surface water storage potential legune station€¦ · 5.3 design criteria for excavated tank 6....

Technical Report WRD95019

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REPORT No: 19/1995 D

LR.RAJARATNAM SURFACE WATER SECTION WATER RESOURCES DlVIS[ON MAY 1995

SURFACE WATER STORAGE POTENTIAL

LEGUNE STATION


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SUi\lJvIARY:

This report details the investigations carried out to assess the potential of surtace water storages fOf stock watering in Legune Cattle Station. It also recommends the type of surface water storages suitable for the station. The station was subdivided into top soil categories, inrclation to surface water runoff and storage. This c1assitication was based on geology, land system, and Satellite imagery. This classification is noted in this report as Land Units. Particle size classification was undertaken to confirm the soil type in land units. It was found that land unit 1 is suitable for excavated tanks, but the location would depend on the depth of soil and its suitability.

The existing surface water storages in the station such as, waterholes, excavated tanks, dams, and billabongs were analysed for their reliability in supplying stock water. Design excavated tanks are recommended for suitable areas based on the yield study using A WB]\;[ model. Gully dams may be feasible where top soil and base rock are suitable. The cattle country covers one half oflhe station area. Half of it is covered by fine sandy soil and the other half with cracking clay soils. The estuarine alluvial plain consists of mud and silt and is saline. Construction of excavated tanks are economical in areas with cracking clay soils.


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TABLE OF CONTENTS

SUNL\1ARY

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

LIST OF APPENDICES

1. INTRODUCTION

2. CLIMATE

2.1 GENERAL

2.2 RAINFALL

EV APORATlON

3. Sl:JRFACE WATER POTENTIAL

3.1 GENeRAL

3.2 EXISTING SURF ACE WATER STORAGES

3.3 TYPES OF MAN MADE SURFACE WATER STORAGE

3.4 LAND SYSTEM AND LAND UNITS

3.5 LAND SUITABILITY FOR SURFACE WATER POTENTIAL

3.6 WATER QUALITY

4. MODEL PARAMETERS OF GAUGED CATCIDv1ENTS

4.1 GAUGED CATCIDv1ENTS

4.2 DAILY WATER BALAl"fCE MODELS

4.3 CALIBRATION OF AWBM MODEL


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5. ESTL.'vLA..TION OF YIELD IN UNGAUGED CATCHMENTS

5.1 GENERAL

5.2 DESIGNOFEXCAVATEDTA..NK

5.3 DESIGN CRITERIA FOR EXCAVATED TANK

6. CONSTRUCTION AND COSTS - EXCAVATED TANK

7. WATERHOLES

8. SPRINGS

9. ABOVE GROUNTI WATER STORAGES

9.1 TURKEY NEST

9.2 GAL V ANI SED IRON ANTI CONCRETE T Al"lKS

10. TRANSFER OF WATER THROUGH PIPES

11. SERVICING EQUIPMENT

12. CONCLUSION

13. RECOJ\1MENDATION

GLOSSARY

REFERENCES

TABLES

FIGURES

MAPS

APPENDICES


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LIST OF TABLES

TABLE 1: Climatic Data ofLegune Station

TABLE 2: Annual(Water Year) Raintl111 in Legune Station

TABLE 3: Evapotranspiration - Legune Station

TABLE 4: Land Units in Legune

TABLE 5: Details of Soil Analysis

TABLE 6' Siock Water Quality Standards

TABLE 7: Average SurHlce Storage Capacity for Hydrologic Soil Cover Complexes

TABLE 8: Details of Calibrations

TABLE 9: Storage Capacity of Design Tanks

TABLE 10: Design Dimensions of Excavated Tanks for 90% Reliability

TABLE 11: Cost Estimate of Excavated Tank - Tank Size: 90 x 90 x 3

TABLE 12: Cost of Excavated Tanks

TABLE 13: Dimensions of Turkey Nests

TABLE) 4: Cost Estimate of Turkey Nest

TABLE 15: Details of Pumps and Pipes

TABLE 16: Servicing Equipment - Cost and Capacity


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LIST OF FIGt fRES

FIG. 1 Locality Map - Legune Station

FIG. 2 Typical OtICreek Excavated Tank

FIG. 3 Typical Drainage Line Excavated Tank

FIG. 4 Test Hole Plan for an Excavated Tank

LIST OF APPEN-:DICES

APPENDIX I

APpmmIX2

APPENDIX 3

APPENDIX 4

APPENDIX 5

APPENDIX 6

Existing Dams and Waterholes in Legune Station

Flood analysis of Bakers dam.

Hydrologic Condition and Hydrologic Soil Group

Site Investigation

Construction Details of Tanks and Turkey Nests

Pipe Network


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INTRODUCTION:

Legunc station is situated in the Western Victoria River Region and the station covers an area of 3,089 sq.km. It comprises of I'll portion 798 and 3222. It is accessed through Ord River irrigation farms trom Kununurra and the distance is about 100 km by road which is not sealed for most of its length. The station borders Western Australian border to the wesl, Spirit Hill station to the south and southeast, Queens channel to the north east, and the Joseph Bonaparte Gulf to the north. The station is drained by Victoria River, Keep River, and its tributaries. At present the station canies 18,000 head of cattle. About 15% of the stock water is obtained from surface water storages such as excavated tanks, excavated \vaterholes, and from springs.

2. CLll'v1ATE:

2.1 GENERAL:

The climate is monsoonal '",ith rainy wet season usually trom November to April. During this period inundation of much of the low lying country is by sheet flow and flood waters from major rivers such as Victoria, and Keep. The dry season experiences hardly any rainfall but warm temperatures. The climatic data for the station other than the rainfall is not available. Kununurra which is about 100km southwest, and Auvergne which is 80 km southeast of Legune station homestead, are the closest places with climatic data. The climatic data of Legune is noted in Table 1. However the statistics of temperature noted is that of Auvergne which would be similar to Legune but slightly higher.

2.2 RAINFALL:

The daily read rainfall recorder at the homestead has been in operation from 1956. Rainfall records are not available tiX the months, January and February 1972, April to October 1973, August to September 1987, May to October1989, April to October 1991, and January to August 1992. Some months had accumulated rainfall amount over a few days. However it was found that the accumulated amounts over a few days are small and needs no modification as tar as the yield analysis is concerned. The missing record of January and February 1972 are important for yield studies because it increases the continuous daily record of 14 years to 31 years. The daily rainfalls cannot be estimated because there were no other rainfall records available any where close enough to the homestead to give a realistic estimate. The annual rainfall representing the water year rainfall is a good indicator of the monsoonal rain. The water year rainfall totals at Legune Homestead are given in Table 2.

2.3 EVAPORATION:

High evaporation rate in these areas demand deep storage for successful water harve,iing. The Climatic Atlas of Australia -Map Set 3 produced by the Bureau of Meteorology(1988) gives the evaporation of class A pan with birdguard. According to the Climatic Atlas, the annual average


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evaporation (class A pan with birdguard) to represent the whole station would be 2900mm. Annual evaporation from large tanks (depth> 3m) approximate to that from a lake. According to Hoy and Stevens(J 977) the mean annual lake evaporation to class A pan coeft1cient for all Australian Lakes has been found to be 0.78. The annual pan coefficient varies vilith climate, particularly relative humidity and rainfall, being greatest in the moist coastal areas and least in the arid interior. The pan factor ,vithout bird guard is related to the mean relative humidiry at 1500 hours(RR,,) and the mean annual rainfalI(p) (Hoy and Stevens, J977). However monthly pan evaporation cannot be estimated using this method.

Morton's method using either radiation or sunshine hours is used to compute the evapotranspiration of the catchment and the lake evaporation for the tank. The average monthly radiation and sunshine hours are available over a three month period and is given in the Climatic Atlas. However this does not give the actual monthly mean. Kununurra is the nearest place to Legune station, where all the relevant data on monthly basis is available tor the computation of evapotranspiration using Mortons equations. The mean monthly temperature at Kununurra is slightly more or less (about O.2"C) than that at Legune. The difference in radiation and temperature at these two places is small that its effect on the yield analysis is small. Therefore the mean monthly global radiation and the mean monthly temperatures at Kununurra were used to compute the mean monthly evapotranspiration in Legune station. The monthly c.atchment evapotranspiration and lake evaporation calculated using Morton's method are b>1Ven in Table 3. The wet environment evaporation noted in Table 3 is used as the catchment evapotranspiration. The annual catchment evapotranspiration and lake evaporation are 2945, and 2643 mm respectively.

3. SURFACE WATER POTENTIAL

3.1 GENERAL:

Excavated tanks, Springs, Billabongs, permanent, and ephemeral water holes are the main sources of surface water supply for stock in Legune Station. Springs may occur at the base of ranges, however these areas are less suitable for stock due to the harsh terrain and poor quality grazing. Most of the existing surface water storages are excavated waterholes, off stream tanks, and drainage line tanks as well as on stream tanks.

EXISTING SURFACE WATER STORAGE:

Details of the existing surfa'~e water storages in the station are given in Appendix 1. M.ost of the tanks have been modified recently by desilting and excavating further. The stock water directly from these excavated tanks. This aggravates the silting problem. Desilting is a major problem because most of the tanks may not completely dry. The most common defects found in these tanks are given bel.ow.

(i) Rill erosion in the bund and silting of tanks. (ii) Inadequate spil1tail channel.


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The defects noted in (i) are due to a lack of appreciation of the soil type existing in the station and inadequate compaction, Some of these tanks over flow during the wet while others do fin up and only a few last till the end of dry, Existing waterboles and billabongs are the otber type of surtace water storage that exist in Legune station, Most of tbe billabongs and waterholes which gets filled during an averag,: wet year, last till the end of dry. Water is tapped from these sources when man made tanks in the vicinity go dry,

3.3 TYPES OF MA,,'! MADE SURFACE WATER STORAGE:

The type of man made surillce water storage is determined by the catchment topography and soil type, Most of the land area in Legune station except those near the ranges, are almost flat and gently sloping alluvial plains, The area closer to the ranges are of low hilly country mostly on sandstone with rock outcrop and skeletal soils, In a flat country, the most suitable surface water storage is tbe excavated tank, There are tbree types of excavated tanks that suits the topography of the region, They are onstream, off creek, and drainage line excavated tank The onstream excavated tank is costly because it needs a very higb standard of construction and design, Therefore it is not recommended, The off creek and drainage line excavated tanks are recommended, This is beC<lUse they are economical and effective, All three types of tanks are found in Legune station, The depth of the tank determines the reliability of lbe available water. Initial cost, maintenance and evaporation are the major factors that contribute to an economical design of an excavated tank, A typical excavated off creek tank is shown in Fig 2, This type is recommended for surface water storage in Legune, An inlet channel from the creek is constructed, and water is diverted into the tank. The bedwidth of the inlet channel gradually expands to tbe width of the tank, before it joins the tank, Tbe bed slope of the inlet chatme! sbould he greater than that of the creek. Three sides of the tank has a slope of 1 on 3, and the flow enters the tank through the side that bas a mild slope of 1 on 10, This mild side slope is rubble packed to stop erosion, The drainage line excavated tank (Fig 3) is same as the otf creek tank but without the inlet channel. This is recommended for a reasonably sized drainage(depression) catchment, which does not have a defined creek system. The sheet flow in the flat country could be harvested in this manner,

\Vhether a silt trap is in place or not, most of the time surface mnotf is produced by moderate intensity, short duration rainfall, and the silt does not have time to settle in the silt trap, Silt is very tlnc particles of material held in suspension, The silt trap functions more as a sediment trap, Sediments at'e large particles of material and will fallout as soon as tbe water slows down. Tbe dams in the station do not have silt or sediment traps and they not recommended either.

The Gully or Embank-ment dams across the creeks, being the most versatile of all farm reservoirs, are suitable for the gently undulating country, These storages are mainly used for irrigation, It should be noted that structural failures are high amongst gully storages, as they require a high standard of design, constmction and management. Though the terrain in the land unit 5 is gently undulating to mostly hill countries, the constmction of these dams are economically not feasible because of rock foundation, The sandstone is likely to be penneab!c, Some times the skeletal soils found in these areas may contain high clay content to a depth of i m, These places may be good


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lor Gully Dams provided the topography is suitable for it. The minimum average depth of the gully storage in Leglme should be 4m inordcr to compensate tor the high evaporation. All excess runotr has to be taken through a by-wash or spill. Constructing a Gully dam at a appropriate location in the region would involve high costs in coping with the foundation condition and Hood t1ows, Thererore they are: not recommended for surface water storage in Leb'Une station especially the gully dam on rock foundation. However it is recommended to consult an Engineering Geologist and a Civil Engineer before planning to construct gully dams on rock foundation. Embankments more than 3m high need licensing from the Water Resources Division. Where the topsoil has high content of clay, gully dams may be possible, The cost of such a dam would be minimum if the station uses its machinery and labour for the construction. The design and construcion supervision should be done by a consultant.

In Legune station the Baker's dam is an example of the Gully dam. This dam was constmcted last year without any design Of proper construction. The two spillways were not sufficient to discharge the floodt10ws that they were scoured by more than O.Sm during this wet in January 95, The dam filled upto 0.7m below the dam crest level. Flood analysis on Baker's dam is given in Appendix 2.

3.4 LA."fD SYSTEM AND LA.'ID UNITS:

The land system based on pasture, cattle carrying capacity, and top soil has been mapped on 1:1,000,000 scale by the Land Research Division of the Commonwealth Scientific and Industrial Research Organisation (CSJRO) in 1970. The explanatory notes is given in Land Research Series No. 28, This map Vias bas(!d 011 the soil map noted in Atlas of Australian Soils(KH.Northcote 1968). Six different land systems are found in the region based on the Land Systems Map, and are noted in Table 4. The digital data of the soil map is on 1: 1,000,000 scale. This digital data ,,,'liS used to produce 1: I 00,00 scale soil map ofthe region. It was found that this map had similar soil formation to that of the Geology map and Satellite imagery of the region. However the layout ofthe soil map had an appr,eciable shift to that of Geology and Satellite imagery. Therefore a soil map of the area related to surface water development was produced based on the Geology and Satellite imagery. The region has been divided into five different land units based on top soil classification, surface water runoff, and surface water storage development. These land units are noted in Table 4. This table also gives the top soil, underlying bed rock type, and the relative surface mnofC whether low, moderate, or high.

3.5 LAND SUITABILITY FOR SURF ACE WATER STORAGE:

Surface water storage are t!conomicaUy established at sites where favourable sub soil conditions exist and have catchment that produce good runoff. There are many major and minor creeks within the station with waterholes as wel! as t1at to gently sloping drainage areas that provide suitable catchments ;;vithin the region for surface water storages, However identiJYing the different subsoil strata to a depth of 4.5m all over the station is not feasible in this study, The topsoil classification noted in the 111l1d units, permits the identification of areas with suitable subsoils tor an excavated tank, However investigations have to be carried out to confirm the suitability of sub


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soil. Soil samples were taken from Corner Dam and Estuarine alluvial plains were analysed. The soil analysis included particle size classification, pH, and Electrical Conductivity(EC). The details of the analysis are noted in Table 5.

The area covered by land unit 1 is most suitable for constructing excavated tanks because this area contains high percentage of cracking clay soils to a depth of 1m to 4m or more. The stock carrying capacity of this area is very high. The clay content of the sample trom Corner Dam is high, and is indicative of the black soil clay content. However the sand content is high because of its close proximity to the escarpment. The particle size classification of Czb area in Spirit Hill as noted in Table 5 would be similar to land unit 1 area in Legune. This soil is suitable for holding water as it contains necessary percentages of clay, silt, and sand. These soil types are found between the floodplains of Victoria and Keep Rivers.

The land unit 2 is also suiltable for constructing excavated tanks where subsoil is suitable. The particle size classification of Czs area in Spirit lIill as noted in Table 5 would be similar to land unit 2 area in Legune. The silt content is low, and the sand content is high when compared with that of in land unit 1. It should be noted that sand pockets are fuund in these alluvial plains. The area covered by land unit 3 has deep sandy soils especially on the left side floodplains of the Keep River. These areas are not recommended for surface water storage development.

The areas covered by land unit 5 is not feasible for water storage development. However drainage line excavated tanks especially within the base of the escarpments may be feasible. The areas indicated by the land unit 5 is mainly ranges, surrounded by ridges, hogbacks, cuestas, rock outcrops, and skeletal soils. There is good surface water lUnon'in these catchments. However the area is too rough or stony for stock but water may be piped to a nearby turkey nest. The land unit 4 has mud, sand and gravel with saline soil, and the development of surtace water storage is not recommended. It is found from the sample analysis, that the clay and silt content is very small as compared to sand content in land unit 4. Details are noted in Table 5 as sample analysis from Qc area.

3.6 WATER QUALITY:

There were hardly any water in the excavated tanks during the time of inspection. Water was sampled dis of the Knapp springs and was to have a pH value of 8.57, with a Ec of 286 us. The water quality standards tor stock as recommended by the National Health and Medical Council, and Australian Water Resources Council is noted in Table 6.

4. MODEL PARAMETERS OF GAUGED CATCI-Th-fENTS:

4.1 GAUGED CATCHlYfENTS:

The only one liver that has been gauged within the station is Keep River at Legune Road crossing. The catclnnent at this location is 3496 sq.km and 95% of it is outside the station. There are 22 gauging, at this location. This catclnnent is very large and not representive of the small


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catchmnets that are analys,;d in this study. There are medium size catchments and a small size catchment in Keep river basin which have been gauged. Gum creek is in \-Vestern Australia, with l8 gaugings and a catchment area of32 sq.km. Moriarty creek has a catchment area of 88 sq.km "lith 31 gaugings. Sulphur bore creek has a catchment area of3 sq.km with 21 gaugings.

4.2 DAILY WATER BALANCE MODELS:

Daily water balance model computes runoff lrom rainfall and evaporation data on a daily basis. It c.ould be used on a gauged or ungauged catchment. There are many models, but the few that are used very often are the Stanford Watershed model, USDA SCS CWve Number Method, and AWBM (Boughton, W.C 1993). The USDA model has been applied to over 20 gauged faml storage catchments in Queensland and was found to pre.dict the average performance of the catchments. This model has been used in a very tew major catchments in the Territory for yield studies. The daily antecedent moisture content, and base flows are taken into account OI'Jy in }\nother Watershed Balane<; Model(A WBM) model. AWBM is a saturation overland !low model which uses daily rainfalls, Recharge into and Discharge from a shallow groundwater aquifer, and estimates of catchment evaporation to calculate daily values of runoff from gauged or ungauged catchments. In the case of gauged catchments, parameters could be estimated by trial and error method. A WBM model is unique in the sense that the parameters do not relate to catchment physical characteristics, and they are not inter-related. This model has been successfully applied to very small to medium size c:atchments in north Queensland.

The A WBM model can be used as a 3-parameter model on ungauged catchments which have a base !low component of runoff. The three parameters are : (i) an average value of surface storage capacity, (ii) the base flow index, which is the ratio of the amount of streamflow appearing as basef10w to the total amount of streamflow, and (iii) the daiJy baseflow recession constant Estimation of the values of parameters for use on ungauged catchments is based on the recommendations of Boughton, 1993. The average surface storage capacity(mm) depends on Hydrologic soil group, Land use or cover, and Hydrologic Condition. The definition of Hydrologic condition and Hydrologic soil groups are given in Appendix 2. The values are given in Table 7. The model can be used on a very small catchment where sheetllow predominates with hardly any baseflow. In this case I-parameter(only one storage capacity) model is used.

4.3 CALIBRATION OF AWBMMODEL:

The daily water balance model A ~'BM was calibrated at the following gauge stations. Some of the medium sized catchments in Legune are similar to that noted in this section. The computed flows at Sulphur Bore Creek (catchment area of3 sq.km) are of poor quality, and an attempt will be made to calibrate the modeL

(i) East Baines River at Victoria Highway (li) West Baines River at Brumpy Hill (iii) Saddle Creek at Victoria Highway


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(iv) Stockade Creek

The details of the calibration of model with flows in (i) and (iii) are noted in the Auverg,\'1e Report(Report No: 55/94D)" and (n) in Waterloo Report(Report No: 57/94D) The details of the catchment and the partial storage capacities used in the calibration are noted in Table 8 The partial areas as recommend<,d by Boughton(J 993) was adopted in the calibration.

5, ESTlM.ATION OF 'YIELD OF UNGAUGED CATCHMENTS

5,1 GENERAL

The medium and small size catchments in the station are ungauged. However based on the calibration oflarge gauged catchments, the 3-parameter A WBM model is used to simulate the daily runoff from the daily rainfall in small ungauged catchments. The off creek type storage design is based on a catchm,~nt area of 1.5 Sq.km or more. The 3-parameter model would be appropriate for such small and medium size catchments. As for smaller catchments of a'{(ent 1.5 Sq.km and less, one parameter model would be appropriate, There were no gauged small catchments to calibrate the one parameter model, and theretbre three parameter model is used to design the drainage line storage which taps the sheet flow from small catchments. The hydrologic condition, the soil type, and the vegetation ofthe catchment determine the average storage capacity of the catchment Table 7 is used to obtain the capacity which is denoted as 5. The area and the three partial areas of the catchment are denoted as A, AI, A2, and A3 respectively, The corresponding surface storage are denoted as S, 51, S2, and S3, For Ullgauged catchments, Boughton's( 1993) recommendation of partial area and storage amounts are noted below,

Al = 0.2 x A; A2= 0.4 x A; A3= 0.4 x A;

SI= 0.5 x 5; 52= 0,75 x S; 53= L5 x S.

The recorded daily rain!all in Legune could be used to compute the daily yield from the catchments.

5,2 DESlGN OF EXCAVATED TANK:

The design of an excavated tank of economical size to supply stock water to 400 head of catile is given below. The tank is designed for 90% reliability.

5.2.1 Stock Water Demand:

The stock water demand ofa tank is related to the stock carrying capacity of the paddock. [I is also related to the size of the paddock. The size of the paddock varies Jiom 30 to 120 sq.km with an average value of 50sq, km. Theretore a paddock would have a minimum of 250 head of cattle


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to a maximum of 800 head of cattle with an average of 400, As for the design purposes, two tank sizes are recommended, om: for olI-creek and the other for drainage line storage, to supply stock water through out the year to a cattle strength of between 250 and 800 depending on the paddock size, The daily consumption is based on average intake of 50 litres per head for 330 days in a year. However for design purpos·es, a daily consumption of 50 litres per day throughout the year is adopted consideling a dry year,

5.2.2 Tank Size:

The top dimensions ofthe existing ot1' creek and drainageline excavated tanks vary between 40 by 40m and 60 by 60m, The depth below the ground level varies between 1 ,5m and 2.8m, There is hardly any storage above the ground leveL It is found that tlus average size is not economical because of insufficient storage and depth. This is the main reason for mo~i of the excavated tanks to dry completely by July or August every year. It is also found that in general, most of the creeks in the region flow every year. This is evident by the annual replineshment oftbe excavated tanks. It would be ideal to design '1 storage to cater for a dry year. Therefore a storage capacity sufficient to store water to cater for a stock water demand of 400, 600 ,and 800 head of cattle in a dry year, and abo to cater for the evaporation is needed. In any open tank evaporation consumes 2.6m height of water over a year. Therefore the remaining depth of water should correspond to a minimum capacity of7.3, 10,95, and 14,6 Jlv1L respectively for the cattle strength noted above and also to cater for the evaporation, If the wet season is completely dry after a good previuos wet, then the cattle would need water from April to December the next year. The total amount of evaporation during this period would amount to 4,6m, Theretore the depth oflhc excavated tank should be more than 4,6m to cater for a dry year. This would mean the minimum depth would be 6m. The excavated tank of 6m depth would be very large. Gully dams of om deep would be ideal to cater for dry year storag,~,

The sizes of typical excavated tanks considered in tills study are, 6Ox60x2.5, 70x70x3.0, 90);.'90x3,O, and 100xI00x4,0. This is the top dimension and depth in meters. This is sitnilar to the typical o.ff creek excavated tank shmvn in Fig.2, The side slopes on the threc sides of the tank is 1 on 3, The side through which the flow enters has a milder slope of 1 on 10. The smaller size tanks (70 x 70 x 3) are recommended for drainage line (hillside) storage. The configuration is same as that of the off creek storag<:: except that there is no inlet channel. Instead, catch drains may be constructed depending on the topography, The storage capacity of these tanks are noted in Table 9. The reduced level of tile tank bottom is assumed as 100.0RL for analysis purposes

5,2.3 Catchment Type and Extent:

The extent of the catchment of a drainage line tank is small. Catchments less than 1.5 sq.km have been considered in the design of such tanks. They are also designed to catcr for a stock strength between 150 and 900, In g€:neral the creeks, medium and minor in the region have catchments of 3 sq, km or more, The off creek tanks are designed for catchments of size between 1.5 to 4 Sq.km, The tanks are designed to cater tor a stock strength between 250 and 1100, These tanks can be suitably located in land unit 1, and near the base of the escarpments located in land unit 5, These


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design tanks are also suitable for land unit 2 but would cater for 15% to 20% less stock. All these catchments could be identified to soil group D (Table 7) interms of runotf. The vegetation in the catchment area is about 50% of its extent. Therefore the hydraulic condition is considered as poor.

5.2.4 Yield Analysis:

The yield analysis is based on the daily water balance model A WBM. The storage routing programme used is SMALLDAlVl develope-d by Barlow(J993). The Legune daily rainfall of 14 years, and the station evaporation data were used in the analysis. A base flow index of .05 for drainageline tanks and 0.15 for off creek tanks were used. The daily recession constant between 0.97 and 0.98 was used. Based on the results of the gauged catchment calibrations and the recommendations of Boughton(J993), the following storage capacities have been used to

compute flows. The param(~ters used for off creek storages are S 1=20, S2=50, and S3=90 for catchments in land unit I. Tn land unit 2 the parameters used are S1=20, S2-=55, and S3=IOO. The parameters used for drainage line storages are SI=20, S2=40, and S3=80 for catchments in land unit J. In land unit 2 the parameters used arc S 1 =20, S2=50, and S3=95. A uniform stock water demand throughout the year was used to analyse the yield capacity. This may not be the ideal situation. In any average "vet year, the stock will not need the water stored in the tank for about two to three months. Therefore the design tanks could cater lor an increased number of stock, say 10010 to 15% in a.., average wet year. The design tank of various sizes tor 90% reliability to cater for a uniJ:ofm demand is analysed for different Full Supply Levels(FSL), and are given in Table 10. These design tanks are recommended fur locations in land lmit 1 with catchments in land units 1 and 5.

5.3 DESIGN CRITERIA FOR EXCAVATED TANK:

5.3.1 GENERAL:

The design capacity of an excavated tank depends the location of the tank and its size. In detail it would depend on the surface salinity, stock water demand, evaporation, catchment type and e;.,.1:e111, and the sub soil strata. The quality of the stock water is maintained if the catchment and the site are outside the area marked as land unit 4 (Mapl). The design procedure is noted below.

(a) STOCK WATERDEiV!lAND:

The stock ",'ater demand of a tank would depend on the cattle carrying capacity of the paddock. The design tanks noted in Table 10 , depending on the catchment extent and type, could cater for a cattle strength between 150 and 1000. If the design tank and its catchment are suitably located in Land Unit 2 areas, then it ;,vould cater for 80% of the stock numbers noted in Table 10. The stock water demand of a tank should be evaluated considering the availability and usage of ground water supply in th,~ same paddock. In Legune station where ground water and surface water are available in the same paddock, surface water is exploited first followed by ground water. This is a very eftective way of water management in the station.


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(b) CATCHl'vlENT TYPE AND EXTENT:

Catchment may be that of a creek or a gently sloping drainage area. In the case of a creek, off creek storage is recommended. Gully dams may be feasible, where the topography and top soil are suitable. Drainageline tanks are recommended for small drainage or depression areas. Areas boardering the escarpments in land unit I may be ideal for drainage line tanks. The catchment location in respect to the land unit is obtained from the Map. The extent of the catchment could be determined from the topographic map. If the catchment is small, the extent could be computed by pacing the catchment. The recommended sizes of the excavated tank are given in Table 10.

(c) SUB-S1.IRFACE EXPLORATION:

The sub surface exploration is carried out to determine the suitability of the subsoil to hold water without any leakage either horizontally or vertically. Also to find the depth of ripable rock. The site investigation (refer Appendix 4) is carried out, which includes Permeability, Soil classification, and Dispersion tests. If the tests yield satisfactory results(refer Appendix 4), the cost of the recommended design tank should be estitnated for economic evaluation.

6. CONSTRUCTION A.c"lJ) COST-EXCAVATED TANK:

The construction of a stock water outlet would comprise the following.

(1) construction of an Excavated Tank and fencing it. (ii) construction of an Inlet Channel (iii) construction of Turkey Nest (iv) installation of Windmill or Pump and Watering Troughs.

The construction of an excavated tank, inlet channel, and a turkey nest are given in AppendLx 3. The construction of the excavated tank is made simple and easy because of the rec.ommended type of design. One side of the tank has mild slope, that the excavating machinery can easily go into the tank, turn and come out of it. The side with mild slope is rubble packed to stop erosion. It is mainly exc-avation as the spoil is dumped to waste. However the spoil can be used to build a bund on three sides of the tank if the ground slope penuits building a hillside dam. The spoil should be suitable tor fiJI purposes. The stability of the bund depends on proper compaction(see appendix 4). The recommended tank sites are on land unit 1 where clayey soils are predominant. Some areas in land unit 2 are also suitable for the construction of slIch tank depending on the suitability of sub soil. The bed width of the inlet channel gradually increases to the width of the tank as shown in Fig,2, before it falls into the tank. The bed slope of the inlet channel should be greater than that of the creek The sediment trap is also built within the tlrst half of the channel length though its effectiveness is questionable.


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The cost of the tank depends on the type and depth of soil and rock. The details of the cost involved in the construction of an excavated tank of size 90 x 90 x 3 is given in Table II. It should be that the mobilisation and the rock excavation are the major factors that CDntribute to the high cost, The mobilisation noted here is for calling a small time contractor to build one tank. In reality a contractor c.omes to build several tanks. This would reduce the cost of mobilisation by one fOUlth. The cost of excavated tanks without any rock excavation is given in Table 12. The tanks are either be built by the station or given out to a contractor. Major contractors from Kununurra, and local CDntractors within v'RD region usually undertake this type of job, The station could save part of the original cost by constructing the tank themselves.

The excavated tanks in Bradshaw Station were constructed by the station workers, using station machinery. It costs them so low that several dams are being constructed in this manner. An excavated tank with top dimension of 40x40, and depth of 3.5m costs only S5,000.00. The station used a hired crawler tractor(used their own operator) and their own one to constlUct the tank. If this would have been given to a contractor, it would have costed $ 15,000.00. The 3.5m deep excavation consisted, 1.5m depth oftop soil and 2m depth of shale.

7. WATER HOLES:

Some of the waterholes do bold water up until the end of dry season. These are like! y to be fed by springs, The major water hole that is being exploited in the station is Alligator Springs Waterhole, This waterhole is deep and has great potential. The actual. depth of a water hole, as related to stored water, is the depth below the cease to tlow(CTF) level. The capacity of any water hole can increased by deepening the bed, provided the sub soil is of low permeability, Caution needs to be exercised in deepening the bed. A detail study is needed to estimate the permeability of the subsoil. However site investigations need to be carried out as noted in Appendix 4, to modify an existing waterhole, Investigations would include soil particle size classification, permeability test and dispersion test. If the bed is just above the rock of type other than shale, further excavation is not recommended. Further information on modifYing water hole is given in appendix 5. A typical modified water hole is same as that of an excavated tank except, that it is narrow and elongated. Waterholes in Land unit 1 may be turther excavated, however excavation should be contlncd to cracking clay soils only,

8, SPR1NGS:

Springs usually occur on the slopes of hlll sides and river valleys. In Lcgune springs are found at the base of the escarpments. Green vegetation in a dry area may also indicate a spring, or you may find one by following 2, stream up to its source. Be sure that a spring water is really seeping from the ground, and is not a stream that has gone under ground. If a spring is found to have more than 21/s lIow at the end of dry, it should be sufficient to supply a Turkey Nest designed to store 3 days supply of stock water for 500 head of cattle,

In Legune station, Knapp springs is being exploited for stock water. Most of the springs are perenial and have great potential.


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9. ABOVE GROm'l'D WATER STORAGES:

These are used as balancing reservoirs between pumps or windmills and stock watering troughs. Generally there are 1 wo types of storages in use, namely Turkey Nests, and Galvanised Iron Tanks. Turkey Nests are fiJund every where because of easy maintenance and long lasting. In Legune station, concrete tanks are being used. this is because of the high content of salt presence in the atmosphere and on the surface.

9.1 TURKEY NEST:

Turkey nests are built above the ground "ith non permeable soil near the excavated tank, bore or at the end of pipeline. The borrow area is usually in the vicinity of the sitc. The following soil tests should be done to check the suitability of the soil to be used for bund construction.

(i) Soil particle .size classification. (ii) Dispersion test

Penneability test has to be l::arried out at the turkey nest site to check for base permcability. The description of these tests are given in the Appendix 4. The optimum size of a turkey nest for a specific stock water demand is given in Table 13. Three days storage capacity is used in the design of turkey nest. The Turkey Nest bund is of a homogeneous fill. The construction details are given Appendix 5. The cost estimate for Turkey Nest construction is given in Table 14.

9.2 GAL VANISED IRON AND CONCRETE TANKS:

The Gavanised iron tanks made of corrugated sheets have been replaced by light weight liner tanks. These are installed at site on a well compacted mound. Mounting ring can be installed but it is costly, about $ 2800. The cost of 26k!, 47k1, and 70k:! capacity liner tanks to install is $3000, $4800, and $6000 respectively. Concrete tanks are also useful but are costly. The capacity of concrete tanks in Legune is 180kl. They were constructed in 1991 and the cost was $6,000.

10. TRANSFER OF WATER THROUGHPlPES:

Polyethylene pipes of 50 and 75mm diameter are being used in Auvergne station to transfer water from waterholes to existing turkey nests, when their respective tanks go dry. Jet pumps can be used to deliver upto 2.5115 of water to a distance of 6 Km through 90mm (class 6 ) pipes. Different types of pumps with variable suction and delivery heads, and dilTerent sizes of pipes can be used to transfer water from one place to another. Depending on the terrain and distance, a booster pump may be required to transfer water to the point of interest. However the main criteria to decide the feasibility of piping water is the overall cost. Typical pump size and delivery heads used are noted in Table 15. This table also shows the time involved in fining a turkev nest to feed

~ -1000 head of cattle with three days storage. Pipe systems in general are noted in Appendix 6.


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11. SERVICING EQUIPlVD3NT:

The equipment that is needed to transfer water from an excavated storage tank to a turkey nest needs critical evaluation. The evaluation is based on lifespan of the equipment, immediate availability of spare parts, initial cost, and maintenance cost The basic equipment is a pump wruch can be driven by three energy sources, diesel fuel, wind or solar. The cost structure of the three methods of driving the pump is as follows. The initial cost of wind or solar powered pump is high but the running costs are low. The low eost and the availability of relatively cheap Diesel motor and centrifugal pump makes trus the favoured option even though the running costs arc rugh and requires manual operation. The advantages are mobility and ease of maintenance. Details of typical equipments used and their costs are given in Table 16.

12 CONCLUSION:

There is a great potential for surface water in Legune Station. Most of the existing tanks are reatively shallow, that they dry in July or August Land unit 1 is mostly of Cracking clay soils. However fine sand is enGOuntered at a depth of 2m and below, Theret,xe detail subsoil investigation is required to locate an excavated tank. Land unit 2 also has clay soils but mostly loamy and sandy soils. Thme is potential for Hillside storage and Gully dams at the base of the escarpments in land unit I. It will not be economical to construct excavated tanks in Land Unit 3.

13. RECOMNIENDAT£ON:

1. All existing and any plaJlned excavated tanks and as well as springs should be tenced. Proper stock watering arrangement should be provided.

2. Excavated tanks and dra.inage line tanks are recommended tbr land unit 1 areas,

3. Gully storages are fe:asible, provided proper investigation, design and construction are proposed.


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GLOSSARY

DEMAl'.'D

DRAFT:

The volumetric flow rate required for stock watering, therefore the rate at which water would be supplied if available.

The volumetric rate at which water is drawn off for use.

FULL SUPPLY LEVELtFSL);

The maximum elevation to which stored water is allowed to rise in normal operation, excluding Hood pernms.

STOR;\.GE CAPACITY:

The volume of water that can be stored in a tank up to its full supply level.

SPILL TAlL CHA..NNEL:

A channel built do\'mstrearn of the spill to direct excess water back into the creek

. RELIABILlTY:

The frequency at which a tank would be able to supply the annual stock water demand. eg: 90% reliability means that the tank would be able to supply annual stock water for every nine years out of ten.

FLAPGATE:

A gate attached to the pipe outlet which allows ,vater to t10w in one direction.

CEASE TO FLOW:

The level in the creek or river, at which water ceases to tlow.

BATTER:

Slope expressed in ratio of horizontal distance to vertical distance.


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INLET S1RUCTIiRE:

A structure that regulates the flow of water into a tan1 ... Usually it is a pipe with upstream and downstream head walls.

SEDllilENT TRAP:

The small pit to collect bed load before it reaches the tank.

WATER YEAR:

YIELD:

A year taken to conunence in September of one year and end in August of the following year, This convention has been adopted so as to separate the stream flow record at a period where the connection between years is the weakest.

The volumetric rate of flow from a catchment.

ABBREyJA TIONS:

u/s upstream dis downstreanl rom millimetre

·m metre k1 kilolitre lfs litre per second M1 Megalitre Sq.m Square metre eu.m Cubic metre

CCNT : Conservation Commission of the Northern Territory


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REFERENCES:

Bureau of Meteorology (1988)

Bureau of Meteorology (1988)

Hoy, R.D. and Stephens, S.JK(1977)

The Institution of Ellooineers-Australia (1987)

Nelson, K.D (1985)

Boughton, W.C (1993)

Department of National Development (1970)

Rajaratnam, L.R (1994)

Rajaratnam, L.R (1994)

Department of Lands and Housing (1987)

Climatic Averages Australia Bureau of Meteorology, July 1988

Climatic Atlas of Australia-Map Set 3 Bureau of Meteorology, 1988

Fjeld Study of Lake Evaporation Analysis of Data From Phase 2 Storages and SlIIl1IlliIl:y of Phase I and Phase 2 Australian water Resources Council Technical Paper No.4 J AGPS Canberra 1979

Australian Rainfall and Runoff A Guide to Flood Estimation-Volume 1 and 2 The Institution of Engineers-Australia, 1987

Deman and Construction of Small Earth Dams Inkata Press, Melbourne, 1985

A Hydrograph-Based Model for Estimating the Water Yield of Un gauged Catchments Hydrology and Water resources Symposium Newcastle, June 1993

Eyaporation from Water Storages Australian Water Resources Council-Hydrlogical Series 4. Department of National Development Canberra-1970

Surface Water Storage Potential-Auverllnc Station Report No: 55!94D, Water Resources Division Power and Water Authority, Darwin, July 1994.

Surface Water Storage Potential-Waterloo Station Report No: 57!94D, Water Resources Division Power and Water Authority, Darwin, July 1994.

Inspection report-Legune Station Department of Lands and Housing, Darv.;in, Aug.87.


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TABLES


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TABLE 1

CLTh1ATIC DATA - r ,EQ!JNE STATION

, ~

MONTH ,

MEAN l'v1EAN *MEANDAILY *JvlEAN DAILY ,

I I RAINFALL RAIN DAYS MINIMUl\f (C) MAXThfl1M (C)

(mm)

JANUARY 281 14 24,7 35,6 ,,',"------

j FEBRUARY 274 12 24,5 34,3 !

MARCH 212 10 23,7 1 34,8 1 --APRIL 30 1 20.3 34.9

MAY 10 0 17.2 32.6

JUNE 1 0 13,5 30.3

JULY 3 0 12,9 "0 ~ .) ,,, AUGUST I 0 0 15,3 32,7 I 1--.

SEPTEMBER I 4 1 19,6 35,6 , OCTOBER I 24 3 24,1 37,6

NOVEMBER 87 5 25,3 38.5

DECEMBER 139 9 24,8 36,9

TOTAl I 1,065 55 T~'-" I

NOTE: *: Temperatures noted are from Auvergne Homestead,


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TABLE 2

MINUAL RAINFALL - LEGUNE STATION

YEAR I QUALITY CODE RAINF ALL(mm) 1

1956 255 I 0

1957 21 604

11958 21 1,455

i1959 21 1,292,5

11960 21 515

1

1961 21 1,002.3 i • •

1962 21 828.3

1963 21 832.1

1964 21 776 r---' 1965 21 1,660.5

1966 21 1,173.2

1967 21 1,410.2 f--

! 1968 21 1,616.1

1969 21 617.3 r---' ._-

1970 21 I 887.6

1971 255 ° 1972 255 ° r----1973 255 ° r----~4 21 1,007.5

11975 21 1,653,8

11976 21 1,220.1 i I

1

1977 I 21 893.5

1978 i 21 707.4 ,

1 1979 I

21 1,017.6 ,

11980 I --J 21 1,0172 I i--

I 1981 125 1,207.1 i --1982 21 1,033.5

1983 21 1,076.8

1984 21 1,038.1 --


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111:~

1(:: 1

199

19~

5

;6 --;7

;8

~9

'0

11

Ji99 "2

i

I I

21 896.3

255 0

255 0

255 0 i

255 0

255 0

255 0

255 I 0

I 1993 __ ~ _____ 2_5_5 ____ -+ ______ 0 ____ ~ 1994 255 0 __ ~ __________ -L ________ ~

QUALITY CODE: 255: Data not available 125: Accumulated data over a period 21: Good periodically read data


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TABLE 3

EVAPOTRAi'l"SPlRATION(mm) - LEGli"N"E STATION

I MONTH POTENTIAL WET LAKE ENVIRONTvlENT

I JAt"lWIRY 327,1 31L7 264,5

'FEBRUARY 231,6 221,6 206,5

MARCH 267,1 239.8 I 227,5 ,

APRlL ,

320,6 279,9 227.4 I I _. -----; MAY 263.1 ')0') 186.1 i - - ,

JUNE 226,1 159.4 155,8 - ---_.-----I JULY 264.2 199.7 172.1 I I .~~GUST I 282,8 226,9 195.2

I SEPTE1VfBER I 292 216,9 212,8 I , l I OCTOBER , 361 279,2 258.7

i I 279,7 : NOYEj\,ffiER 397,5 343.7 , I DECR/mER 315,8 264.8 I 256,6

Technical R

eport WR

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TABLE 4

UNO UNITS IN LEGUNE

,-----,----- ........ _..... . ........... _-_......... ... -DESCRIPTION

]

t~ . __ ----:-_~=;:-;:: ...... -_ ... -_ . __ ..... __ ._...........j _"_ L .... __ Mostly flat alluvial plains with cracking clay soils. Surfuce JUnotr moderate to high. Surface water storage development is economically feasible. The land

system is similar to Legune , and.~J;.v.:;.an=h=o:.:e=. _____ _

2 Gently sloping alluvial plains with leached loamy and sandy soils. Surface runoff moderate. Surface water storage development is feasible where subsoil

is suitable. The land system is similar to Argyle.

3 Gently undulating country on sandstone with colluvium and sandy soiL Surface runoff low to moderate. Snrface water storage development would

depend on the sub soil strata and may not be economically feasible. The land system is similar to Cockatoo.

~---+------------~-Estuarine alluvial plains with saline soils, and mud. Surface water storage

development is not recommended. The land system is similar to Carpentaria. - .. ~.--..

Hilly country with ridges, rock out crop and skeletal soils. Surface water I1moff high. Surface water storage development is not feasible. The land

~ system is similar to Pinkerton.


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TABLE 5

£Qil" CLASSIFICATION IN LEGtJl'iE STATION

,-------------------~------------------------.-----~---.

k:~LE DESCRIPTION

I Corner Dam at 2.5m d=e:!:pt:::h~_=

SOIL CLASSIFICATION(,%) Ee pH

CLAY SILT F.SAND CS~J~l)+ ____

35 5 23 38 I 136 9.37

i Corner Dam at I. 5m d:..:.ep~t=h~. +-~=___+__=_ __ +---=-=___-+ __ :::.:::._ __ +__=---:..:.-

IlsamPJe in Qc area at O.3m

32 6 41 22 38.8 7.38 - ----

6 4 70 21 9.6 5.63

~-----~d~~~th~--.--~----~--_4----~~----~- -------~ Sample in Czb area at O.3m 57 17 21 5

I--___ depth-Spirit HiIJ --- _.

50 7 23 21

J Sample in Czs area at O.35m

depth-Spirit HiH ___ L-__ L-_---.L ___ L.-__ -L __ -L __ _

NOTE: F.SA.'-Il): Fine sand; C.SANl): Coarse Sand; Ee: Electrical Conductivity(~s/s)

TABLE 6

STOCK WATER OUALITY ST ANPARDS

SUBSTANCE UNIT GUIDELINE

pH range 5.5 - 9.0

Total mglL 8000 Solids

Sodium mgIL 75% oftotaJ Chloride dissolved solids near limit.

Sulphate mg/L 2000

Nitrate mg/L 400

Fluoride 111g/L 5.0

Magnisium mg/L 300


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TABLE 7

A VER.A.GE SURFACE STORAGE CAPACITY FOR HYDROLOGIC SOlL COVER CO!vlPLEXES *

LAl"",;TI USE OR COVER

Pasture or Ranae

"

HYDROLOGIC CONDITION

Poor

Fair

Good

HYDROLOGIC SOIL GROUP A .6. C 12

204 120 72 53

196 120 86

265 157 113

'" The definition of Hydrologic Condition, and Hydrologic Soil Cover are given in Appendix 2.

Technical R

eport WR

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TABLE 8

DETAJLS OF CATCHMENT AND CALIBRATION

-----.. -.-- ____ ".0._ .. .. _-"

CATOlMENi'- , PARTIAL ,iORAG' r I NAME AND CATCHMENT TYPE REJ\IARKS LOCATION OF GAUGE EXTENT (Sq.Km) CAPACITIES (mm)

I STATION SI; S2; S3 ---- - ."-_._- ~ .. --.~ ~-

I East Baines at Victoria Hogbacks, Ridges, Rock 2,432 20; 70; 105 I 85% ofBullita Rainfall I

Highway outcrops, with Skeletal produced good soils. representation of flows.

Saddle Creek at Victoria Moderatly undulating plains 234 20 75' 105 , , Newry rainfall records Highway on shale. Some areas are between 1968 and 1976

red earth with leached were used in the loamy soil and limestone calibration.

outcrops. -West Baines river at Alluvial floodplains with 162 17; 38; 75 Waterloo rainfall between

BrnmpyHili cracking clays. 1968 and 1984 were used in the calibration. Pluvio records between 77/78 and 80/81 were nsed -.. ~.-~ .. --. -- ----


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TABLE 9 STORAGE CAPACITY OF TANKS

SIDE SLOPES: Ion 3 for three sides; 1 on 10 fOf the tburth side.

TAl'\i1( SIZE: 60 x 60 x 2 Sm DEPTH(m) SURFACE AREA(Hac) YOLUME(lvll)

0 0.12 0

0.5 0.16 (l,n _.

1 0.21 1.64

• 1.5 0.25 2.19 I •

2 0.3 ! 4.1:> r- I I ._-

2.5 0.36 5.84 ~-- .---.. ----

TANK SIZE: 70 x 70 x 3m . " --.

I DEPTI-Hm) -- . SURFACE AREA(Hac) VOL UlvIE(lVn)

0 0.16 0

0.6 0.22 1.13 -_ .. ---1.2 0.28 I 2.6 _. 1.8 1 0.34 I 4,45

2.4 0.41 6.71

! 0 0.49 9.42 0

TANK SIZE: 90 x 90 x 3m '-r--==~~~~~--,-~~~~~

DEPTH(m) -+_.:...S"'URF::.::.::.:...A.:...CE:..:.:....:..::AR:..::E"'Ac:.(ccH=3"-'C)-'--+_...:."-"O"'L:..:Ucc·lV"'1E::,:(Ml=)C--l o O~ 0 • J

0.6 0.63 3.63 I 1.2 0.67 7.51 I

1.8 (J.n 11.67

2.4 0.16 i 16.1

3 0.8! I 20.82

TANK SIZE: 100"100,, 4m


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TABLE to

DESIGN DIMENS[ON OF EXCAVATED TANKS FOR 90% RELIABILITY IN LAND UNIT [ N'W ON THE BORDER WITH LAND l JNIL5.

I CATCHiVlENT DESIGNTA.NKSlZE STORAGETYPE ! STOCK Nos. I F1JLL EXTENT (metres) TOP I (water demand i SUPPLY

DIMENSIONS AND • Jan. to Dec.), LEVEL

!f-~~~~~-I-~._D_EPT~H~~-t~~~~~~-+~~~~ __ L._J I 2.0 Sq.Km 70 x 70 x 3 OFF CREEK 250 I 102.5

f--io's;iK~- 70 x 70 x 3 ;~O=:I 3001 I 102.5 I STORAGE

4.0 Sq.Km 70 x 70 x 3 OFF CREEK II 350 ! 102.5 '.1 i r_~~~~-+~_~~~~~-+~~ST~O~RA~G~E=-~~ __ -~~-+!~~~~-11

OFF CREEK 400 I 102.5 I STORAGE I

1.5 Sq.Km 90x90x3

2.5 Sq.Km !I: 90 x 90 x 3 OFF CREEK STORAGE i

500 102.5 ! ~--------~~------------!---------t--------~

4.0 Sq.Km II 90 x 90 x 3 OFF CREEK 600 I STORAGE I

102.5

102.5 6 Sq.Km I, 90 x 90 x 3 OFFCREEK 700 II

STORAGE

OFFCREEK 900 II

STORAGE 10 Sq.Km 90x90x3 102.5

I 20 Sq. Km 90x90x3 OFFCREEEK 1,100 I STORAGE I 102.5 :

I 1.5 Sq.KIll

I I,·S KIll ! •. , q.'

100 x 100x4

OFFCREEEK 1,100! 103.5 100x 100x4

OFF CREEEK 900 Ii

STORAGE 103.5

! STORAGE I I !---2.-5S-q·.-Km~r---!-1 --1·CI·-0-X-I-0-o-x-4--+---0~~~o~C:!~ci:~K--~,----9-0-0---1-~·--10-3--l

I 100 x 100x4 OFFCREEK 1,000 I 103 I 4.0 Sq.Km I STORAGE

0.5 Sq.Kn1

!! 100 x 100 x 4 DRAINAGE LJNE 400 104 II

STOR."'GE i

1.0 Sq.Km DRAJNAGELlNE 900 104 I.

STORAGE !

lOOx 100x4

1 DR~'i3,.~~1NE 300 II ,I

~'--------+-'-'~---------r---~~-----+---------!-------~ I LO Sq.Km 90 x 90 x 3 DRAINAGE LINE 550 103,

0.5 Sq.Km 90x90x3 103

l-___ ~_ ... __ ~r__.-_~------+---=S:..:T:..:O~RA~GE"---+_--------r_------_1 ! 1.5 Sq.Km 90 x 90 x 3 DRAINAGE LLNE 650 103 I STORAGE L. __ •. _____ ...L.. _______ --'-_.::..:c.=::..:.=_--'-___ --' __ ...... J


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I

, I DRAINAGE LINE ~-~---,

0.5 Sq.Km 70 x 70 x 3 250 103 i ! STORAGE !

I I ---I

1.0 Sq.Km 70 x 70 x 3 DRAL."IAGE LINe 350 I 103 ! STORAGE I I ,

I1.5Sq.Km

I I . DRALNAGE lJNE I , .--- -~

70 x 70 x 3 400 I 103 I STORAGE i

! J I

DRAINAGE LINE I I I O.5Sq.Km 70 x 70x 3 150 102.5 I

I i

STORAGE ! I

.-. ~~'-j LOSq.Km 70 x 70 x3 DRAINAGE LINE

I 200 I 102.5 I

STORAGE I , I i -- -~-~--~-t--~--·~,·- - ----I 1.5 Sq.Km

I

70x 70 x3 DRAINAGE LTh'E 230 I 102.5 I i I I

STORAGE I ~~ ____ ..,.....J


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TABLE II

COST ESTIMATE - EXCAVATED TANK(90 x 90 x 3)

ITEM DESCRIPTION UNIT QIJA.NTITY RA .. TE AMOUNT ($) ($)

1 Mobilisation Item 5,000

2 Clearing oflight to medium vegetation Sq,m 10,000 0,15 1,500

3 Excavation of inlet channel including Cu.m 3,600 0,85 3,060 clearing the site,

4 Excavation of Tank, spoil to \vaste Cu,m 20,800 J 20,800

5 Bund formation on three sides of the tank Cu.m 2,200 1 2~200

6 Rubble packing the mildly sloping side Sq.m 3,500 0.4 1,400

7 Contingencies 4,040

TOTAL 38,000

TABLE 12

COST OF E..XCt\. VATED TANK WITHOlIT BlTND FORMATION

DESCRIPTION

Excavated tank: 60 x 60 x 2,5; depth of cracking clay soil: 2,5m

Excavated tank: 80 x 80 x 3; depth of cracking clay soil: 3m

Excavated tarue 100 x 80 x 3; depth of cracking clay soil: 3m

COST

20,000

28,000

34,000


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TABLE 13

DIMENSION OF TURKEY NEST

NU?vlBEROF Il-lNER RADIUS OUlER RADIUS J-lEIGHT (metrej BANKBATfER I , CATTLE (metre) (metre)

I 200 ~ 6.25 1.1 25 ')-J . , ....... :)

500 4 7.75 1.5 ! 2.5, 2.5 -i 1,000 5 9.25 1.7 ? 5 ? ~

, , ~. , ...... .:) I , -

TABLE 14

COST ESTIMATE OF TURKEY NEST

I I~';,M t ITEM DESCRJJ?TlON IUNITiRATE QUANTITY! ~-'---.

I TOTAL

I I I i AlvfOUN'!: , ,

I I Clearing oflight to medium Sq.m 0.3 3,000 900 , . vegetation and scarifying top soil I

I

lF~cavate tIll ma.terial, transport, fill , . --_. __ ._-

" CU.m 4 800 3,200 ~

i and compact

3 f Provision of outlet pipe and troughs Item I 1,000

4 i Contiingencies Item 1,100 -+-- -~-, 5 , Total 6,000 I

TABLE 15

TRAl'<SFER OF WATER THROJ JGH PIPES

DETAILS OF PI.iMPS AND PIPES

PU1vlP I PIPE SIZE! SUCTION DELIVERY PIPE I DELIVERY: PUI\·'1PING MODEL i CLASS(mm) HEAD(m) HEAD(m) FRICTION I RATE HOURS (1\1ono) ! 1 1

S 800 I

75/9 4.6 i 34 8m1km I 2.15!!s 20 ! 1 1 .

S 800 I 75/9 7.6 27 5mJkm I 1.5IJs I 28 I

I ,

I I S 800 75/6 7.6 I 27 3.6mlkm l.5!!s 28 , -

S 800 I 90/6 7.6 27 1.5m/km I 1.5118 I

28 , , ! ,

I i i ,

S 801 90/6 4.6 27 3.7m/km 2.511s 17 ,

I I . 1


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TABLE 16

SERVICING EQOTPMENT - CQST Ai'lD CAPACITY

Specification for servicing equipment would depend on the size of Turkey Nest and depth of tank. The specification of equipment to serve 400 cattle with three days of storage in the turkey nest, is noted below.

I lNlTIAL COST SOl}RCE OF E1'I'ERGY TYPE OF EQUIPl'vIENT I 2,700 FUEL Centrifugal Pump(Sl!s), 7m head

9,000 WIND Windmill(2S.7Kl!day) - 13 m head --

9,000 SOLAR I Solar Pump(13Kl!day) - 6m head I ~-~- ,


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FIGURES

I


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101ii:P1f

LEGUNE

110N.~.-UlrE

G"lF

NT '?IJ[ Ueg

AOS'lWCOO

TENNANi

) /

,4,i,Ni!."tG}/£ .'ir Pe( .Yilt;

I.MA,\'EifNJ /) NT fIG: S~Q

! \ . ,

./

KATl;ERINE

\ \

CREEK

( ALICE SPRINGS~

/

.

S'-'--// f

GREUORY NATlON.ll PARK

II

<W

LOCA liON MAP LEGUNE

i(~1r.".·rri! I'-=~ .-' I

Fig. 1


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A

,-, 80m ______ ._. __ ._. ___ --.i ,

~-3 ---_-_-_--_-_-_-_--_-_;]_'_-J_u_r,_c-,-,-'--_e_ve_-'_-_-_-:i~_~_-__ ~;;-SCALE Y-, ~

~~- ----------50rr: ----t-'------------som I

H 1

SECTION BB

',0

SCALE Y-, ~ H 1

SECTION AA

---~------10:JJ1' --

B

I -----------.--~

I

! '

B NOT TO SCALE

PLAN

TYPICAL OFF CREEK EXCAVATED TANK

AS :0 !

Fig. 2


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- -10<.5-

LOIVEST POINT OF

SECTION BB NO r 10 SCALE

SECTION AA Nor TO SCALf

. ___ BYWASH '''---. BYIVASH AT R_t m,o "" ~ ~-- I

1040--J S lOflE PH CHING

---.--..,.....-----,-' =====' ~"" , s~~~SCL '1 11'1\ - 100r:-,

, I ' "

c I . , I ~. -~;

: il \ I f- -i i I ·'1 r11

I I j- II ,

:~_ J~ I 103.5 - ------ - -I , i\:; I A--lF - -- - - - - -

f I ; ! ,

r" -: I I

I

~~/ I I 1

: -i ~., , , .

\lAIN IVAll PARAllEL .., TO CONTOUR

PLAN Nor TO SCALE

LEGEND

-

.,

/ /

[-- -

~'"

104.0-- - CQIfTOUR LINE AT Rl.90.C

A .,<"+-\'/All EXTENDS UP '" /;1 StOPE TO RU04.2 L tf .' i !

I - - - --10. 0- - -

~ L !

i

, ~~ .f ~ I ,

~-

;

1t!,=- -=-A -

l: ffJJ.S-- - -

i I : . , : , ; i I

, I

W.J ; ; ,

:

--- 10JO -~-

TYPICAL DRAINAGE LINE (HILLSIDE) STORAGE

Fig 3


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O!I: <:> ~

~

\ I ! I , I I

\TH5 TH4

\

\ , I

\ \

"-r-

I = I-- .~ , r- I -,

I I • ! THl I I I , I , ,

£ / I11II

• THl , TEST HOLE No 1 { •• el

TEST HOLE PLAN FOR AN EXCAVATED TANK

Fig 4


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MAP


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I

( ,

(/

LEGUNE STATION

SURFACE WATER RESOURCES MAP

SCALE 1 500000 km 0 5 10 15 km

DESCRIPTION

Mostly flat ailuvial plains with cracking clay soils. Surface runoff moderate to high. Surface water storage development is economicatl:l feasible.

Gently sloping alluvial plains with leached foamy and sandy solis. SUrface runoff moderate. Surface wat~r storage development is feasibJe where subsoil is suitable,

I ! Gently undulating country on sandstone with Jaterile and sandy soils. SUrface

1_c-3 ____ -r_'_"_n_O_ff __ m_o_d_'_'r_a_'_e __ t_o __ IO_W __ ._s_" __ rt_a_c_e __ W_8 __ le_r __ s_to __ ra_9_e __ d __ e_v_e_IO_p_f11 __ e_"_t_w_O __ "_ld __ d_e_p_e_n_d ___ O_" __ th_e __ -1 .'- subsoil sir.Elta and may not be economically feasible.

4 Estuarine llliluvia! plains with saline soils, and mud. Surface water de .... elopment is not recommended.

__ Ii Hilly countt 'f with ridges, rock outcrop and skeletal soils. Surface water runoff high. Surf-ace w.elter storage dev@iopment is not feasible.

i


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APPENDICES


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APPENDIX 1

EXISTING DAMS al\lD WATERHOLES IN I.EGJ,JNE

l.Stud Paddock Dam:

This is a small excavated tank and it is shallow. It goes dry by August. According to the station manager, about 400 head of cattle water from this tank. It was found that with 300 head of cattle, the demand being fi'om January to July, the reliability of the tank was 80%. This tank was constructed last year. Further excavation is recommended, howcv'er subsoil investigation is required to make sure the soil; is suitable. The excavation should stop well above the rock layer.

2. Snow's Dam:

This excavated t.ank is similar to a drainageline tank and dries up by September. About 250 head of cattle could be fed from this tank on a daily basis over a year with a reliability of 90%. With the non uniform demand as pra·ctised, the demand being from January to August, the dam can cater for 650 head of cattle with a reliability of87%. According to the station manager, it serves 700 head of cattle at present. There is a natural inlet channel to this dam.

3. Billabong Hole:

This is a excavated waterhole. The catchment is alluvium and the topography is gently undulating. The excavated tank dries by June. The tank depth is shallow, and would cater for 100 head of cattle from January to May with 90%, reliability. Subsoil investigation needs to b<! carried out to improve the capacity of the tank.

4. Hill Paddock Dam:

This is an onstream excavated dam. The catchment is of cracking clay soils, and the topography is undulating. The tank dries by September. The tank was built in 1993. the banks were washed out in Feb. 1994 and has been reconstructed now. This can cater for 200 head of cattle on a daily basis from January to August with 90"/0 reliability. It is recommended that a spillway and a spill tail channel be constructed. Any deepening of the dam would depend on the results of the sub soil investigations.

'D ') ~, am~:

This is a waterhole excavated in 1994. It dries in August. This is similar to a drainageline dam and is small, not economical to supply water through out the year. However from January to May it can supply water to a head of 150 cattle with a reliability of90%.


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6. Baker's Dam:

This dam is a gully dam and 6m high. It was constructed in 1994. It has two spillways near the abutments on either side. It was built tor the purposes of irrigation and stock watering. During 94/95 wet it spilled and the water level v,ras 75mm below the crest of the dam. Both the spills were eroded during this wet and rubble packing was done to stop further erosion. It was found that over a year, 800 head of cattle could be fed on a daily basis with 90% reliability. The manager intends to fed 200 caHle and the balance tor irrigation. At present the irrigation demand is not known. It is rec-ommended that the spills be extended to more than 17m each to accomodate a 1 in 5 year flood.

The bund was constructed Ulsing a Dozer, and hence compaction may not be up to the standard. The spill lengths arc inadequate. Since the uls slope of the bund is not protected, the impact of waves resulting in erosion is yet to be seen. This dam is analysed further in Appendix 2.

7. Red Rock Turkey Nest Borrow Pits:

There are four rectangular borrow pits around the Turkey Nest. These pits go dry by June. It was found that 700 head of carti," could be fed from this TN from January to May on a daily basis with 90% reliability. Usually January and February are wet months, and hence the TN can cater for 850 head of cattle with 90% reliability. It is recommended that these pits be further excavated so that they could sture more water. Hmvever subsoil investigation has to proceed before any excavation.

8. Weaner Dam:

This is a typical drainageline dam smail and shallow. It dries up in September It is found that it could supply 200 head of cattle on a daily basis from January to August with 90% reliability. Usually January and February are wet months, and the dam could cater for 250 head of cattle with 90% reliability for a six month daily supply. It is recommended that the dam be expanded and deepened so that it could supply till the end of dry. However deepening will be subject to the availability of suitable subsoil.

9. Corner Dam:

This dam is similar to an exc:avated hillside storage. The bund slopes are steep and weak. It is very likely that proper compaction was not done. The dam goes dry by August. Jt is found that it could cater for 200 head of cattle on daily basis from January to July with 90% reliability. However with the usual wet months of January and February, it could cater for 250 head of cattle. It is recommended that the dam be expanded and deepened. Any further excavation would depend on the results of the subsoil investigation.


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APPENDIX 2

I~LOOD ANALYSIS ON BAKERS DAM

Bakers dam has a catchment area of 6. 71 sq. km., and has two spillways, each with a vvidth of about 6m. The lower spill is 1.5m below the bund crest, and the other spill is I m below the bund crest. Inadequate spill lengths is the cause for heavy erosion ofthe spills during the last wet. Using the thump rule, width of the spill was found to be 60m for a flood of 1 in 50 year return period. The formula used was ",idth = 5(A)O; , A is the catchment area in acres, and width is in feet

The time of concentration was found to be more than 2 hours. Using the Rational furmula, it was found that the peak flow for a return period of 10 years, was 277 m'/s. This was obtained using a coefficient of runoff of. 85 aLnd the corresponding intensity of 48. 7mmibour. The capacity of the dam was computed using the topo sheet contours and the relative approximate measurements taken at site. The catchment was divided into sub catchments and RORB model was applied tDr various rainfall intensities of 1 in 1 0 year return period. In each case the catch ment was assumed to be tull to get the worst case scenario. It was found that a rainfall of 2 Om in duration was found to produce the highest peak flow. The m and kc values were assumed to be 0.8 and 2.6 as recommended by the AR&R. Each spill was assumed to be 20m wide. The peak flow was found to be 308m3!s and was 1m above the bund crest. It is recommended that the spills be increased to more than 17m.


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APPENDIX 3

HYDROLOGIC SOlI, GRill]P AND HYDROLOGIC COl\lTIITION

HYDROLOGIC SOIL GROUP

SOIL GROUP DESCRIPTION OF SOIL CHARA.CTERISTICS

A Soils having very low runolf potential. For example, deep sands with very little silt or clay.

B Light Soils andlor well structured soils having above-average infiltration I when thoroughly wetted. For example, light sandy loams, silty loams. i

I l

C Medium soils and shallow soils having below-average infilttration when I thoroughly wetted. For example, clay loams. I

D I

Soils having high runolf potential. For example, heavy soils, particularly i

clay horizons. clays of high swelling capacity, and very shallow soils underlain by dense I

HYDROLOGJC CONDITHlli:

Native Pasture:

Pasture in poor condition is sparse, heavily grazed pasture with less than half the total catchment area under plant cover. Pasture in fuir condition is moderately grazed and \vith between half and thnoe quarters of the catchment under plant cover. Pasture in good condition is lightly grazed and with more than three quarters of the catchment area under plant cover.


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APPENDIX 4

SITE INVESTIGATIONS

Having determined the suitable catchment(sub section3.5) that supplies the required stock water of reliable quality, the next step would be to locate the most economical site for storing water. The economical site depends on the sub soil strata. The subsoil exploration is earned out to determine the suitability of the site for excavated tank.

I. SUB-SURFACE EXPLORATION:

The purpose of sub-surface exploration for an excavated tank is:

(i) determine th,~ e.xtent of impervious material (li) ascertain the depth of ground water (Iii) reveal the pn~sence of rock (iv) pro .... ide information on subsoil. (v) identification of well graded materials

I.1 Soil Sampling:

The commonly used method of sub-surface exploration is Auger boring. The readily available tool for the work is the standard hand operated 100 mm earth auger with extension pipes. Auger holes to a depth of 4 to 5 m are sunk, and samples of 100 grams of each different type of soil is collected. These samples should be placed in bags, with identification tags for analysis purposes. Excavated tanks should havle, a minimum of five test holes, one in the centre, and the other four positioned in the mid point of each corner as shown in Fig 4. As for the modification of an existing waterhole, auger holes are sunk at SOm apart along the centre of the bed, and 100m apart along the edges ofthe bed. Holes are sunk to a depth of 3m.

2. SEEPAGE LOSS:

Seepage is related to the pn;:sence of pervious soil and the ground water conditions prevailing at the site. The ground water table in the region is at a depth of 8m. Therefore seepage loss depends on the permeability of the soil, as the storage is located well above the water table. A simple test to determine the seepage is the permeability test.

2.1 Permeability Test:

The auger holes already sunk for sub-surface exploration is used for permeability test. Presoak the holc to a depth of 1m below the ground level. Add water to keep the ,vater level 1 m below the ground level, and record the water added. Continue this test for a day. The soil is too permeable if the "''liter added is more than 30 litres per hour. The soil is suitable for excavated tank, if the water added is less than 3 litres per hour. If the rate is between 3 and 30 litres per hour, further investigation is required and would need professional advice.


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3. CLASSJFICATION OF SOILS:

Soils are di,ided into four main groups, namely Gravels, Sands, Silts, and Clays. Jnterms of size, gravel is the largest and clay is the smallest. The size classification is noted below;

gravels: sands silts clays

fi'om 75 to 5 mm from 5 to 0.07 mm from 0.07 to 0.002 mm less than 0.002 mm

Gravels and sands can be id,:ntified easily, but clays and silts when dry cannot be differentiated. Silt is unstable in water.

3.1 Simple te~ts for days and silts:

(a) A simple test to differentiate clay from silt is to wet the sample and feel it. Clay would be sticky. Pin<~h a sample between the thump and fore finger, if it is clay, a thread of diameter 1.5 mm and length 40 mm could be fanned.

(b) A simple test to identifY the water holding qualities of clay is the bottle test. A 750 millilitre plastic bottle is used. The bottom of the bottle is cut open, inverted and filled with powdered dry clay to one third of the volume. The bottle is filled with water. The clay has good water holding qualities, if no water seeps through the soil within 24 hours.

(c) All clays have to be tested for dispersion. Some types of clays tend to breakdown in water torming fine particles. This would lead to high permeability. Dispersion has been the cause of many dam failures. About 5 to 10 grams of dried soil crumbs are dropped into a 100 millilitre beaker filled with distilled \Y<lter. If a halo forms around the soil after an hour, the soil is dispersive.

(d) The percentacge of gravel, sand, silt, and clay in a soil is found by soil classification analysis. This could be done by the CCNT soil laboratory at a nominal cost.


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AppENDLX 5

CONSTR!JCTJON DETAiLS OF EXCAVATED TANKS AND TIJRKEY NESTS

1. CONSTRUCTION OF EXCA V A TED TANKS:

The site investigations as noted in Appendix 4 have to be carried out and satisfied before proceeding with any excavation for construction of off creek or drainage line tanks. This is a square or recta!lgular excavation cut below the natural surface. The site is first cleared of vegetation. The excavated material is usually stockpiled in the form of a bund with a minimum berm width of 20m The tank is fenced on three sides with the bund. Sheepfoot rollers to be used for compaction. This type of fenced excavated tank is economical if the ground slope is greater than 1 percent because there is storage above ground level. This type of storage is known as the hill side storage and is shown in Fig. 3. In most cases the land area is flat, t..'1at the bund does not provide any storage above the ground leveL The top soil should be removed to impervious layer before constructing the bund. Three sides of the tank have a slope of 1 on 3 and the fourth side through which the flow enters the tank, has a milder slope of I on 10. This would allow easy excavation of the tank as machinery would go into the tank, excavate, turn and come out "vith ease. The side through which the flow enters is rubble packed to prevent erosion. Major contractors have the capability of constructing excavated tanks with a batter of 1 on 2.5, but as for a small contractor, the maximum batter they cloud handle is 1 on 3. Rippers could be used to rip Angalari Siltstone, and this is available with major contractors.

The inlet channel details of the off creek excavated tank is shown in Fig. 2. The tank should be located in close vicinity to the creek. The total length of the inlet channel should not be more than I aOm. The initial SOm length of the channel should have a bedslope greater than that of the creek The bedwidth of the inlet channel should be atleast I.S times that of the creek. The bed;,.yidth in the last SOm length increas()s gradually to the width of the tank as shown in Fig.2. This area is rubble packed to stop erosion. A drainage line excavated tank is not fenced with bund. A sedinlent trap is constructed before the tank proper along the flow path.

2. CONSTRUCTION OF TURKEY NESTS:

The black soil that is generally used to construct Turkey Nests, should be well graded. The Soil Sampling and Dispersion test are recommended to check the suitability of soil for bund construction. The soil should have 20 to 35 percent clay, and the balance made up of silt, sand and some gravel. The minimum slope generally recommended is 1 on 2.5 for inside and 1 on 2 for outside. Compacting is done to increase the density of the fIlL There is an optimum water content to achieve the ma.ximum compaction. Vibratory Rollers are used for compaction because of the smallness of the bund but these may not be economical in the remote areas. Compaction is best achieved if the turkey nest is built soon after the wet when the soil is moist. Any heavy machinery available in the station without tracts could be used for compaction, however it would be good if compacting machinery is used. Every 100 mm layer of loose soil is compacted, Minimum amount of water is added to each layer ofloose soil before compaction to achieve the optimum density.


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3. MODIFYlNG WATERHOLES:

Modil}ing an existing water-hole literarily means constructing a narrow excavated tank within the v..aterhole. Typical dimension of this type of storage would be 200 m long, 20m wide and 2.5 m deep. Site investigations noted in Appendix 3 have to be done to check the suitability of subsoil for modifications Tfthe sub-soil is impermeable, non-dispersive, and no rock found within 2m depth, the excavation would be possible with the station ov..ned scraper. However if rippable rock is found, then a suitable machinery with a ripper is needed. The longitudinal batter could be 1 on 3 or less. The cross sectional batter should not be more than 1 on 2.


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APPEN1)IX 6

PIPE NETWORK

Pipes can be made of plastiG ( PVC or Polyihene), or steel. Pol~ihene pipes are the cheapest and easy to install. However they do not withstand very high pressure. Although there are high density polythene pipes, that can withstand high pressure but not to the extent of steel pipes. Polyihene pipes of class 3, 4.5, 6, 9 12, and 15 can withstand pressure upto 30, 45, 60, 90, 120, and 150m head respectively. As the strength of the pipe increases, the cost, and the friction head loss too increases. lfthe drop of a pipe outlet is more than 60m from the storage tank, tben steel pipes are preferred.

The size of the pipes would depend on the flow that is required to be transfered. Also it would depend on the pipe material, the pressure it could withstand, and to a lesser extent on the pipe slope. The strength of a pipe is measured in terms of the pressure it can withstand. It is generally expressed in 'metres head of water'. In other words a pipe line can withstand pressure upto some metres head, the pipeline should not drop more than that number of metres below the highest point unless it is open at the bottom end. Pressure cannot build up in the case of a gravity pipe from a spring to a storage tacnk which is allowed to overflow. If a gravity pipeline experiences too mucb pressure, storage tanks called 'break pressure tanks' could be bulit at intervals. Increase in temperature can reduce the pressure it could withstand lIpto 30%.

Correct pipe laying is an important tactor for an effective pipe network. Pipes should be laid 0.3m deep in a trench. \\'bere the terrain is hard, it should be laid on the ground and covere-d with soil forming a 0.3 high embankment. The main reason for burying plastic pipes are as foHows.

(i) To protect from bushfire (ii) To avoid being exposed by accidental ploughing, and soil erosion. (iii) To keep the pipe temperature below that of the atmosphere.

There are several types of control valves used in the pipe networks. Most commonly used valves in the cattle station are Stop valves, Washout valves, Air release valves, and Pressure control valves. Stop valves are used to force a gate across a pipe line. Air release valves as the name implies is used to release trapped air from the lines. These are found at the highest point on the line. \Vashout valves are used to clear the line, and are located at the lowest point in the line.

surface water storage potential legune station€¦ · 5.3 design criteria for excavated tank 6....

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