Water - South Australia - Water Technical Report
Surface and Groundwater Management, Availability, Allocation and Efficiency of Use
South Australian Technical Report
Surface Water Methodology
Definition of Surface Water Management Area
South Australia has been divided into 34 Surface Water Management Areas. These correspond to 27 AWRC catchment boundaries and are summarised in table 2.
All or parts of four SWMAs have been prescribed under the Water Resources Act 1997. The level of development and regional significance of the resources in these areas has warranted a higher level of management, and authorisation is required to take water. These areas are:
· The Murray River (426.SA1) which is prescribed along its full length in South Australia.
· The Barossa Valley, which lies within the Gawler River (505.2).
· The Clare Valley, which lies within the Wakefield (506) and Broughton (507) catchments.
· The Little Para River channel, which is prescribed for the purpose of maintaining natural recharge to the Northern Adelaide Plains aquifers (S9 and S10).
Four AWRC basins have been subdivided for the following reasons:
1. Basin 239 is divided into four SWMAs to distinguish between sources of the surface flow.
· Millicent 1 is predominately sourced within SA.
· Millicent 2 has a significant Victorian input.
· Millicent 3 is predominately groundwater sourced.
· Millicent 4 has new drainage works in progress and runoff has been assumed to be equal to zero in this audit.
2. Basin 426 is divided into two SWMAs, separating the flow in the Murray River from interstate, and that flow sourced within SA.
3. Basin 505 is divided into three SWMAs
· Light River is a drier catchment and has little irrigation development.
· Gawler River has a heavy irrigation commitment and a large reservoir serving Adelaide’s domestic demand.
· Little Para supplies a large reservoir serving Adelaide’s domestic demand.
4. Basin507 is divided into two SWMAs
· The Broughton River has irrigation and domestic demand.
The Yorke Peninsula has little defined surface water resource.
Compilation of Surface Water Use Data
There are only three areas within the State where the surface resource is prescribed and the use is monitored. These areas include the Murray River, Barossa Valley and Clare Valley. Of these only the Murray River is volumetrically licensed, the remainder are crop area based allocations and use is estimated on an equivalent crop usage rate and area. Long term metered usage data is available only in the Murray River. Short term data of use from farm dams is available in the Clare Valley.
The Prescribed areas make up only a small proportion (by area) of the total surface water development in the State and for completeness an estimate of farm dam development is included in this report.
Apart from the River Murray, development of surface water resources in South Australia occurs almost totally by the construction of farm dams sized typically less than 100 megalitres. A number of surveys have been completed which locate and estimate the size of the existing dams and the potential use from these structures. For this study it has been assumed that an irrigation dam (dam volumes > 5 megalitres) can supply one half of the dam capacity, and a stock and domestic dam can supply one third of its capacity. The developed yield within the catchment is then calculated as the total volume of farm dams multiplied by the possible supply from the dams.
Where domestic water supply reservoirs co-exist in a catchment the developed yield is equated to the sum of urban/industrial consumption from reservoir and the developed yield of farm dams.
Compilation of Surface Water Allocation Data
Only four areas within the 34 SWMAs, the Murray River, Barossa Valley, Clare and the McLaren Vale have a formal allocation. Of these only the Murray River is volumetrically allocated, the remainder are crop area based allocations and use is estimated based on an equivalent crop usage rate and area. This data is stored Department for Water Resources license database.
| SWMA | Type of Allocation | Volume Allocated | |
|---|---|---|---|
| Murray River | 426.1SA | Volumetric | 736,000 ML/year # |
| Barossa Valley | 505.2 | Area based | 2750 ML/year * |
| Clare |
506 & 507.1 |
Area based | 1500 ML/year * |
| McLaren Vale | 503 | Area based | Not defined yet. |
| Little Para | 505.3 | Prohibits diversion | No use allocation. |
Table 1 Water Allocation Data in South Australia
* Volumetric allocation calculated based on crop equivalents.
# Volumetric allocation limited by MDBC cap
Adelaide domestic water supply information and Domestic supplies from the Murray River were drawn from DWR annual report "Water Use, Annual Returns".
Remaining use is estimated based on the estimated volume of farm dams within the SWMAs.
Hydrological Characterisation
The key stream gauging stations were chosen on quality of record and location within the catchment. In many cases there was only one gauging site suitable to define the surface resource of the SWMA.
For information in table 2, data reliability codes, indicating the suitability of the gauging network for measuring streamflow, were defined as a category from A to D. These categories are:
· Category A) indicates a good network of gauging stations that enable direct measurement of flow both upstream and downstream of major storage. Some interpolation was required where Murray River water is imported into the catchment and where SA Water use from the main reservoirs occurs. Current and natural flows were calculated here by a combination of direct measurement and interpretation of other measured externals.
· Category B) indicates a limited gauging network but the available gauging stations were well positioned to give an accurate measurement of flow. Limitations of estimates at these sites would be the spatial variation of flow within the catchment and a measured recording of flow leaving the basin. Little information is available of spatial variation within the catchment and losses that occur. Current flow was estimated as the recorded flow plus an estimated contribution from areas downstream of the gauge. Natural flow was calculated estimating the amount of water trapped in farm dams and reservoirs and adding this to the current flow.
· Category C) indicates a limited gauging network with more than 50% of the management area ungauged. These management areas required significant interpolation to infill and estimate streamflow. Current flow in the ungauged areas was infilled using correlation with local gauged subcatchments. Natural flow was calculated estimating the amount of water trapped in farm dams and reservoirs and adding this to the current flow.
· Category D) indicates very limited gauging within the management area and requires significant interpolation to infill. In these areas farm dam information was generally not available and no estimation of natural flow was attempted.
Where gauging sites were not available or where a significant proportion of the catchment was ungauged, stream flow was derived using a computer model utilising local rainfall.
Stream gauging information is held in DWR database (Hydsys), and rainfall data used was a mixture of Bureau of Meteorology daily rainfall stations and DWR pluviometer stations.
Mean Annual Flow and Mean Annual Outflow
The methods used to provide the monthly flow data and determine the mean annual flow varied depending on the availability of gauging station information (refer, hydrological classification above).
Typically the gauging station furthest downstream was assessed over the 20 year period 1978 to 1997. This period of record was maintained for all of the SWMAs to ensure an unbiased comparison.
Where sufficient gauging data was not available, either due to limited record, or the station location not being representative of the total catchment, a computer model of the catchment was used. The model was calibrated on known data and then use to infill missing record.
In many catchments in the State - particularly those in the Mid to Far North- there are significant losses between where the flow is generated and where it is discharged to the sea or inland water body. In most cases, no gauging station information was available to define these losses. Because of this, the mean annual outflow is simply assumed to be the volume measured at the best available gauging site.
A comparison of mean annual flow is not considered to be an appropriate indicator of resource availability in SA. This is particularly true for the Far North of the State where mean flows overstate the resource capability of the region.
| Basin No | Surface Water Management Areas | Data Reliability Category | Mean Annual Current Flow ML/year | Use Cat. | Mean Annual Natural Flow ML/year | |
|---|---|---|---|---|---|---|
| 1 | 001 | Georgina River | na | 0 # | na | 0 # |
| 2 | 002 | Diamantina River | B | 953,000 ** | 1 | na ** |
| 3 | 003 | Cooper Creek | B | 1,120,000 ** | 1 | na ** |
| 4 | 004 | Lake Frome | D | 410,000 ++ | 1 | 410,000 |
| 5 | 005 | Finke River | D | 0 # | na | 42,000 |
| 6 | 007 | Hay River | na | 0 # | na | 0 # |
| 7 | 021 | Gairdner | na | 0 # | na | 0 # |
| 8 | 022 | Nullabor | na | 0 # | na | 0 # |
| 9 | 023 | Warburton | D | 0 # | na | 25,000 |
| 10 | 026 | Mackay | na | 0 # | na | 0 # |
| 11 | 238 | Glenelg | na | 0 # | na | 0 # |
|
12 13 14 15 |
239 |
239.1Millicent Coast region 1 239.2 Millicent 2 239.3 Millicent 3 239.4 Millicent 4 |
A B D na |
209,000 16,000 151,000 0 # |
1 1 1 1 |
209,000 16,000 151,000 0 # |
| 16 | 414 | Mallee | na | 0 # | 1 | 0 # |
|
17 18 |
426 |
426.1 River Murray 426.2 RM catchment |
A C |
7,220,000 ** 121,600 |
3* 1 |
13,900,000 ** 131500 |
| 19 | 501 | Fleurieu Peninsula | C | 118,400 | 1 | 121,000 |
| 20 | 502 | Myponga River | A | 2,900 | 4 | 17,400 |
| 21 | 503 | Onkaparinga River | A | 63,000 | 4 | 114,400 |
| 22 | 504 | Torrens River | A | 101,500 | 4 | 145,600 |
|
23 24 25 |
505 |
505.1 Light River 505.2 Gawler River 505.3 Little Para |
C A B |
22,900 31,100 2,200 |
2 4 4 |
24,400 65,200 10,000 |
| 26 | 506 | Wakefield River | B | 9,200 | 2 | 10,500 |
|
27 28 |
507 |
507.1 Broughton R. 507.2 Yorke Pen. |
C na |
61,500 0 # |
2 na |
65,000 0 # |
| 29 | 508 | Mambray Coast | D | 38,000 ++ | 2 | 38,000 |
| 30 | 509 | Willochra Creek | B | 7,800 ++ | 2 | 7,800 |
| 31 | 510 | Lake Torrens | D | 63,000 ++ | 1 | 63,000 |
| 32 | 511 | Spencer Gulf | na | 0 # | na | 0 # |
| 33 | 512 | Eyre Peninsula | C | 26,200 | 2 | 30,000 |
| 34 | 513 | Kangaroo Island | C | 240,000 ++ | 1 | 240,000 |
Table 2 Surface Water Management Areas in South Australia
** Most of the flow generated outside of the State
# Resource limited and therefore assumed 0, no assessment made.
++ No use information available, assumed that current = natural flow.
na no assessment
Developed Yield
Farm dams were included in the South Australian work for the National Land and Water Resources Audit (NLWRA) as they represent the majority of the new surface water development in the State. The concept of sustainable yield as provided in the audit was difficult to apply to such structures because of the high evaporation losses expected and the low security of supply at which farm dams operate. Catchments containing large reservoirs were treated in a similar manner to those with only farm dam development.
Developed yields of Adelaide’s water supply reservoirs and the irrigation use from the Murray River have been accurately metered. Use from the remainder of the surface water is primarily from farm dams and this has been estimated using the procedure described in the section "Divertible yield" below.
A number of surveys have been completed which locate and estimate the size and potential use from farm dams. Volume of farm dam storage was estimated by measuring the surface area of farm dams from aerial photographs and using a simple formula to convert the areas to a volume. In the prescribed SWMAs of the Barossa and Clare Valleys the calculated volumes of the irrigation dams have been verified with license information.
The developed yield from farm dams has been estimated as no usage information currently exists. Studies of two South Australian Surface Water Prescribed Areas in the Barossa and Clare Valleys identified that the divertible yield ultimately depends on annual rainfall, the amount of unregulated area in the catchment, dam size and design, all of which may vary significantly. The studies indicated that 30-50% of the annual volume captured in a farm dam could be diverted on a reasonably consistent basis. The remaining 50 to 70% of dam capacity was lost as evaporation, recharge/leakage or could be accounted as carry over volume and unfilled storage. For this audit it has been assumed that the developed yield of an irrigation dam (a dam with volume exceeding 5 megalitres) equals one half of the dam capacity, and for a stock and domestic dam, one third of its capacity.
Where domestic water supply reservoirs co-exist in a catchment the developed yield is equated to the sum of urban/industrial consumption from reservoir (which is metered) and the estimated developed yield of farm dams.
Current use has been assumed to equal the developed yield in South Australia. Adelaide's water supply reservoirs currently operate at full capacity with limited carry over. Shortfalls are supplied from the Murray River. In a good year local catchments can just supply Adelaide's total requirement, but in dry years this share may fall below 10% of demand. Farm dams are typically utilised as an opportunistic supply. Farm dams are either used for crops that can sustain a low reliability of supply or where a back up supply is available, usually groundwater, to supplement their use over dry years.
Divertible Yield
The divertible yield for farm dams is calculated as being a fraction of the median annual flow of the sub-unit.
Studies of two South Australian Surface Water Prescribed Areas in the Barossa and Clare Valleys indicated that the maximum total volume of farm dam development within a catchment should not exceed 50% of the natural median annual runoff. The studies also showed that 30-50% of the annual volume captured in a farm dam could be used on a reasonably consistent basis (see section on “Developed Yield”).
Based on this knowledge, the divertible yield from surface water management areas (SWMA’s) was taken as 25% of the median annual runoff from the SWMA. This figure has become widely accepted in controlling farm dam development in South Australia and represents a reasonable estimation of expected rates of supply.
Where domestic water supply reservoirs co-exist in a catchment the total divertible yield was equated to the sum of urban/industrial consumption from reservoir and the divertible yield of farm dams.
Environmental Flow Requirements
The limit on farm dam development, defined in divertible yield above, aims to ensure that environmental flow requirements of the catchment are met. This limit has been adopted as a means of determining the environmental flow requirements at least until more information from environmental flow studies becomes available.
A number of studies targeted at assessing the environmental flow requirements of ephemeral streams under the maximum permitted levels of farm dam development (50% median natural runoff) have been initiated. Preliminary results based on limited data indicate that while such levels reduce the mean annual flow in the order of 20%, the environmental flow requirements are maintained. Monitoring procedures are currently being developed to enable environmental flows to be more accurately assessed.
Sustainable Yield
The sustainable yield has been equated to the divertible yield as this takes the environmental flow requirements into account.
A number of studies targeted at assessing the environmental flow requirements of ephemeral streams under the maximum permitted levels of farm dam development (50% median natural runoff) have been initiated (see section on environmental flows).
Categorisation
Catchment categorisation follows the definition provided in the Project Specifications.
The use and allocation categories adopted were:
· Category 1 - Use or allocation < 30% sustainable yield. Most of the available resource is undeveloped.
· Category 2 - Use or allocation between 30 and 70%. Still significant potential for development.
· Category 3 - Use or allocation between 70 and 100% sustainable yield. Limited development potential.
· Category 3* - Use or allocation = 100% of sustainable yield. No development potential.
· Category 4 - Use > 100%. The resource is over used or allocated.
Where little use information was available a best estimate was made based on known development in SWMAs of similar rainfall. Most Far-North areas have been defined as use category one. Willochra creek was assumed to be use category 2 based on rainfall similarities between it and the Light River.
Salinity categorisation similarly follows the definition provided in the Project Specifications. The salinity categories adopted were:
· Fresh < 500mg/L
· Marginal 500 to 1500 mg/L
· Brackish 1500 to 5000mg/L
· Saline 5000 to 14000 mg/L
The use of straight averages or medians does not give the true picture of water quality available for development in South Australia. When large flow occurs the water quality is predominately fresh but deteriorates rapidly on the flow recession.
To ensure this fresh to marginal water was identified, flow weighted averages were used. The salinity percentages provided in the study define the potential availability of large volumes of low salinity water even though it may only occur over one or two days in the year.
Management Goals and Objectives
The management goals and objectives are comprehensively defined in the State Water Plan and the Water resources Act,1997.
The surface water resources within the State are required to be managed in such a way that those who rely on the resource will obtain the best environmental, social and economic gain from them, whilst not compromising the ability of future generations to enjoying the same benefits. The South Australian Water Resources Act 1997 places prime importance on protecting water resources against the detrimental effects of use and development and preserving ecosystems that depend them.
Groundwater Methodology
Definition of Groundwater Management Unit Boundaries
South Australia has been divided into fifteen groundwater provinces. A groundwater province is defined as a major area having a broad uniformity of hydrogeological and geological conditions, with reasonably uniform water bearing characteristics, and identified as either predominantly sedimentary or fractured rock. A province may include several, independent or mutually dependent, aquifer systems; and may have a partial cover of surficial sediments (1985 Review of Australia’s Water Resources and Water Use).
The Groundwater Management Units (GMUs) within South Australia are defined either by hydrogeologic boundaries, legislative boundaries, or by the intensive level of abstraction within a defined area. The unincorporated areas (UAs) are defined on a province scale. A number of GMUs with small sustainable yields (the smallest being Penong with 2 ML/year) have been defined to highlight the importance of smaller groundwater resources within South Australia.
Thirty of the thirty-six GMU boundaries are legislative boundaries, formally managed either as Prescribed Areas, Notice of Restriction Areas (under the Water Resources Act 1997), or Water Protection Areas (under the Environment Protection Act 1983). The remaining six GMU boundaries are based on areas of intensive groundwater abstraction, or sediment boundaries. A GMU refers to only one aquifer or a group of interconnected aquifers. In some cases, one GMU may overlie another GMU.
The area of the province, which has not been classified as a GMU, has been defined as the unincorporated area (UA). As with the GMUs, an UA refers to only one aquifer or group of interconnected aquifers, and one UA may overly another UA. The unincorporated areas of the Adelaide Geosyncline have been separated based on water quality. The UA-Mt Lofty Ranges contains lower salinity groundwater than the UA-Flinders Ranges.
Where a GMU or UA overlies another, a numerical suffix has been appended to the name. The upper is represented by the suffix ‘1’ and the lower represented by the suffix ‘2’.
A nominal average thickness of 200 m has been given for fractured rock aquifers. It should be noted that the actual thickness of the sedimentary aquifers might depart considerably from the average value.
A summary of provinces, GMUs and UAs for South Australia is given in the following table.
| Province Name | GMU/UA Name | Boundary |
|---|---|---|
| Adelaide Geosyncline | Barossa Valley Sediments | Part of Prescribed Area |
| Barossa Fractured Rock | Part of Prescribed Area | |
| Clare Valley | Prescribed Area | |
| Booborowie Valley | Sediment Boundary | |
| Willochra Basin | Sediment Boundary | |
| Walloway Basin | Sediment Boundary | |
| Unincorporated Area - Mt Lofty | Province below Barossa GMUs | |
| Unincorporated Area - Flinders Ranges | Province above Barossa GMUs | |
| Kangaroo Island | Unincorporated Area | Province |
| St Vincent Basin | Northern Adelaide Plains (NAP)-T1 | Prescribed Area |
| Northern Adelaide Plains (NAP)-T2 | Prescribed Area | |
| Adelaide Metropolitan-T1 | Sediment and NAP Boundary | |
| Adelaide Metropolitan-T2 | Sediment and NAP Boundary | |
| Willunga Embayment | Prescribed Area/Sediment Boundary | |
| Unincorporated Area | Province | |
| Pirie Basin | Unincorporated Area | Province |
| Torrens Basin | Unincorporated Area | Province |
| Murray Basin | Angas Bremer | Prescribed Area |
| Mallee-1 | Prescribed Area | |
| Mallee-2 | Prescribed Area | |
| Marne | Notice of Restriction Area | |
| Tatiara-1 | Prescribed Area | |
| Tatiara-2 | Prescribed Area | |
| Padthaway-1 | Prescribed Area | |
| Padthaway-2 | Prescribed Area | |
| Naracoorte-1 | Prescribed Area | |
| Naracoorte-2 | Prescribed Area | |
| Tintinara-1 | Notice of Restriction Area | |
| Tintinara-2 | Notice of Restriction Area | |
| Unincorporated Area-1, Murray Group Limestone | Province | |
| Unincorporated Area-2, Renmark Group | Province | |
| Otway Basin | Comaum Caroline-1 | Prescribed Area |
| Comaum Caroline-2 | Prescribed Area | |
| Lacepede-Kongorong-1 | Prescribed Area | |
| Lacepede-Kongorong-2 | Prescribed Area | |
| Eyre Peninsula | County Musgrave | Prescribed Area |
| Southern Basins | Prescribed Area | |
| Unincorporated Area | Province | |
| Great Artesian Basin (GAB) | Curdimurka (Wellfield A) | Prescribed Area |
| Muloorina (Wellfield B) | Prescribed Area | |
| Total GAB | Province | |
| Gawler Craton | Penong | Water Protection Area |
| Robinson Basin | Water Protection Area | |
| Carribie Basin | Water Protection Area | |
| Para Wurlie Basin | Water Protection Area | |
| Unincorporated Area | Province | |
| Eucla Basin | Unincorporated Area | Province |
| Officer Basin | Unincorporated Area | Province |
| Peake Denison | Unincorporated Area | Province |
| Hamilton Sub-Basin | Unincorporated Area | Province |
| Musgrave Block | Unincorporated Area | Province |
Table 3 A summary of provinces, GMUs and UAs for South Australia
Groundwater Abstraction
There are 17 groundwater resource areas (26 GMUs) either prescribed or are Notice of Restriction areas under the Water Resources Act, 1997. In these areas the level of water resource development and regional significance have warranted a higher level of management than other areas of the State. Authorisation is required to take water in these areas. An annual groundwater use of 343500 ML/year is recorded within the prescribed areas and is summarised in table 4. The majority of the use in the State is measured using crop areas and crop usage equivalents.
|
Type of Allocation/ Measurement |
Abstraction ML/year |
|
|---|---|---|
| Comaum-Caroline | Crop Area Based | 33,800 ML * |
| Tatiara | Crop Area Based | 60,900 ML * |
| Naracoorte | Crop Area Based | 41,000 ML * |
| Padthaway | Crop Area Based | 24,200 ML * |
| Lacepede-Kongorong | Crop Area Based | 84,700 ML * |
| Tintinara | Crop Area Based | 25,500 ML * |
| Mallee | Crop Area Based | 17,500 ML * |
| Great Artesian Basin (2 areas) | Volumetric | 11,000 ML # |
| Angas Bremer | Volumetric | 1,700 ML |
| Barossa Valley | Volumetric | 4,400 ML |
| Northern Adelaide Plains | Volumetric | 18,400 ML |
| McLaren Vale | Crop Area Based | 6,500 ML ** |
| Clare Valley | Crop Area Based | 2,650 ML * |
| Southern Basins (Eyre Pen) | Crop Area Based | 10,300 ML* |
| County Musgrave (Eyre Pen) | Crop Area Based | 900 ML * |
| Total | 343450 ML |
Table 4 Groundwater Abstraction Information
# Use not including flowing bores
** Use limit, allocation currently being negotiated
* Volume calculated based on crop equivalents
Groundwater Allocation
Within the prescribed areas of the State the total volume allocated is 638,550 megalitres, the majority of which is located in the Millicent Coast region.
Level 2 usage data is generally available in areas with area based allocation systems but less so where volumetric systems are used. Area based systems however do not provide accurate measurement of use.
The gradual conversion to volumetric allocation will likely mean that level 2 data will become less available.
| Type of Allocation |
Volume of Allocation ML/year |
|
|---|---|---|
| Comaum-Caroline | Crop Area Based | 69,800 * |
| Tatiara | Crop Area Based | 90,500 * |
| Naracoorte | Crop Area Based | 78,700 * |
| Padthaway | Crop Area Based | 35,100 * |
| Lacepede-Kongorong | Crop Area Based | 178,100 * |
| Tintinara | Crop Area Based | 25,500 ** |
| Mallee | Crop Area Based | 35,900 * |
| Great Artesian Basin (2 areas) | No Allocation | 60,000 # |
| Angas Bremer | Volumetric | 6,500 |
| Barossa Valley | Volumetric | 5,200 |
| Northern Adelaide Plains | Volumetric | 26,500 |
| McLaren Vale | Crop Area Based | 6,000 ** |
| Clare Valley | Crop Area Based | 2,650 * |
| Southern Basins (Eyre Pen) | Crop Area Based | 12,100 ** |
| County Musgrave (Eyre Pen) | Crop Area Based | 6,000 ** |
| Total | 638550 |
Table 5 Summary of Groundwater Allocation in South Australia
# Use limit, including flowing bores
** Use limit, allocation currently being negotiated
* Volume calculated based on crop equivalents
Selection of Key Monitoring and Major Abstraction Bores
Key monitoring bores for the National Land and Water Resources Audit have been selected using the following criteria:
· Good spatial representation of aquifer (or aquifer of major use, in areas where a complex and interconnected series of aquifers exist)
· Part of existing groundwater monitoring network
In areas of concentrated pumping
Groundwater Level Change Assessment
Monitoring bore water level data is stored in the Department for Water Resources State Groundwater Database. Changes in groundwater levels are assessed from hydrograph trends, combined with climatic and recharge event data, and expert knowledge of the resource.
Declines in groundwater levels are evident in parts of South Australia. The declines are attributed to lower than average rainfall, and intensive pumping, which may be in excess of the sustainable yield in some small discrete areas.
Rising water levels are evident in some GMUs in the upper south east of the State. This can be attributed to increased vertical recharge, following native vegetation clearance, and the loss of high water use lucerne pastures.
There is a clear link between seasonal rainfalls and groundwater levels. Water levels are generally highest during September/October following winter recharge, and lowest in April/May following summer abstraction and natural discharge. During late 1992 and early 1993, higher than average rainfalls were recorded and as a result groundwater levels were generally high. Since 1992, rainfall has been below average, resulting in declines in water levels in many areas.
Groundwater Salinity Determination
Monitoring bore salinity data is stored on the Department for Water Resources State Groundwater Database. Salinity is measured in electrical conductivity, and conversion to total dissolved salts (mg/L) is undertaken using a non-linear conversion scale developed by the State Water Laboratory.
Average salinities for the GMUs, vary between 650 and 3800 mg/L and the average salinities for UAs vary between 1500 and 14 000 mg/L. Maximum salinities in the UAs range between 5000 and 100 000 mg/L.
Salinity data indicates large seasonal variations, due to lower than average rainfall, recycling of irrigation waters, flushing of the unsaturated zone salts due to clearing, and intensive pumping.
Some of the monitoring bores used to measure salinity are production bores. It is probable that regional salinity increases (in some areas) result from pumping induced stresses on the overlying confining beds, causing leakage of groundwater from adjacent more saline aquifers.
Sustainable Yield
The following general definition for sustainable yield has been used in most cases:
The groundwater extraction regime, measured over a specified planning timeframe that allows acceptable levels of stress and protects the higher value uses associated with the total resource.
Sustainable yield is determined by the rate at which groundwater can be pumped without causing:
· Long term decline of potentiometric surface (or watertable)
· Undesirable effects – such as salinity increases. This may mean extraction rates less than recharge as sustainability from the salinity view point may be considerably less than sustainability from the hydraulic perspective
For sedimentary aquifers where abstraction data exists, sustainable yield has been determined using water level, salinity and metering records in combination with recharge analysis involving rainfall recharge estimates, lateral throughflow estimation, chloride analysis, and numerical groundwater modelling.
Very little is known about how water is stored and transported in fractured rock aquifers. In fact, there are no reliable methods for estimating sustainable yield from them. Fractured rock aquifers are characterised by high spatial variability in hydraulic conductivity, making traditional hydraulic methods for estimating groundwater flow difficult to apply. Specific yield may also be extremely variable and difficult to measure, making groundwater recharge estimation from hydrographs unreliable. Sufficiently accurate data on aquifer thickness or porosity is generally not possible for reliable determination of aquifer storage. For these reasons, numerical values given for sustainable yield are an estimate.
In fifteen GMU/UA areas, sustainable yield investigations have not been conducted, and the numerical value given for sustainable yield has been based on estimated abstractions, or an educated guess.
Mining of groundwater has been included in the sustainable yield estimate for the unconfined aquifer of the Mallee. The existing permissible annual volume for the Mallee is based on components of recharge, lateral throughflow and groundwater mining. The resultant drawdown is 5 cm/year averaged over the whole region. The current controlled mining policy for irrigation extraction is forecast to deplete the resource by up to 15% over the next 300 years.
Ecosystems are included in the sustainable yield estimation for the Great Artesian Basin. In the two formally managed areas within the GAB, Curdimurka and Muloorina Prescribed Well Areas, groundwater extraction is subject to restrictions including drawdown limits, which ensure the protection of ecologically significant mound springs nearby. In other GMU/UAs, greater emphasis will be placed on sustainable yields, particularly to ensure the maintainence of stream baseflow, in future water allocation plans as the environmental requirements become clearer. In the Mt lofty ranges for instance, the sustainable yield has been set at 75% of the recharge, to account for environmental flows in streams.
Categorisation
The criteria used to categorise a GMU/UA are a combination of the major and minor definitions of categorisation defined in the Project Specifications. In the absence of abstraction or allocation data, categorisation has been based solely on the minor definitions of categorisation defined in the Project Specifications.
Category 1-Most of the available water resource undeveloped/unused.
Category 2 - Significant potential for future infrastructure development and additional water use.
Category 3 - Can sustain only minor future infrastructure development and additional water use.
Category 3* - No further development. Development has reached sustainable level
Category 4 - Current use unsustainable.
The GMU/UA areas of the State are categorised by use as follows:
· 37% Category 1
· 23% Category 2
· 12% Category 3
· 24% Category 3*
· 4% Category 4
Allocations are made in 26 of the GMUs (prescribed areas) and the allocation is categorised as:
· 0% Category 1
· 19% Category 2
· 26% Category 3
· 48% Category 3*
· 4% Category 4
Management Goals and Objectives
The management goals and objectives are comprehensively defined in the State Water Plan and the Water Resources Act,1997.
There is a strong demand for water to support economic development. The State has sufficient water for our present and future needs, provided that we are careful, flexible and innovative in the use of our water resources and water infrastructure. As development continues we must ensure that environmental water needs are being met. Over committing water resources before their sustainable limits or environmental water requirements are known could threaten long term sustainable use.
Assessment of Joint Groundwater and Surface Water Use
There are two areas of the State, Barossa and Clare Valley, which are prescribed for both surface and groundwater resources. Rules for aquifer recharge are currently in their developmental stage. Currently, credits for artificial recharge are recognised in Angas Bremer (groundwater prescribed), Barossa Valley and Clare Valley. A licence allocation is granted for a fraction (ranging for 60 to 100%) of the measured water recharged.
Artificial recharge has been successfully utilised to supplement aquifer supply in the Angas Bremer prescribed area for many years and presently there are 26 ASR trials being carried out in the Barossa Valley. The potential and risk of artificial recharge of sewage effluent and stormwater is currently being examined in the Northern Adelaide Plains and McLaren Vale with a view to reuse sewage effluent that is currently discharged to the ocean in winter. This carries the added benefit of reducing the environmental impact to our coastal marine environments.
Streamflow from the Mt Lofty and Flinders Ranges often occurs rapidly. The diversion of some of this flow to settlement ponds and thence to underground aquifers (both alluvial and fractured rock) could supplement current groundwater extractions that are close to sustainable limits. The lower salinity stream flows could also be used to improve the quality of saline groundwater.
In many areas of South Australia it is common for irrigators to have more than one source of water. The farm dams often provide the better quality water but at a lower reliability than local groundwater. The mixing of the two waters provides the optimum supply.
Alternatively the use of surface water when it is available allows the recovery of the groundwater for use during stream drought years.
Development Potential
Demand for Water
About 1100 GL per year of our water resources are currently extracted for use in the developed areas of the State. Improved management of irrigation use is estimated to have the potential to at least double the productivity of current water use by better meeting crop requirements with water applications and by choice of higher value crops, where water quality and other conditions permit.
It is estimated that a further 925 GL of natural resources per year could be developed for sustainable uses, 75% of which is contributed by South East groundwater. Unused water resources within the River Murray cap on extractions (70 GL per year) makes up about half of the surface water with potential for development. In addition, the reuse of stormwater and sewage effluent also will provide significant development potential, but this has not been assessed in this study.
Constraints to Development
Limited resource availability
The level of development of many of our prescribed water resources is approaching or has reached the sustainable level and usage has been limited to this level. In some cases, the sustainable limit has been exceeded, and these areas are continually assessed to ensure that salinity and water level or pressure remain at acceptable levels.
Water resources which are available in some areas are being transferred to areas of need
through innovative use of existing pipeline and storage infrastructure.
Pollution of resources
The Mount Lofty Ranges, is already subject to development which pollutes the streams, has
undergone substantial farm dam development and has suffered extensive stream ecosystem
degradation. Significant water quality impacts have been measured in the metropolitan water supply catchments, the Watershed.
Salinisation of resources
The Murray River, a major water supply source for urban and irrigation uses, is subject to
increasing salt loads from its catchment which will lead to significant increases in salinity in the coming decades.
Extensive clearing of the agricultural areas of the State has led to land salinisation and
erosion of catchments and stream beds, with consequential impacts on the productivity of the land and the health of streams.
Environmental Impact
The Murray Rivers ecosystems have been altered by significant flow reduction, change in flow patterns and pollutant discharges, that have led to such symptoms of degradation as constriction and closure of the Murray Mouth and more frequent toxic algal blooms.
Farm dam development has the potential to significantly impact on the environmental requirements of streams.
The highly valued water supplies and ecosystems supported by the Lake Eyre Basin and Great Artesian Basin will be placed at risk if development is not carefully controlled.
Polluted urban discharges to Gulf St Vincent and altered flow regimes in our rivers have
degraded our estuaries and coastal marine environments.
Many resources are already completely allocated
Much of the South East groundwater and the River Murray are, effectively, fully allocated. However, there is still considerable scope for further development of these water resources through improved operation of the water allocation transfer market. The indicative price for permanent transfer of water allocations ranges from $800/ML to $1200/ML for these areas, but can be five or more times this in areas of shortage where high value crops are grown.
Improved Irrigation Management
Improved management of irrigation use is estimated to have the potential to at least double the productivity of current water use by better meeting crop requirements with water applications and by choice of higher value crops, where water quality and other conditions permit.
Non Traditional Resources
The non-traditional water resources make up the majority of un-allocated water resources which are amenable to development. Treated sewage effluent is one which is being developed in recent times. Up to 45 GL per year is planned to be delivered to supplement existing irrigation development based on groundwater on the fringes of the metropolitan area. The potential to treat and re-use stormwater is being explored in conjunction with aquifer storage and recovery techniques to enable this resource to be made available when there is a demand for it.
Forecast Use
In January 1997 the South Australian Premier launched the State Food Plan – Towards 2010, through which the South Australian food industry plans to grow to $15 billion a year by 2010. This target will be met by creating a responsive environment and maintaining a commitment to innovation, value adding, education, investments and building an international reputation as a supplier of safe quality food.
Of the $15 billion dollar target, $4 to $5 billion is to be achieved through better use of existing resources such as more efficient use of water.
The forecast water use estimates used for the audit were taken from “Water and the Australian Economy”, Australian Academy of Technological Sciences and Engineering. The report subdivides South Australia into 4 areas.
| Area |
Growth Rate (% per year) |
|---|---|
|
Murray Darling in South Australia South East Coast of South Australia Adelaide and Hinterland South Australia, Eyre Peninsula and North |
1.7 2.1 1.4 1.8 |
Table 5 Growth rates of water use assumed in NLWRA
The report indicates little difference between “no water availability constraint” and the “water stressed” scenario at least to 2020. In reality this is unlikely as many areas are already heavily allocated and constraints on the transfer such as cost, salinity or local drawdown issues may severely effect resource availability. In addition the continual review of sustainable yield, as more information on actual water use becomes available, may ultimately indicate that less water is available than is currently estimated
There are considerable volumes of water within some prescribed areas that are allocated and either used in part only or not at all. Improved irrigation practice and a more flexible and sophisticated water entitlement market will become critical factors in supplying water to meet predicted developments. The price demanded for permanent transfer of a water licence rapidly increases as the developing prescribed areas approach their full allocation.
The growth rates defined in table 5 were used with the following exceptions.
1. The projections for Adelaide, based on the Australian Bureau of Statistics Series 1 model, indicate Adelaide’s population will increase from 1088000 to 1189000 in 2050. SA Water has a diversion license for an average use of 130 GL/year with spare capacity of 19GL/year which is sufficient to meet the projected development. Further development may require the transfer of an interstate water license to South Australia or incorporate the use of alternative supplies of water such as stormwater and sewage effluent. In addition the volume of water demanded per person is continually falling as urban consolidation takes place and garden areas reduce, and homes utilise water efficient technologies. The growth rate for Adelaide is closer to 0.04%
2. Country Towns are currently showing a stable to declining population. Zero growth rate was assumed for towns in South Australia.
3. Resource Development in the Mid-North, Northern areas and Eyre Peninsula is difficult to assess. This development is likely to be for mining or processing industries and the location throughout the region will depend on the location of the industries rather than availability of water. In addition the available resources and the potential environmental impact within these areas is not well understood, and highlighting certain areas as having development potential would not be appropriate.
The Great Artesian Basin was defined as having no development potential due to the large volumes of water lost by flowing wells. Development is possible once rehabilitation of these wells is completed.
Data and Information Gaps
· Assessments need to be conducted to quantify environmental needs of both surface water and groundwater.
· Monitoring data is available for most developed areas for at least 20 years but over much of the State data is limited.
· Existing regional groundwater monitoring networks need to be reviewed to ensure adequate spatial distribution, and correct well construction. Installation of automated monitoring equipment is recommended, at specific groundwater sites, to enable more accurate determination of water level fluctuation resulting from pumping or recharge. Continuous salinity information is required on surface water monitoring.
· The surface water monitoring network must be reviewed to ensure that the future monitoring requirements, as defined by the Water Resources Act and the State Water Plan, are met.
· Sustainable yield investigations have been conducted in some areas. These values need to be reviewed as new techniques become available, and as the definition of sustainable yield develops. Investigations need to be conducted in areas where the sustainable yield is unknown.
· Metering of production bores and farm dams is carried out in a limited number of developed areas. Most areas are unmetered. Abstraction volumes for unmetered areas are estimated using information collected from licensees, aerial photographs, and irrigated crop water requirements. Metering is likely to be implemented as part of future groundwater and surface water resource management.
· Insufficient knowledge exists regarding aquifer interconnection in some areas. Hydrogeological investigations should be conducted to increase the level of understanding regarding interconnectivity, and the resultant effects following aquifer development.
· Insufficient information exists regarding the nature and extent of aquifers in some areas. Investigations should be conducted to increase the knowledge of groundwater resources.
Insufficient knowledge exists regarding surface/groundwater interaction. Investigations should be conducted to improve understanding and ensure resources are not over allocated.
Data Management
The Department for Water Resources manages surface water resource data. Licence use and allocation and the stream gauging network are readily available in database form.
Data is currently used to assess the impact of use in prescribed areas, resource evaluation for Adelaide's water supply, and for environmental flow analysis. It is recognised that a comprehensive review of the stream gauging network is required to ensure that the correct data at the appropriate accuracy is being collected.
This State water monitoring review project will:
· Assess the relevance of the current monitoring network.
· Define the future monitoring requirements, particularly those required under the current management plans and the State Water Plan.
· Develop a cost sharing strategy for all stakeholders.
The Department for Water Resources also manages groundwater resource data. Well construction, and time-series groundwater resource data is readily available through the State groundwater database. A program of data validation has been in progress for some years, and has been concentrated on areas of most importance. The original papers are still in existence and are archived. An existing microfiche system is being replaced by an imaging system. In addition, resource investigation and evaluation reports, hydrogeological maps, and GIS systems exist.
Ground and Surface water resource data is not yet fully utilised. It is expected that over the next few years there will be considerable resources devoted to further development of integrated State water databases, GIS systems, Internet sites, and computer models of many regions.
Future Research and Development
The recent establishment of the new Department for Water Resources in South Australia, offers the possibility of better coordination of research and development. Research and development will involve:
· Improved monitoring networks and monitoring programs, which will provide the basis for the development of surface and groundwater resources management.
· Ensuring sustainability by managing surface and groundwater resources to protect them for current and future use. Sustainable yields will need to be refined, as new techniques become available for its estimation. Investigations are required in areas where the sustainable yield is unknown.
· Metering of groundwater abstraction in areas of intensive groundwater use. Metering is likely to be implemented as part of future groundwater resource management.
· Continuing investigation into the nature and extent of aquifers in areas hwere there is little knowledge, and the assessment of the potential for aquifer interconnection in developed areas.
· Continuing studies to develop methods to determine and monitor environmental water requirements for the ephemeral streams in South Australia.
· Metering of farm dams and developing means to increase the efficiency of surface water irrigation.
· Increasing productivity by using and managing surface and groundwater resources to achieve maximum return. There is a strong demand for the state resources to service economic development in irrigation, mining and industry.
· Developing effective partnerships between the Government, community and the private sector, which will increase the effectiveness and efficiency of the management of surface and groundwater resources.
Continuing to develop aquifer storage and recovery, which promises to be an effective water resource management tool to conjunctively manage surface and groundwater, and reduces the dependence of both urban and rural users on the River Murray.
References
Government of South Australia, GSA (1997) Water Resources Act 1997, Government of South Australia.
Government of South Australia, GSA (2000) State Water Plan 2000, Government of South Australia.
Philpott A, Rixon S & Pikusa E (1999) Determination of Environmental Water Requirements for the Gawler River System, Evaluation Branch, EPA, Department for Environment, Heritage and Aboriginal Affairs unpublished report.
Cresswell D J (1991) Integrated Management of Farm Dams in the Barossa Valley, Engineering and Water Supply Department, Report EWS 91/7, April 1991.
Greenwood A J B (2000a) Regionalised Estimates of Runoff Capture by Farm Dams, Department of Water Resources SA, unpublished report.
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