Australia

© Merike Johnson 1978

This book is copyright. Apart from any fair dealing for the purpose of private study, research, criticism, or review, as permitted under the Copyright Act, no part may be reproduced by any process without written permission. Inquiries should be made to the publisher.

National Library of Australia Cataloguing-in-Publication entry

Johnson, Merike.Natural water quality.

(Botany Bay project working paper; no. 4)ISBN 0 7081 0340 5

1. Water, Underground. 2. Water quality. 3. Water — Analysis. I. Title. (Series).

United Kingdom, Europe, Middle East, and Africa: Eurospan Ltd, 3 Henrietta St, London WC2E 8LU, England North America: Books Australia, Norwalk, Conn., USA Southeast Asia: Angus & Robertson (S.E. Asia) Pty Ltd, Singapore Japan: United Publishers Services Ltd, Tokyo

628.161

FOREWORD

One of the objects of the Botany Bay Project was to encourage environmental studies of Botany Bay on topics selected approved by the Project Committee and carried out over relatively long periods by individual investigators. This approach offered a means of having some in-depth studies to supplement the broader group research of the Project team.The Project was fortunate in being able to interest Ms Merike Johnson in a Ph.D. scholarship to work for a three- year period on a scientific investigation of water quality, with some special reference to underground water, an important resource in the area. This working paper reports in a more popular form the main outlines of her findings and offers a good deal of novel scientific appraisal of groundwater quality, particularly in relation to base-line quality evaluations.

In common with other working papers of the Project, only minimal editing has been carried out in order to preserve the approach of the author. No adaptations have been made to force the scientific findings into a more explicit social relevance. This editorial constraint has been made easier by Merike Johnson’s own definite views on the matter.

N.G. Butlin June 1978

v

CONTENTSForeword v1. INTRODUCTION 12. THE EFFECT OF THE PAST ON THE PRESENT 1

2.1 Geological Events 12.2 The Human Element 22.3 Progress 5

3. RAIN WATER CHARACTERISTICS 53.1 The Weather 53.2 Salinity 73.3 Chemical Composition 103.4 The Terrestrial Component 14

3.4.1 The Sulphate Problem 143.4.2 Nutrients in Rainfall 19

3.5 Summary 224. THE UNDERGROUND RESERVOIR 22

4.1 The Nature of this Reservoir 224.2 The Quantity of Water 274.3 Characteristics of the Water 28

4.3.1 Area 1 314.4 The Presence of Iron 34

4.4.1 Area 2 354.4.2 Areas 3 and 4 364.4.3 Area 5 374.4.4 Area 6 39

4.5 The Sodium Chloride Problem 424.6 The I.C.I. Salt Stockpile 454.7 Appraisal 45

5. OUR IMPACT ON THE NATURAL WATER QUALITY 465.1 Scarborough Swamp - An Aquatic

Environment in Distress 465.2 Human Influences on the Ground Water Quality 48

5.2.1 From Landfills 485.2.2 From Sewage 48

5.3 The Consequences 526. THE RIVERS OF THE BOTANY BAY CATCHMENT AREA 54

6.1 General Characteristics 546.1.1 Physical Aspects 556.1.2 Chemical Characteristics 55

vii

6.2 The Georges River 576.2.1 The Human Impact 59

6.3 The Cooks River 616.3.1 Quality Aspects 636.3.2 Perspective 64

7. CONCLUSION 64

References 66

viii

TEXT TABLES

Table I Rain Water Composition 12II Comparison Between Various Types

of Waters 33III Chemical Compositions of Kurnell

Waters 37IV Leachate from Sand and Iron

Sulphide 41V Leachate from Peat 41VI Chemical Characteristics of Waters

from the Botany-Banksmeadow Area 44VII Chemical Characteristics of

Wianamatta Shale Waters 56

ix

TEXT FIGURES

Figure 1 Drainage Area of Botany Bay 32 Rain Water Sampling Locations 63 Monthly Rain Water Salinity 84 Relation Between Chloride

Concentration and Distance fromthe Coast 9

5 Total Atmospheric Input 1126 Tonnes of Atmospheric Salts/km /Annum 13

7 Sulphate Concentrations, June 1974 158 Tonnes/sq km/14 months of Land

Derived Sulphate 169 Distribution of 'Excess’ Rain Water

Sulphate (milligrams/litre) 1810 Distribution of Nitrate in Rainfall 2111 Genesis of Rain Water Salinity 2312 Direction of Ground Water Movement

within the Boundaries of the Botany Basin 25

13 Representation of Cross Section ofBotany Basin 26

14 (a) Distribution of Ground Water Types 29(b) Distribution of Sampling Points 30

15 Range of Sulphate and CalciumConcentrations 32

16 (a) Bicarbonate Distribution 38(b) Calcium Distribution 38

17 Salty Sediments in the Botany-Banksmeadow Area 43

18 Effect of Tip Leachate on ScarboroughSwamp 49

x

51Figure 19 Nitrate Ion Distribution, Kurnell20 Relation Between Nitrate

Concentration and Sewerage Pipeline 5321 Influence of Geological Regimes on

Water Salinity in the Georges River Drainage Area 58

22 Nitrate Concentrations, Georges River 6023 Cooks River Drainage System 62

xi

1. INTRODUCTION

W ater i s one o f th e b a s ic r e q u ire m e n ts o f l i f e and i t s a v a i l a b i l i t y i s a p rim e d e te rm in a n t o f human o c c u p a tio n o f an a r e a . C o n se q u e n tly th e h i s t o r y o f th e deve lopm en t o f a c i t y i s in s e p a r a b l e from th e h i s t o r y o f i t s w a te r s u p p ly , and so to o i s th e developm en t o f Sydney u b iq u i to u s ly l in k e d w ith th e B otany Bay r e g io n .

D u rin g more th a n a c e n tu ry o f in te n s e r u r a l , u rb an and i n d u s t r i a l a c t i v i t y , th e r e g io n ’ s m ost im p o r ta n t r e s o u r c e , f r e s h w a te r , h a s been s u b je c te d to a m u l t i tu d e o f e x tra n e o u s s t r e s s e s , b u t a s y e t we know l i t t l e a b o u t th e w a te r s y s te m 's c a p a c i ty to a b so rb th e s e i n t r u s i o n s . Up to th e p r e s e n t t im e , h y d ro c h e m ic a l s tu d i e s have been c o n f in e d to s u r f a c e w a te r d a ta c o l l e c t i o n and r a r e l y h a s any a tte m p t been made to e x te n d t h i s to an i n t e r p r e t a t i o n o f th e s ig n i f i c a n c e o f th e m easu rem en ts . The u n d e rg ro u n d w a te r sy s te m h a s r e c e iv e d even l e s s a t t e n t i o n .

Each body o f w a te r a c q u i r e s u n iq u e c h e m ic a l , b i o l o g i c a l and p h y s ic a l c h a r a c t e r i s t i c s th ro u g h th e n a t u r a l p r o c e s s e s o f e n v iro n m e n ta l i n t e r a c t i o n . I t i s th e s e i n t r i n s i c p a ra m e te rs w h ich d e te rm in e th e way in w hich each p a r t o f th e h y d r o lo g ic a l c y c le re sp o n d s to th e i n c r e a s i n g v a r i e t y o f u rb an and in d u s t r i a l com ponen ts , and a know ledge o f th e s e b a s i c p r i n c i p l e s i s im p e r a t iv e to e f f e c t i v e deve lopm en t o f w a te r r e s o u r c e s and w a s te d i s p o s a l .

T h is r e p o r t d e s c r ib e s an i n v e s t i g a t i o n c a r r i e d o u t to g a in some u n d e rs ta n d in g o f th e fu n d am e n ta l n a tu r e o f th e w a te r sy s te m s w i th in th e B otany Bay ca tch m en t a r e a . I t aim s p r im a r i ly to i d e n t i f y th e r e l a t i o n s h i p s be tw een th e c h e m ica l c h a r a c t e r o f th e w a te r and i t s n a t u r a l e n v iro n m e n t.

2 . THE EFFECT OF THE PAST ON THE PRESENT

2 .1 G e o lo g ic a l E v en ts

The p a s t f o r th e B otany Bay re g io n s t r e t c h e s back to th e T r i a s s i c P e r io d , more th a n 200 m i l l i o n y e a r s a g o , when th e fo u n d a t io n s o f to d a y ’ s h y d ro c h e m is try w ere l a i d w ith th e d e p o s i t io n o f th e Hawkesbury S a n d s to n e s e d im e n ts in a f r e s h w a te r l a k e e n v iro n m en t and th e s h a le s o f th e W ianam atta Group i n a b r a c k i s h swamp s i t u a t i o n .

T hese se d im e n ts w ere s u b s e q u e n t ly e ro d e d to a low p l a i n by an a n t i c e d e n t d ra in a g e sy s te m b e a r in g a c lo s e s i m i l a r i t y to th e p r e s e n t . E a r th movements d u r in g th e T e r t i a r y P e r io d

1

u n e v e n l y w a r p e d t h i s p e n e p l a n e s o t h a t t h e l a n d t o t h e s o u t h w e s t o f B o t a n y Bay was u p l i f t e d t o fo r m t h e Woronora P l a t e a u w h e r e a s t o t h e w e s t , t h e C u m b er l an d P l a i n , was r e l a t i v e l y u n a f f e c t e d . As a c o n s e q u e n c e o f t h i s w a r p i n g , w a t e r c o u r s e s w e r e r e j u v e n a t e d an d b e g a n t o i n c i s e t h e u p l i f t e d a r e a s . The s e a l e v e l a t t h a t t i m e was many m e t r e s l o w e r t h a n i t i s now and t h e c o a s t e x t e n d e d f a r t h e r e a s t .

The s t r e a m s d r a i n i n g t o t h e c o a s t p a s s e d t h r o u g h a s h a l l o w t e c t o n i c d e p r e s s i o n i n t h e H awkes bur y S a n d s t o n e i n t h e B o t a n y Bay a r e a and c a r v e d o u t d ee p t r e n c h e s on t h e f l o o r o f t h i s B a s i n a s t h e y c a r r i e d t h e i r s e d i m e n t l o a d f r om t h e u p l a n d s t o t h e s e a . But so m e t im e d u r i n g t h e e a r l y P l e i s t o c e n e t h e s e a l e v e l r o s e a t t h e en d o f a n o t h e r g l a c i a t i o n p e r i o d an d t h e s a n d s t o n e d e p r e s s i o n was s u b m e r g e d . The v e l o c i t y o f t h e s t r e a m w a t e r s s l o w e d and t h e s e d i m e n t l o a d s w e r e d e p o s i t e d i n t h e s t r e a m v a l l e y s .

T h r o u g h o u t t h e P l e i s t o c e n e P e r i o d e u s t a t i c f l u c t u a t i o n s c o n t i n u e d t o s h a p e t h e s e d i m e n t s o f t h e B o t a n y B a s i n . P e r i o d s o f s u b m e r g e n c e r e s u l t e d i n m a r i n e s a n d , mud and s h e l l b e d s b e i n g d e p o s i t e d ; t h e r e w e r e t i m e s when t h e s e d i m e n t s w e r e ab o v e s e a l e v e l l o n g en ough f o r s o i l s t o d e v e l o p , an d t h e s e w e r e t o become b u r i e d p o d s o l h o r i z o n s when t h e s e a o n c e a g a i n r o s e ; an d t h e r e w e r e many t i m e s when e x t e n s i v e swamps and f o r e s t s c o v e r e d t h e a r e a a s t e s t i f i e d by t h e n um ero us p e a t l a y e r s w i t h i n t h e s e d i m e n t s . Much a d d i t i o n a l s a n d was b r o u g h t i n t o t h e Bay a r e a f rom t h e s e a w a r d s i d e by o c e a n c u r r e n t s and t h e w in d r e w o r k e d some o f t h e s e d i m e n t s by d e p o s i t i n g t h e s a n d d u n es w h ic h m a n t l e t h e c l i f f t o p s .

T h e s e a r e b r o a d l y t h e g e o l o g i c a l p r o c e s s e s o f t h e p a s t w h i c h s h a p e d t h e a q u a t i c e n v i r o n m e n t o f t h e B o tan y Bay r e g i o n . T h i s r e g i o n i s d e l i n e a t e d , by t h e s u r f a c e d r a i n a g e a r e a o f B o t a n y Bay an d c o m p r i s e s t h e Hawkesbury S a n d s t o n e and W i a n a m a t t a s h a l e c a t c h m e n t a r e a o f t h e G e o rg es R i v e r and i t s t r i b u t a r i e s , t h e p r e d o m i n a n t l y W i a n a m a t t a s h a l e c a t c h m e n t o f t h e Cooks R i v e r , and t h e u n c o n s o l i d a t e d s e d i m e n t a r e a s u r r o u n d i n g t h e Bay w i t h i t s swamps, p o n d s an d s t o r e o f g r o u n d w a t e r .

2 .2 The Human E lem en t

The g e o l o g i c a l p r o c e s s e s fo rm ed t h e b l u e p r i n t upon w h ic h human h a b i t a t i o n h a s s u b s e q u e n t l y w r o u g h t i t s e f f e c t s .

The A b o r i g i n e s a r e known t o h a v e l i v e d i n t h e B o t a n y Bay r e g i o n f o r t h o u s a n d s o f y e a r s , b u t t h e i r s m a l l num ber s and l a c k o f t e c h n o l o g y n e g a t e d t h e n e e d and l i m i t e d t h e i r a b i l i t y t o m o d i f y t h e e n v i r o n m e n t e x t e n s i v e l y ; p e r h a p s t h e f i r e s t i c k

2

F i g u r e 1 D r a in a g e A re a o f B o tan y Bay

BOTANYBAY

PORT HACKING

t . . I Alluvium

Hawkesbury sandstone

Wianamatta shale

3

was their main instrument of change. Two hundred years ago to Captain Cook and his crew, the Bay area still presented 'a vision of silent forests, charming meadows and extensive swamps filled with wild flowers'.1

To Captain Phillip, who arrived 18 years later with the first settlers, the extensive swamps ironically posed a threat to health as such swamps were known to do in other lands, and so he sited the settlement away from these swamps on the banks of a small stream fed by springs in the Hawkesbury Sandstone which forms the northern rim of the Botany Basin. But recurring calamitous droughts, population growth and gross pollution, soon caused the abandonment of this as a water supply and Sydney was forced to turn back to the swamps for its life-line.

For several years water was brought from the Botany Basin by horse and cart and the residents paid high prices for their daily needs. This situation was improved in 1830 by the laborious excavation, by convicts, of a tunnel through the hard sandstone to reach the swamps of the present day Centennial Park. The completed tunnel delivered 13,000,000 litres per week to a standpipe in Hyde Park.

The swamps formed a continuous chain of ponds to the Bay shore and from 1858 the tunnel supply was superseded by the more abundant supply from the lower swamps. The pumpage rate from this source was recorded in 1867 as 90,000,000 litres per week.2

Through the succeeding years, Sydney’s growing population necessitated continual additions to be made to this water supply in the way of diversions of water from other swamps to the main stream, and the building of a series of dams along the watercourse. It was in this way that the Botany Basin served as Sydney's only source of water for 60 years until the Nepean River Scheme took over in 1886.

But by this time too, the area had experienced considerable changes. The tall timber was gone; it had been used for firewood. Many of the swamps had been drained to allow market gardening. The marshland vegetation was no more and the ground had become hardened by the trampling of cattle, resulting in flooding when it rained. Industry too, had established itself near the supply of fresh water and many of the small creeks draining to the Bay were reported to be discoloured by the foul wastes of tanneries and tallow works.Water continued to be drawn from the Basin by way of open

dams, wells and spear points, and later the introduction of

4

b o r e h o l e pumps r e s u l t e d i n an i n t e n s i v e u t i l i s a t i o n o f t h e g r o u n d w a t e r w h i c h h a s b e e n m a i n t a i n e d t o t h e p r e s e n t t i m e .

2 . 3 P r o g r e s s

The p h y s i o g r a p h y o f t h e B o t a n y Bay c a t c h m e n t a r e a t o d a y r a n g e s f rom u n h a b i t e d , r u g g e d b u s h l a n d , t h r o u g h s u b u r b a n t o d e n s e l y h a b i t e d u r b a n and i n d u s t r i a l r e g i o n s . Many w a t e r c o u r s e s a r e s t i l l i n t h e i r p r i s t i n e s t a t e w h i l e o t h e r s h a v e b e e n c o n v e r t e d i n t o cem e n t c a n a l s . Many s t r e a m s h a v e r e c e i v e d l a r g e f l o w s o f l i q u i d an d s o l i d w a s t e s . Swamps an d b a y s h a v e b e e n ' r e c l a i m e d ' by f i l l i n g w i t h t h e c i t y ' s g a r b a g e . Sand m i n i n g h a s dug h o l e s i n t h e r i v e r b e d s and i n t h e s a n d h i l l s , an d t h e s u b u r b a n s p r a w l h a s c o v e r e d t h e l a n d w i t h t a r an d c e m e n t .

T h r o u g h o u t a l l t h i s , w h a t h a s h a p p e n e d t o t h e q u a l i t y o f t h e w a t e r ? What a f f e c t s t h e c h e m i s t r y o f t h e s t r e a m more - t h e g e o l o g y o r t h e c a n a l i s a t i o n ? What a r e t h e i m p o r t a n t f a c t o r s c o n t r i b u t i n g t o t h e q u a l i t y o f t h e g r o u n d w a t e r i n t h e B o ta n y B a s i n , and h a s more t h a n 150 y e a r s o f E u r o p e a n o c c u p a t i o n i n f l u e n c e d t h e w a t e r c o m p o s i t i o n a t a l l ?

3. RAIN WATER CHARACTERISTICS

S i n c e a l l o f t h e s u r f a c e w a t e r an d g r o u n d w a t e r i n t h e B o t a n y Bay c a t c h m e n t a r e a i s d e r i v e d f r om r a i n f a l l , a s t u d y o f t h e c h e m i c a l c o m p o s i t i o n o f r a i n w a t e r was t h e l o g i c a l s t a r t i n g p o i n t f rom w h ich t o t r a c e t h e o r i g i n s o f t h e c h e m i c a l e l e m e n t s i n o u r w a t e r s y s t e m s .

3. 1 The W e a t h e r

O u t s i d e t h e t r o p i c s , Sydney i s one o f t h e w e t t e s t m a j o r c i t i e s o f t h e w o r l d an d i s c e r t a i n l y t h e w e t t e s t c a p i t a l c i t y i n A u s t r a l i a . ^ T h e r e i s a h i g h v a r i a b i l i t y i n S y d n e y ' s r a i n f a l l due t o t h e i n f l u e n c e o f o c c a s i o n a l m a j o r s t o r m s . T h es e come m a i n l y f rom t h e s o u t h - w e s t d u r i n g t h e w i n t e r m o n t h s , and t h e s o u t h - e a s t i n summer . The p a t t e r n i s c o m p l i c a t e d by t h e p r e p o n d e r a n c e o f t h u n d e r s t o r m s w h i c h c a u s e marked a r e a l v a r i a t i o n s i n t h e t o t a l volume o f r a i n r e c e i v e d .

R a in w a t e r was c o l l e c t e d f rom t h e l o c a t i o n s shown i n F i g . 2 on a m o n th ly b a s i s o v e r a p e r i o d o f 14 m o n t h s , f r om O c t o b e r 1973 t o November 1974. D u r i n g t h i s p e r i o d s e v e r a l v i o l e n t s t o r m s and t o r r e n t i a l r a i n s o c c u r r e d . I n f a c t , J a n u a r y 1974 h e r a l d e d i n some o f t h e w o r s t f l o o d s i n A u s t r a l i a t h i s c e n t u r y . D u r i n g A u g u s t 1974, a f o u r - d a y downpour d e p o s i t e d

5

Figure 2 Rain Water Sampling Locations

VILLAWOOD

CABRAMATT, MOORE PARK

WATERLOO#BE ACONSFIELD

CLOVELLYKENSINGTON

BANKSMEADOWARNCLIFFE

HILLSDALEPICNIC POINT

BOTANY CEMETERYBOTANYBLAKEHURST BAY

PORT HACKING

k ilo m e tre s

6

227 millimetres on the suburb of Randwick and caused severe flooding in areas south and west of Sydney.Over the 12 months’ period from December 1973 to November

1974, the recorded rainfall at the Sydney Observatory (Department of Meteorology records), was 1607 mm (63 inches) and at Randwick for the same period it was 1827 mm (72 inches). These figures illustrate the fact that it was an exceptionally wet year, although there were some months which were relatively dry.

3.2 SalinityThe rain waters collected from the sampling locations, which encompassed industrial, city and suburban areas, contained a mixture of rain and dry fallout, or bulk precipitation, which represents the combined effects of all water soluble components of the atmosphere.

The study has shown that the total salt content of the precipitation in Sydney varies in the extreme from month to month and from location to location. The electrical conductivity values, which measure the number of ions in solution, ranged from 4 micromhos/cm to 300 micromhos/cm. The salinity distribution for several of the sampling locations is shown in Fig. 3. As a comparison, the electrical conductivity of Sydney tap water can be taken as being 130 micromhos/cm.Notable is the much higher salinity experienced at Botany

and Clovelly compared with Engadine and Cabramatta. The geographical location in relation to maritime influence is the major factor responsible for this difference. The effect of oceanic salts decreases rapidly with distance inland, as shown in Fig. 4 where the chloride ion concentration during the February and May storms is plotted against distance from the coast. There is a five-fold decrease in the chloride content for the same rain mass within a distance of 30 kilometres.Locations at similar distances from the ocean can also

experience differences in salinity, as for example, Clovelly, situated less than 1 km from the coast, experiences less saline rain than Botany because Clovelly receives a predominantly easterly maritime influence, whereas the Botany location is exposed not only to the easterly winds but also to the blusterly, salt-laden southerlies coming across Botany Bay.

The interaction of several factors is responsible for the variations in salinity from month to month. A major influence being the direction and strength of the rain-bearing winds. Storms predominantly from the south or south-east, carry large

7

illi

Figure 3 Monthly Rain Water Salinity

(a) Monthly rainwater salinity.

Iou•H

Botany Clovelly Waterloo Engadine Cabramat ta

I I_________I_________ ■ i_________I I_________ I_________ I___ I I I IOct N D J F M A M J A S O Nov

1973 4--- ---» 1974

(b) Monthly rainfall distribution, Randwick.

1973 ♦

NOTE: No rain fell in some locations during July 1974 and hencethe July results have not been included.

8

Figure 4 Relation Between Chloride Concentration and Distance from the Coast

May /

u 30 February

Cabramatta Blakehurst ClovellyPicnicPoint

30 20 k ilo m e tre s'0 Distance from the coast

9

q u a n t i t i e s o f o c e a n ic a e r o s o l s and c h a r a c t e r i s e t h e r a i n w a te r by h ig h s a l i n i t i e s . In c o n t r a s t , when th e r a i n comes p r e d o m in a n tly from th e w e s t , as th e f l o o d i n g r a i n s i n August 1974, t h e s a l i n i t y i s low b e c a u s e o f t h e l a c k o f o c e a n ic a e r o s o l s .

The s a l i n i t y o f th e r a i n does n o t a p p e a r to be d i r e c t l y r e l a t e d to t h e volum e. A s a l i n e r a i n from th e s o u t h - e a s t w i l l c o n t in u e t o be h i g h l y s a l i n e no m a t t e r how much r a i n f a l l s , b u t when th e r a i n f a l l f o r th e month i s v e ry low th e i n f l u e n c e o f d ry f a l l o u t , w hich c o n s i s t s o f th e w a t e r - s o l u b l e p a r t s o f c i t y d u s t , s o i l p a r t i c l e s , o r g a n ic m a t t e r and o c e a n ic s a l t s , becomes p re d o m in a n t . T h is d r y f a l l c o l l e c t s on th e f u n n e l and i s washed i n t o t h e sam ple b o t t l e w i th s u b s e q u e n t r a i n s c a u s in g th e s a l i n i t y o f th e b u lk p r e c i p i t a t i o n to be h ig h as was th e c a se d u r in g th e low r a i n f a l l months o f December 1973, and J u ly and Sep tem ber 1974.

I t was found t h a t th e p r e s e n c e o f v e g e t a t i o n o r b u i l d i n g s e x e r t e d a s t r o n g i n f l u e n c e on th e t o t a l s a l i n i t y o f p r e c i p i t a t i o n i n p a r t i c u l a r l o c a t i o n s due t o a e r o s o l i n t e r c e p t i o n . D r i f t i n g a tm o s p h e r ic a e r o s o l s w ere c a p tu r e d by th e l e a v e s and b r a n c h e s o f t r e e s and by t a l l b u i l d i n g s , c o n s e q u e n t ly th e p r e c i p i t a t i o n c o l l e c t e d u n d e r a t r e e had a h i g h e r s a l i n i t y th a n t h a t c o l l e c t e d i n th e open b e c a u s e th e c a p tu r e d s a l t was s u b s e q u e n t ly washed o f f th e l e a v e s by th e n e x t r a i n f a l l . On th e o t h e r h a n d , a l o c a t i o n s h e l t e r e d by a b u i l d i n g w hich i n t e r c e p t e d much o f t h e d r y f a l l d u r in g n o n - r a i n p e r i o d s had a lo w er s a l i n i t y b u lk p r e c i p i t a t i o n .

3 .3 Chem ical C om posit ion

The p r o p o r t i o n s o f th e v a r i o u s c o n s t i t u e n t s o f t h e r a i n w a te r som etim es v a r i e d c o n s id e r a b l y from month to month. T h is was v e ry much d e p e n d en t on th e d i r e c t i o n o f th e w in d , as can be i l l u s t r a t e d by a com par ison o f th e t o t a l i n p u t s from s e a and la n d d u r in g two d i f f e r e n t m onth ly p e r i o d s (F ig . 5 ) .

May 1974, was a month o f s t r o n g o n - s h o r e w in d s , and o c e a n ic a e r o s o l s dom ina ted th e r a i n w a te r c o m p o s i t io n th ro u g h o u t th e c a tc h m e n t . On th e o t h e r han d , d u r in g November 1973 t h e r e was an e q u a l d i s t r i b u t i o n o f winds from a l l d i r e c t i o n s , and th e a tm o s p h e r ic c o m p o s i t io n was dom ina ted by a e r o s o l s d e r i v e d from t e r r e s t r i a l s o u r c e s .

These two m onths , how ever, r e p r e s e n t ex trem e s i t u a t i o n s under u n u su a l a tm o s p h e r ic c o n d i t i o n s . O v e r a l l , t h e c h e m ica l c o m p o s i t io n s v a r i e d w i t h i n n a r ro w e r l i m i t s and i t i s c l e a r t h a t o c e a n ic s a l t s a r e g e n e r a l l y th e m ajo r components o f th e

10

F ig u re 5 T o ta l A tm o sp h e r ic I n p u t

10000

16000

14000

12000

10000

6000

2000

C Mo4-» (TJ

rH 00 0-rH C<U -H> CO Uo c o—I n oD U X

*-i T3 *-»D-> O 4J

b u l k o f S y d n e y ’ s r a i n f a l l .T a b l e I g i v e s e x a m p l e s o f r a i n w a t e r c o m p o s i t i o n s ( a s

p e r c e n t a g e s o f t h e t o t a l c o n c e n t r a t i o n e x p r e s s e d a s e q u i v a l e n t s ) w h ic h r e p r e s e n t t h e t y p e o f c o m p o s i t i o n e x h i b i t e d by t h e m a j o r i t y o f r a i n w a t e r s i n t h e c i t y a r e a . A c o m p a r i s o n i s made w i t h t h e e q u i v a l e n t s e a w a t e r p e r c e n t a g e s . The s i m i l a r i t y t o s e a w a t e r c o m p o s i t i o n i s e v i d e n t f r om t h e T a b l e e x c e p t f o r t h e n o t a b l y g r e a t e r p e r c e n t a g e s o f b o t h c a l c i u m and s u l p h a t e i o n s .

T a b l e I R a in W a t e r C o m p o s i t i o n

( a ) A v e r a g e c o m p o s i t i o n o f Sydney c i t y r a i n

Cl % Na+% S 0 . +%4 Ca"<~*"% M g ^ K+%

H i l l s d a l e 4 1 . 3 3 6 .4 9 . 1 3 . 7 8 . 6 0 . 8Moore P a r k 3 9 .6 3 5 .6 10 .6 5 . 1 8 . 4 0 . 7B o tan y 4 2 . 2 3 6 . 1 7 .5 4 . 7 8 . 4 1 .0W a t e r l o o 3 8 . 7 3 4 . 7 11.2 6 . 2 8 . 2 1 .0C l o v e l l y 4 4 . 6 3 7 .5 5 . 1 3 . 0 8 . 6 1 . 1S ea W a te r 4 5 . 2 3 8 .9 4 . 5 1.7 8 .9 0 . 8

(b) A p p r o x i m a t e l y 30 km from t h e c o a s t

V i l l a w o o d 2 4 .9 2 2 . 5 2 6 . 3 18.9 5 . 2 2 . 3C a b r a m a t t a 27. 1 2 2 . 3 2 6 . 4 9 . 5 10.5 4 . 1

As t h e d i s t a n c e f rom t h e c o a s t i n c r e a s e s an d t h e m a r i t i m e i n f l u e n c e d e c r e a s e s , t h e c o m p o s i t i o n o f t h e r a i n f a l l c h a n g e s t o one o f a l e s s e r p e r c e n t a g e o f s o d iu m and c h l o r i d e an d a h i g h e r p e r c e n t a g e o f c a l c i u m an d s u l p h a t e i o n s , a s e x e m p l i f i e d by t h e c o m p o s i t i o n s a t V i l l a w o o d and C a b r a m a t t a .

I f t h e 14 m o n t h s ' p e r i o d s t u d i e d can b e t a k e n as r e p r e s e n t a t i v e o f t h e b u l k p r e c i p i t a t i o n ( i . e . r a i n f a l l an d d r y f a l l ) i n Sydney an d s u b u r b s g e n e r a l l y , t h e n t h e i n f o r m a t i o n g a t h e r e d h e r e shows t h a t t h e a n n u a l i n p u t o f a t m o s p h e r i c s a l t s i n t h e B o tan y Bay c a t c h m e n t a r e a r a n g e s f rom more t h a n 70 m e t r i c t o n n e s / k m 2 on t h e e x p o s e d s a n d du nes a t K u m e l l , t o b e t w e e n 30 t o 40 m e t r i c t o n n e s / k m 2 i n t h e c i t y a r e a , t o l e s s t h a n 20 m e t r i c t o n n e s / k m 2 i n t h e w e s t e r n s u b u r b s . T h i s i s i l l u s t r a t e d i n F i g . 6 , t o g e t h e r w i t h t h e p e r c e n t a g e o f t h e t o n n a g e w h ic h i s due t o s e a - s a l t .

When t h e s e a - s a l t p o r t i o n i s s u b t r a c t e d f rom t h e t o t a l s a l t s t h e r e m a i n d e r , w h ich c o m p r i s e t h e t e r r e s t r i a l p o r t i o n o f t h e

12

Figure 6 Tonnes of Atmospheric Salts/km /Annum

PERCENTAGE OF SEA-SALT IN PRECIPITATION

60-70’ VILLAWOOD*1 9 /

CABRAMATT/ / • 15

WATERLOO • 3* /

KENSINGTON '5e fC L 0 V E L L Y

/ 1 l8ANKSMEADOW J « .____

X * « « 4 7 C HILLSOALOPICNIC POINT

^ •2 4 I,I BOTANY/ BOfTANY CEMETERY

/ ' b a y e f f e c t iv e/ /CJ WIND y \ . c>—-O * DIRECTION

BLAKI

PORT HACKING

13

s o l u b l e s a l t s i n t h e r a i n w a t e r , a c c o u n t s f o r be tw een 6 t o 9 m e t r i c t onnes /km ^/annum and i s r e m a rk a b l y u n i f o r m l y d i s t r i b u t e d o v e r t h e whole a r e a , e x c e p t f o r a m ass ive 20 t o n n es a t Banksmeadow where t h e s a m p l in g c o n t a i n e r was s i t u a t e d u n d e r a t r e e and hence r e c e i v e d t h e e x t r a s a l t s i n t e r c e p t e d by t h e t r e e .

3 .4 The T e r r e s t r i a l Component

Almost t h e whole o f t h e t e r r e s t r i a l component o f t h e r a i n w a t e r was found t o be made up o f : ( 1) a y e a r - r o u n d p r e s e n c eo f Ca"1-** and S04~ i o n s , and (2) n u t r i e n t i o n s such as K+ i n some l o c a t i o n s and NO3- i n l a r g e q u a n t i t i e s a t c e r t a i n t im e s o f t h e y e a r .

3 . 4 . 1 The S u l p h a t e Problem

S u l p h a t e i s an i m p o r t a n t and i n t e r e s t i n g component o f r a i n w a t e r b e c a u s e i t s p r e s e n c e u s u a l l y r a i s e s t h e q u e s t i o n as to what d e g re e i t i s due t o e i t h e r a n t h r o p o g e n i c o r n a t u r a l s o u r c e s .

I n t h e Botany Bay c a t c h m e n t , i t was found t h a t s e a - s a l t a e r o s o l s c o n t r i b u t e a s i g n i f i c a n t b u t n o t a m a jo r p r o p o r t i o n o f t h e s u l p h a t e i n t h e r a i n f a l l .

Th is can be s e e n from t h e s u l p h a t e c o n c e n t r a t i o n p r o f i l e i n F i g . 7, where t h e o c e a n i c and t e r r e s t r i a l s u l p h a t e components o f t h e June 1974 r a i n w a t e r s have be e n s e p a r a t e d .

A n o t e w o r t h y f e a t u r e o f F i g . 7, i s t h e u n i f o r m i t y o f t h e l a n d - d e r i v e d s u l p h a t e a t t h e v a r i o u s l o c a t i o n s . T h i s u n i f o r m ity o f t h e t e r r e s t r i a l component i n i n d i v i d u a l r a i n s i s r e f l e c t e d i n t h e t o t a l i n p u t o f t e r r e s t r i a l s u l p h a t e o v e r t h e ca tc hm e n t ( F i g . 8 ) .

Between 2-3 t o n n e s o f l a n d - d e r i v e d s u l p h a t e f e l l i n a l l subu rban a r e a s o v e r t h e s tu d y p e r i o d , and th e t o t a l amount a t C l o v e l l y was s i m i l a r t o t h e t o t a l amount a t C a b r a m a t t a , 30 km away. Th is may i n d i c a t e t h a t t h e r e i s a r e g i o n a l s o u r c e o f s u l p h a t e which a f f e c t s a l l a r e a s o f t h e c a t c h m e n t .

I n some l o c a t i o n s however ( n o t a b l y t h e i n d u s t r i a l / c o m m e r c i a l l o c a t i o n s ) , a lm o s t tw i c e as much t e r r e s t r i a l s u l p h a t e f e l l p e r s q u a r e k i l o m e t e r as i n subu rban l o c a t i o n s , i n d i c a t i n g t h a t i n d u s t r i a l e m i s s i o n s c o n s t i t u t e an a d d i t i o n a l s o u r c e o f s u l p h a t e i n l o c a l i s e d a r e a s .

S u l p h a t e c o n c e n t r a t i o n s i n e x c e s s o f t h a t which can be a t t r i b u t e d t o a s e a - s a l t o r an a n t h r o p o g e n i c o r i g i n i s a u n i v e r s a l f e a t u r e o f r a i n w a t e r c o m p o s i t i o n . Such ’ e x c e s s ’ s u l p h a t e i s p r e s e n t i n u n c o n ta m in a t e d m a r i t i m e a i r masses even

14

F ig u r e 7 S u lp h a te C o n c e n t r a t i o n s , June 1974

i

4 r

r~30

—[ i n20 10 o

kilometresDistance from the coast

15

AX

WW

WW

WW

WW

WW

WW

WW

WW

F ig u re 8 T o n n e s /sq k m /14 months o f Land D e r iv e d S u lp h a te

, / VILLAWOOD1 • /\ b A yCABRAMATT,

/ • 2.5 WATERLOO

KENSINGTON 2 j< C L 0 V E L L Y

ARNCLIFFE J • • a / \ iy . 6 HILLSD^LEp

\ IB O T A N Y J * botany cemetery

BAY \ fPICNIC POINT

BLAKEHURST

POftT HACKING

kilometres

16

in the polar regions.^Rain waters collected during the study period (1974/75) from

remote parts of inland Australia, which can be considered to be far removed from industrial pollution, were found to have sulphate concentrations which were quite comparable to those found in rain waters in the Botany Bay catchment, as can be seen from the comparison in Fig. 9.

The sulphate in inland rain waters is derived primarily from the solution of gypsum which is abundantly present in the soil and which is carried aloft as soil dust by the wind.A similar particulate source of sulphate is also possible in

city areas. For example, Sumi, Corkery and Monkman^ identified gypsum (Ca SO4 : 2H2O) as the principal crystalline component of urban dust in Baltimore, U.S.A.

In Sydney, samples of city dust, when leached with water, proved to be highly soluble, and the resultant solutions contained significant amounts of SO4- ions, although the principal components were Ca-1-1" and HCO3- ions.

Another significant source of atmospheric sulphate is hydrogen sulphide (H2S) produced by the anaerobic decay of organic matter. This form of sulphur emission into the atmosphere is particularly important in coastal areas where large amounts of H2S are released from inshore marine muds.

The H2S is rapidly oxidised in the atmosphere to SO2, with the subsequent formation of H2 SO4 in cloud droplets.

In undisturbed forested areas where there is little atmospheric dust, this continuous emission of H2S results in the rain water composition consisting predominantly of H"*" and SO4- ions, i.e. a weak solution of sulphuric acid.^

It is probable that a substantial part of the evenly distributed 2-3 tonnes/kmz of land-derived sulphate in the Botany Bay catchment is due to similar natural emissions. Robinson and Robbins^ evaluated that even in urban atmospheres only about one-third of the sulphur reaching the atmosphere comes from pollutant sources, whereas two-thirds is derived from natural emissions, principally in the form of H2S.

Unfortunately, no measurements of H2S have been made in Sydney’s airshed which might give some indication of the extent of such natural inputs, or even gauge the effect of the thousands of sewerage vents throughout the suburbs.However, sulphuric acid droplets have been detected in the

atmosphere over Sydney.^ In contrast to the dust-free atmosphere of forested regions, Sydney’s air also contains appreciable amounts of dust whose main component is calcium carbonate. The calcareous dust has a neutralising effect on

17

Figure 9 Distribution of 'Excess' Rain Water Sulphate (mi 11 i gr ams / li t r e )

ALICE SPRINGS ° 2.2

OTHE OLGASGILES (Met Stat

4 .0 O

I-------------

COOLGARDIEWARRUMBUNGLE,

2 7 MENINDEE O (Nat Pk ) /

WA.' 1 .9° o 4 .4 3 4 /2 . 0 - . , m o s s ig e l XO?,’ OLYNDHURSTa Si \ 1-9 /

7.1 '$■'BALLADONIA IUNDARABILLA

ESPERANCEJERRYMUNGUB1

kilometres VNote: 'Excess SO^ ''means the concentration of SO^ remainingafter the (SO^ ) associated with (Cl ) in a standard seawater proportion, has been subtracted.

18

the sulphuric acid, and the products of the reaction, calcium and sulphate ions, are washed down in the rainfall.There was a good correlation between high Ca++ concentra

tions and high S0^= concentrations in the rain waters which could be due to the ready adsorption of either H2S or S0^= on solid aerosols where the oxidation of the gases to H2 SO^ could take place. Thus, when there is a high dust content in the atmosphere, there could be a correspondingly high proportion of calcium and sulphate in dustfall.

Air pollution in the industrial and commercial locations was evidenced by the presence of a variety of heavy metals in the rain waters which were absent in the rains from the suburban locations.

The approximate 1:2 ratio of S04= input in rainfall in suburban vs industrial areas, is similar to the proportion of atmospheric SO2 in suburban vs industrial areas, as measured by the State Pollution Control Commission. ̂ This greater amount of SO2, and consequently higher concentration of H2 SO4, outweighs the amount which can react with dust aerosols, resulting in a greater proportion of SO4" compared to Ca++, in the rainfall at the industrial locations.It seems, therefore, that the sulphate content of the

precipitation in the Botany Bay catchment area comprises an oceanic component, a substantial terrestrial component, probably of natural origin and in both particulate and gaseous form, and a definite indication of added sulphate from anthropogenic sources in industrial locations.3.4.2 Nutrients in RainfallRain water from locations in close proximity to trees continually contained more potassium than rain water at locations away from trees. The loss of potassium from living leaves through leaf excretion, is well documented although the precise chemical form of the potassium is still in doubt. The effect was quite localised and probably constitutes a year-round mini-nutrient cycle where the potassium washed off the leaves by rain into the soil is extracted again by the roots.

In contrast to the year-round occurrence of excess potassium, the two spring periods covered by this rainfall study revealed a remarkable atmospheric phenomenon which appears to be peculiar to Australia. This phenomenon was exhibited by nitrate concentrations in the rain water such as have not been recorded in any of the voluminous literature on rain water nitrate in Europe or America.

19

During the study the nitrate concentrations ranged from 0 to 70 mg/1. The monthly distribution pattern can be exemplified by the Blakehurst, Clovelly and Picnic Point locations in Fig. 10, the peaks coinciding with the spring/ summer season with practically no nitrate being recorded in winter. This general pattern was repeated at all locations with the highest concentrations being recorded at Picnic Point and the lowest at Waterloo.

The presence of ammonia and nitrate nitrogen in rain water has been known since the beginning of the 19th century but their origin is still a matter of considerable conjecture. Relatively high ammonia values have been recorded in a number of rain waters and biological activity in the soil has been inferred as the source,^ but nitrate values have always been low and although spring/summer maxima are observed in the nitrate concentrations of European and American rains, these ’high values' are usually in the 1-2 mg/1 range, i.e. in no way do they approach the high concentrations observed during the present study.

There is little doubt that the nitrate content here is related to the presence of vegetation and specially to the spring season when the flowers are in full bloom.Pollen seems an obvious possibility as a source of nitrate

during this period of maximum pollen dispersion. However, Richerson, Moshiri and Godshalk^ found that pollen made only a small contribution to the annual input of nitrogen to the nutrient budget of a small watershed under study in California. Furthermore, pollen, being present universally, would not explain why the nitrate concentrations in Sydney's rain are so much higher than those recorded elsewhere.

At the location with the highest concentrations of nitrate, Picnic Point, it was noted that two very large Terpentine trees were in full bloom nearby during the months when the nitrate was exceptionally high. These trees are native to Australia and belong to the family Myretaceae, to which a large number of Australian plants belong, including the Eucalypts.

A property peculiar to many native Australian plants is that they are unusually aromatic. The bush and trees are rich in natural oils which are emitted as droplets of oil consisting principally of hydrocarbons such as terpenes.

Very little work has been done on the isolation of components other than hydrocarbons, but as early as 1913, Challinor discovered that the peculiar herring-brine odour which was given off by Rhagodia hastata, a native 'salt

20

lill

igrams/litre N

O mi

llig

rams

/lit

riFigure 10 Distribution of Nitrate in Rainfall (mg/1)

Blakehurst 1Clovelly

0 No'Oct. N

Picnic Pt

Oct . N1974

21

bush* commonly g r o w i n g i n g a r d e n s i n S y dney , was due t o t r i m e t h y l a m i n e . T h i s t r i m e t h y l a m i n e was e m i t t e d i n t h e s p r i n g and summer m o n t h s , and was most p r o n o u n c e d i n m o i s t w e a t h e r . ^

More r e c e n t r e s e a r c h h a s shown t h e p r e s e n c e o f c y a n i d e c o n t a i n i n g v o l a t i l e s i n E u c a l y p t u s l e a v e s . ^

B e c a u s e t h e h i g h n i t r a t e c o n c e n t r a t i o n s a p p e a r t o be u n i q u e t o A u s t r a l i a n r a i n w a t e r s ( t h e i n l a n d r a i n w a t e r s a l s o c o n t a i n e d r e l a t i v e l y h i g h n i t r a t e c o n c e n t r a t i o n s ) a n d , c o n s i d e r i n g t h a t A u s t r a l i a n n a t i v e p l a n t s do h a v e e x c e p t i o n a l a r o m a t i c p r o p e r t i e s , i t i s p o s s i b l e t h a t n i t r o g e n c o n t a i n i n g v o l a t i l e s , e m i t t e d by A u s t r a l i a n p l a n t s d u r i n g s p r i n g a r e r e s p o n s i b l e f o r t h e n i t r a t e c o n c e n t r a t i o n s i n t h e r a i n w a t e r s .

W h a te v e r t h e s e a s y e t u n i d e n t i f i e d s u b s t a n c e s a r e , an d w h a t p r o c e s s e s a r e r e s p o n s i b l e f o r t h e e v e n t u a l f o r m a t i o n o f n i t r a t e i o n s , r e m a i n a m a t t e r f o r s p e c u l a t i o n u n t i l more r e s e a r c h i s c a r r i e d o u t i n t o t h e e f f e c t s o f A u s t r a l i a n p l a n t s on t h e e n v i r o n m e n t . For t h e p r e s e n t , s u f f i c e t o s a y t h a t c o n s i d e r a b l e q u a n t i t i e s o f a p o t e n t i a l n u t r i e n t a r e b e i n g r e l e a s e d i n t o t h e a t m o s p h e r e a n n u a l l y and must p l a y a s i g n i f i c a n t r o l e i n t h e n u t r i e n t b u d g e t o f t h e A u s t r a l i a n e c o s y s t e m .

3 .5 Summary

The r a i n w a t e r s t u d y h a s shown t h a t t h e r e i s a s u b s t a n t i a l i n p u t o f s a l t s t o t h e B o tany Bay w a t e r s h e d v i a t h e a t m o s p h e r e , t h e p r i n c i p a l s o u r c e b e i n g t h e o c e a n .

The r a i n w a t e r c h e m i s t r y i s c o n t r o l l e d by a com plex i n t e r a c t i o n o f o c e a n i c , m i n e r a l o g i c a l , g e o g r a p h i c a l , b i o l o g i c a l and m e t e o r o l o g i c a l i n f l u e n c e s . Much more r e s e a r c h n e e d s t o be done i n s p e c i f i c f i e l d s b e f o r e t h e i n t e r r e l a t i o n s h i p s a r e f u l l y u n d e r s t o o d an d t h e s c h e m a t i c d i a g r a m o f F i g . 11 i s m e r e l y an i n t e r p r e t a t i o n o f some o f t h e p o s s i b l e p r o c e s s e s i n v o l v e d a s i n f e r r e d f rom t h e p r e s e n t d a t a .

4. THE UNDERGROUND RESERVOIR

4 . 1 The N a t u r e o f t h i s R e s e r v o i r

The s u c c e s s i o n o f p a s t g e o l o g i c a l e v e n t s h a s l e f t a l e g a c y i n t h e form o f a s a n d s t o n e b a s i n w h ich i s f i l l e d w i t h a h e t e r o g e n e o u s m i x t u r e o f m a r i n e c l a y s , s h e l l b e d s , swamp p e a t s , r i v e r an d b e a c h s a n d , and w i n d - b l o w n d u n e s .

22

Figure 1

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ain

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23

The a r e a e x t e n t o f t h e B a s i n i s shown i n F i g . 12,'*' and t h e t h i c k n e s s o f t h e s e d i m e n t s v a r i e s f r o m l e s s t h a n a m e t r e t o 80 m e t r e s . An e a s t - w e s t c r o s s s e c t i o n o f t h e B a s i n w o u ld l o o k s o m e t h i n g l i k e t h a t r e p r e s e n t e d b y t h e s c h e m a t i c d i a g r a m , F i g . 13. The c o m b i n a t i o n o f an i m p e r v i o u s s a n d s t o n e b a s e and p o r o u s u n c o n s o l i d a t e d s e d i m e n t s , forms a p e r f e c t r a i n w a t e r t r a p an d t h e s e d i m e n t s a r e g e n e r a l l y s a t u r a t e d t o w i t h i n a few m e t r e s o f t h e s u r f a c e .

The t o p o g r a p h y o f t h i s a r e a i s c h a r a c t e r i s e d by g e n t l y u n d u l a t i n g , i r r e g u l a r s a n d h i l l s , w i t h nu m ero u s swamps and p o n d s w h e re t h e dune s w a l e s d i p b e lo w t h e w a t e r t a b l e . On t h e n o r t h e r n an d w e s t e r n s i d e s o f B o t a n y Bay, h o u s e s , home u n i t s and i n d u s t r y h a v e r e p l a c e d t h e E u c a l y p t s , A n g ophora s and B a n k s i a s c r u b t h a t o n c e c o v e r e d t h e d u n es an d most o f t h e p o n d s h a v e d i s a p p e a r e d u n d e r n e a t h t h e u r b a n and s u b u r b a n o n s l a u g h t .

M i r a c u l o u s l y t h r o u g h a l l t h i s some o f i t h a s s u r v i v e d ; p e r h a p s n o t i n i t s o r i g i n a l fo r m b u t n e v e r t h e l e s s a l a r g e g r e e n - b e l t , c u t t i n g a s w a t h e t h r o u g h t h e d e n s e s t o f s u b u r b i a , h a s p r e s e r v e d t h e c h a i n o f swamps w h i c h w e r e S y d n e y ' s o r i g i n a l w a t e r s u p p l y . The f i v e g o l f c o u r s e s and C e n t e n n i a l P a r k w h i c h made up t h i s open a r e a b e l t can b e s e e n on t h e map i n F i g . 12.

But t h e i r s u r v i v a l so f a r i s no g u a r a n t e e f o r t h e f u t u r e . Many o f t h e r e m a i n i n g d u n es a r e a l r e a d y b e i n g d e m o l i s h e d t o p r o v i d e b u i l d i n g s a n d f o r o u r c o n c r e t e s t r u c t u r e s , w h i l e o t h e r s a r e e a r m a r k e d f o r t h e same p u r p o s e . The r e m a i n i n g swamps and p o n d s t o o a r e r a p i d l y d i s a p p e a r i n g , and one can o b s e r v e t h e p r o g r e s s i o n , f rom s w a m p - t o - g a r b a g e t i p - t o - s p o r t s f i e l d , t a k i n g p l a c e r e p e a t e d l y .

To t h e s o u t h o f B o t a n y Bay, t h e K u m e l l P e n i n s u l a h a s e s c a p e d much o f t h e a c t i v i t y o f c i v i l i s a t i o n b e c a u s e o f i t s r e l a t i v e i s o l a t i o n . A l t h o u g h i t h a s h a d i t s p r o b l e m s t o o ; f i r s t t h e l o s s o f much o f i t s t i m b e r more t h a n a c e n t u r y ago , t h e n t h e g r a z i n g o f s h e e p and c a t t l e , an d now s a n d e x t r a c t i o n , h a s r e d u c e d l a r g e a r e a s i n t o b a r e , m o b i l e s a n d h i l l s . But away f rom t h e s i g h t o f r o a d s , p o w e r l i n e s , s e w e r a g e v e n t s and i n d u s t r y ; i n t h e s w a l e s b e t w e e n t h e dunes p i l e d h i g h on t h e s a n d s t o n e c l i f f s w h ich p lumme t s t e e p l y down to t h e o c e a n , i s a n o t h e r w o r l d o f c l e a r r e f l e c t i v e p o o l s and o f w i l d e r n e s s h e a t h l a n d w h e re t h e w i l d f l o w e r s s t i l l b lo o m f o r w h i c h Botany Bay was named.

How ever , ev e n i n t h a t r e m o te h a v e n , w h e re s a n d - m i n e r s h av e n o t y e t r e a c h e d , t h e d e l i c a t e l y b a l a n c e d dune v e g e t a t i o n i s s u f f e r i n g b e c a u s e o f t r a i l - b i k e t r a c k s w h i c h c r i s s - c r o s s t h e

24

Figure 12 Direction of Ground Water Movement Within the Boundries of the Botany Basin

KINGSFORD

m a r q u b r a

Kingsford Smith

AirportARNCLIFFE

LA , PEROUSE

BOTANY BAY

KURNELL

SYLVANIA

CARLTON

B otany Basin

G reen belt

D irec tion of ground w a ter m ovem ent

0

CARINGBAH

CRONULLA

k ilom e tres

25

26

Fig

ure

13 R

epresen

tation

o

f C

ross S

ection

of

Botany

Basin

area. The bare tops of many of the dunes bear witness to the damage already done.

Steps have been taken by conservation groups and the National Parks and Wildlife Service to stop the use of this area by motorised vehicles, and in places re-stabilisation has been attempted. It is hoped that these measures will be successful otherwise this remaining natural heathland so close to Sydney will also disappear.Out of the 1,100 km of N.S.W. coastline, there are only two

other areas of heath and woodland which contain sizeable fresh water swamps and lakes, these are the Myall Lakes region situated 270 km north of Sydney and the Wooli Lakes region 500 km north of Sydney. Unfortunately the sand-miners have discovered these areas too.

4.2 The Quantity of WaterThe volume of usable water actually contained by the Basin has been the subject of considerable interest in the past and in 1942 a governmental Commission investigated the water-bearing potential of the sand beds with a view to using the ground water to supply Sydney in the event of a national emergency.^ No such emergency arose, but it was estimated then that the northern portion of the Basin which comprises about one-third of the whole Basin, could contain in the vicinity of 136,300 million litres of water, which is quite comparable to the capacity of our surface storage reservoirs.Water is extracted from the sands by either shallow spear

points where centrifugal pumps lift the water from depths of 3 to 6 metres, or gravel-packed bores where turbine line shaft pumps lift up to 90,800 litres per day from depths of 30 metres or more. Extraction has been estimated at approximately 50 million litres per day,iD the bulk of which is used for various industrial purposes, but a portion is used for watering private gardens, parks, sports fields and golf courses. The current rate of withdrawal appears to be well within the capacity of the sand beds.

While direct absorption of rain water by the unconsolidated sediments is the main means of ground water accession to the Basin, an important contribution to the water budget is made by the Hawkesbury Sandstone rim-rock, through direct run-off from its impervious surface and by the springs which can be seen to feed many of the ponds on the periphery of the Basin.

Regional ground water movements are generally in the directions shown by the arrows in Fig. 12. It can be seen

27

that while the loss of open space areas close to the Bay would have little effect on the water yields in the rest of the Basin, open space areas on the up-slope end of the hydraulic gradient, such as Centennial Park, are intake areas for large sections of the sand beds. Thus any reduction of open space in these locations would result in a significant decline in the Basin's water storage capacity.

4.3 Characteristics of the WaterAs with all water supplies it is the quality rather than the quantity which is the final determinant of its usefulness.The 'purity and excellence' of the Botany Basin swamp water was a feature often commented upon by the early residents of Sydney and the first detailed chemical analysis of the water, in 1867, confirmed its low salt content.The present study of the hydrochemistry of the Basin has

revealed a complex system where the interaction of a variety of factors has resulted in six distinctive chemical types of water which are distributed over the Basin as shown in Fig.14 (a & b) .The type of salinity is represented in Fig. 14 (a) by a

hexagon whose shape is determined by the concentrations of six major ions plotted along three horizontal axes to the scale indicated in Fig. 14 (a), for example:

mi Hi-equivalents/lit re1__1__1__1__1__ __1__1__1__L 1

\\\l__i__!\ | |7/

1 |I 1

i__i__

\ 1 1 \\\\\\\\

--1--1

I I5 4 3 2 1 1 1

1 2 2--1--1

4 5

HCO,

28

Figure 14 (a) Distribution of Ground Water Types

29

F i g u r e 14 (b) D i s t r i b u t i o n o f S am p l in g P o i n t s

•*% • * ; . •

• Bore sample

A Surface sainple

30

4 . 3 . 1 A r e a 1

A re a 1 c o m p r i s e s a m a j o r p o r t i o n o f t h e n o r t h e r n s a n d b e d s an d i n c l u d e s t h e r e m a i n i n g p o n d s o f t h e o l d Sydney w a t e r s u p p l y . The g r o u n d and s u r f a c e w a t e r s w i t h i n t h i s a e o l i a n dune a r e a a r e c h a r a c t e r i s e d by t h e i r low s a l i n i t y , b e i n g w i t h o u t e x c e p t i o n , l e s s t h a n 200 mg/1 .

The c h e m i c a l c o m p o s i t i o n b e a r s a c l o s e r e s e m b l a n c e t o t h e c o m p o s i t i o n o f r a i n w a t e r , p a r t i c u l a r l y t h e r a i n w a t e r s c o n t a i n i n g t h e m o s t t e r r e s t r i a l s a l t s , i . e . t h e most d r y f a l l . The g r o u n d w a t e r s a l t s a r e , t h e r e f o r e , p r e d o m i n a n t l y o f o c e a n i c o r i g i n w i t h an e x c e s s o f t e r r e s t r i a l c a l c i u m and s u l p h a t e i o n s . The e x c e s s o f c a l c i u m an d s u l p h a t e , h o w e v e r , i s g e n e r a l l y g r e a t e r i n t h e g r o u n d and s u r f a c e w a t e r s t h a n i n t h e r a i n wTa t e r s ; t h i s ca n b e s e e n i n t h e c o m p a r i s o n o f t h e r a n g e o f c o n c e n t r a t i o n s i n F i g . 15.

The ad d e d co m p o n en t s do n o t a p p e a r t o b e c o n t r i b u t e d by t h e s e d i m e n t s . W a t e r s c o l l e c t e d f r o m f l o w i n g g u t t e r s ( a s d i s t i n c t f rom d r a i n s w h ic h c o n t a i n g r o u n d w a t e r ) d u r i n g r a i n s t o r m s h a v e c o m p o s i t i o n s r e m a r k a b l y s i m i l a r t o t h e low s a l i n i t y g r o u n d w a t e r s . A c o m p a r i s o n b e t w e e n a b o r e w a t e r and a t y p i c a l g u t t e r w a t e r , i n T a b l e I I , i l l u s t r a t e s t h i s s i m i l a r i t y i n t e r m s o f t h e a b s o l u t e c o n c e n t r a t i o n s .

The b o r e a b s t r a c t s w a t e r f r o m a d e p t h o f 36 m e t r e s , y e t i t s c o m p o s i t i o n i s s i m i l a r t o t h a t o f t h e g u t t e r w a t e r w h ich h a s h ad no c o n t a c t w i t h t h e s e d i m e n t s . Pond w a t e r s and deep g r o u n d w a t e r s show s i m i l a r c o m p o s i t i o n s . C l e a r l y , t h e r e f o r e , t h e s e d i m e n t s do n o t make a s i g n i f i c a n t c o n t r i b u t i o n t o t h e m a j o r i o n s i n t h e w a t e r .

Ground an d s u r f a c e w a t e r s f r o m s i m i l a r s i l i c i o u s c o a s t a l s a n d a r e a s , s u c h a s M y a l l L a k e s and Wool i L a k e s , d e r i v e t h e i r s o l u b l e c o m p o n en t s a l m o s t e n t i r e l y f rom r a i n w a t e r . The c o m p o s i t i o n s o f t h e s e w a t e r s g e n e r a l l y show some e x c e s s SO^- ( a l t h o u g h t h i s i s l e s s t h a n t h e e x c e s s SO^- u s u a l l y fo u n d i n t h e B o tan y B a s i n ) , b u t o f s i g n i f i c a n c e i s t h e f a c t t h a t t h e r e i s v e r y l i t t l e , i f a n y , e x c e s s Ca~*~+' , a s ca n b e s e e n f rom t h e e x a m p le s i n T a b l e I I .

S i m i l a r l y , w a t e r s o b t a i n e d f rom u n i n h a b i t e d Hawkesbury S a n d s t o n e a r e a s w h ich a r e away f r om t h e s u b u r b a n a r e a s o f S y d n ey , a l s o show a s m a l l e x c e s s o f S0/ = , w i t h p r a c t i c a l l y no e x c e s s Ca .

What t h e s e a r e a s h av e i n common i s t h e f a c t t h a t t h e y a r e r e l a t i v e l y u n d i s t u r b e d and h e a v i l y v e g e t a t e d . C o n s e q u e n t l y , t h e r e i s l i t t l e a t m o s p h e r i c d u s t . The p r e s e n c e o r a b s e n c e o f d u s t h a s a d i r e c t b e a r i n g on w a t e r c o m p o s i t i o n . F o r

31

Figure 15 Range of Sulphate and Calcium Concentrations

Terrestrial sulphate

Waterloo [• • •• 7*m •Rain

Vlllawood ••• • •• • • • • • • •Rain

ClovellyRain

BoreWaters

PondWaters

GutterWaters

milligrams/litre

WaterlooRain

VlllawoodRain

ClovellyRain

BoreWaters

PondWaters

GutterWaters

Terrestrial calcium

[• • • •

milligrams/litre

32

Table I I Comparison Between V a r ious Types o f W ate rs

Cl" Na+ S04" Ca** Mg++ K+

(mg/1)

1. Sep tember r a i n w a t e r a t W ate r loo c o n t a i n i n g a h i g h p r o p o r t i o n of d r y f a l l

T o t a l c o n c e n t r a t i o n 24 15 11.0 3 .4 1.6 0 . 8T e r r e s t r i a l p o r t i o n 1.6 7 .8 2 .9 0 0 . 3

2. Bore w a t e r , Rowland P a rk , f romd e p th o f 36 m e t r e s

T o t a l c o n c e n t r a t i o n 25 14 27 .0 14.0 3 .0 6 . 8T e r r e s t r i a l p o r t i o n 0 .1 23 .6 13.5 1.3 6 .2

3. F lowing g u t t e r w a t e r a t LordS t r e e t , R o s e v i l l e

T o t a l c o n c e n t r a t i o n 29 16 33 .0 14.5 3 .9 5 .6T e r r e s t r i a l p o r t i o n 0 29.1 13.9 2 .0 5 . 0

4. Bore w a t e r , Myal l Lakes a r e a

T o t a l c o n c e n t r a t i o n 41 23 7 .0 0 . 8 2 .6 1.1T e r r e s t r i a l p o r t i o n 0 . 2 1.5 0 0 0 . 3

5. Reedy Swamp, Wooli Lakes a r e a

T o t a l c o n c e n t r a t i o n 33 18 18.0 1.0 2 .4 0 . 8T e r r e s t r i a l p o r t i o n 0 13.6 0 . 3 0 .2 0 . 1

6 . Upper Reaches o f t h e GeorgesR i v e r a t t h e ’Woolwash’

T o t a l c o n c e n t r a t i o n 31 16 8 .0 1.0 2 .5 1 .0T e r r e s t r i a l p o r t i o n 0 3 .8 0 . 3 0 . 4 0 . 3

33

e x a m p l e , i n t h e e l e v a t e d a l p i n e e n v i r o n m e n t o f Mt K o s c i u s k o , w h e re b o t h t e r r e s t r i a l d u s t an d o c e a n i c a e r o s o l s a r e a t an e x t r e m e minimum, t h e s a l i n i t y o f t h e Snowy R i v e r i s n o t much more t h a n t h a t o f d i s t i l l e d w a t e r .

On t h e o t h e r h a n d , much o f S y d n e y ’ s d u s t y a t m o s p h e r e i s d e r i v e d f r om ce men t p a r t i c l e s s w ep t o f f c i t y s t r e e t s by t h e w i n d . T h i s i s s u b s e q u e n t l y r e t u r n e d a s c a l c i u m s u l p h a t e i n d u s t f a i l , a f t e r c h e m i c a l r e a c t i o n s i n t h e a t m o s p h e r e .

The c i t y an d s u b u r b a n g u t t e r s w e r e fo u n d t o b e c a p a b l e o f r e l e a s i n g Ca+ + , HCO3- and SO4- i o n s i n t o s o l u t i o n , and t h e c o m b i n a t i o n o f r a i n w a t e r c o m p o n e n t s and t h e i o n s r e l e a s e d f rom t h e g u t t e r m a t e r i a l i t s e l f a c c o u n t s f o r t h e c o m p o s i t i o n o f mos t o f t h e g u t t e r w a t e r s s a m p l e d d u r i n g t h i s s t u d y .

The r e m a r k a b l e s i m i l a r i t y b e t w e e n t h e c h e m i c a l c h a r a c t e r i s t i c s o f g u t t e r w a t e r s and t h o s e o f t h e low s a l i n i t y w a t e r s o f t h e B o t a n y B a s i n s e d i m e n t s , i n d i c a t e s t h a t t h e c h e m i s t r y o f t h e po nd and g r o u n d w a t e r s i s c o n s i d e r a b l y i n f l u e n c e d by t h e u r b a n e n v i r o n m e n t . F i r s t , by way o f m o d i f i c a t i o n o f t h e r a i n w a t e r c o m p o s i t i o n due t o t h e d u s t i n e s s o f t h e a t m o s p h e r e ; and s e c o n d l y , t h r o u g h c i t y r u n - o f f , w h ich c o n t r i b u t e s s o l u b l e co m ponen t s d e r i v e d f rom s e t t l e d d u s t , and s t r e e t an d g u t t e r m a t e r i a l .

4 . 4 The P r e s e n c e o f I r o n

An o u t s t a n d i n g f e a t u r e o f t h e s i l i c i o u s d u n es o f t h e B o tan y B a s i n , w h ich d o es a f f e c t t h e c h e m i c a l c h a r a c t e r o f t h e n a t u r a l w a t e r , i s t h e r i c h n e s s o f i r o n i n t h e s a n d s . T h i s can be w i t n e s s e d by t h e p r e s e n c e o f p o d s o l s o i l s w i t h t h e i r r e d , i r o n - r i c h , B- h o r i z o n s ; by t h e e x t e n s i v e l i m o n i t e t e r r a c e s b o r d e r i n g swamps; by t h e r e d g e l a t i n o u s p r e c i p i t a t e s c o a t i n g t h e b e d s o f c r e e k s , and by t h e i r r i d e s c e n t f i l m s on u n d i s t u r b e d p o o l s o f w a t e r .

I r o n i s one o f t h e mos t t r o u b l e s o m e co m p o n en t s o f any w a t e r s u p p l y and c o n c e n t r a t i o n s o v e r as l i t t l e a s 0 . 3 m i l l i g r a m s / l i t r e b e g i n t o i m p a r t u n d e s i r a b l e t a s t e and c o l o u r t o t h e w a t e r . I r o n i n c o n c e n t r a t i o n s w e l l above t h i s l i m i t i s a f r e q u e n t com ponen t o f t h e g r o u n d w a t e r t h r o u g h o u t t h e B o tany B a s i n .

The s o l u b i l i s a t i o n o f t h e i r o n i n t h e dune s a n d s comes a b o u t due t o t h e p r e s e n c e o f a b u n d a n t o r g a n i c m a t t e r w h i c h h a s a c c u m u l a t e d t h r o u g h t h e r e c u r r e n t b u r i a l o f s o i l h o r i z o n s w i t h t h e i r a c c o m p a n y i n g v e g e t a t i o n , and t h e r e d i s t r i b u t i o n o f p e a t y m a t e r i a l f r om o l d , f r e s h - w a t e r swamp d e p o s i t s .

The dec ay p r o c e s s e s o f o r g a n i c m a t t e r r e q u i r e ox y g en w h ich

34

i s p r o v i d e d by t h e d i s s o l v e d oxygen i n r e c h a r g e w a t e r , b u t when t h e o x ygen become s d e p l e t e d , r e d u c i n g c o n d i t i o n s p r e v a i l i n t h e g r o u n d w a t e r e n v i r o n m e n t . The i r o n o x i d e m i n e r a l s c o a t i n g t h e s a n d g r a i n s a r e no l o n g e r s t a b l e i n t h e ch a n g e d e n v i r o n m e n t an d t h e i r o n i s r e d u c e d . T h i s b r i n g s f e r r o u s i o n s i n t o s o l u t i o n t h u s m o b i l i s i n g t h e i r o n .

When t h e m o b i l i s e d f e r r o u s i o n s e n c o u n t e r an o x i d i s i n g e n v i r o n m e n t , s u c h a s a swamp o r p o n d , w h e r e t h e g r o u n d w a t e r i n t e r s e c t s t h e s u r f a c e , t h e f e r r o u s i o n s a r e o x i d i s e d b a c k t o t h e f e r r i c s t a t e by t h e d i s s o l v e d o xygen i n t h e a e r a t e d w a t e r , an d r e - p r e c i p i t a t e d a s a f e r r i c o x y h y d r o x i d e , t o fo r m t h e r e d t e r r a c e s on t h e e d g e s o f swamps.

When b u r i e d , t h e s e i r r e g u l a r i r o n t e r r a c e s become d i s t i n c t i v e h o r i z o n s i n t h e s t r a t a , w h ic h a r e commonly c a l l e d W a t e r l o o Rock i n t h e B o t a n y B a s i n b u t a r e known by o t h e r n a m e s , s u c h a s W ool loom olo o Rock , s a n d r o c k o r c o f f e e r o c k , i n o t h e r c o a s t a l s a n d a r e a s .

I n s p i t e o f t h e a b u n d a n t o r g a n i c m a t t e r , h o w e v e r , a l l t h e p o n d s i n t h e B o t a n y B a s i n , i n c l u d i n g t h e c l i f f - t o p p o n d s a t K u r n e l l , a r e o u t c r o p p i n g s o f t h e g e n e r a l w a t e r t a b l e an d n o t p e r c h e d on i m p e r m e a b l e o r g a n i c l a y e r s s u c h a s t h e dune l a k e s a l o n g t h e Q u e e n s l a n d c o a s t an d F r a s e r I s l a n d . A p p a r e n t l y a much more p r o f u s e v e g e t a t i o n t h a n t h a t w h i c h e x i s t e d i n t h e B o t a n y B a s i n i s n e c e s s a r y f o r t h e f o r m a t i o n o f s u c h humus- b o u n d l a y e r s .

4 . 4 . 1 Area 2

A r e a 2 c o m p r i s e s t h e r e g i o n s u r r o u n d i n g A l e x a n d r a C a n a l , and e n c o m p a s s e s Moore P a r k G o l f C o u rse w h i c h i s t h e m a j o r i n t a k e a r e a f o r t h i s r e g i o n and f r om w h e r e g r o u n d w a t e r f l o w s i n a s o u t h - w e s t e r l y d i r e c t i o n t o w a r d s t h e C a n a l .

P r i o r t o t h e c o n s t r u c t i o n o f t h e C an a l i n 1896, much o f t h e a r e a c o n s i s t e d o f m a r s h e s w h ic h w e r e d r a i n e d by a s m a l l s l u g g i s h c r e e k c a l l e d S h e a ’ s C r e e k . When t h e C a n a l was dug , t h e l e v e l o f t h e s u r r o u n d i n g l a n d was r a i s e d by i n f i l l i n g w i t h m a t e r i a l f rom t h e e x c a v a t i o n . The s t r a t a c o n s i s t e d o f e s t u a r i n e c l a y s w i t h many s c a t t e r e d s h e l l b e d s a l t e r n a t i n g w i t h s a n d an d p e a t l a y e r s c o n t a i n i n g s i z e a b l e o r g a n i c r e m a i n s s u c h as t r e e s t u m p s .

T h i s h e t e r o g e n e o u s s t r a t a h a s r e s u l t e d i n t h e g r o u n d w a t e r i n t h i s a r e a h a v i n g a v e r y v a r i a b l e s a l i n i t y , r a n g i n g f rom 200 t o 700 m i l l i g r a m s / l i t r e . The s a l i n i t y i s l e a s t a r o u n d t h e e d g e s o f t h e r e g i o n and h i g h e s t n e a r t h e n o r t h e r n en d o f t h e C a n a l . The d o m in an t c h e m i c a l c h a r a c t e r i s t i c o f t h e w a t e r

35

i s t h e p r e s e n c e o f h i g h c o n c e n t r a t i o n s o f Ca*"*" an d HCO^~ i o n s , o r i g i n a t i n g f r om t h e s h e l l y n a t u r e o f t h e s e d i m e n t s .

V a r i a b l e c o n c e n t r a t i o n s o f s u l p h a t e i o n s a r e a l s o f o u n d i n t h e b o r e w a t e r s . The s o u r c e o f t h i s s u l p h a t e can b e t r a c e d b a c k t o t h e swamp c o n d i t i o n s w h i c h h a v e e x i s t e d i n t h e a r e a . The d e c a y o f l a r g e am oun ts o f swamp v e g e t a t i o n , e s p e c i a l l y u n d e r b r a c k i s h w a t e r c o n d i t i o n s , h a s r e s u l t e d i n t h e f o r m a t i o n o f s u l p h i d e m i n e r a l s , w h i c h h a v e b e e n d e t e c t e d i n t h e s e d i m e n t s . On s u b s e q u e n t o x i d a t i o n by oxygen c o n t a i n i n g g r o u n d w a t e r s u l p h u r i c a c i d i s p r o d u c e d , w h i c h i n t h e s e s e d i m e n t s , c o n t a i n i n g a b u n d a n t s h e l l s , i s n e u t r a l i s e d by t h e c a l c i u m c a r b o n a t e , f o r m i n g a s o l u t i o n o f Ca"^ an d S0^= i o n s .

A f u r t h e r d i s t i n g u i s h i n g f e a t u r e o f t h e g r o u n d w a t e r i n t h e c e n t r a l c r o s s - h a t c h e d p o r t i o n o f a r e a 2 , i s t h e Na+ i o n c o n c e n t r a t i o n s i n e x c e s s o f t h a t a s s o c i a t e d w i t h t h e c h l o r i d e p r e s e n t . L e a c h i n g e x p e r i m e n t s c a r r i e d o u t on v a r i o u s p e a t s p r o d u c e d s i m i l a r e x c e s s e s o f s o d i u m i o n s i n s o l u t i o n an d t h e p r e s e n t e v i d e n c e s u g g e s t s t h a t t h e s o d iu m i s d e r i v e d f r o m s o d i u m h u m a t e s a s s o c i a t e d w i t h t h e p e a t y s t r a t a .

On t h e w e s t e r n s i d e o f t h e C an a l o n l y one b o r e was a v a i l a b l e f o r o b s e r v a t i o n b u t t h e c h e m i c a l c o m p o s i t i o n o f t h e w a t e r f r om t h i s b o r e e x h i b i t e d t h e t y p i c a l c h a r a c t e r i s t i c s o f w a t e r a s s o c i a t e d w i t h W i a n a m a t t a s h a l e and i t seems t h a t t h e s a n d w e s t o f t h e C a n a l r e c e i v e s some s e e p a g e w a t e r f r om t h e W i a n a m a t t a s h a l e o u t c r o p p i n g a s t h e r i m - r o c k i n t h i s p o r t i o n o f t h e B a s i n .

4 . 4 . 2 A re as 3 and 4

A re as 3 and 4 r e f e r t o t h e u n i q u e h y d r o l o g i c s y s t e m o f t h e K u m e l l P e n i n s u l a .

The Ha wk esbury S a n d s t o n e t i p o f K u r n e l l was o n ce an i s l a n d b u t became l a n d l o c k e d by t h e e m e r g e n c e o f a t o m b o lo a b o u t 8 , 0 0 0 t o 6 , 0 0 0 y e a r s ago . S e d i m e n t s f o r m i n g t h e c o n n e c t i n g s p i t w e r e b r o u g h t by o c e a n c u r r e n t s and w e re r i c h i n c a l c a r e o u s m a t e r i a l s u c h as s h e l l f r a g m e n t s and c a l c a r e o u s a l g a e . T hese s e d i m e n t s w e re l a t e r s u b j e c t e d t o c o n s i d e r a b l e wind a c t i o n w h ic h c r e a t e d l a r g e dunes r e a c h i n g h e i g h t s o f more t h a n 30 m e t r e s , w h ic h now cap t h e s a n d s t o n e .

One o f t h e c o n s e q u e n c e s o f t h i s w ind a c t i o n was a c h e m i c a l s o r t i n g o f t h e s a n d so t h a t t h e c a l c a r e o u s m a t e r i a l was l e f t b e h i n d on t h e s p i t and a l m o s t p u r e q u a r t z g r a i n s w e r e p i l e d up i n t o t h e h i g h d u n e s .

T h i s g e o l o g i c a l e v e n t now m a n i f e s t s i t s e l f i n t h e two c h e m i c a l t y p e s o f g ro u n d w a t e r fou nd on t h e P e n i n s u l a . The

36

d i f f e r e n c e be tw een t h e w a t e r s can be s e e n when th e p e r c e n ta g e c o m p o s i t io n s a r e t a b u l a t e d i n T ab le I I I .

T a b le I I I Chem ical C o m p o s it io n s o f K u m e l l W aters

Na+ C l" Mg'1"* Ca++ HCO3" S04=*-J • • cy cy 0/ 0/ 0/ 0/

/o /o /o /o /o /o

( 1)( 2)

840 9 .7 9 .7 5 .2 34 .0 30 .2 9 .2540 36 .7 4 2 .7 9 .1 2 .5 1 .0 6 .9

( 1) = w a t e r a s s o c i a t e d w i th m arines a n d s o f th e s p i t

( 2 ) = w a t e r a s s o c i a t e d w i th th ea e o l i a n dunes

E.C . = e l e c t r i c a l c o n d u c t i v i t y in m icrom hos/cm .

The d i s t r i b u t i o n o f t h e s e two ty p e s o f w a te r s i s c l e a r l y d e l i n e a t e d by th e a r e a l p l o t s o f t h e Ca"^ and HC03~ concent r a t i o n s i n F ig . 16 (a and b ) .

The w a te r s a s s o c i a t e d w i th t h e h i g h l y c a l c a r e o u s sand o f th e s p i t a r e o f t e n s a t u r a t e d s o l u t i o n s o f c a lc iu m c a r b o n a te , a l t h o u g h t h e r e i s n o t a d i r e c t r e l a t i o n s h i p be tw een th e Ca++ and HCO3” c o n c e n t r a t i o n s b e c a u s e some o f th e b i c a r b o n a t e i s d e r i v e d from magnesium c a r b o n a te w hich i s i n c o r p o r a t e d i n v a r y i n g amounts i n t o th e c a r b o n a te s k e l e t o n s o f o rg a n is m s .Some o f th e c a lc iu m i s a l s o a s s o c i a t e d w i th th e s o l u t i o n o f gypsum c r y s t a l s w hich a r e p r e s e n t i n t h e s p i t s a n d . ^

A d i s t i n g u i s h i n g f e a t u r e o f a l l t h e w a t e r s a t K u m e l l i s th e c h l o r i d e c o n c e n t r a t i o n s e n c o u n te r e d . These a r e g e n e r a l l y tw ic e as h ig h as t h o s e found on th e n o r t h e r n s i d e o f Botany Bay, and on t h e c l i f f t o p s f a c i n g th e ocean and c h l o r i d e v a lu e s a r e up to 10 t im e s h i g h e r . T h is i s due to th e d i r e c t e x p o s u re o f t h e P e n i n s u l a t o t h e s t r o n g s a l t - l a d e n s o u t h e r l y w in d s . T h is e f f e c t i s a p p a r e n t l y m in im ised on th e n o r t h e r n s i d e by th e b u f f e r i n g a c t i o n o f B otany Bay.

W ater a s s o c i a t e d w i th t h e s i l i c i o u s a e o l i a n dunes o f K u m e l l i s th u s c h a r a c t e r i s e d by i t s h ig h s a l t c o n t e n t , composed a lm o s t e n t i r e l y o f o c e a n ic s a l t s t r a n s p o r t e d v i a th e a tm osp h e re .

4 . 4 . 3 Area 5

A rea 5 r e f e r s to th e n a rro w b e l t o f sand dunes b o r d e r i n g Lady R o b in so n ’ s Beach on th e w e s t e r n s h o re o f Botany Bay. The dunes r e a c h a h e ig h t o f o n ly 8 m e t r e s above s e a l e v e l and

37

Figure 16 (a) Bicarbonate Distribution in mg/1

BOTANY BA Y

300 3fi? 7/ b

BA TE BA Y

Figure 16 (b) Calcium Distribution in mg/1

BOTANY BAY

BA TE BA Y

38

r e p r e s e n t a s e r i e s o f w a v e - b u i l t b a r s a l l i g n e d p a r a l l e l t o t h e b e a c h .

Between t h i s sand r i d g e and th e Hawkesbury S a n d s to n e r im - r o c k to t h e w e s t , l i e s an e x t e n s i v e a r e a o f m a rs h la n d cons i s t i n g o f b o th s h a l lo w re e d y swamp and deep open w a t e r , w h ich d r a i n s i n a s o u t h e r l y d i r e c t i o n i n t o B otany Bay.

The g round w a t e r i n t h e dune a r e a i s p r e d o m in a n t ly c h a r a c t e r i s e d by Ca"*“ ̂ and HCO3- i o n s , r e f l e c t i n g th e p r e dom inance o f s h e l l s and s h e l l g r i t i n th e s t r a t a . But t h e s h e l l s a r e random ly d i s t r i b u t e d th ro u g h o u t t h e s a n d and th e w a t e r s a r e n o t q u i t e as c o n c e n t r a t e d i n CaCHCOß^ a s th o s e a t K u m e l l . I t seems t h a t th e c a l c a r e o u s sand i s tem p e re d w i th s a n d composed e n t i r e l y o f s i l i c a b e c a u s e th e h y d ro c h e m ic a l d i s t r i b u t i o n i s one o f CaCHCOß^ r i c h w a t e r s i n t e r s p e r s e d a t i r r e g u l a r i n t e r v a l s w i th v e ry d i l u t e w a t e r s c o n t a i n i n g on ly r a i n w a t e r s a l t s . These d i l u t e w a t e r s can be found from b o r e s w i t h i n a few f e e t o f t h e s h o re o f t h e Bay.

The m a rs h la n d i s f e d by g round w a t e r s e e p in g from th e f l a n k i n g dunes and th e c h e m ic a l c o m p o s i t io n o f th e w a t e r i n t h e swamp i s b a s i c a l l y s i m i l a r t o t h e w a te r pumped from th e s u r r o u n d i n g b o r e s , how ever , a v a r i e t y o f human i n f l u e n c e s have m o d i f ie d some a s p e c t s o f th e w a t e r c h e m i s t r y , t h e s e w i l l be d i s c u s s e d l a t e r .

I n f l u x e s o f s a l t w a t e r from th e Bay o c c u r o c c a s i o n a l l y and t h i s , c o u p le d w i th p o o r c i r c u l a t i o n ( a c c e n t u a t e d by s e v e r a l ro a d s d i s s e c t i n g th e swamp a r e a ) can r e s u l t i n m arked s a l i n i t y f l u c t u a t i o n s i n t h e swamp w a t e r a t t im e s .

4 . 4 . 4 A rea 6

A rea 6 , on F ig . 12, encom passes t h e n o r t h e r n s h o re o f Botany Bay and i n c l u d e s th e h e a v i l y i n d u s t r i a l i s e d a r e a s o f Botany and Banksmeadow. T h is a r e a h a s e a r n e d an in fam ous r e p u t a t i o n f o r th e o f t e n r e p o r t e d ground w a t e r p o l l u t i o n w hich has se e m in g ly o c c u r r e d due to i n d u s t r i a l d i s c h a r g e s .

The o u t s t a n d i n g c h e m ica l c h a r a c t e r i s t i c o f t h e g round w a te r w hich h a s l e d to t h i s s u s p i c i o n , i s i t s h ig h s a l i n i t y comp a re d to o t h e r a r e a s o f t h e B otany B a s in . T h is s a l i n i t y i s due to v a r i a b l e amounts o f sod ium , c h l o r i d e , c a lc iu m , s u l p h a t e and i r o n , and a s s o c i a t e d w i th t h i s s a l i n i t y i s a v e ry s i g n i f i c a n t a c i d i t y .

A cid d i s c h a r g e s from v a r i o u s c h e m ic a l i n d u s t r i e s and a l a r g e s a l t s t o c k - p i l e b e lo n g in g to I . C . I . A u s t r a l i a L im i te d have b een th e m ost commonly im p l ie d s o u r c e s o f t h e s e com ponents , a l th o u g h such c o n c lu s io n s have u s u a l l y been b a s e d on c o n je c -

39

ture and only one serious attempt in the past has been made to actually study the hydrological features of the area.This study was made by J.V. Smart^ and the major finding was that the direction of the water movement in the area has been changed due to the heavy industrial pumping.The present three-year investigation of the hydrochemistry

of the area has revealed that, while industrial pollution cannot be completely discounted, any effect on the ground water composition from such a source is quite over-shadowed by the overwhelming influence of the natural geological features of the region.These unusual geological properties are the result of the

swamp conditions which have existed in the Botany-Banksmeadow area for many thousands of years. The sequence of peat horizons, some several metres in thickness, extends to at least 54 metres below present sea level. The radiocarbon age of a peat sample taken from a depth of 27 metres has been given as greater than 30,000 years B.P. (Before Present), but this figure is the limit of the method used and thus indicates only that the swamp sediments predate the Wurm glacial period. The many peat layers are interspersed by marine clay horizons, indicating that the sea frequently transgressed over the swamp.

Swamp conditions still exist over some of the area, much of it at elevation close to sea level and a thick layer of relatively recent peat (dated 8,880 + 200 years B.P.) directly underlies the present swamp.The paleoenvironment, of swamp material with its rich store

of organic matter, and subsequent sea water transgressions, resulted in severe anoxic conditions, where enormous quantities of hydrogen sulphide were produced by the metabolic reduction of sea water sulphate. The reduction process was also responsible for the extraction of iron from clay minerals and the liberated iron reacted from the hydrogen sulphide to form the range of iron - sulphur compounds, such as pyrite and marcasite, which now impregnate the sediments.

These iron sulphides are unstable in the combined presence of oxygen and water, and hence any oxygen carried down to the sediments by the ground water will oxidise the iron sulphides to ferric sulphate and sulphuric acid although a range of intermediate products is possible. Hydrolysis of ferric sulphate will result in the production of more sulphuric acid and extremely acid ground waters will result.This process can be demonstrated in the laboratory by

40

l e a c h i n g w i th w a t e r , sam ples o f p e a t , c la y and sand from t h e s e a n c i e n t swamp d e p o s i t s . Below in T ab le IV, i s an example o f t h e r e s u l t a n t s o l u t i o n o b t a i n e d when some s a n d , w hich had become cem ented i n t o a h a rd s a n d ro c k by a m ix tu re o f p y r i t e and m a r c a s i t e , was l e a c h e d w i th d i s t i l l e d w a t e r .

T a b le IV L e a c h a te from Sand and I r o n S u lp h id e

pH Cl" Na+ Mg"1”1” Ca*H’ S O ^ Fe SiC>2 K+

2 .5 0 8 1.6 5 >2,000 1 ,100 15 4 .5

N ote : Sand + FeS2 , 100 gm in 500 ml w a t e r( c o n c e n t r a t i o n s i n m g /1 ) .

I t can be c l e a r l y s e e n t h a t th e l e a c h a t e y i e l d e d a s o l u t i o n o f s u l p h u r i c a c id and i r o n s u l p h a t e ( b o th a s f e r r i c and f e r r o u s ) .

But th e m arine t r a n s g r e s s i o n s a l s o d e p o s i t e d i n t h e s e d i m ents m arine o rg an ism s w i th t h e i r s k e l e t a l p a r t s made m ain ly o f c a lc iu m c a r b o n a te . Under th e v e ry a c i d c o n d i t i o n s , how ever , most o f th e s h e l l s have lo n g been d e s t r o y e d and t h e i r p l a c e t a k e n by th e r e a c t i o n p r o d u c t s such as c a lc iu m s u l p h a t e , o f t e n found i n th e form o f l a r g e and l u s t e r o u s c r y s t a l s o f gypsum, i n th e dry s e d im e n t .

When s e d im e n ts a l s o c o n t a i n i n g th e a l t e r a t i o n p r o d u c t s o f m ar ine o rg an ism s a r e l e a c h e d , t h e r e s u l t a n t s o l u t i o n s show c o m p o s i t io n s s i m i l a r to t h e example g iv en i n T ab le V.

T ab le V L e a c h a te from P e a t

pH Cl" Na+ Mg** Ca"1"1" SO^“ Fe SiC>2 K+

2 .8 1.5 20 70 210 1,500 30 40 7 .6

N ote : P e a t from a d e p th o f 30 m e tre s in B o tany -Banksmeadow a r e a , 100 gm + 500 ml w a te r ( c o n c e n t r a t i o n s i n m g /1 ) .

The h ig h CaSO^ c o n te n t in th e l e a c h a t e i s e v i d e n t . The s i l i c a i n s o l u t i o n a p p e a r s to be d e r iv e d from th e d i s s o l u t i o n o f hyd ro u s s i l i c o n d io x id e o r o p a l , w hich i s a l s o a component o f th e s k e l e t a l m a t e r i a l o f many m ar ine o rg a n is m s .

The s e d im e n ta ry h o r i z o n s which r e a c t w i th w a te r to p roduce th e s o r t o f s o l u t i o n d e p ic t e d i n T ab le V, and w hich a l s o t y p i f i e s th e common c h a r a c t e r i s t i c s o f many o f th e ground

41

w a t e r s , a r e most numerous i n t h e c e n t r a l c r o s s - h a t c h e d p o r t i o n o f a r e a 6 on F ig . 12 b u t e x te n d l a t e r a l l y b o th e a s t and w e s t a lo n g th e n o r t h e r n s h o re o f th e Bay. Where t h e s e h o r i z o n s a r e s p a r s e and i n t e r s p e r s e d w i th a b u n d a n t s a n d , t h e g round w a te r i s n o t s e v e r e l y a f f e c t e d by them , b u t i n p a r t s o f t h e B o ta n y - Banksmeadow a r e a t h e g round w a t e r h a s no o p t io n b u t to move i n i n t i m a t e c o n t a c t w i t h t h e s e a c id p r o d u c in g s e d i m e n t s .

The r e s u l t a n t e f f e c t s a r e v i s i b l e i n t h e c r e e k s w hich a r e f e d by t h i s ground w a t e r . Enormous q u a n t i t i e s o f i r o n i n s o l u t i o n p r e c i p i t a t e o u t u n d e r t h e d i f f e r e n t o x i d a t i o n c o n d i t i o n s i n t h e c r e e k , c o a t i n g t h e f l o o r s o f t h e c r e e k s w i th a r e d g e l a t i n o u s m ass.

The c h e m ica l r e a c t i o n s be tw een r e c h a r g e w a t e r and th e s e d im e n ts a r e v i r t u a l l y i n s t a n t a n e o u s and hence t h e r e i s no d i l u t i o n e f f e c t even d u r in g heavy r a i n p e r i o d s . These a re i n t r i n s i c p r o p e r t i e s o f th e a r e a and th e c h a in o f i n t e r a c t i o n s h a s b een o p e r a t i n g and w i l l c o n t in u e to o p e r a t e w i th o r w i th o u t t h e p r e s e n c e o f modern c i v i l i s a t i o n . I t was j u s t u n f o r t u n a t e t h a t t h e many i n d u s t r i e s who n e e d and u se ground w a t e r chose an a n c i e n t swamp s i t e on w hich t o l o c a t e t h e i r b o r e s .

4 .5 The Sodium C h lo r id e P rob lem

A s i t u a t i o n h a s a r i s e n i n r e c e n t y e a r s w here ground w a t e r h a s s lo w ly i n c r e a s e d i n s a l i n i t y and a c i d i t y i n a r e a s w hich p r e v i o u s l y p ro d u ce d w a t e r o f low s a l i n i t y . A h ig h sodium c h l o r i d e c o n te n t h a s a l s o been a s s o c i a t e d w i th t h i s s a l i n i t y i n c r e a s e and s i n c e t h e movement h a s been i n a s o u th t o n o r th d i r e c t i o n , s e a w a t e r i n t r u s i o n i n t o th e a q u i f e r from th e Bay th ro u g h heavy w i th d ra w a l by i n d u s t r y h a s been a s u g g e s t e d p o s s i b i l i t y . However, from b o th c h e m ic a l and h y d r o l o g i c a l c o n s i d e r a t i o n s , p r e s e n t day s e a w a t e r en c ro ach m en t can be d i s c o u n te d .

But s e a w a t e r d id t r a n s g r e s s once more i n t o t h e low l y i n g swamp on th e edge o f th e Bay som etim e d u r in g th e p a s t 9 ,0 0 0 y e a r s , t o s a t u r a t e t h e e x p o sed d e p o s i t s w i th s a l t . W hether t h i s l a s t t r a n s g r e s s i o n was due to t h e s t i l l c o n t r o v e r s i a l L a te -H o lo c e n e o s c i l l a t i o n s i n s e a l e v e l o r due to i n c r e a s e d s to r m in e s s when s to rm waves b ro k e o v e r t h e sand r i d g e w hich s e p a r a t e s th e swamp from th e Bay, i s a m a t t e r o f s p e c u l a t i o n , b u t t h e e f f e c t o f t h i s t r a n s g r e s s i o n i s s t i l l m a n i f e s t to d a y .

The r e g io n w here t h i s e v e n t i s most e v id e n t i s i n th e d e p re s s e d a r e a c o n t a i n i n g n e a r - s u r f a c e p e a t a p p ro x im a t in g to th e a r e a i n d i c a t e d i n F ig . 17. The p o n d s , g round w a t e r and

42

Figure 17 Salty Sediments in the Botany-Banksmeadow Area

even s m a l l p u d d le s , a s s o c i a t e d w i th t h i s p e a t a r e q u i t e s a l i n e and a m a jo r p o r t i o n o f t h e s a l i n i t y i s due t o sodium c h l o r i d e . T a b le VI shows some o f th e ch e m ica l c h a r a c t e r i s t i c s o f t h e w a te r and th e p e a t .

Due to t h e t h i c k n e s s o f th e com pressed p e a t in t h i s a r e a and th e low e l e v a t i o n , w a te r c i r c u l a t i o n i s v e ry s low and t h e r e h a s b e e n in c o m p le te f l u s h i n g o u t o f th e c o n n a te s a l t s t r a p p e d i n th e p e a t .

T h is s i t u a t i o n i s n o t uncommon i n c o a s t a l swampy a r e a s and a v e ry s i m i l a r e n v iro n m e n t e x i s t s i n th e n o r t h c o a s t swampl a n d o f t h e M acleay R iv e r a l l u v i a l s n e a r Kempsey, w here th e e x c e s s i v e ground w a t e r and swamp w a te r s a l i n i t y i s d e r iv e d from c o n n a te s e a w a te r w i t h i n t h e s e d i m e n t s . 19 The w a te r s a t Kempsey a r e a l s o h i g h l y c o n c e n t r a t e d i n s u l p h a t e s and a re v e ry a c id due to t h e accom panying o c c u r r e n c e o f ' a c i d s u l p h a t e 1 s e d im e n ts o r c a t - c l a y s , w i t h i n a few f e e t o f th e w a t e r t a b l e .

What h a s happened i n t h e Botany-Banksmeadow a r e a to b r i n g t h i s s i t u a t i o n to p rom inance i s th e i n c r e a s e d i n d u s t r i a l w i th d ra w a l t o th e n o r t h o f t h e swamp w hich h a s changed th e p a t t e r n o f ground w a t e r f low as e s t a b l i s h e d by S m a r t ^ and th e s a l t y w a te r from th e swamp a r e a has b e e n drawn n o r th w a r d . The w a te r now b e in g dumped from b o re s a t some d i s t a n c e to th e n o r t h e x h i b i t s a l l t h e ch e m ica l c h a r a c t e r i s t i c s o f th e w a te r i n t h e s o u th e r n s a l t y a r e a .

T ab le VI Chem ical C h a r a c t e r i s t i c s o f W ate rs from th e B o tany-Banksmeadow Area

Cl Na+ Mg"*-*" Ca4-1-

ii<r

oto Fe S i0 2 K+

(1) 490 260 24 117 236 10 13 18(2) 1 ,490 950 9 110 245 6 37 9(3) 3 ,024 1,900 25 240 540 0 .2 5 .5 18

N o te : (1) = b o re w a te r from swamp a r e aa t a d e p th o f 24 m e tre s

(2) = pond w a t e r from swamp a r e a(3) = l e a c h a t e from s u r f a c e p e a t

in swamp a r e a , 100 gm i n 500 ml w a te r ( c o n c e n t r a t i o n s in m i l l i g r a m s / l i t r e )

44

4 .6 The I . C . I . S a l t S t o c k p i l e

The p o s s i b i l i t y o f t h e I . C . I . s a l t s t o c k p i l e b e in g th e s o u rc e o f sodium c h l o r i d e i n t h e ground w a t e r can be d i s c o u n te d on many c o n s i d e r a t i o n s . Some o f t h e s e a r e :

(a ) P a s t c h e m ic a l r e c o r d s show t h a t w a t e r t o t h e s o u th o f t h e s t o c k p i l e s i t e was s a l t y even b e f o r e t h e s a l t p i l e was e s t a b l i s h e d .

(b) Ground w a t e r a t some d i s t a n c e from th e s a l t p i l e , and s e p a r a t e d from i t by two c r e e k s , c o n ta i n s sod ium c h l o r i d e e q u a l i n c o n c e n t r a t i o n to t h a t found i n g round w a t e r n e a r t h e s a l t p i l e . Such a s i t u a t i o n i s u n l i k e l y t o o c c u r w i t h a p o i n t s o u rc e o f c o n ta m in a t io n .

(c ) The i n c r e a s e i n s a l i n i t y i n p r e v i o u s l y low s a l i n i t y a r e a s h a s a lw ays b een accom panied by a d e c r e a s e i n pH and i n c r e a s e s i n compone n t s o t h e r th a n NaCl, such as Ca*"*", SO^- and F e . The I . C . I . s a l t i s a lm o s t t o t a l l y composed o f NaCl and t h e n e a r n e u t r a l s o l u t i o n s c o n ta i n o n ly f a i n t t r a c e s o f o t h e r i o n s .

(d) W aters a s s o c i a t e d w i th t h e s a l t y p e a t have i o d id e c o n c e n t r a t i o n s many t im e s t h a t o f s e a w a t e r . T h is i s c h a r a c t e r i s t i c o f c o n n a te w a te r s w here i o d i d e i s d e r iv e d from th e p r o c e s s o f b i o c o n c e n t r a t i o n and s u b s e q u e n t decay . W ate r i n new ly s a l i n e a r e a s a l s o shows th e p r e s e n c e o f i o d i d e , b u t s o l u t i o n s o f s a l t from th e I . C . I . s t o c k p i l e c o n ta in e d no i o d i d e .

4 .7 A p p r a i s a l

The Botany-Banksmeadow s i t u a t i o n h a s been d i s c u s s e d a t l e n g t h ; b e c a u s e t h e p rob lem s t h e r e have been m a t t e r s o f c o n j e c t u r e f o r a c o n s i d e r a b l e t im e .

I t p ro v ed to be a s u r p r i s i n g l y complex r e g io n w i th a w ide v a r i e t y o f h y d ro c h e m ic a l f a c t o r s i n t e r a c t i n g to p ro d u ce th e o u t s t a n d i n g c h a r a c t e r i s t i c s o f th e w a t e r .

The outcome o f th e s tu d y c l e a r l y i l l u s t r a t e s t h e need a lw ays f o r a b a s i c u n d e r s t a n d in g o f th e n a t u r a l e n v iro n m en t b e f o r e p o l l u t i o n , as d e f i n e d by human i n f l u e n c e s , can even be d e l i n e a t e d .

45

5 . OUR IMPACT ON THE NATURAL WATER QUALITY

The e n v iro n m e n t c o n s t i t u t e s a dynamic s y s te m and th ro u g h o u t g e o l o g i c a l t im e n a t u r a l d i s t u r b a n c e s o f b o th l a r g e and s m a l l m agn itude have t a k e n p l a c e , b u t to t h e s e n a t u r a l phenomena i s now added a new d im e n s io n , th e human i n f l u e n c e , and f o r n e a r l y a l l w a t e r sy s te m s t h i s i n f l u e n c e i s d e t r i m e n t a l . In th e Sydney r e g io n th e w o r s t u rban a f f l i c t i o n s on th e w a t e r sy s te m s a r e g a rb a g e and sew age.

The c o u n c i l t i p i s a t e r m i n a l a i lm e n t f o r any w a te rb o d y f o r i t q u i c k l y l e a d s t o i t s r a d i c a l d e g r a d a t i o n and i s t h e u l t i m a t e im p a c t on th e a q u a t i c e n v iro n m e n t . The use o f any a v a i l a b l e w a t e r h a b i t a t , be i t a ree d y swamp o r a l e a f y c r e e k g u l l y , f o r t h e dumping o f ga rb a g e f o r th e s a k e o f e x p e d ie n c y , i s r e p r e h e n s i b l e n o t o n ly b e c a u s e such ’w e t t i p p i n g ’ c a u se s w orse c h e m ic a l and b i o l o g i c a l e f f e c t s on th e e n v iro n m en t th a n ’ d ry t i p p i n g ' away from w a t e r c o u r s e s , b u t a l s o b e c a u s e i t r e s u l t s i n t h e l o s s o f a v a l u a b l e e n v i r o n m e n ta l am e n i ty .

The im p a c t o f sewage on o u r w a t e r sy s te m s i s p ro fo u n d and f a r r e a c h in g . The e f f e c t s a r e f e l t i n t h e c o a s t a l ocean w a t e r , i n t h e r i v e r s , c r e e k s and swamps and even i n th e g round w a t e r . Some o f th e e f f e c t s a r e p e rm a n e n t , o t h e r s o n ly tem p o ra ry d e p e n d in g on t h e s e l f - p u r i f y i n g c a p a c i t y o f th e i n d i v i d u a l w a te rb o d y and th e p a r t i c u l a r c o n d i t i o n s o f each s i t u a t i o n .

I t was n o t t h e p u rp o se o f th e p r e s e n t s tu d y t o i n v e s t i g a t e p o l l u t i o n p e r s e and i t i s n o t i n te n d e d h e r e to r e l a t e a l l t h e m a n i f e s t a t i o n s o f human i n f l u e n c e s w hich w ere u n a v o id a b ly n o te d d u r in g th e s t u d y , b u t one exam ple , t h a t o f th e u n f o r t u n a t e S c a rb o ro u g h Swamp, can be t a k e n to p o r t r a y many o f t h e b u rd e n s w hich b e f a l l on an open w a te rb o d y i n an u rb an s i t u a t i o n .

5 .1 S c a rb o ro u g h Swamp - An A q u a t ic E nv ironm en t i n D i s t r e s s

L ike any o t h e r m a r s h la n d , S ca rb o ro u g h Swamp l y i n g b e h in d th e dunes o f t h e w e s t e r n s h o re o f Botany Bay, w ould i n th e lo n g te rm n a t u r a l c o u rs e o f e v e n t s d i s a p p e a r th ro u g h th e a g e in g p r o c e s s , as a c o n t i n u a l b u i l d - u p o f n u t r i e n t s c a u se s i n c r e a s e d b i o l o g i c a l p r o d u c t i o n , heavy growth o f a q u a t i c m ac ro p h y te s and accom panying s i l t i n g .

A ll t h e symptoms o f e u t r o p h i c a t i o n a r e c l e a r l y a p p a r e n t in S c a rb o ro u g h Swamp a t p r e s e n t and to what e x t e n t th e s e c o n d i t i o n s would have p r o g r e s s e d under u n d i s t u r b e d c o n d i t i o n s i s i m p o s s ib l e t o a s c e r t a i n , b u t th e n u t r i e n t c o n te n t ( n i t r o g e n

46

and phosphorous) of the Swamp water exceeds by a factor of 10 and at times by a factor of 100, the accepted threshold concentrations needed for the growth of nuisance algal blooms. Phosphate levels for example average around 0.4 to 0.9 mg/1 but the values fluctuate dramatically and concentrations as high as 4.0 mg/1 have been measured. Concentrations within the same range are observed in lakes in other countries where eutrophication is known to have been caused by cultural enrichment.

Increased phosphate build-up in the sediments of Scarborough Swamp probably began late last century when much of the swampland was drained for market gardening. The resultant agricultural drainage, rich in phosphorous, would have been scavenged and absorbed by the Swamp sediments, in later years to be mobilised again when conditions in the Swamp become anaerobic as happens when sewage flows into the Swamp to add its share to the phosphate load.

The dramatic impact of a sewage inflow on the Swamp ecosystem was observed during March of 1976 when after a period of prolonged and heavy rai_n, a sewage pumping station, located on the shore of the Swamp, could not cope with the excess storm water and sewage overflowed directly into the Swamp. Water throughout the major part of the Swamp turned completely septic. There was an extremely offensive odour over the whole area, the water was coloured black from the formation of sulphides, and all fish in the Swamp were killed, the last remaining ones were seen gasping for their last breath at the surface of the water.

The completely deoxygenated conditions lasted for approximately 10 days after which the first signs of an algal bloom (identified as the polluted water algae, Pyrobotrys) was seen as a green irridescence in the water. It took about one month for the effects of the sewage spill to abate and after five months the fish population had not regenerated beyond miniature species.

This was a catastrophic event for a whole ecosystem and water pollution in the extreme, yet the Pollution Control Commission displayed no interest. Local residents worried for their children who play by the Swamp, were not informed of the cause of the awful condition of the Swamp. The Metropolitan Water, Sewerage and Drainage Board denied a sewage spill, even though similar incidents occur in many of Sydney's waterways with unfortunate regularity every time there is a heavy storm.

A local council tip, located at the upstream end of the Swamp, was suggested by the Metropolitan Water, Sewerage and

47

D r a i n a g e B o a r d a s t h e s o u r c e o f t h e c o m p o n en t s c a u s i n g t h e s u d d e n s e v e r e s e p t i c c o n d i t i o n s o f t h e Swamp w a t e r . L e a c h a t e f r o m t h e u n s i g h t l y t i p can b e d e t e c t e d t h r o u g h i n c r e a s i n g b i c a r b o n a t e , c a l c i u m , s o l u b l e i r o n , s i l i c a an d f l u o r i d e co n c e n t r a t i o n s a s t h e t i p i s a p p r o a c h e d . The d i s t r i b u t i o n o f s i l i c a an d i r o n i n F i g . 18 s e r v e s t o i l l u s t r a t e t h i s e f f e c t . T h e r e i s e v i d e n c e t o s u g g e s t t h a t magnes ium , c h l o r i d e and s u l p h a t e i o n s a r e a l s o b e i n g l e a c h e d t o some e x t e n t f r o m t h e t i p b u t i t i s d i f f i c u l t t o s e p a r a t e t h e e x a c t c o n t r i b u t i o n o f t h e s e i o n s f r o m e a c h o f t h e v a r i o u s c o n t r i b u t i n g s o u r c e s .

Oxygen v a l u e s i n t h e pond a d j a c e n t t o t h e t i p a r e co n t i n u a l l y low ( a b o u t 20% s a t u r a t i o n ) b u t c o n s t a n t , and t h i s pond was t h e o n l y p a r t o f t h e Swamp s t i l l c o n t a i n i n g some o xygen d u r i n g t h e s e p t i c c o n d i t i o n s o f March 1976, t h u s e l i m i n a t i n g t h e t i p a s a p o s s i b l e c a u s e o f t h e c o n d i t i o n .

The f u t u r e f o r S c a r b o r o u g h Swamp l o o k s as b l e a k a s t h a t o f o t h e r s i m i l a r a r e a s . A f t e r a l l , a s t i l l l a r g e t r a c t o f swampl a n d n o t y e t a l l f i l l e d w i t h g a r b a g e , i s a s i t u a t i o n w h ic h i s n o t l i k e l y t o l a s t f o r much l o n g e r ; b e s i d e s t h e l o c a t i o n i s a p r o p o s e d s i t e f o r an e x p r e s s w a y and s o t h e r e i s no room f o r a swamp anyway. B u t , e v e n i f t h e s e s i t u a t i o n s do n o t e v e n t u a t e , i t s c u l t u r a l l y a c c e l e r a t e d e u t r o p h i c a t i o n w i l l h a s t e n i t s d e m i s e .

5 . 2 Human I n f l u e n c e s on t h e Ground W a t e r Q u a l i t y

5 . 2 . 1 From L a n d f i l l s

The g r o u n d w a t e r s a l i n i t y p a t t e r n o v e r t h e B a s i n i s c o m p l i c a t e d by t h e o c c u r r e n c e o f l a n d f i l l s i t e s whose l e a c h a t e s e n t e r t h e g r o u n d w a t e r s y s t e m . The l e a c h a t e s can b e d e t e c t e d i n t h e w a t e r f r o m n e a r b y b o r e s b y i n c r e a s e s i n t o t a l s a l i n i t y an d u n u s u a l l y h i g h c o n c e n t r a t i o n s o f a v a r i a b l e number o f c o m p o n en t s d e p e n d i n g on t h e p a r t i c u l a r c o m p o s i t i o n o f t h e l a n d f i l l an d t h e s t a g e o f d e c o m p o s i t i o n . T h ese e f f e c t s , w h i l e o b v i o u s l y o p e r a t i v e f o r l o n g p e r i o d s o f t i m e , a r e f a i r l y l o c a l i s e d and w i t h d i s t a n c e a p p e a r to b e r a p i d l y d i l u t e d t h r o u g h d i s p e r s i o n .

5 . 2 . 2 From Sewage

The n a t u r a l c o n c e n t r a t i o n s o f n i t r a t e a r e q u i t e low i n t h e g r o u n d w a t e r s o f c o a s t a l s a n d a r e a s . The n i t r a t e c o n t r i b u t e d t o a c a t c h m e n t a r e a by r a i n w a t e r i s p a r t o f t h e n a t u r a l n u t r i e n t c y c l e an d i s t h e r e f o r e q u i c k l y a s s i m i l a t e d a g a i n , and i n a b a l a n c e d e c o s y s t e m t h e r e i s no s u r p l u s n i t r a t e . T h u s , t h e u b i q u i t o u s p r e s e n c e o f s i g n i f i c a n t c o n c e n t r a t i o n s o f

48

Figure 18 Effect of Tip Leachate on Scarborough Swamp

Mo.

PRESIDENT

BARTON — ST'

Pumping / Station

------- CULVER ST-

SP = Reclaimed land now

sports field

Flood gates

Ah. Bulrushes

Natural

Drainage

Direction

kilom etre

49

n i t r a t e i n th e b o r e w a te r s o f th e B otany B a s in was an u n u su a l and p e r p l e x i n g f e a t u r e ,

A few o f t h e l a n d f i l l s i t e s were found to c o n t r i b u t e n i t r a t e to s o l u t i o n , b u t n i t r a t e was a l s o found i n a r e a s w here t h e r e w ere no l a n d f i l l s . Bore w a t e r from g o l f c o u r s e s and b o w lin g g ree n s u s in g f e r t i l i s e r s d id n o t c o n ta i n any h i g h e r concen t r a t i o n s o f n i t r a t e th a n b o r e s i n r e s i d e n t i a l a r e a s . Nor d id t h e i n d u s t r i a l a r e a s show any s i g n i f i c a n t d i f f e r e n c e s i n th e ran g e o f n i t r a t e c o n c e n t r a t i o n s compared to n o n - i n d u s t r i a l l o c a t i o n s .

The p o s s i b i l i t y t h a t t h e abundan t p e a ty m a t e r i a l i n th e s t r a t a c o u ld be th e s o u rc e o f n i t r a t e was t h o r o u g h ly i n v e s t i g a te d b u t t h e p e a t i s p a s t th e s t a g e o f d e c o m p o s i t io n when n i t r a t e c o u ld be form ed i n s i g n i f i c a n t q u a n t i t i e s and th e n i t r o g e n now i n th e p e a t i s f ix e d i n a form u n a v a i l a b l e f o r s o l u t i o n .

I t was n o t u n t i l t h e n i t r a t e s i t u a t i o n on th e K u m e l l P e n i n s u l a was s t u d i e d , w here th e d e n s i t y o f u rb an and su b u rb an deve lopm en t i s n o t so g r e a t , t h a t t h e s o u r c e o f th e n i t r a t e became a p p a r e n t . F ig u re 19 i l l u s t r a t e s t h e n i t r a t e io n d i s t r i b u t i o n i n b o th seepage w a te r s and b o r e w a t e r s on th e P e n i n s u l a . The n a t u r a l w a te r i n th e u n i n h a b i t e d d u n e s , even though r i c h i n o r g a n i c m a t t e r , does n o t c o n t a i n n i t r a t e .The t h r e e r e g io n s w here n i t r a t e i s p r e s e n t a r e a s s o c i a t e d i n one way o r a n o th e r w i th sewage.

Area A c o n ta i n s a sewage t r e a tm e n t p l a n t w i t h s lu d g e s e t t l i n g and i n f i l t r a t i o n ponds . Area B i s an unsew ered r e s i d e n t i a l a r e a w i th some b o re s d raw ing w a t e r dow nstream from t h e i r s e p t i c t a n k s . Area C i s t h e sw a le b e tw e en p a r a l l e l dunes w hich f o l lo w s th e p i p e l i n e c a r r y i n g t h e sewage from th e t r e a t m e n t p l a n t t o th e o u t f a l l a t P o t t e r P o i n t . A l l th e se ep a g e w a t e r i n p u d d le s a lo n g t h i s sw a le c o n ta i n e d n i t r a t e , b u t w a t e r be tw een o t h e r p a r a l l e l dunes d id n o t .

The c re e k a t Woolooware c o n ta i n in g 6 0^m g/l NO3 , i n F ig .19, runs p a r a l l e l t o a m a jo r sewage c a r r i e r and was r e p o r t e d to have tu r n e d b l a c k and s e p t i c d u r in g th e heavy r a i n p e r i o d o f March 1976 when th e p r e v i o u s ly d i s c u s s e d i n c i d e n t a t Sca rbo rough Swamp o c c u r r e d .

I t i s d i f f i c u l t to s o r t th ro u g h th e com plex maze o f n i t r a t e d i s t r i b u t i o n s i n th e h e a v i l y u r b a n i s e d sew ered a r e a s o f th e B asin to show t h a t th e p r e s e n c e o f s ew erag e p i p e s i s r e s p o n s i b l e f o r the n i t r a t e c o n te n t o f the ground w a t e r , b u t th e b o r e s grouped n e a r th e Snape P a rk a r e a in Randwick th ro u g h w hich a main sewage c a r r i e r a l s o p a s s e s , can s e r v e t o i l l u s t r a t e th e s i t u a t i o n .

50

Figure 1

9 Nitrate

Ion

Distribution,

Kurnell

(mg/1)

O

51

WO

OLO

OW

AR

I

Figure 20 shows the locations of the bores in relation to the pipe and the nitrate concentrations of the water as measured during February 1976. Approximately 280 metres away from the pipe the effect, although obviously decreased, is still apparent.

It is a known fact that sewerage pipes do leak, through defective sewerage joints or through cracks developed with age and seasonal soil movement, and it is the myriads of small street sewerage carrers and individual household connections which appear to be sources of nitrate in the ground waters all over the Botany Basin. In one notably high nitrate area, Monterey, the excessive nitrate can be related to the rapid development of high-rise accommodation. The sewerage system, which was originally built for single dwelling housing, cannot cope adequately with the increased volumes from high density housing.

5.3 The ConsequencesWhile the connection between sewage and nitrate in the ground water is evident, the mechanisms through which the process takes place are not at all clear.

In spite of the magnitude of the ground water nitrate concentrations, it is doubtful if large volumes of liquid sewage are actually flowing out of the underground pipes.Yet, somehow nitrate is finding its way into the ground water system apparently independently of the other components present in sewage. Cesspool leachate has been studied in cities where this has caused nitrate contamination of an underground water resource, such as Long Island, New York, and in metropolitan areas of California,^^>^2 and it has been found that ammonia released from the sewage is remarkably quickly oxidised to nitrate within a very short distance of the point of release. This would account for the fact that no ammonia or nitrite'was present in any of the bore waters studied here, even in those at Snape Park where the bores are only a few metres away from the sewerage pipeline.

The nitification is apparently taking place on the solid soil/water interface and the ground water simply carries the formed nitrate away. The nitrification process can be stimulated by very minor deviations in organic matter or pH or even non-biological factors, but very little is known of these processes and, in view of the extensiveness of the effect on the ground water, it is a field which deserves further study.

52

Figure 20 Relation Between Nitrate Concentration and Sewerage Pipeline

\\

\ ---------- SNAPE ST— — — ------111 19 711 SNAPE PARK

M117; 14 9 >

STOREY ST-

13— -GALE ST

|17-----------s------------------— BOYCE ST..................—

i 19\

\ SEWERAGE n n PI PEUNE

\\

14 = Nitrate concentration in bore water (February 1976) in milligrams/litre.

The consequences of this added component in the ground water system cannot be considered to be entirely detrimental. Many gardens in the Basin, watered with bore water, are flourishing due to the added supply of nutrient. The possibility of bacterial contamination can also be considered to be minimal, the sand being an extremely good filter of bacteria. The magnitude of the effectiveness was demonstrated at Kumell, where a ground water seepage pool and a sludge infiltration pool at the sewage treatment works, were in juxtapositions on opposite sides of a sand hill. The ground water seepage pool was clearly receiving nitrate (50 mg/1) from the sludge pond, but when tested for bacterial pollution, no diagnostic organisms were found.

In spite of this example, however, there is always the possibility of bacterial contamination, especially with shallow bores, and this factor needs to be considered if the water is to be used for such purposes as food manufacturing processes or in public or private swimming pools.

6. THE RIVERS OF THE BOTANY BAY CATCHMENT AREA

The two major rivers, the Georges River and the Cooks River, which drain into Botany Bay, have been examined by a great number of governmental, local council and independent organisations. Innumerable reports have been written in the past. Most of these have been concerned with pollution aspects and have dealt with biological parameters of the rivers such as bacterial counts and the oxygen regime.

This study did not wish to duplicate these investigations but attempted to look briefly at some of the natural geochemical processes taking place in the catchment area which might have an influence on the character of the two rivers.

It is not possible, however, to study highly urbanised rivers and avoid the human impact which may often be predominant. Those anthropogenic factors which appeared to have a significant influence on the river environment are, therefore, also described.

6.1 General CharacteristicsThe Sydney region has two distinct types of fresh water streams; those that traverse Hawkesbury Sandstone and those that traverse Wianamatta shale, and these two types differ markedly both in their physical and chemical characteristics.

54

6 . 1 . 1 P h y s i c a l A spec ts

The t y p i c a l Hawkesbury S a n d s to n e c r e e k o r i g i n a t e s on an e l e v a t e d p l a t e a u from e x t e n s i v e a r e a s o f 'h a n g in g swamps' w here w a t e r i s r e t a i n e d d u r in g r a i n p e r i o d s and r e l e a s e d s lo w ly o v e r a p e r i o d o f t im e . The Hawkesbury S a n d s to n e has th e p r o p e r t y o f w e a th e r in g a lo n g ro c k j o i n t s and c o n s e q u e n t ly b r e a k s up i n l a r g e s l a b s , so t h a t th e s a n d s to n e s t r e a m plummets down s t e e p w a t e r f a l l s and r a p i d s and tu m b les n o i s i l y o v e r t h e f a l l e n b o u l d e r s .

T hus , w i t h i n a r e l a t i v e l y s h o r t d i s t a n c e o f i t s b e g in n i n g , t h e s t r e a m h a s d e e p ly i n c i s e d i n t o t h e p l a t e a u , fo rm ing th e c h a r a c t e r i s t i c s t e e p and i n a c c e s s i b l e v a l l e y .

In c o n t r a s t , t h e W ianam atta s h a l e s t r e a m s a r e u s u a l l y l i t t l e more th a n s h a l lo w c h a n n e l s , w i th s i d e s o n ly a few m e t r e s deep c u t i n t o a c la y o f f r i a b l e s h a l e s t r a t u m . They t r a v e r s e f l a t to u n d u l a t i n g t e r r a i n and th e c h a n n e l t e n d s t o m a in ta in i t s s h a l lo w d e p th th ro u g h o u t i t s c o u r s e . T h e i r g e n e s i s a p p e a r s t o b e from a b ru p t s lu m p -h o le s l o c a t e d i n t h e p a th o f m ajo r o v e r l a n d flow r i l l s . At t h e b o t to m o f th e s lum p , a p o o l o f w a t e r a c c u m u la te s from w a t e r s e e p i n g th ro u g h th e w a l l s . Cons e q u e n t l y , s t r e a m flow b e g i n s , w i t h t h e volume o f th e w a te r b e i n g augmented dow nstream by f u r t h e r ground w a t e r s e ep a g e from th e b a n k s .

6 . 1 . 2 Chem ical C h a r a c t e r i s t i c s

W ate r i n c o n t a c t w i th Hawkesbury S a n d s to n e i s c h a r a c t e r i s t i c a l l y low i n d i s s o l v e d s a l t s . Under n a t u r a l c o n d i t i o n s , th e s a l i n i t y i s l e s s th a n 200 m i l l i g r a m s / l i t r e and th e c o n s t i t u e n t s a r e p re d o m in a n t ly o f o c e a n ic a e r o s o l o r i g i n . C o n t r ib u t io n to th e s a l i n i t y by th e s a n d s to n e i s i n th e form o f s o l u b l e s i l i c a d e r i v e d from th e w e a th e re d s u r f a c e l a y e r o f b e d ro c k , and i r o n , w hich p a s s e s i n t o s o l u t i o n u n d e r t h e m i ld ly r e d u c in g c o n d i t i o n s o f th e ground w a te r e n v iro n m e n t .

S in c e th e s o u rc e o f th e s a l i n i t y i s r a i n w a te r s a l t s and th e s i l i c a c o n te n t a t t a i n s a r a p i d e q u i l i b r i u m c o n c e n t r a t i o n , t h e Hawkesbury S a n d s to n e s t r e a m w i l l show l i t t l e v a r i a t i o n in s a l i n i t y th ro u g h o u t i t s c o u rs e as t h e a d d i t i o n o f more r u n - o f f w a t e r w i l l s im p ly add w a t e r o f th e same c o m p o s i t io n to t h e m a in s tre am . S i m i l a r l y , th e r u n - o f f w a te r e n t e r i n g th e c r a c k s , j o i n t s and b e d d in g p l a n e s o f t h e ground w a te r s y s te m , h a s a l r e a d y a c q u i r e d i t s c h e m ica l c o m p o s i t io n w h i le i n f i l t r a t i n g t h e s u r f a c e zone and w i l l m a in ta in t h i s c o m p o s i t io n th ro u g h o u t i t s p a th o f t r a v e l . D uring b a s e - f lo w t im e s when th e r i v e r f low i s m a in ta in e d m a in ly by ground w a t e r s e e p a g e , t h e s t r e a m

55

will still exhibit the same salinity.Wianamatta shale streams exhibit high salinities which often

exceed what is considered to be the upper limit of fresh water. The typical Wianamatta shale water is very much dominant in

_1_ __ I INa and Cl ions and contains a significant proportion of Mg ions. The ratio of Na+ to Cl- is constant and equivalent to that of sea water, but considerable variations occur in the proportions of the other major ions. Table VII shows analyses of a bore water and a creek water which have been in contact with Wianamatta shale.

Table VII Chemical Characteristics of Wianamatta Shale WatersBore Water, Moorebank, depth 45 metres (mg/1)

Cabramatta Creek, Edmondson Park (mg/1)

HC03" 946 600Cl" 5,922 7,330S04= 422 370Ca"*-*" 124 130Mg++ 683 640Na+ 2,944 3,800K+ 32 5Total ions 11,073 12,875

The most significant feature of these examples is the exceptionally high salinities and the similarity between the creek water and the ground water.

The creek water sample was taken during a non-storm period when the creek was at its normal base flow and thus contained only ground water. This accounts for the similarity between the bore water and the surface water. The very high salinity of the Wianamatta shale waters is a consequence of the original brackish water conditions under which the sediments were deposited and the lack of subsequent flushing of the retained salts due to the absence of direct external drainage.

There has been very little investigation into the nature of these 180 million year old connate salts. Some of the ground waters have exhibited salt contents greater than that of sea water.^3 a cursory appraisal of the available chemical analysis shows that the most significant modification to have

56

taken place is a reduction of the potassium content and the addition of considerable amounts of bicarbonate.

In contrast to the constancy of the salinity of the Hawkesbury Sandstone waters, Wianamatta shale creeks show extreme variations in salinity along their course. Fluctuations take place within a few hundred metres because the salinity of the ground water seeping in from the banks is very variable. For example, salinity measurements of Cabramatta Creek varied from 14,000 micromhos cm~^ to 1,700 micromhos cm on the same day. Some of the variations are due to the diluting effect of low lying swampy areas adjacent to the banks. During heavy rain periods, 20 to 50 fold decreases in salinity were observed in the same part of the creek.

6.2 The Georges RiverThe Georges River drains an area of approximately 930 sq km and the drainage system is shown in Fig. 21. The headwaters originate on densely timbered sandstone terrain of the Woronora Plateau, at an elevation of about 400 metres, but the streams fall abruptly within the first 30 km to reach the undulating topography of the Wianamatta shale region.

The marked parallelism of the drainage features in the southern portion of the catchment area is a result of the tilting of the region into a ramp-like structure during the Tertiary Period. Consequently, although the Georges River rises only 10 km from the ocean, it travels a distance of 90 km before entering the sea.

The southern tributaries of the River almost exclusively drain Hawkesbury Sandstone and the northern and western tributaries drain Wianamatta shale. The marked salinity divisions of the tributaries, shown in Fig. 21, reflect the two kinds of geological influences. For a considerable distance downstream the only tributaries of any significance to join the main stream come from the Hawkesbury Sandstone, and the river chemistry reflects the influence of this rock unit. It is not until only 7 km from the Liverpool Weir that the first major tributary draining the shale country joins the River. This tributary, however, has only a minor effect because of its small flow. It is in the remaining short distance to the Weir that the Georges River itself enters the Wianamatta shale and the salinity of the River increases. Prospect Creek and Cabramatta Creek, two very saline streams, join the River below the Liverpool Weir, but their influence

57

Figure 21 Influence of Geological Regimes on Water Salinity in the Georges River Drainage Area

Cooks River

Catchment

Nepean

River

Catchment

Port Hacking

River

Catchment

j Hawkesbury Sandstone

Wianamatta Shale

kilometres

58

i s overshadow ed by th e i n f l u x o f s e a w a t e r i n t h i s t i d a l p o r t i o n o f th e R iv e r .

D u r in g i t s f low e a s tw a r d , t h e n o r t h e r n t r i b u t a r i e s c o n t in u e t o be i n f l u e n c e d by th e s h a l e and th e t r i b u t a r i e s from th e s o u th r e f l e c t th e low s a l i n i t y o f th e s a n d s t o n e , b u t th e e f f e c t o f any o f t h e s e on t h e r i v e r c h e m is t r y i s m in im al b e c a u s e o f th e o v e r - r i d i n g i n f l u e n c e o f th e t i d e s .

6 . 2 . 1 The Human Im pact

As y e t t h e b e a u t i f u l u p p e r r e a c h e s o f th e Georges R iv e r have e s c a p e d th e human i n f l u e n c e b e c a u s e much o f th e a r e a h a s been a r e s t r i c t e d m i l i t a r y r e s e r v e . S in ce t h e ca tc h m e n t a r e a o f t h e uppe r r e a c h e s c o n s i s t s e x c l u s i v e l y o f t h i s u n i n h a b i t e d b u s h la n d , t h e w a t e r i s q u i t e p o l l u t i o n f r e e u n t i l t h e conf lu e n c e o f B u n b u rry -C u rra n Creek w hich d r a i n s th e newly s u b u r b a n i s e d Campbelltown a r e a . Between th e c o n f lu e n c e and th e L iv e r p o o l W eir , th e G l e n f i e l d Sewage T re a tm e n t Works d i s c h a r g e s i t s lo a d o f e f f l u e n t . Below th e W eir , t h e w a t e r , now u n d e r t i d a l i n f l u e n c e , r e c e i v e s a n o th e r i n j e c t i o n o f sewage from th e L iv e r p o o l T re a tm e n t Works and f u r t h e r downs t r e a m s t i l l P r o s p e c t Creek adds i t s lo a d o f e f f l u e n t from th e F a i r f i e l d T re a tm e n t W orks.

The e f f e c t on th e R iv e r can be s e e n in t h e n i t r a t e p r o f i l e i n F ig . 22. In k e e p in g w i t h a b a la n c e d e c o s y s te m , th e uppe r r e a c h e s o f th e R iv e r c o n t a i n no n i t r a t e , b u t dow nstream th e r e s u l t o f t h e lo a d o f e x c e s s o r g a n i c m a t t e r p o u re d i n t o th e sy s te m by th e sewage t r e a t m e n t w orks i s c l e a r l y e v i d e n t . T h is i s a c o n t in u o u s i n p u t , a f f o r d i n g th e R iv e r no r e s p i t e and p l a c i n g an enormous s t r e s s on th e w a t e r ' s c a p a c i t y to d e a l e f f e c t i v e l y w i th t h e s i t u a t i o n . At t im e s i t h a s f a i l e d , w i th d r a s t i c c o n s e q u e n c e s .

As th e R iv e r c o n t in u e s on i t s way i t s e n v iro n m en t r e f l e c t s t h e p r o d ig y o f u r b a n i s a t i o n . I t s t r i b u t a r i e s have been c a n a l i s e d and t h e i r c l e a r w a t e r s exchanged f o r f r o t h y , t u r b i d s u l l a g e . I t s banks have become r e c e p t a c l e s f o r g a rb a g e , and r a r e i s t h e c r e e k g u l ly to d a y w hich i s n o t f i l l e d o r i n th e p r o c e s s o f b e in g f i l l e d w i th u rban r e f u s e .

The e f f e c t o f such g a rb a g e dumps on th e R iv e r w a te r q u a l i t y m ust be a s s e s s e d w i t h i n t h e h y d ro g e o c h e m ic a l framework o f each s i t u a t i o n . A ' t i p ' im m e d ia te ly a d j a c e n t to th e R iv e r o r a c r e e k w i l l d i r e c t l y p o l l u t e t h e w a t e r w i th u ndeg raded o r g a n i c m a t t e r and b a c t e r i a . But t h e e f f e c t i s som etim es n o t l i m i t e d to c lo s e p r o x im i t y . Due to t h e p h y s i c a l s t r u c t u r e o f th e ro ck u n i t , dump l o c a t i o n s on Hawkesbury S a n d s to n e , even a t a d i s t a n c e from a c r e e k , a r e c a p a b le o f c o n t r i b u t i n g b a c t e r i a l

59

Figure 22 Nitrate Concentrations, Georges River

60

p o l l u t i o n t o t h e c r e e k . The Haw kesbury S a n d s t o n e , i s v e r y i m p e r v i o u s an d l e a c h a t e f rom a dump w o u l d e n t e r t h e c r a c k s an d j o i n t s i n t h e s a n d s t o n e t o l a t e r em erge as g r o u n d w a t e r s e e p a g e i n t o a s t r e a m . W a t e r movement t h r o u g h t h e s e p e r m e a b l e z o n e s i s r a p i d and b a c t e r i a w o u ld f lo w t h r o u g h t h e s e as r e a d i l y a s t h r o u g h a p i p e .

I f , h o w e v e r , t h e ’ t i p ’ was l o c a t e d i n a p e r v i o u s r o c k a r e a , w i t h s u f f i c i e n t s o i l c o v e r , and a t some d i s t a n c e f r o m t h e r i v e r o r c r e e k , d e g r a d a t i o n and m i n e r a l i s a t i o n o f t h e o r g a n i c m a t t e r w i l l t a k e p l a c e w i t h i n t h e dump a r e a a n d , s i n c e b a c t e r i a a r e removed by s o i l p a r t i c l e s w i t h i n a few m e t r e s o f t r a v e l , s e e p a g e f rom s u c h a s a n i t a r y l a n d f i l l w i l l b e c o n f i n e d t o h i g h c o n c e n t r a t i o n s o f v a r i o u s i n o r g a n i c i o n s . Such a s a l i n e l e a c h a t e c o u l d p o s s i b l y a l t e r t h e b i o c h e m i s t r y o f a v e r y low s a l i n i t y H aw k esb u ry S a n d s t o n e c r e e k , b u t w o u ld h a v e a m i n im a l e f f e c t on a W i a n a m a t t a s h a l e s t r e a m w h i c h h a s a n o r m a l w a t e r s a l i n i t y i n t h e o r d e r o f t h o u s a n d s o f p a r t s p e r m i l l i o n and w h e r e t h e f a u n a and f l o r a a r e o b v i o u s l y a d a p t e d t o w i d e and e r r a t i c f l u c t u a t i o n s i n s a l i n i t y .

B u t w h a t e v e r t h e c h e m i c a l e f f e c t s o f g a r b a g e t i p s on t h e R i v e r may b e , t h e s e a r e s u r p a s s e d by t h e v i s u a l p o l l u t i o n w h i c h t h e y c r e a t e an d t h e c o n s e q u e n t l o s s o f so much o f t h e a q u a t i c e n v i r o n m e n t o f t h i s R i v e r .

6 . 3 The Cooks R i v e r

The Cooks R i v e r p a s s e s t h r o u g h a m o s t d e n s e l y u r b a n i s e d p o r t i o n o f Sydney . I t s r e c e n t h i s t o r y h a s b e e n one o f c o n t i n u o u s m o d i f i c a t i o n by human i n f l u e n c e s . I t s t r i b u t a r i e s h a v e b e e n o b l i t e r a t e d o r h i d d e n i n s t o r m w a t e r p i p e s , i t s s u r r o u n d i n g w e t l a n d s h a v e b e e n ’ r e c l a i m e d ' , i t s c h a n n e l h a s b e e n r e l o c a t e d , s t r a i g h t e n e d and c e m e n t e d , a n d i t s s i d e s p u n c t u r e d w i t h s e w e r a g e v e n t s .

I t s c a t c h m e n t a r e a i s a p p r o x i m a t e l y 100 sq km and i t r i s e s a t an e l e v a t i o n o f 50 m e t r e s , 18 km w e s t o f B o ta n y B ay . The d r a i n a g e f e a t u r e s a r e shown i n F i g . 2 3 . I t s o n l y t r i b u t a r y f rom t h e n o r t h i s A l e x a n d r a C an a l w h i c h d r a i n s t h e a l l u v i u m o f t h e B o t a n y B a s i n . The t r i b u t a r i e s f rom t h e s o u t h p r e d o m i n a n t l y d r a i n W i a n a m a t t a s h a l e and t h i s i s r e f l e c t e d by t h e s a l i n i t i e s o f t h e t r i b u t a r i e s a l s o shown i n F i g . 2 3 .

The Cooks R i v e r can be d e s c r i b e d a s a t r u l y i n t e r m i t t e n t r i v e r . S a l t w a t e r f rom t h e t i d a l i n f l u x e n c r o a c h e s f o r 11 km u p s t r e a m and d u r i n g n o n - s t o r m p e r i o d s t h i s c o n s t i t u t e s t h e b u l k o f t h e w a t e r i n t h e R i v e r . A s m a l l t r i c k l e o f t y p i c a l l y s a l i n e W i a n a m a t t a s h a l e w a t e r , w h i c h s e e p s i n t h r o u g h o p e n i n g s

61

Figure 23 Cooks River Drainage System(Values represent salinity of river and creek water as measured by electrical conductivity in micromhos/cm)

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i n t h e cem ented b a n k s , i s t h e R i v e r ' s f r e s h w a t e r s o u rc e e x c e p t f o r o c c a s i o n a l i n f l u x e s o f o v e r f lo w w a t e r r e l e a s e d from P o o ts H i l l R e s e r v o i r , w hich th e n d i l u t e s t h e s h a l e w a t e r .

D ur ing heavy r a i n p e r i o d s , how ever , enormous q u a n t i t i e s o f r u n - o f f w a t e r from th e im p e rv io u s c i t y s t r e e t s po u r i n t o th e R iv e r c a u s in g f l a s h f lo o d i n g .

6 . 3 . 1 Q u a l i t y A sp e c ts

The u n f o r t u n a t e g e n e s i s o f t h e R iv e r i n th e r a i lw a y w orkshops a t C h u l l o r a , r e s u l t i n g i n an a lm o s t pe rm anen t f i l m o f o i l on th e w a t e r , and th e f l o a t i n g t r a s h throw n i n by r e s i d e n t s (a bag o f dead a n im a ls and a T.V. s e t , h ave b een among th e f l o a t a b l e s o b se rv e d ) a r e some o f th e f e a t u r e s o f t h i s R iv e r , b u t t h e most dom inant i n f l u e n c e s on th e r i v e r w a t e r q u a l i t y a r e th e c a n a l i s a t i o n o f th e s t r e a m bed and s to r m sew er o v e r f l o w s .

The cem en tin g o f a w a te rw ay , t h e r e b y t u r n i n g i t i n t o a c a n a l o r d r a i n , d e s t r o y s t h e f e a t u r e s o f th e s t r e a m c h a n n e l w hich a r e e s s e n t i a l to th e R i v e r ' s s e l f - p u r i f y i n g p r o c e s s . The w a t e r can no l o n g e r d e a l a d e q u a te ly w i th even s m a l l amounts o f o r g a n i c m a t t e r and th e w a te r i s p e rm a n e n t ly i n an u n h e a l th y s t a t e .

Such i s t h e s t a t e o f th e u p p e r r e a c h e s o f t h e Cooks R iv e r and i t s t r i b u t a r y d r a i n s , d u r in g d ry w e a th e r . The t i d a l p o r t i o n o f th e Cooks R i v e r , u n l ik e th e G eorges R i v e r , does n o t r e c e i v e a c o n t in u o u s i n p u t o f sewage e f f l u e n t and d u r in g d ry w e a th e r f low p e r i o d s i t i s r e l a t i v e l y p o l l u t i o n f r e e .

D u r in g p e r i o d s o f m o d era te r a i n f a l l , d u s t , l i t t e r and o i l from paved a r e a s a r e f l u s h e d i n t o t h e R i v e r , b u t t h i s f l u s h i n g i s f a i r l y r a p i d and s h o r t l y a f t e r th e commencement o f r a i n , c i t y r u n - o f f w a t e r i n g u t t e r s h a s been found to c o n s i s t o f p u re r a i n w a t e r .

The r e s u l t o f a s e v e r e s to rm on th e R iv e r w a t e r i s , how ever, q u i t e d i f f e r e n t . W hile th e c i t y ' s g u t t e r s s t i l l d i s c h a r g e c le a n r a i n w a t e r , th e d r a i n s , w hich a r e c o n n e c te d to a l a r g e number o f s to rm sewage o v e r f lo w p o i n t s , d i s c h a r g e raw sewage i n t o t h e R iv e r . Samples o f w a t e r ta k e n from t h e R iv e r a t such t im e s show a h ig h b a c t e r i a l c o n te n t and d e v e lo p g row ths o f sewage fu n g u s .

These e v e n t s w ere a b le to be c h e m ic a l ly fo l lo w e d d u r in g th e s tu d y p e r i o d by th e changes i n n i t r a t e c o n c e n t r a t i o n s i n th e R i v e r , d r a i n s and g u t t e r s .

63

6.3.2 PerspectiveThe Cooks River, more than any other waterbody in the Botany Bay catchment area, is a parody in misdirected priorities.It has received prominent publicity; a copious number of reports have been written about it; and it has been held up as an example of the worst that industry can do to a waterway.

But, surely the ultimate pollution of the River comes not from trace quantities of heavy metals in the water but from the destruction of the natural ecosystem through its transformation into a drain. It seems pointless and futile to monitor chemical parameters in a water which no longer even resembles a viable aquatic habitat.

There may be 40 or more parks surrounding the River, but there is no environmental amenity in a cement canal.

7. CONCLUSION

This study has ascertained that the predominant influence on the chemistry of the water systems of the Botany Bay region is still the natural environment. It has also demonstrated the necessity for a basic understanding of the processes and relationships within the natural system before human influences can be adequately comprehended.The Botany Bay region’s close proximity to the ocean results

in a large input of sea-salt aerosols to the area in the rainfall, and this constitutes a major source of water salinity.When rain water falls on Hawkesbury Sandstone and becomes

a stream there is little change in chemical composition as the stream rushes through the characteristic deep and narrow gorges of this terrain. In contrast, the streams which form when rain water falls on Wianamatta shale, meander sluggishly along shallow clay-banked channels and become brackish solutions as sea-salts, left in the sediments millions of years age, are 'dissolved.

In the area of Quaternary sediments surrounding Botany Bay the hydrochemical properties are determined by the varied geological history of the sediments.In the wind moulded dunes composed of quartz grains, the

ground water contains only the salts brought by the rain.Where ocean currents have brought sediments to the area,

the infiltrating rain water now dissolves the remains of marine organisms to form alkaline ground waters rich in calcium bicarbonate.

64

In places where there are ancient swamp deposits the chemical and biological processes of the past have left their legacy in the form of iron sulphides, gypsum and fossil sea- salts, which permeate the many peat horizons. Water in contact with these swamp sediments becomes an acidic solution containing an excess of sulphate, iron, calcium, sodium and chloride ions.Human activities influence the water chemistry by way of

modification of the rain water composition through industrial emissions of sulphur dioxide, and by the removal of vegetation, which results in increased dust in the atmosphere.

The continuous injection of liquid wastes from sewage treatment plants and the intermittent overflow from sewers during storms, are significant human influences on the chemistry of most surface waterbodies in the region.The ground water system is affected in a small way by

leachate from municipal landfill sites but there is a more widespread effect from the network of underground sewerage pipes carrying city sewage, which results in high concentrations of nitrate ions in the water.

There are, however, much more obvious and - not infrequently - devastating human influences on the water systems which overwhelm all other considerations.

The conversion of waterways into cement canals, and the use of river-bank wetlands and creek gullies as the city's garbage tips, does not affect the chemistry of the water to a significant extent but more importantly, it results in the destruction of complete ecosystems.

Clearly there needs to be a change in attitude and a reappraisal of priorities regarding the use of water systems.Too often actions have been justified by false economics because there has been no accounting for intangeable social costs. In the crowded city a water resource may have its greatest value in serving aesthetic and recreational needs rather than as a carrier of wastes.

'Our water resources are a heritage of the whole nation - a heritage which must be protected both for the people of the present and for posterity.'24

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R e fe re n c e s

A u s t r a l i a - The F i r s t Hundred Y e a r s . Ed . The Hon. A. G a r ra n . Pub. Ure S m ith , Sydney, 1974.

N.S.W. P a r l i a m e n ta r y P a p e rs (1 8 6 9 ) . R e p o r t o f th e Commission A p p o in ted t o I n q u i r e i n t o t h e Supply o f V a te r to Sydney and S u b u rb s , 1867, M inu tes o f E v id e n c e . Sydney.

W h ite , D.G. A verage R a i n f a l l V a r i a t i o n s Over Sydnej A rea . J . N.S.W. M e te o r o lo g i c a l S o c . , V ol. 1, No. 2 , S ep tenbe r 1973.

J u n g e , C.E. A i r C hem is try and R a d i o a c t i v i t y . Academic P r e s s , New Y ork , 1963.

Sumi, L. , C o rk e ry , A. and Monkman, J . L . Calc ium S u lpha te C o n te n t o f Urban A i r . Am. Geophys. Union Geophys. , Mon.3 , 1959, p p . 6 9 -8 0 .

L ik e n s , G.E. and Borman, F.H. N u t r i e n t C y c l in g in E co sy s tem s . From E cosystem S t r u c t u r e and F u n c t io n , Ed. J .A . W e is s , P r o c . 3 1 s t Ann. B i o c o l l o q . , 1971, p p . 2 f -6 7 .

R o b in so n , E. and R o b b in s , R. C. Gaseous S u lp h u r P o l l u t a n t s from Urban and N a t u r a l S o u rc e s . J . A i r l o l l u t . C o n t ro l A s s . , Vol. 20 , No. 4 , 1970.

Twomey, S .T . The C om posit ion o f H y d ro sc o p ic P a r t i c l e s i n t h e A tm osphere . J . M e te o ro lo g y , V ol. 11, No. 4 , 19f4 .

Annual R ep o r t o f th e S t a t e P o l l u t i o n C o n t r o l Commission,1975.

Y aa lo n , D.A. C o n c e n t r a t i o n s o f Ammonia and N i t r a t e i n Rain W a te rs . T e l l u s , Vol. 16, No. 2 , 1964.

R ic h e r s o n , P . J . , M o s h i r i , G.A. and G odsha lk , G.L. C e r ta in E c o l o g ic a l A sp e c ts o f P o l l e n D i s p e r s io n in Lake Tahce ( C a l i f . - N e v a d a ) . L im nol. O cean o g r . , V o l. 15, 1970.

C h a l l i n o r , R.W. The O c c u rre n c e o f T r im e th y la m in e ard i t s O r ig in i n t h e A u s t r a l i a n S a l t Bush. J . Royal See. N.S.W. , XLVII, 1913.

L a s s a k , E. Museum o f A p p l ie d A r ts and S c i e n c e s , Sycney,1976. P e r s . Comm.

G r i f f i n , R .J . The Botany B a s in . B u l l . Geol. S u rv . N.S.W. , No. 18, 1963.

15 Sheil, G. Water Bearing Capacity of the Botany Sand Beds Emergency Water Supply Investigations, Geol. Surv. N.S.W. File G.S. 1942/077 (unpubl.), 1942.

16 Smart, J.V. The Geology, Hydrology and Groundwater Chemistry of Part of the Botany Basin, New South Wales. M.Sc. Thesis, Dept, of Geology and Geophysics, Univ. of Sydney, 1974.

17 Byrnes, J.C. A Vertical Sequence in Quaternary Sand at Kumell Isthmus. Geol. Surv. N.S.W. , unpublished Mineralogical Report No. 75/20, 1976.

18 Smart, J.V., op. cit.19 Walker, P.H. Groundwater Characteristics of the Kempsey

District, N.S.W. C.S.I.R.O. Divisional Report 1/61,1961.

20 Smart, J.V., op. cit.21 Fetter, C.W. Water Quality and Pollution - South Fork of

Long Island, New York. Water Resources Bulletin, Vol. 10 No. 4, 1974.

22 Schmidt, K.D. Nitrate in Ground Water of the Fresno- Clovis Metropolitan Area, California. Ground Water,Vol. 10, No. 1, 1972.

23 Old, A.N. The Wianamatta Shale Waters of the Sydney District. The Agriculture Gazette, Vol. 53, No. 5, 1942 (N.S.W. Dept, of Agriculture).

24 Report from the Senate Select Committee on Water Pollution, 1970.

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Botany Bay Project Series editor: N.G. Butlin

ReportsNo. 1 N.G. Butlin (ed.)

Sydney's environmental amenity 1970—19752 N.G. Butlin (ed.)

Factory waste potential in Sydney3 N.G. Butlin (ed.)

The impact of Port Botany in preparation

4 Sydney's environmental policy 1870—1970

Working papersNo. 1 Pamela Coward

Environmental law in Sydney2 C. Joy, W. Hickson and M. Buchanan

Liquid waste management3 W. Ryder

Air pollution control4 Merike Johnson


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