sediments, nutrients and pesticide residues in event flow conditions

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Marine Pollution Bulletin 51 (2005) 23–36

Sediments, nutrients and pesticide residues in event flow conditionsin streams of the Mackay Whitsunday Region, Australia

C. Mitchell a, J. Brodie b,*, I. White c

a Mackay Whitsunday Natural Resource Management Group, Mackay, 4740, Australiab Australian Centre for Tropical Freshwater Research, James Cook University, Townsville, Qld 4811, Australia

c Department of Natural Resources and Mines, Mackay, 4740, Australia

Abstract

The Mackay Whitsunday region covers 9000km2 in northeastern Australia. A study of diffuse pollutants during high flow events

was conducted in coastal streams in this region. Sampling was conducted in the Pioneer River catchment during a high flow event in

February 2002 and in Gooseponds Creek, Sandy Creek and Carmila Creek in March 2003. Concentrations of five herbicides; atra-

zine (1.3lg l�1), diuron (8.5lg l�1), 2,4-D (0.4lg l�1), hexazinone (0.3lg l�1) and ametryn (0.3lg l�1) and high concentrations ofnutrients (total nitrogen 1.14mgl�1, total phosphorus 0.20mgl�1) and suspended sediments (620mgl�1) were measured at Dumble-

ton Weir on the lower reaches of the Pioneer River. Drinking water guidelines for atrazine and 2,4-D were exceeded at Dumbleton

Weir, low reliability trigger values for ecosystem protection for diuron were exceeded at three sites and primary industry guidelines

for irrigation levels of diuron were also exceeded at Dumbleton Weir. Similar concentrations were found in the three smaller streams

measured in 2003. Herbicides and fertilisers used in sugarcane cultivation were identified as the most likely major source of the her-

bicide residues and nutrients found.

� 2004 Elsevier Ltd. All rights reserved.

Keywords: Nutrients; Pesticide residues; Pioneer river; Mackay; Sugarcane cultivation

1. Introduction

The Mackay Whitsunday region is one of fourteen

Natural Resource Management regions in Queensland.

The major rivers of the region include the Proserpine,

O�Connell and Pioneer and in addition there are manysmaller streams which discharge directly to the sea,including importantly for this study, Carmilla, Sandy

and Gooseponds Creeks (Fig. 1). The receiving waters

for discharge from all these rivers and streams form part

of the Great Barrier Reef (GBR) Lagoon and western

Coral Sea (Devlin et al., 2001a). The catchments of the

streams in this study have high proportions of agricul-

0025-326X/$ - see front matter � 2004 Elsevier Ltd. All rights reserved.

doi:10.1016/j.marpolbul.2004.10.036

* Corresponding author. Tel.: +61 7 4781 6435; fax: +61 7 4781

5589.

E-mail address: [email protected] (J. Brodie).

tural land uses dominated by sugarcane cultivation

and beef grazing with smaller areas of urban use and

in some cases considerable areas of native forest. For

the combined catchment area of the Pioneer River, Bak-

ers Creek, Sandy Creek and Gooseponds Creek

(2200km2 see Fig. 1) sugarcane occupies 690km2, beef

grazing 610km2, forest 670km2, urban 150km2 andother uses 83km2.

The water quality of Queensland�s east coast streamshas been of concern for some time (Arthington et al.,

1997) and especially the potential for pollution and deg-

radation of parts of the Great Barrier Reef (Brodie,

2002; Furnas, 2003). The streams and rivers of the

northeast Australian coast form a convenient set for

comparative studies with tropical and sub-tropical cli-matic regimes. Many of the rivers have headwaters in

natural forest, middle courses in areas of rangeland beef

mailto:[email protected]

Fig. 1. Study area and sampling sites.

24 C. Mitchell et al. / Marine Pollution Bulletin 51 (2005) 23–36

grazing and the lower floodplain area developed for sug-

arcane cultivation with smaller areas of other crops,

often horticulture, and urban development. Monitoring

and modelling of catchment loads of suspended sedi-

ments and nutrients, and their likely change with mod-

ern agricultural development, has occurred on a

number of these catchments. Comprehensive studieson the Barron River (Cogle et al., 2000), Johnstone

River (Hunter et al., 1997, 2001), Tully River (Mitchell

et al., 2001; Mitchell and Furnas, 2001), Herbert River

(Bramley and Roth, 2002; Johnson et al., 2001) and

Fitzroy River (Noble et al., 1997; Noble and Collins,

2000) have been published and long-term comparative

studies of the Normanby, Johnstone, Tully, Herbert,

Burdekin and Fitzroy Rivers are also available (Furnasand Mitchell, 2001; Furnas, 2003). No studies of this

type, incorporating whole of catchment sampling in

event flows and baseflow, have occurred in the Mackay

Whitsunday region although a study of baseflow water

quality recently occurred in the northern rivers of the

Region in the Proserpine and O�Connell catchments(Faithful, 2003). Studies from other Queensland catch-

ments in summary show that elevated concentrationsand loads of nutrients and suspended sediments are

present in the rivers in the high discharge periods follow-

ing monsoonal and cyclonic rainfall events. Nutrient

concentrations in baseflow conditions from the Tully

River (Mitchell et al., 2001), show particulate nitrogen

and nitrate have increased by 130% and 16% respec-

tively over 13 years of measurement.

Assessments using the limited water quality data avail-able in the Mackay Whitsunday region and modelling

C. Mitchell et al. / Marine Pollution Bulletin 51 (2005) 23–36 25

suggest that many streams in the region are in relatively

poor condition (Brodie, 2004). It is estimated from mod-

elling that the region�s rivers contribute over two milliontonnes of suspended sediments to the inshore regions of

the Great Barrier Reef (GBR) along with 6000tonnes of

nitrogen and 1600tonnes of phosphorus annually onaverage (Brodie et al., 2003). These loads are estimated

to be respectively eight, seven and 10 times the pre-

development loads (before modern agricultural and

urban development) of the rivers (Brodie et al., 2003).

Individual rivers of the region are all considered to be

of high risk with respect to exposure of GBR coral reefs

to terrestrial pollutants (Devlin et al., 2003). Coral reefs

in coastal waters adjacent to the Region have been de-graded and the degradation attributed to elevated sedi-

ment and nutrient discharge from the rivers of the

Region (van Woesik et al., 1999). Recently developed

preliminary targets for reductions of sediment and nutri-

ent discharge to the GBR require reductions in sus-

pended sediments, total nitrogen and total phosphorus

loads of 50% by 2011 for all four major basins of the

Mackay Whitsunday region (Proserpine, O�Connell,Pioneer, Plane) which are at the highest level of reduc-

tion for any catchment for which targets were set (Bro-

die et al., 2001).

Pesticide residues are also an issue in these Queens-

land east coast catchments. Residues of commonly used

herbicides (notably diuron and atrazine) have been de-

tected in coastal sediments and seagrasses along the

Queensland east coast (Haynes et al., 2000a). These res-idues may cause damage to seagrass beds (Haynes et al.,

2000b), corals (Jones et al., 2003) and mangroves (Duke

et al., 2003). Diuron is used in anti-fouling paints but the

main use of both diuron and atrazine in Queensland is in

sugarcane cultivation (Jones et al., 2003). There are little

data available on concentrations and loads of pesticide

residues in event flow in Queensland rivers and a specific

target of the present study was to collect data of thistype in the Mackay Whitsunday region. In the estuarine

areas of the Pioneer catchment dieback of the mangrove

species Avicennia marina has occurred since at least 1997

(Duke et al., 2001). Concentrations of diuron have been

measured in the sediments in the area of dieback and the

presence of herbicides asserted to be the most likely

cause of the dieback (Duke et al., 2003; Duke and Bell,

in press).

2. Methods

During the afternoon and early evening of the 13th

February, 2002 there were small run-off events in both

Cattle Creek and the Pioneer River above Mirani Weir

which had the effect of flushing out the river system.Early on the 14th Feb 2002 a more significant rainfall

event occurred with substantial rain falling on much of

the land under agriculture. Sampling of the event oc-

curred at various points throughout the rising and fall-

ing stages of the stream hydrograph at two sites,

Dumbleton Weir (DNRME gauging station 125013A)

and Finch Hatton Creek (DNRME gauging station

125006A). Samples at only one point in the hydrographwere taken at Pioneer River at Mia Mia and Cattle

Creek at Gargett (Fig. 1). The Finch Hatton Creek site

was selected to reflect a largely unimpacted stream in

the Pioneer Catchment. Samples were collected by

Hydrographic staff (streamflow monitoring) from

the Department of Natural Resources, Mines and

Energy (DNRME), Mackay and a number of trained

volunteers.On the 25th of February 2003 a significant rainfall

event occurred in the Gooseponds Creek catchment

which appeared to be an isolated event with rainfall pre-

dominately in the Gooseponds catchment area. Four

samples were collected across the hydrograph, sampling

rising, peak and falling stages of the event. The hydro-

graph and flows for the Gooseponds event were calcu-

lated from stream height and profile, as the stream isnot gauged. On the 2nd March 2003 a small rainfall

event occurred in the Sandy Creek catchment, four sam-

ples were collected during the event at points immedi-

ately preceding the peak of the hydrograph as well as

the falling stage. Minor flows preceded sampling at both

Gooseponds Creek and Sandy Creek. Samples from

Carmilla Creek were collected on the 1st of March

2003 during a small rainfall and flow event. The major-ity of samples from Carmilla Creek were collected dur-

ing the rising stage of the hydrograph prior to the

peak and for this reason no loads were calculated. Sam-

ples for Sandy and Carmilla creeks were collected within

500m of a DNRME Gauging Station and the samples

from Gooseponds Creek were collected within 100m

of a Bureau of Meteorology flood warning station in

order to calculate flow for the event. Samples were col-lected in the appropriate bottles supplied by Queensland

Health Scientific services and using DNRME sampling

protocols (Alexander, 2000). Where possible samples

were taken from the centre of the stream however where

this was not possible, samples were taken from the bank

according to DNRME procedures (Alexander, 2000).

Analysis was carried out by the DNRME laboratory

in Brisbane, which is National Association of TestingAuthorities accredited.

Nutrient analysis followed a standard protocol where

unfiltered samples are analysed for total nitrogen (TN)

and total phosphorus (TP) following a digestion and fil-

tered samples (filtered on collection through 0.45lm fil-

ters) analysed for total dissolved nitrogen (TDN) and

total dissolved phosphorus (TDP) following digestion.

Nitrate plus nitrite (NOx), ammonia and filterable reac-tive phosphorus (FRP, referred to as orthophosphate in

this paper) are analysed directly on filtered samples.


Although nitrate and nitrite were not analysed sepa-

rately it can be reasonably assumed that, for the type

of event samples collected in this study, NOx is domi-

nated by nitrate (for example see Furnas, 2003) and

throughout the discussion of the results it will be as-

sumed that most of the NOx is present as nitrate. Nutri-ent species reported in this paper were calculated from

the measured parameters as follows:

Particulate nitrogen (PN) = TN � TDN.

Particulate phosphorus (PP) = TP � TDP.

Dissolved organic nitrogen (DON) = TDN � NOx �NH3.

Dissolved organic phosphorus (DOP) = TDP � FRP.

The methodology involved in the calculations of the

loads followed the traditional method of hydrograph

subdivision. Linear equations were developed from sam-

ple point to sample point based on the concentration

and the instantaneous flow. Point concentrations were

then interpolated by using the flow values throughout

the streamflow hydrograph. Integration between thesepoints was used to calculate actual volumes. In order

to get the complete picture for the entire flow hydro-

graph it was necessary to extrapolate to get a point con-

centration at the very start and end of the hydrograph.

The calculations were all done within the Surface Water

Database of DNRME. No calculations for loads were

done at the Pioneer River at Mia Mia and Cattle Creek

at Gargett as these were only single point samples anddetermination of loads is not possible from a single sam-

ple. No load determinations were made at Carmilla

Creek for the 2003 event due to the samples being col-

lected prior to the main flow event.

3. Results

Comparisons with previous flows show that the flow

at Dumbleton Weir was approximately a one in two

year event. The timing of the event was not unusual with

a mean annual rainfall for February of 376mm at Finch

Hatton post office between 1914 and 1991 (QDPI, 1993).

Dumbleton Point Sa

2/142

0

500

1000

1500

2000

2/12/02 0:00 2/13/02 23:45

Cumecs Poin

Fig. 2. Dumbleton hydrogra

However, this was the first major flow in the river since

the previous wet season 10–11 months earlier. A priority

of the sampling program was to try to sample through-

out both the rising and falling stages of the high flow

event in the river. To a large degree this was achieved

at Dumbleton Weir where samples were taken, enablingdefinition of the actual shape of the hydrograph and

sampling at various flow rates on both the rising and

falling limbs of the event (Fig. 2). The very start of the

rising stage was missed, as these events are difficult to

predict. It was much more difficult to get the full hydro-

graph at Finch Hatton Ck due to the very swift change

in stream conditions in the upper catchment. However,

whilst the hydrograph was less defined, sampling wasconducted on both rising and falling stages (Fig. 3). In

2003 sampling samples were taken throughout the hyd-

rograph in the Gooseponds event and just prior to the

event peak and on the falling stage due to the sharp ris-

ing stage of the event. All the events sampled in this

study were single events in the year of sampling and,

as such, cannot be considered representative of the

range of events possible in these systems. The PioneerRiver, if not the smaller streams, has a large enough

catchment area such that rainfall can be localised to

areas of the catchment with varying land uses. Concen-

trations and loads of suspended sediments, nutrients and

pesticides will vary considerably depending on the loca-

tion of the most intense rainfall and runoff.

TN, TP and suspended sediment (SS) concentrations

in Dumbleton Weir were highest at the peak of the hyd-rograph. Comparisons of filtered and unfiltered samples

at the peak of the hydrograph show that 55% of nitro-

gen (N) and 95% of phosphorus (P) were carried on par-

ticulate matter (Table 1). Concentrations of nutrients

and sediments measured during the event were much

higher than those measured in Dumbleton Weir during

baseflow which are typically 10mgl�1 for SS, 0.4mgl�1

TN, 0.04mgl�1 TP, 0.1mgl�1 nitrate, 0.01mgl�1 DIPand 0.02mgl�1 ammonium (Brodie, 2004). Residues of

five herbicides (diuron, ametryn, atrazine, hexazinone

and 2,4-D) were found at Dumbleton Weir during the

event. Desethylatrazine, a degradation product of

atrazine, was also recorded on the rising stage of the

mple Times

/02 8:15 AM/14/02 9:45 AM

2/14/02 2:45 PM

2/14/02 11:00 PM

2/14/02 11:30 PM

2/15/02 9:00 AM

2/14/02 14:15 2/15/02 5:30

t Samples

ph and sampling times.

Finch Hatton Ck Point Sample Times

2/14/02 7:30 AM

2/14/02 8:30 AM

2/14/02 10:20 AM

020406080

100

2/12/020:00

2/13/0214:40

2/14/020:20

2/14/023:10

2/14/025:40

2/14/028:00

2/14/0210:00

2/14/0212:50

2/14/0216:00

2/14/0223:30

2/15/0221:00

1

1.01

1.02

1.03

1.04

Cumecs Point Sample Times

Fig. 3. Finch Hatton Ck hydrograph and sampling times.

Table 1

Suspended sediment, nutrient species and herbicide concentrations at Dumbleton

Sampling time in February, 2002

Substance 8.15 14th 9.00 14th 15.00 14th 23.25 14th 9.00 15th

SS, mgl�1 190 NS 620 230 49

TN, mgl�1 1.87 1.69 2.66 1.55 1.09

NOx (1), mgl�1 0.867 0.749 0.648 0.327 0.360

NH3 (2), mgl�1 0.040 0.037 0.038 <0.002 0.022

DIN (3), mgl�1 0.907 0.786 0.686 0.328 0.382

DON (4), mgl�1 0.513 0.464 0.504 0.482 0.468

PN (5), mg l�1 0.45 0.44 1.47 0.74 0.24

TP, mgl�1 0.32 0.29 0.50 0.42 0.16

PO4 (6), mgl�1 0.094 0.099 0.023 0.104 0.086

PP (7), mgl�1 0.21 0.18 0.46 0.28 0.05

DOP (8), mg l�1 0.016 0.011 0.017 0.036 0.024

Diuron, lg l�1 8.5 NS 2.5 1.1 0.9

Atrazine, lg l�1 1.3 NS 0.48 0.37 0.29

Desethylatrazine, lg l�1 0.10 NS 0.05 NDR NDR

Hexazinone, lg l�1 0.30 NS 0.25 0.14 0.11

Ametryn, lg l�1 0.30 NS 0.13 0.11 0.10

2,4-D, lg l�1 0.40 NS NDR 0.2 NDR

2,4,5-T, lg l�1 NDR NS NDR NDR NDR

MCPA, lg l�1 NDR NS NDR NDR NDR

(1) NOx = nitrate plus nitrite; (2) NH3 = ammonia; (3) DIN = dissolved inorganic nitrogen; (4) DON = dissolved organic nitrogen; (5) PN = par-

ticulate nitrogen; (6) PO4 = orthophosphate (also filterable reactive phosphorus); (7) PP = particulate phosphorus. (8) DOP = dissolved organic

phosphorus; NS = no sample and NDR = no detectable residue.


hydrograph. Concentrations of all herbicides were high-

est during the initial runoff and became diluted as the

event progressed. Concentrations of most parameters

detected at Mia Mia (Pioneer River) and Gargett (Cattle

Creek) were intermediate (Table 2) between those found

at Finch Hatton and those at Dumbleton reflecting the

position of these sites in the middle course of the wholeriver (Fig. 1).

Concentrations of nutrients and suspended solids at

Finch Hatton were lower than those found at Dumble-

ton weir during the event (Table 3). Highest concentra-

tions of TN were measured on the receding side of the

hydrograph and at this time 24% of TN was carried

on particulate matter. Highest concentrations of TP

were measured near the peak of the hydrograph andat this time 25% of TP was carried on particulate matter.

No pesticide residues were detected at Finch Hatton

during any stage of the event.

Residues of diuron, ametryn, atrazine, hexazinone, 2,

4-D and desethylatrazine were detected during the event

at the Gooseponds (Table 4). Concentrations increased

throughout the event with the highest concentrations

occurring at the final stage of the event. Highest concen-trations for TN (5mgl�1) and TP (0.63mgl�1) greatly

exceed the default trigger values (TVs) for physical

and chemical stressors for tropical Australia for

slightly disturbed ecosystems (TN 0.2–0.3mgl�1, TP

0.010mgl�1) (ANZECC and ARMCANZ, 2000). TN

and TP levels at Gooseponds during the event also ex-

ceeded the highest concentrations sampled at Dumble-

ton Weir during the 2002 event (TN 2.66mgl�1, TP0.50mgl�1). Diuron was the only herbicide detected

Table 2

Suspended sediment, nutrient species and herbicide concentrations at

Mia Mia and Gargett

Sampling sites in February, 2002

Substance Mia Mia 14th 10.30 Gargett 14th 10.55

SS, mgl�1 330 110

TN, mgl�1 1.74 1.18

NOx-N, mgl�1 0.327 0.432

NH3-N, mgl�1 0.002 0.009

DIN, mgl�1 0.33 0.44

DON, mgl�1 0.48 0.40

PN, mgl�1 0.93 0.34

TP, mgl�1 0.42 0.26

PO4-P, mgl�1 0.104 0.079

PP, mgl�1 0.28 0.16

DOP, mgl�1 0.036 0.021

Diuron, lg l�1 0.4 1.0

Atrazine, lg l�1 0.07 0.2

Desethylatrazine, lg l�1 NDR NDR

Hexazinone, lg l�1 0.07 0.10

Ametryn, lg l�1 NDR 0.05

2,4-D, lg l�1 NDR NDR

Table 3

Suspended sediment, nutrient species and herbicide concentrations in

Finch Hatton Creek

Substance Sampling time in February, 2002

7.30 14th 8.30 14th 10.30 14th

SS, mgl�1 33 24 13

TN, mgl�1 0.58 1.02 1.14

NOx-N, mgl�1 0.128 0.449 0.761

NH3-N, mgl�1 0.007 0.003 0.003

DIN, mgl�1 0.135 0.452 0.764

DON, mgl�1 0.245 0.278 0.206

PN, mgl�1 0.20 0.29 0.17

TP, mgl�1 0.20 0.09 0.12

PO4-P, mgl�1 0.120 0.070 0.091

PP, mgl�1 0.05 <0.01 <0.01

DOP, mgl�1 0.03 0.02 0.03

No pesticide residues were detected at Finch Hatton.


during sampling at Carmilla Creek with a concentration

during the rising stage of the event of 0.6lg l�1 (seeTable 5). These exceed low-level confidence TVs for

ecosystem protection of 0.2lg l�1 (ANZECC and ARM-CANZ, 2000). Highest concentrations of TN

(2.98mgl�1) and TP (0.30mgl�1) exceeded the default

TVs for physical and chemical stressors for tropical

Australia for slightly disturbed ecosystems (ANZECCand ARMCANZ, 2000). TN and TP levels at Goose-

ponds during the event were comparable to the highest

concentrations sampled at Dumbleton Weir during the

2002 event (TN 2.66mgl�1, TP 0.50mgl�1). Concentra-

tions of SS and nutrients in Sandy Creek were moderate

compared to some of the other streams sampled in this

Table 4

Suspended sediment, nutrient species and herbicide concentrations in Goose

Substance Sampling time in March, 2003

23.05 25th 3.0

SS, mgl�1 160 39

TN, mgl�1 1.34 4.6

NOx-N, mgl�1 0.34 2.4

NH3-N, mgl�1 0.047 0.1

DIN, mgl�1 0.387 2.5

DON, mgl�1 0.463 0.8

PN, mgl�1 0.49 1.2

TP, mgl�1 0.25 0.5

PO4-P, mgl�1 0.17 0.3

PP, mgl�1 0.08 0.2

DOP, mgl�1 <0.01 <0

Diuron, lg l�1 0.56 2.5

Atrazine, lg l�1 0.67 1.8

Desethylatrazine, lg l�1 NDR 0.0

Hexazinone, lg l�1 NDR ND

Ametryn, lg l�1 0.71 0.1

2,4-D, lg l�1 0.19 ND

study (Table 6). However, considerable amounts of her-

bicides were detected with diuron concentrations in all

four samples exceeding low-level confidence TV for eco-

system protection of 0.2lg l�1 (ANZECC and ARM-

CANZ, 2000).

Total calculated loads for the events at Dumbleton,Finch Hatton, Gooseponds and Sandy Creek are sum-

marised in Table 7. The relatively large amounts of diu-

ron (470kg) and atrazine (75kg) discharged in the

Pioneer River at Dumbleton are noteworthy.

4. Discussion

Results from Mackay Whitsunday streams can be

compared with other northeastern Australian rivers

including some with limited catchment development

(Jardine and Annan well to the north of Mackay) to

ponds Creek

5 26th 7.05 26th 11.35 26th

0 150 78

5 4.8

3.3 3.2

4 0.14 0.096

4 3.44 3.30

4 0.86 0.904

2 0.70 0.60

7 0.63 0.56

3 0.34 0.35

4 0.25 0.16

.01 0.04 0.05

2.8 5.3

2.1 4.1

9 0.10 0.17

R 0.43 1.0

8 0.12 0.14

R NDR NDR

Table 5

Suspended sediment, nutrient species and herbicide concentrations in Carmilla Creek

Substance Sampling time

8.30 1st 10.30 1st 12.30 1st 14.30 1st 16.30 1st

SS, mgl�1 2 2 3 <1 173

TN, mgl�1 1.94 2.09 2.19 2.16 2.98

NOx-N, mgl�1 1.31 1.63 1.65 1.65 0.88

NH3-N, mgl�1 0.10 0.03 0.02 0.03 0.14

DIN, mgl�1 1.41 1.66 1.67 1.68 1.02

DON, mgl�1 0.42 0.43 0.42 0.37 0.48

PN, mgl�1 0.11 <0.01 0.10 0.11 1.48

TP, mgl�1 0.07 0.03 0.02 0.01 0.30

PO4-P, mgl�1 0.06 0.03 0.02 0.02 0.05

PP, mgl�1 0.03 <0.01 <0.01 <0.01 0.24

DOP, mgl�1 <0.01 <0.01 0.01 <0.01 0.01

Diuron, lg l�1 NDR NDR NDR ND 0.6

Atrazine, lg l�1 NDR NDR NDR NDR NDR

Desethylatrazine, lg l�1 NDR NDR NDR NDR NDR

Hexazinone, lg l�1 NDR NDR NDR NDR NDR

Ametryn, lg l�1 NDR NDR NDR NDR NDR

2,4-D, lg l�1 NDR NDR NDR NDR NDR

Table 6

Suspended sediment, nutrient species and herbicide concentrations at Sandy Creek

Substance Sampling time in March, 2003

12.20 2nd 18.40 2nd 0.35 3rd 7.30 4th

SS, mgl�1 188 151 307 13

TN, mgl�1 1.78 1.38 1.24 1.04

NOx-N, mgl�1 0.44 0.34 0.31 0.20

NH3-N, mgl�1 0.04 0.03 0.03 0.03

DIN, mgl�1 0.48 0.37 0.34 0.23

DON, mgl�1 0.68 0.64 0.67 0.57

PN, mgl�1 0.62 0.37 0.23 0.24

TP, mgl�1 0.30 0.31 0.31 0.30

PO4-P, mgl�1 0.13 0.17 0.21 0.22

PP, mgl�1 0.17 0.17 0.12 0.10

DOP, mgl�1 <0.01 <0.01 <0.01 <0.01

Diuron, lg l�1 0.87 1.1 1.6 0.6

Atrazine, lg l�1 NDR NDR NDR NDR

Desethylatrazine, lg l�1 NDR NDR NDR NDR

Hexazinone, lg l�1 0.1 NDR NDR NDR

Ametryn, lg l�1 NDR NDR NDR NDR

2,4-D, lg l�1 0.87 1.1 1.6 0.6


large rivers in the Queensland dry tropics with land uses

dominated by rangeland beef grazing (Normanby,

Burdekin, Fitzroy) to those rivers with similar develop-

ment to the Pioneer (urban, cropping and beef grazing

uses) and in similar rainfall regimes (e.g., Johnstone,

Barron, Richmond, Tully and Herbert). Suspended sed-

iment (SS) concentrations in the Pioneer at Dumbleton

during the event were similar to those found in mostother rivers peaking at a concentration of 620mgl�1.

Peak concentrations of SS in dry tropics Queensland riv-

ers are generally considerably higher than these results

with, for example, values closer to 2000–3000mgl�1 in

the Burdekin River (Furnas and Mitchell, 2001). How-

ever, the SS results from the Mackay Whitsunday

streams in the present study are in the same range as

those rivers with similar land uses and rainfall regimes

e.g. Johnstone (100–1300mgl�1) (Hunter et al., 1997),

Herbert (50–800mgl�1) (Mitchell et al., 1997) and Rich-

mond (300–700mgl�1) (Hossein et al., 2002). SS concen-

trations mirror the rise of the hydrograph as hydraulic

power is the principal soil eroding factor and potential

SS in the catchment is virtually inexhaustible in theduration (2–3 days) of this event. Concentrations of

TP and orthophosphate (PO4) were similar to those in

other northeastern Australian rivers. TP concentrations

for the Pioneer at Dumbleton were in the range 160–

500lg l�1, comparable to those found in the Barron

River (30–110lg l�1) (Cogle et al., 2000), Fitzroy River

Table 7

Calculated loads during each event

Loads Dumbleton Finch Hatton Gooseponds Ck Sandy Ck

Flow volumes for the period (ML) 126,000 985 26,000 2100

Loads

TN, tonnes 243 0.68 5.85 30.3

TP, tonnes 44 0.178 1 7.9

Nitrate + nitrite, tonnes 78 0.3

SS, tonnes 41,500 29.5 358 4410

Diuron, kg 470 NDR 6.9 26

Ametryn, kg 22 NDR 0.5 NDR

Atrazine, kg 75 NDR 5.3 NDR

Hexazinone, kg 28 NDR NDR NDR


(120–640lg l�1) (Furnas, 2003) and Richmond River

(50–600lg l�1) (McKee et al., 2000). In contrast the con-centrations of TN and nitrate plus nitrite (NOx) were

higher in the Pioneer than for most other rivers. NOx

concentrations of 300–900lg l�1 are similar to those

from the Tully River which has nitrate in stormflow in

the range 100–1000lg l�1 (Mitchell et al., 2001; Furnas,2003). Rivers such as the Jardine and Annan have verylow nitrate concentrations (e.g. for the Jardine in flow

conditions in the range 2–13lg l�1, Eyre and Davies,

1996) at all times reflecting the lack of human-influenced

catchment sources (sewage, fertiliser, atmospheric depo-

sition). At Dumbleton, NOx showed a strong �first flush�behaviour with the highest concentrations occurring

early in the event and tailing off quickly as the event pro-

gressed. This suggests a limited supply of NOx in thecatchment, derived mostly from applied nitrogen fertil-

iser, which was quickly exhausted, and possibly under-

went a dilution effect late in the hydrograph as low

nitrate water from the upper catchment (with little fertil-

iser use) finally made its way to Dumbleton. On the

other hand dissolved organic nitrogen concentrations

at both Dumbleton and Finch Hatton were quite con-

stant through the event albeit with the Dumbleton con-centrations about double that at Finch Hatton.

Concentrations of many parameters were lower at

Finch Hatton than at Dumbleton as expected. However

elevated concentrations of NOx (760lg l�1) and TN

(1140lg l�1) were detected suggesting a source of nitrateabove the sampling point. The increase in total nitrogen

at Finch Hatton (Table 4) was due entirely to an in-

crease in NOx with particulate nitrogen, ammonia,and dissolved organic nitrogen staying almost un-

changed. The late rise in the NOx concentration com-

pared to the hydrograph at Finch Hatton suggests

that a sub-surface flow of nitrate-rich water may have

been involved. Water at Finch Hatton, even in the peak

of the flow (�7.30am) had quite low suspended solids

(33mgl�1) and virtually no particulate phosphorus.

The rather higher concentrations of nitrate and ortho-phosphate suggest these soluble nutrients may have

arisen from septic systems or animal waste. While the

Finch Hatton sampling site had initially been selected

to reflect a largely unimpacted stream in the region it

was later found to have a considerable rural residential

and small scale tourism infrastructure above the sam-

pling point all served by infiltration septic sewage sys-

tems. Considerable areas of the catchment above the

sampling point have been cleared and riparian vegeta-

tion disturbed. The elevated nitrate concentrations(0.76mgl�1 NO3-N) compared to those normally found

in event runoff from undisturbed rainforest in north

Queensland (e.g. 0.04mgl�1 NO3-N in the Russell–Mul-

grave catchment, Devlin et al., 2001b) reflect this catch-

ment development.

In Gooseponds Creek SS concentrations peaked at

390mgl�1, a lower value that those often seen in larger

rivers in event flow. Similar peak concentrations seenin Sandy Creek (307mgl�1) and Carmilla Creek

(173mgl�1 before the peak) show that levels of ground

cover in these catchments are relatively high and with

the limited rainfall intensity and hydraulic power of

the 2003 events relatively low rates of soil erosion oc-

curred. Over the last decade sugarcane cultivation in

the Mackay Whitsunday region has moved from a sys-

tem where the cane was burned before harvest, and thusno crop residues were retained on the soil between crops,

to one where the cane is harvested green and the cane

leaves are left on the soil as a trash blanket. The older

harvest practice, associated with a high level of tillage,

led to very high soil erosion rates, between 42 and

227tonnesha�1yr�1 (Sallaway, 1979). The modern prac-

tice of green cane harvesting and trash blanketing

(GCTB), associated also with reduced tillage, has re-duced soil erosion rates in sugarcane cultivation to low

values, probably in the range 5–15tonnesha�1yr�1

(Prove and Hicks, 1991; Prove et al., 1995; Rayment,

2003). While some areas of sugarcane cultivation opera-

tions are still erosion prone e.g. headroads and drains,

and many urban development sites in the region are sed-

iment sources, the relatively low SS concentrations

found in the streams draining large areas of sugarcanein the present study show the effectiveness of GCTB as

a soil erosion preventative measure.


Nutrient concentrations in Gooseponds were high

compared to the other study sites. The high nitrate con-

centrations peaking late in the event may indicate a

combination of surface and sub-surface flows. It has

been suggested that old septic systems, recently replaced

by reticulated sewage collection, in the urban part of theGooseponds catchment may be still leaching nitrates

into sub-surface water flows. However, Gooseponds

catchment also has a large area of sugarcane cultivation

and this may be another source of some of the nitrate.

Concentrations of nutrients in SandyCreek in the 2003

event were all relatively low. In other studies (Wilhelm,

2001) Sandy Creek has been shown to have the highest ni-

trate concentrations in event flows of any of the 11streams analysed in catchments containing significant

sugarcane areas in Queensland. In high discharge periods

Wilhelm (2001) found nitrate concentrations ranging

from 1 to 2.5mgl�1 NO3-N, total nitrogen from 2 to

4mgl�1 and total phosphorus from 0.1 to 0.3mgl�1 in

SandyCreek at the same site sampled in the present study.

The relatively low values found in the present study may

reflect the small scale and low intensity of the event.In Carmilla Creek (Table 5) most samples (first four)

were taken in the baseflow period before the main event.

The relatively high nitrate concentrations in the base-

flow period (1.6mgl�1 NO3-N) may reflect a stable

source of nitrate possibly also associated with sub-sur-

face flow of high nitrate water. Nitrate is known to leach

strongly from soluble nitrogen fertilisers (urea and

ammonium nitrate) used on sugarcane in wet areas ofnorth Queensland (Rasiah and Armour, 2001; Rasiah

et al., 2003; Bohl et al., 2000). Rural residential septic

sewage systems may also be a source of nitrate as shown

in the Johnstone catchment (Hunter and Walton, 1997).

In Carmilla Creek event flow concentrations (sample

five) appear to be rising to the higher concentrations

seen in the other streams in this study except for nitrate

where a dilution of the nitrate rich baseflow with lowernitrate surface flow seems to have occurred.

Nutrient species composition (especially for nitrogen)

in the range of streams sampled in this study follows the

patterns seen in other tropical areas (Lewis et al., 1999;

Downing et al., 1999). Undisturbed tropical landscapes

appear to have high nitrogen loss rates compared to

temperate systems (Downing et al., 1999). Thus tropical

rivers may have higher concentrations of inorganicnitrogen than would be expected from their pristine

state. However the predominant form of N lost from

undisturbed forests, in both tropical and temperate

conditions, is dissolved organic nitrogen (DON) (Lewis

et al., 1999; Perakis and Hedin, 2002). As catch-

ment development proceeds, no matter whether the

development occurs as deforestation, grazing, fertilised

cropping, urbanization or industrial developmentand atmospheric N deposition, proportionally greater

amounts of dissolved inorganic nitrogen (predominantly

nitrate) are exported in rivers and streams (Downing

et al., 1999; Caraco and Cole, 1999; Harris, 2001; Turner

et al., 2003). Runoff from undisturbed catchments in

tropical America in moderate runoff climatic conditions

has volume-weighted mean concentrations of 102lg l�1

NO3-N, 119lg l�1 DON, 86lg l�1 PN and 376lg l�1

TN (Lewis et al., 1999). The limited data available from

north Queensland undisturbed wet tropics streams in

event flows suggest nitrate and PN values are less than

this, perhaps averaging near 50lg l�1 NO3-N and

50lg l�1 PN respectively (Brodie et al., 2003) while the

DON concentrations are similar to tropical America at

150lg l�1 DON. The streams in the present study areobviously not undisturbed and the concentrationsranges of the nitrogen species reflect the degree of distur-

bance and intensity of land use. Nitrate concentrations

in event flow range from 130 to 3300lg l�1 NO3-N,DON from 210 to 900lg l�1 and PN from 170 to

1480lg l�1.These results do show the changes in nitrogen species

composition and concentration anticipated from knowl-

edge of the major intensive land uses in the area i.e. sug-arcane cultivation and urban development. Elevated

concentrations of nitrate and PN are seen compared to

natural forest systems and increases in nitrate and PN

as proportions of the total nitrogen (TN) occur. A mod-

erate increase in DON above natural levels but with

DON as a lower proportion of the TN also occurs. Run-

off in stormwater discharge events from sugarcane fields

in north Queensland can have concentrations of nitratein the range of 500–6000lg l�1 NO3-N (Bramley and

Roth, 2002; Pearson et al., 2003; Faithful and Finlay-

son, in press) and ammonia concentrations can also

reach 5,000lg l�1 NH3-N (Pearson et al., 2003). Nitrate

also leaches to shallow sub-surface waters and ground-

water in high concentrations under sugarcane cultiva-

tion with concentrations similar to that seen in surface

runoff, 1–10mgl�1 NO3-N (Rasiah and Armour, 2001;Rasiah et al., 2003; Biggs et al., 2001). It has been shown

that this nitrate-rich shallow groundwater can eventu-

ally be discharged into adjacent streams (Rasiah et al.,

2003). PN concentrations are typically in the range

100–1,500lg l�1 in stormflow runoff (Bramley and Roth,2002). Urban runoff may also contain similarly elevated

concentrations of nitrate and PN (Chiew and McMa-

hon, 1999). This high concentration water from theareas of catchments under intensive land uses is diluted

with water from low intensity land uses (natural forest,

rangeland grazing, woodlands). The process produces

the characteristic water quality at end-of-catchment sites

where intensive land uses occupy 20–60% of the catch-

ment area as in the present study, with nitrate concen-

trations near 400–2000lg l�1, PN near 500–1000lg l�1

and DON near 300–600lg l�1.Nitrogen to phosphorus molar ratios from the peak

discharge period in each stream are shown in Table 8.

Table 8

Nitrogen to phosphorus molar ratios in peak discharge waters

Stream site TN:TP DIN:PO4

Dumbleton 12:1 17:1

Finch Hatton 22:1 19:1

Gooseponds 18:1 22:1

Sandy 13:1 4:1

Carmilla 22:1 43:1


Both TN:TP and DIN:PO4 are shown, as while TN:TP

ratios have often been used to predict nutrient limita-

tion, DIN:PO4 may give a more accurate indication

due to the presence of large and often unknown

amounts of non-bioavailable forms of nitrogen (often

DON) in the TN. Plant requirements for N and P arebelieved to occur in the ratio of the intracellular N:P

content of organisms—16:1 for phytoplankton (Redfield

et al., 1963; Harris, 1999). Large deviations from this

ratio in waters indicate a growth-limiting deficiency of

one element (Turner et al., 2003). Waters in the present

study show N:P ratios close to the Redfield ratio with

only one site, Carmilla Creek, showing a considerable

deviation from the Redfield ratio. The Carmilla Creekresults come from only one sample in the event flow per-

iod and may not be completely representative of the N

and P forms in the complete event. With N:P ratios of

these values the event flow waters show no strong ten-

dency to cause either N or P limitation to algal growth.

Concentrations of herbicide residues at Dumbleton

(Table 1) also showed a strong �first flush� behaviour.Diuron had the highest concentration of the herbicidesdetected with a peak concentration of 8.5lg l�1. Thereis little data available on diuron concentrations in river

water for comparison but concentrations of 2.3lg l�1

were detected in the Johnstone River under flow condi-

tions (Hunter et al., 2001). Diuron was not detected

in irrigation channel sediments in the Homebush area

in the Sandy Creek catchment in surveys carried out in

1998 (Muller et al., 2000) but has been detected in Pio-neer River estuarine sediments (Duke et al., 2001; Duke

and Bell, in press). Atrazine concentrations peaked at

1.3lg l�1 at Dumbleton early in the flow event but othervalues at Dumbleton, Gargett (Cattle Creek) and Mia

Mia (mid course Pioneer River) were less than 0.5lg l�1.These concentrations were comparable to those found in

the Fitzroy Basin (Dawson River) during 1993–1999 by

Noble et al. (1997) and Noble and Collins (2000) (gener-ally in the range of 0.1–2.31lg l�1, with one value of

6.5lg l�1) and in the Johnstone River (Hunter et al.,

2001) where concentrations up to 0.7lg l�1 were regu-larly found. Concentrations of 2,4-D (max. 0.4lg l�1

at Dumbleton) are not great when compared to other

river systems for which data exists (e.g. ranges of 0.18–

15.6lg l�1 in the Johnstone River, Hunter et al., 2001).Similar concentrations of herbicides to those found in

this study have also been found in the Mary River sys-

tem (south-east Queensland) by McMahon et al.

(2003) where diuron was the most commonly detected

herbicide, but in relatively low concentrations (0.02–

0.1lg l�1), and simazine found in the highest concentra-tions with three sites with concentrations between 3.2and 4.2lg l�1.The concentrations of herbicide residues and dis-

solved nutrients found in Mackay Whitsunday region

surface waters during these events can also be compared

to concentrations found in recent studies in the Pioneer

basin in groundwater (Baskeran et al., 2002). Ground-

water samples for this study were collected in the lower

Pioneer Valley in April–May 1997. The study showedthat thirty percent of samples were contaminated with

one or more herbicides (ametryn, atrazine, desethylatr-

azine, bromacil, diuron and hexazinone), though none

were present at concentrations exceeding the Drinking

Water Guideline Values (NHMRC, 1996). The concen-

trations found in the groundwater were similar to those

found in the event surface water sampling at Dumble-

ton. In the groundwater diuron was most commonlyfound (nine of 14 bores) at concentrations up to

1.80lg l�1 while atrazine was found in six bores at con-centrations up to 0.12lg l�1.Diuron and to a lesser extent atrazine have the lon-

gest half-lives and are the most soluble of the pesticides

used widely in sugarcane cultivation in Queensland

(Hargreaves et al., 1999). It is thus not unexpected that

these are the pesticides found most commonly in off-farm environments in sugarcane growing regions

whether these are marine sediments (Haynes et al.,

2000a), mangrove sediments (Duke et al., 2001; Duke

and Bell, in press), groundwater (Baskeran et al., 2002)

or, as in the case of the present study, surface water

event flow.

In all four sampling locations ANZECC TVs for TP,

orthophosphate, TN and nitrate were exceeded. In factall concentrations of these four parameters measured

during this study exceed these TVs. This was not entirely

surprising as the TVs are for �slightly disturbed ecosys-tems� (ANZECC and ARMCANZ, 2000) and these re-

sults confirm that the Pioneer River, even in some of

its upper reaches, is more heavily disturbed than

�slightly�. It would also be expected that maximum val-

ues of these parameters would occur under stormflowconditions. It is known from the DNRME statewide

river monitoring data set that, for example, TN gener-

ally exceeded the ANZECC TV in baseflow conditions

at Dumbleton (Brodie, 2004).

A number of the pesticide residue concentrations

were also of some concern. Maximum atrazine concen-

trations at Dumbleton Weir exceeded the ecosystem

health TV. Atrazine and 2,4-D concentrations also ex-ceeded the drinking water guideline value but not the

health value. For drinking water this implies the source

Table 9

Event loads at Dumbleton compared to estimated mean annual loads

Substance 2002 event at Dumbleton Estimated annual mean loads

Clarke, 2003 (1) NLWRA, 2001 (3) Furnas, 2003 (2) Brodie et al., 2003 (4)

SS, tonnes 41,540 288,000 50,000 406,000

TN, tonnes 243 771 1073 471 1224

TP, tonnes 44 276 50 373

(1) Clarke (2003) estimated TN loads using a model based on DNRM statewide monitoring data for the Pioneer at Marian Weir tailwater; (2) Furnas

(2003), estimated SS, TN and TP loads for north and central Queensland east coast rivers from the Australian Institute of Marine Science (AIMS)

long term monitoring of the Normanby, Johnstone, Tully, Herbert, Burdekin, and Fitzroy Rivers. The model was then extrapolated to rivers (such as

the Pioneer) for which AIMS did not have monitoring data; (3) NLWRA (National Land and Water Resources Audit, 2001) used a catchment model

based on land type, erosion capability and river transport capacity to model catchments in Australia. The Pioneer was one such catchment; (4) Brodie

et al. (2003) used the model SedNet and its nutrient sub-model ANNEX with regional water quality data to model GBR catchment export loads.


of such pesticides should be identified and action taken

to prevent further contamination (NHMRC, 1996).

Unfortunately only low confidence ecosystem health

TVs for diuron were available. The large quantity of

diuron discharged past Dumbleton in the two days pf

the event (470kg) is also of concern providing evidence

of the probable source of the diuron detected in man-

grove sediments (Duke et al., 2001) and responsiblefor the mangrove dieback in the Mackay region (Duke

et al., 2003). Anecdotal reports from the Bureau of

Sugar Experiment Stations (BSES) in Mackay suggest

that herbicide application would have occurred between

November and January. Diuron and hexazinone are ac-

tive ingredients used in Velpar K4, which is sprayed for

knockdown and residual control of vine and weed

growth. This activity occurs mainly between Novemberand January and Velpar K4 is estimated to be used on

30% of the area under cane at a rate of 3–3.5kgha�1.

Velpar contains 468gkg�1 diuron and 132gkg�1 hexaz-

inone. Atrazine and 2,4-D are also used from November

to February for knockdown and residual control of

vines. Atrazine is used at a rate between 2 and

2.2kgha�1 and constitute 900gkg�1 active ingredient

(Willcox, 2002, pers. comm.).It is notable (Table 9) that a large fraction of the

mean annual load of SS, TN and TP can move through

the river and be discharged at the mouth in short periods

of time. While this event produced about 15% of the

mean annual flow (125,000ML out of 900,000ML) the

effect on loads of materials such as SS, nitrogen, phos-

phorus and pesticide residues may be variable dependent

on the spatial pattern of the rainfall. In this event rain-fall was concentrated in the middle of the catchment on

both days. This is an area of high-density sugarcane

landuse. The loads of TN, TP and SS measured over

the two days of the 2002 event at Dumbleton Weir

can be compared to annual estimated loads for these

substances for the Pioneer River (Table 9). The methods

for the estimation of annual loads are also explained as a

footnote to Table 9. For this event it appears about 20–25% of the mean annual loads of TN and TP were dis-

charged in the two days. Modelled estimates of mean

annual SS export vary greatly (Table 9) and no compar-

ison with the measured event discharge is useful. The

data from this study will be used to refine the modelled

load estimates which at present are still producing

widely varying values. Comparison of the fluxes mea-

sured in the two day 2002 event at Dumbleton with

the estimated mean annual loads highlights the well

established conclusion that the great majority of mate-rial transport occurs in the biggest events of the year.

The pattern of rainfall and the nature of the contam-

inants found in significant concentrations at Dumbleton

(nitrogen, phosphorus and herbicide residues) but in

lower concentrations or absent in the middle of the

catchment and at Finch Hatton lead us to conclude that

the landuses in the high intensity rainfall area were the

main sources of these materials at Dumbleton. Nitrogenand phosphorus, from fertiliser application, and herbi-

cide residues are commonly found in waterways sur-

rounding intensive sugarcane cultivation whether in

the USA (Florida—Scott et al., 2002; Louisiana—Beng-

ston et al., 1997; Southwick et al., 2002) or Queensland

(Johnstone Catchment—Hunter et al., 2001; Burdekin

Delta—Keating et al., 1996; Herbert Catchment—

Bramley and Roth, 2002). Further studies targeting run-off at different times of the year may help to track down

cane cultivation practices which are leading to unaccept-

able losses of some nutrients and herbicides.

5. Conclusions

As sugar cane production is the only significant userof the herbicides detected during this study it has been

assumed that this land use, which represents 19% of to-

tal catchment area, was the main contributor to the lev-

els of pesticides found. Greater than 90% adoption of

green cane harvest and trash blanketing (a form of stub-

ble retention) in the catchment is thought to have made

a large reduction in the amount of herbicides used and

also the amount of sediment loss from farms (Willcox,2002, personal communication). The plant cane phase,

10–30% of total cane area, is considered a possible


contributor of pesticide, nutrient and sediment run off

due to the high levels of cultivation currently employed

and the high degree of exposure. Sallaway (1979) shows

that high levels of cultivation lead to significant erosion.

Methods currently being trailed such as minimum till-

age, controlled traffic farming and multi-row plantingare all thought to reduce loss of these pollutants (Ray-

ment, 2003).

In a study of the contributions of different rural land

uses to water quality in the lower Herbert River catch-

ment it was demonstrated that nitrogen and phosphorus

concentrations in stream waters increase as the propor-

tion of land under sugarcane cultivation increases

(Bramley and Roth, 2002). It was inferred from these re-sults that, on a unit area basis, land under sugarcane is a

higher contributor of N and P to streams compared to

forests and cattle grazing, the other major land uses in

the lower catchment. This is likely to also be the case

in the Mackay Whitsunday region with a mix of land

uses very similar to the lower Herbert and similar cli-

matic regime. It is also known that many Queensland

sugarcane farms use fertilisers at rates beyond the plantuptake need (Schroeder et al., 1998; Bramley et al., 2003;

Rayment, 2003) and that, particularly for phosphorus,

considerable stores of nutrient have been built up in sug-

arcane soils (Bloesch et al., 1997). Bramley et al. (1996)

noted that canelands in long term use in north Queens-

land contained levels of acid-extractable P approxi-

mately five times greater than was needed for crop

nutrition. The need for better fertiliser management inQueensland cropping systems is well recognised (Bram-

ley and Quabba, 2001) and specifically the justification

for management of phosphorus in sugarcane cultivation

(Bramley et al., 2003). Bramley et al. (2003) also note the

requirement that responsible fertiliser management

strategies for sugarcane should embody environmental,

in addition to production imperatives.

For the intensive agricultural areas, improved meth-ods of herbicide use (Simpson et al., 2001), reduced till-

age and integrated pest management are required to

decrease loss of resources from farms. Containment of

potential pollutants on farms through erosion and run

off control is required to prevent pollution of streams.

These need to be priority issues for land management.

Trapping of nutrients and sediments before they reach

streams as well as identifying and rectifying sources ofthese pollutants are also needed to minimise offsite im-

pacts on aquatic ecosystem health. Current improve-

ments in land management practices should be further

encouraged with suitable monitoring programs to con-

firm the effectiveness of these measures. Future monitor-

ing should also aim to quantify the improvements in

water quality resulting from positive changes in land

and water management in urban areas (e.g. upgradesto sewage treatment plants). An important outcome of

this event monitoring has been to show the usefulness

of such monitoring in improving estimates of material

budgets for the Pioneer catchment and finding the

sources of suspended solids, nutrients and pesticide res-

idues in the catchment. Continuation of such monitor-

ing will eventually allow accurate identification of

catchment areas, landuses and land management prac-tices which contribute to the elevated concentrations

and loads of suspended solids, nutrients and pesticide

residues in the waters of the Mackay Whitsunday

region.

Acknowledgments

The authors would like to thank the Mackay Whit-

sunday Healthy Waterways technical panel for their

direction and input. We would also like to thank Mr.

Steve O�Connor of Finch Hatton, Mr. Edward Old-

meadow of Gooseponds Creek, Mr. Gary Lay of Sandy

Creek and Mr. Darren Russell of Carmilla Creek for

their willing participation and the Mackay Whitsunday

Natural Resource Management Group and Natural Re-sources and Mines for their ongoing support and Bruce

Simpson (DNRME) for facilitating the sample analysis.

Mark Thomas (DNRME) prepared the map for us.

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