Australian Natural Resources Atlas

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Water - Victoria - Water Technical Report

Surface and Groundwater Management, Availability, Allocation and Efficiency of Use
Victorian Technical Report

Surface Water Methodology

Definition of Surface Water Management Area

For the purposes of this Audit, the basins as designated by the Australian Water Resources Council (AWRC) have been adopted as the basic reporting unit. There are 30 AWRC basins in Victoria, of which 11 are located north of the Great Dividing Range and form part of the Murray Darling Basin. Two of the AWRC basins (the Thomson River and Upper Murray) have been further subdivided for reporting purposes, to distinguish between the relatively developed and undeveloped river systems within the basins. In cases where the AWRC basin crosses State borders, the basins have been subdivided at the border to create a Victorian component. The data reported to the Audit refers only to the area that is located within Victoria. These basins include the Upper Murray, Snowy River, East Gippsland, Murray Riverina, Mallee, Glenelg River, and Millicent Coast. The Victorian component of the Murray Riverina has been named the Mid-Murray River (Hume to SA Border) (Vic) and data reported refers to the Victorian share of the water resource. The boundary for the Murray Riverina has been defined by buffering the Murray River on the Victorian side by approximately 5.5 km and extends downstream from Lake Hume to the South Australian border.

All reporting units are referred to as Surface Water Management Areas (SWMAs). A total of 32 have been defined for Victoria and these are shown in Figure 1.

Compilation of Surface Water Use Data

Average annual water use, representative of 1996/97 levels of development, has been estimated for both Level One and Level Two types of water use for all SWMAs in Victoria. This data has been compiled using information sourced from water authorities across the State. The methods used to derive the water use data for the urban/industrial, irrigation and rural water use types are summarised below.

Urban/Industrial Water Use

Melbourne's water use represents approximately 60% of the total urban/industrial use in Victoria. The water supply to Melbourne is delivered via three retail water companies: Yarra Valley Water, City West Water and South East Water. The headworks operator, the Melbourne Water Corporation, provides bulk water supply to these retail companies.

Melbourne's water supply is an integrated system, currently sourcing water from three SMWA's including the Thomson River, Yarra River and Goulburn River. The water supply district is spread across four SWMAs: Yarra River, Bunyip River, Maribyrnong River and Werribee River.

The Melbourne Water Corporation provided the total volume of water supplied from the major water sources to the Melbourne water supply district. The retail companies provided data for their relevant supply districts and reported on the following Level Two types of use: domestic, industrial/commercial, and system losses.

The volume of water used within each SWMA, for supply to the Melbourne water supply district, was based on the estimated number of connections located within the management area. Water sourced from the Goulburn Basin was assumed to be available to supply consumers located within the Werribee, Maribyrnong and Yarra Basins. Water sourced from the Thomson and Yarra basins was assumed to be available to supply all consumers.

A total of 15 non-metropolitan urban water authorities (NMUs) manage the delivery of water to urban/industrial consumers outside of Melbourne. Most NMUs were able to provide annual surface water use data for the base reporting year adopted by the Audit, which is 1996/97. Where information was not available for 1996/97, the most recent year of record was used to compile data

Figure 1. Surface Water Management Areas in Victoria

All authorities were able to provide a breakdown of the total water use to at least the following Level Two types of use: domestic, industrial/commercial, and system losses.

A number of water authorities were also able to provide the volume of treated effluent that is reused or returned to waterways. As not all water authorities could provide this information, the data was only reported for a SWMA if available for all towns located within the SWMA

Irrigation Water Use

There are four regional Rural Water Authorities that provide bulk water and irrigation services and licencing of surface and groundwater diversions. These are:

Each authority was able to provide the total volume of irrigation water supplied within their irrigation districts. In northern Victoria, the main source of irrigation diversion data was the Murray Darling Basin Audit Monitoring Report (1996/97) prepared by Goulburn Murray Water for submission to the Murray Darling Basin Commission.

The total volume of irrigation water used by private diverters was available for all northern and south-eastern basins. There was limited data available for the basins in the south-west of the State. An estimate of the total volume of water used in these basins was made using irrigated crop area data, sourced from the Australian Bureau of Statistics 1996/97 census information, and crop application rates.

The breakdown to Level Two types of irrigation use was also determined using irrigated crop area data and crop application rates.

The source of the irrigated crop area data for the various SWMAs is summarised in Table 1.

Table 1. Source of Irrigated Crop Area Data for each SWMA

Surface Water Management Area Data Source
Mitta Mitta River, Kiewa River, Ovens River, Broken River, Goulburn River, Campaspe River, Loddon River, Avoca River
  • Department of Natural Resources and Environment (NRE)1, Tatura; and
  • Goulburn Murray Water Annual Report (1996/1997)
Upper Murray, Werribee River, Barwon River, Corangamite, Otway Coast, Hopkins River, Portland Coast, Glenelg River, Wimmera-Avon Rivers, Mallee
  • Australian Bureau of Statistics Irrigated Crop Areas, 1996/97 Census data.

South-East SWMAs including:

East Gippsland, Snowy River, Tambo River, Mitchell River, Avon River, Thomson/Macalister Rivers, LaTrobe River, South Gippsland, Bunyip River
  • Southern Rural Water, Farm Survey Data
Maribyrnong River
  • Draft Publication: The Irrigation Water Requirements of Licensed Diverters of Southern Rural Water and Melbourne Water in the Keilor Region of Victoria.
Moorabool River
  • PRIDE Irrigation model of the Moorabool River 2

1 Data provided by NRE included a GIS representation of District irrigated areas for the following: perennially active crops, autumn active crops, and summer active crops.

2 The model estimated crop application volumes based on the following input parameters: rainfall, evaporation, crop type, crop application rates and various catchment parameters.

The total volume of returned and reclaimed irrigation water was estimated for all irrigation districts as follows:

In all cases the Level Two data for the volume of reclaimed and returned water was determined by applying the same breakdown as the Level Two water use data.

Rural Water Use

Rural water use refers to water used in rural areas excluding water used in rural towns and irrigation use. It mostly comprises on-farm domestic and stock use, but also includes small volumes used commercially and for some industries and institutions. It includes minor supplies drawn from major pipelines and self-extracted water drawn from farm dams or direct from waterways.

The volume of rural water delivered via the Wimmera-Mallee Stock and Domestic channel system represents about 70% of the total rural water use in Victoria. This usage is metered and data was provided by Wimmera Mallee Rural Water Authority. Distribution losses for this system are high and are estimated to represent approximately 70% of the diversion volume.

Metered records of usage by private rural water diverters are not available. In all SWMAs it was assumed that rural water use represents 90% of the licenced volume.

Climatic Adjustment Factors

Water use data collated for the 1996/97 year was converted to a long-term average value for both Level One and Level Two types of use, by applying climatic adjustment factors. These factors were generally determined as a proportion of the total 1996/97 diversion volume and the total average diversion volume. Individual factors were derived for each SWMA located in the Murray Darling basin. A common adjustment factor was applied to the south-west and south-east management areas.

The following describes the derivation of these factors for the SWMAs located in the Murray Darling Basin.

For the SWMAs located south of the Great Dividing Range, separate conversion factors were applied to the urban/industrial and irrigation Level One types of use. Two sets of factors were derived for application to the south-west and south-east management areas. The assumptions/methods used to derive these climatic adjustment factors are summarised in Table 2. Rural water use was assumed to experience limited variation with climate in southern Victoria and hence an adjustment factor was not applied to the rural water use data.

Table 2. Assumptions/Method for the Derivation of Climatic Adjustment Factors - Southern SWMAs

Type of Use South-East South-West2
Urban/Industrial1 It was assumed that the 1996/97 diversion volumes were representative of an average year. Hence, no adjustment was made. Estimated as a proportion of the 1996/97 annual diversion for Ballarat and the average annual diversion determined using a simulation model of the Ballarat supply system.
Irrigation Estimated as a proportion of the 1996/97 irrigation use for the Macalister Irrigation District and the average irrigation diversion estimated using a simulation model of the Thomson/Macalister supply system. Estimated as a proportion of the 1996/97 irrigation use for the Maribyrnong irrigation users and the average irrigation diversion estimated using a simulation model of the Maribyrnong supply system.

1 A separate factor was derived for Melbourne based on the proportion of the 1996/97 consumption and average consumption.

2The adjustment factor applied to the diversions from Rocklands Reservoir and Moora Moora Reservoir (located in the Glenelg River SWMA), was determined as a proportion of the 1996/97 annual diversion and the average annual diversion determined using a simulation model of the Wimmera Mallee Stock and Domestic Supply System.

Compilation of Surface Water Allocation Data

Water is allocated in Victoria in the form of bulk entitlements (BEs) and licensing provisions.

BEs represent a specification of property rights to water that are explicit (regarding volume and reliability), exclusive, enforceable and tradeable. They define the maximum volume of water that can be diverted at specified locations, and are granted to both urban and rural water authorities. BEs for rural water authorities cover the water rights held by irrigators in authority-supplied districts, plus the losses incurred by the authority in distributing the water.

In irrigation districts, in any particular year, the total volume of water available for irrigation in the coming season is determined by considering the volume actually held in storages, losses incurred in storing and delivering the water (eg. seepage, evaporation), likely inflows over coming months (conservatively estimated), and carryover storage requirements for the following season. Allocations to individual irrigators are then announced in terms of the percentage of 'water right' available plus an additional percentage of 'sales' water.

Outside of irrigation districts, individuals taking water are required to have a licence issued by the Minister, except for water used for domestic and stock purposes taken from a waterway on private land, and for surface flows before they reach a waterway.

Simulation models have been developed for most water supply systems in Victoria to assist with the assessment of BEs. Where these simulation models are available, they have been used to define the long-term average allocations under the maximum level of development (with current infrastructure in place). For the SWMAs located in the Murray Darling Basin, the long-term average allocations are limited to the 1993/94 levels of development (in accordance with the Murray Darling Basin Ministerial Council (MDBMC) Cap arrangements), and hence are equal to the assessed long-term average diversion for the SWMAs. For the remaining SWMAs, the average allocations were assumed to represent 90% of the licence volumes plus 90% of the BE volumes, unless the average diversion exceeded this volume. Where this was the case the average allocation was assumed to equal the average diversion. A summary of the methods used to determine the average allocation in each SWMA is given in Table 3.

Table 3. Methodology Applied to Derive Average Allocation

SWMA Method

Upper Murray River (Vic)

Mitta Mitta River

Kiewa River

Ovens River

Broken River

Goulburn River

Campaspe River

Loddon River

Wimmera-Avon Rivers

Mid-Murray River (Hume to SA border) (Vic)

 Simulation model based on the 1993/94 level of development (in accordance with the MDBMC Cap).
Thomson-Macalister Rivers Simulation model based on the maximum level of development under existing Bulk Entitlements (BEs). The model takes into account unregulated private and irrigation diverters.

Latrobe River

Bunyip River

Yarra River

Maribyrnong River

Moorabool River

 Simulation model based on the maximum level of development under existing BEs, plus 90% of the unregulated private irrigation and rural licence volumes.
Barwon River Simulation model based on the maximum level of development under the existing BE for the Geelong Water Supply System plus 90% of the private irrigation and rural licence volumes plus 90% of the BE volume for the White Swan supply to Ballarat.
Werribee River Simulation model based on the maximum level of development (under the existing BE for the Werribee Irrigation system and the Western Water urban supply to Melton, Myrniong, Macedon, Gisborne and Bacchus Marsh) plus 90% of the private irrigation and rural licence volumes plus 90% of the BE volume for the Blackwood and Ballan Water Supply system.
Glenelg River (VIC) Simulation model based on the maximum level of development under existing BEs plus 90% of the private irrigation and rural licence volumes plus 90% of the BE volume for urban water supply systems.

East Gippsland (VIC)

Snowy River (VIC)

Tambo River

Mitchell River

Corangamite

Hopkins River

Millicent Coast

South Gippsland

 90% of the BE volume plus 90% of the private irrigation and rural licence volume.

Avoca River

Avon River

 Allocation equal to average diversion.

Note: The Mallee SWMA for Victoria has limited surface water resources. Hence the allocation is zero.

The Level One allocation data was provided for each Level One type of use by distributing the total allocation volume on the basis of the average annual volumes diverted to each type of use.

Hydrological Characterisation

For each SWMA a number of key stream gauging sites were selected to broadly describe the hydrological characteristics of the SWMA and assess the impact that development of the water resource has had on the flow characteristics. The following criteria were used to select the stream gauging sites:

The period of record selected to describe the flow regime of the management area was limited to the most recent 10 to 20 years of data. The flow series is assumed to be stationary over this period, with negligible change in upstream development and diversions. This enables a direct comparison between natural and current flow conditions to be made. In SWMAs known to have experienced significant development, the period of record was limited to a 10-year period, to increase the likelihood that the selected period is stationary.

The recorded streamflow data was sourced from the Victorian Water Quantity Network (VWQN) database. The management of the database and the operation and maintenance of the stream gauging network is undertaken by an external contractor funded by the Victorian Government. This data is now also available via the Victorian Water Resources Data Warehouse (http://www.dse.vic.gov.au/ vwrmn).

The natural flow series for the period of interest was derived at each gauge using a range of methods including:

At a number of sites, the available flow data was extended to December 1998 using a HYDROLOG rainfall-runoff model. This was undertaken by the University of Melbourne as part of the Flow Extension Project for the Audit.

The minimum, maximum and mean annual rainfall within the catchment of each key gauging site and the percentage of rainfall that contributes to the runoff at each site were also assessed. An estimate of rainfall within each gauged catchment was determined using the Geographic Information System (GIS) of rainfall prepared by the Bureau of Meteorology (BoM). The BoM data set provides an average annual rainfall estimate at a 2.5 km_ resolution. The representative average annual rainfall for the catchment was determined as the average of the annual rainfall depths reported within the catchment boundary.

In order to determine the minimum and maximum annual rainfall it was necessary to derive a representative time series of rainfall. An annual time series was produced for each site by applying a factor to an existing time series of rainfall data that is available for defined Rainfall Districts within the State. The factor was determined as the proportion of catchment average annual rainfall (as derived from the BoM GIS data) and the average annual District rainfall. The minimum and maximum annual rainfall was determined from the derived time series.

The minimum, maximum and average percentage of annual rainfall that becomes runoff was determined from the annual time series of natural flow and catchment rainfall. The percentage was calculated for each year, from which the minimum, maximum and average percentages were determined.

Mean Annual Flow and Mean Annual Outflow (Undeveloped Conditions)

For all SWMAs in Victoria it is assumed that flow in the major rivers increase downstream. The flow is therefore greatest at the catchment outlet and represents both the mean annual flow and mean annual outflow (for undeveloped conditions). The mean annual flow from the SWMA was derived by applying one of the following methods:

Mean Annual Flow and Mean Annual Outflow (Current Development)

The mean annual outflow under current development was determined by applying one of the following methods:

Divertible Yield

The divertible yield has been defined as the average annual volume of surface water that can be diverted utilising both existing infrastructure and potential infrastructure under the ultimate level of development.

In Victoria, potential future dam sites have been identified as part of an earlier study, which considered the options for surface water development in the State. The study was published by the previous Rural Water Commission of Victoria in June 1986 and was titled "Long Run Incremental Cost of Annual Regulated Flow in Victoria's River Basins" (Alexander and Haydon 1986). An essential component of the study involved the determination of the incremental costs of future water resources developments in Victoria. A rapid appraisal method for assessing storage yield and construction costs at possible dam sites was developed which allowed selected sites to be ranked on a comparative basis. The construction cost was based on the volume of the dam embankment, catchment area and a parameter obtained from a relationship derived from existing dam embankment construction costs.

The main assumptions adopted in the assessment of potential storage sites and the estimation of yields from storages are listed below:

Some factors that are likely to influence actual storage costs and yields were not considered within the scope of the study. For example, costs associated with spillway construction, road construction, and land purchase were not taken into account in the cost equation. Other factors not considered included environmental considerations, variable demands, potential inter- and intra-basin transfers, site geology and water treatment requirements.

For this Audit, the divertible yield was reported as the sum of the developed yield for the SWMA and the incremental yield from the potential storage sites identified in the study noted above.

Dam sites with an effective cost greater than $2000/ML, as determined in 1985,were not included in the estimate of divertible yield as these were considered to be uneconomical. This cost is equivalent to around $3300/ML in 1996.

Developed Yield

The developed yield refers to the annual volume of water that is available for diversion at a defined level of reliability, taking account of environmental water requirements.

The bulk entitlement process, initiated in Victoria in the early 1990s, has involved a comprehensive assessment of the developed water resource. The determination of the developed resource or yield of water supply systems has been established using Resource Allocation Models (REALM) of the various water supply systems. The system yields have been assessed with current operational rules in place. For some systems, environmental water requirements have also been incorporated in the system models.

For the majority of basins in Victoria the developed resource has been fully allocated. Hence, for these basins the developed yield is equivalent to the average allocation. The approach used to define the average allocation is described in an earlier section of this report, 'Compilation of Surface Water Allocation Data', and is summarised for each SWMA in Table 3. The methodology is generally based on an assessment of the developed resource using the REALM simulation model.

There are two SWMAs where the developed resource is not fully allocated. These include the LaTrobe River, where 40 GL/a of the available yield from Blue Rock Reservoir remains unallocated, and the Werribee River, where 2.5 GL/a of the available yield from Merrimu Reservoir remains unallocated. The developed yield of the LaTrobe and Werribee Rivers is equivalent to the average allocation plus the unallocated portion of the resource.

Environmental Water Requirements

Environmental water requirements refer to the flow regime needed to sustain water dependent ecosystems, including both biological processes and biological diversity, at a low level of risk.

Victoria is addressing the provision of water allocations for the environment via a number of programs. The first of these involves the conversion of existing rights to water to well-defined, legal rights to water via the bulk entitlement (BE) conversion process. This process provides the opportunity for negotiation of enhanced environmental flows (through adjustments to water authority operating rules), and for the definition of BEs specifically for the environment. Formal BEs are being progressively granted and associated regulatory systems to monitor and manage the entitlement system, including water trading, are being implemented. Ecological sustainability must be assessed before any revisions can be made to a BE, and environmental requirements must also be met before any new BEs are granted.

Provisions for environmental water requirements are also being made in Streamflow Management Plans (SMPs) for unregulated rivers that are not covered by the BE process. SMPs differ from BEs in that they are plans for the management of diversion licences on unregulated rivers rather than an explicit property right. These SMPs establish environmental objectives, environmental flow provisions, rostering rules for diversions in times of reduced flows, trading rules, and rules governing the granting of new licenses. The plans include mechanisms for reallocating water where negotiated environmental flows fall short of environmental flow requirements.

While improvements to environmental flows are achieved in about 90% of cases in the conversion of BEs, these improvements are often at the margin - the emphasis is on preventing further decline and on clarifying and protecting the rights of existing users. In a number of streams, further action to restore flows is called for. A further program, the Stressed Rivers Program, involves the identification of rivers that are stressed due to inadequate flow regimes, and the development and implementation of comprehensive work plans (River Restoration Plans) to improve their condition. These Plans will build on existing environmental provisions. They will establish clear objectives for the improvement of river health and will identify mechanisms for enhancing the environmental flow regime, and the complementary instream and riparian habitat works that will maximize environmental gains.

A more recent initiative involves the establishment of a review process and consultative program aimed at bringing farm dams that are not on waterways (and therefore do not require a license) into the water allocation framework. This initiative is in recognition of the fact that continued growth in farm dams threatens both environmental values and the security of existing rights to water.

While Victoria has a variety of programs underway aimed at identifying, improving and protecting environmental water requirements, the technical task of actually determining an appropriate water allocation for any specific environmental system is complex and there is much investigation that is still required before environmental water requirements can be routinely estimated and simply applied in the operation of water systems and the assessment of future alternatives. To date, detailed environmental flow assessments have been undertaken for only a small number of systems in Victoria.

Given the short timeframe of this Audit, the environmental flow requirements have been broadly defined as the difference between the Total Available Water (TAW) and the estimated sustainable yield. The Total Available Water is determined as the sum of the mean annual flow, inflow from upstream catchments and cross catchment transfers that contribute to the available resource in a waterway.

It should be noted that where management areas flow into river or lake systems, such as the northern basins, which flow into the Murray River and the basins flowing to the Gippsland Lakes in the south-east of the State, the environmental water requirement at the outlet of the basin consists of the flow needed to sustain the environmental system within the SWMA plus the requirements for downstream SWMAs. This includes requirements for both the downstream environment and consumers. Generally, the downstream requirements for any particular SWMA can be reduced, provided environmental water contributions increase by the same amount in the downstream SWMA (ie. diversions from the downstream SWMA would need to decrease). This can be achieved through trade.

Sustainable Yield

The sustainable yield is the estimated maximum volume of water than can be diverted after taking account of in-stream environmental water requirements.

Sustainable Yield Methodology

While the concept of sustainable yield as defined above is straightforward, in practice it is very difficult to determine. Once environmental water requirements at particular points within a SWMA have been determined, using simulation models, it is possible to derive an estimate of the average volumetric 'environmental allocation' and the 'sustainable yield' for the SWMA. While Victoria has a variety of programs underway aimed at identifying, improving and protecting environmental water requirements, the necessary investigations take considerable time and resources and have not been completed for most catchments.

Given the short time frame of the Audit, it was necessary to make some broad assumptions, and use a variety of approaches, to derive estimates of the sustainable yield for surface water management areas (SWMAs) in Victoria. Consideration was given to environmental water requirements (known and likely), existing user rights, and related social and economic impacts. The reported allocations to the environment represent the water that can currently be maintained or made available in an attempt to meet environmental water requirements.

Within the Murray Darling Basin, sustainable yields were determined in the context of the 1996 agreement to cap diversions within the Basin at 1993/94 levels of development. By ensuring that diversions in the Murray-Darling Basin will not increase, the Cap protects the security of supply of existing users at a regional scale while, in effect, defining the remaining water as an environmental allocation. The sustainable yields for the SWMAs located within the Basin were reported as the average annual diversions from each SWMA with the Cap in place. The average annual diversions were estimated using water resource allocation models (REALM) of the relevant water supply systems. It should be noted that the Cap is a critical first step in countering ecological degradation. To halt degradation fully it may need to be lowered (and therefore sustainable yields may need to be redefined), but it is too early to tell whether this is the case.

For SWMAs in the southern part of Victoria, sustainable yields were defined using two approaches:

Sustainable Yield - Assumptions, Reliability and Errors

Where sustainable yields have been limited in accordance with the Murray-Darling Basin Cap, or the current allocations within the SWMA, it is assumed that the current environmental water provisions represent the maximum volume of water that can currently be made available to the environment after consideration is given to the rights of existing users, and related social and economic impacts. In some situations these provisions may not fully meet the environment's requirements.

In the longer term, there may be further scope for freeing up additional water to improve environmental regimes by improving distribution and water use efficiencies (other options for improving environmental regimes will be considered as part of the Victorian River Health Strategy). In SWMAs where a significant portion of the available resource is committed to a downstream SWMA, there is also potential for trading of entitlements between the two SWMAs. This will result in a change to both the sustainable yield and the environmental allocation in both SWMAs. Trade out of a SWMA would decrease the sustainable yield of the SWMA and a trade of water rights into a SWMA would increase the sustainable yield. However, the sum of the sustainable yields for the two SWMAs would remain unchanged.

Sustainable yields determined using the ISC hydrology sub-index approach are based on the following assumptions:

The estimates of sustainable yield made using the ISC hydrology sub-index are considered to be relatively conservative, as the methodology assumes that diversions occur only during the period May to November (i.e. the flow regime for the period December through to April must remain unchanged). However, the approach was found to give inconsistent results across the State and could not be universally applied. The estimates of sustainable yields determined using this approach can therefore only be considered to be interim measures, pending the outcome of detailed environmental flow assessments.

The major limitation associated with the concept of the sustainable yield for a SWMA is that the assessment is undertaken at the furthest downstream location on rivers/streams within a SWMA. Therefore the sustainable yield represents an average across a SWMA, and it does not take into account the impact of diversions on specific river reaches within the catchment. Consequently, where the sustainable yield of a SWMAs is specified as being equal to or greater than the allocated volume, there still could be river reaches within the SWMA that are over allocated, potentially over-used and, therefore, stressed. These situations will be identified and addressed in the context of established programs (in particular, the Streamflow Management Plan and Stressed Rivers programs) aimed at addressing the provision of water for the environment. Conversely, where the sustainable yield is specified as being equal to the allocated volume, there may still be 'spare' capacity on some river reaches, in the sense that further diversions could occur without stressing the particular river reaches. A further complication is that where SWMAs are nested (as in the Murray Darling Basin), a portion of the flows from upstream SWMAs are often required to meet commitments to downstream SWMAs. This means that current allocations for use within the upstream SWMA (and therefore the defined sustainable yields) are relatively low compared to what they would be if resources generated within the upstream SWMA were to be utilised only within this (upstream) SWMA.

For the reasons outlined above, the concept of sustainable yield for a SWMA is not a particularly useful management tool, as proper management requires consideration of the environmental flow requirements for specific river reaches.

Categorisation

The categorisation of SWMAs in terms of the current level of development has been based on the proportion of the volumes currently diverted and allocated relative to the sustainable yield. Five categories have been defined for this purpose:

Category 1: Low level of development: 0-30%

Category 2: Medium level of development: 31-70%

Category 3: High level of development: 71-99%

Category 3*: Fully developed: 100%

Category 4: Over allocated/used resource: > 100%

The fully developed category refers to those SWMAs where sustainable yield has been nominally set at the current allocation due to one of the following reasons:

Management Goals and Objectives

The Victorian Government is committed to ensuring the sustainable use of all water resources. The water reforms that have been undertaken to date in Victoria and the management initiatives currently underway (which are all consistent with the national water reform agenda) provide a sound foundation for ensuring the sustainable management of the State's water resources into the future. Continued commitment and effort are required to complete these initiatives over the next five to ten years or so.

The Government's overall aims, broadly stated, are, by continuing to work within a consultative framework with all stakeholders, to maintain reliable supplies for water users, to improve the efficiency of use of the resource and the delivery of water services, and to ensure that the environmental values of rivers and wetlands are sustained and restored where necessary.

More specifically, management goals and objectives can be defined as follows:

The management goals and objectives for each SWMA have been defined in the context of the objectives set for the State and by considering the beneficial uses, the current development status, and the key water resource management issues relevant to the SWMA.

Groundwater Methodology

The National Land and Water Resources Audit (the Audit) required the collation of information on groundwater allocation, use, monitoring and management of groundwater resources. This included the determination of what resources are available for use, how they are currently used, and forecasts of likely future use. To compile this information, various government bodies were consulted throughout the project. The primary sources of groundwater information were:

The understanding of groundwater systems in Victoria is rapidly improving as a result of current initiatives. Extensive programs involving the compilation of use and sustainable yield information, combined with the augmentation of monitoring networks, are enhancing current knowledge and, in turn, the management capability of Rural Water Authorities who are responsible for managing the resource. Compared with the situation at the time of the last major audit of the resource (for 'Review 85'), there is now much more comprehensive monitoring and more intensive management of groundwater resources occurring through the establishment of Groundwater Management Units (GMUs) (see below for definition of GMUs).

Definition of Groundwater Management Unit Boundaries

The Audit requires information to be supplied at a minimum scale of Groundwater Management Units (GMUs), moving up to Province and then State level information. The Victorian GMU boundaries are based on the Groundwater Management Areas (GMAs) defined by the Department of Natural Resources and Environment from 1996 onwards. The boundaries for these GMAs were defined by first considering geology, and then taking roads, rivers, and other geographical features into account.

All GMAs created since 1996 have been reported on in this Audit, including GMAs that were proposed as recently as November 1999, although there is as yet limited information available for these areas.

In the case of groundwater systems spanning the South Australian/Victorian Border, there is overlap between recently defined GMAs and the historically defined Border Zone. The Border Zone was created under the Groundwater (Border Agreement) Act 1985 which provides a framework for joint management of groundwater resources within a 40km wide strip along the length of the South Australian and Victorian Border. This area is referred to as the Designated Area, and is split into 11 sub-zones, which are divided into parts A and B either side of the border. These groundwater management zones are managed by the relevant South Australian and Victorian water authorities, unlike GMAs which are managed by community consultative groups, which include representatives from the relevant rural water authorities and government departments. Because of this disparity, GMAs have been established by NRE which cover part of the Designated Area. To avoid duplication of resource information, only the GMAs or the Designated Area zones could be used for reporting purposes for the Audit. To maintain consistency across the State the GMAs were used, leaving the rest of the Designated Area as Unincorporated Areas (see below).

GMA boundaries are constantly being revised and updated as new information becomes available, so the defined GMUs for the purposes of the Audit should be considered to be a snapshot of the status of GMAs in Victoria as at November 1999.

Areas outside of the GMUs are called Unincorporated Areas (UA). These areas are based on hydrogeological basins and are referred to as 'Provinces'. The UAs are split according to aquifer type. It should be noted that the boundaries of UAs are indicated as extending to the edge of the relevant Provinces. In reality however, many of the aquifers are intermittent or less extensive in area than the Province. For simplicity, all aquifers are assumed to extend over the entire Province area. GMU and UA depths have also been approximated based on a typical depth of aquifer in the denser extraction regions. For more information on aquifer extents, refer to the Audit Website for information on each GMU or UA.

The GMUs and UAs are shown in Figure 2, with basic information for each GMU given in Table 4. As can be seen in this diagram many of the GMUs appear to overlap each other, especially in the Gippsland Basin, where nearly the entire Basin is covered by GMUs. In reality they lie at different depths and cover different aquifers.

Figure 2. Groundwater Management Units in Victoria

Table 4. Groundwater Management Unit and Unincorporated Area Definition

GMU Province GMU ID GMU Name GMU Area (kmē) GMU depth to top of aquifer (m) GMU average aquifer saturated thickness (m)
Gippsland V1 Wy-Yung 92 0 25
Gippsland V2 Seacombe 6,661 150 150
Gippsland V3 Sale GSPA 1,400 50 150
Gippsland V4 Wa-De-Lock 628 5 20
Gippsland V5 Denison GSPA 200 0 25
Gippsland V6 Moe 360 0 200
Gippsland V7 Leongatha 190 20 50
Gippsland V8 Tarwin 30 5 20
Gippsland V62 Rosedale 3,690 25 200
Gippsland V63 giffard 1,100 50 80
Gippsland V67 UA - Gippsland (Watertable aquifer) 10,230 5 20
Gippsland V68 UA - Gippsland (Upper Tertiary Aquifer) 7,127 30 30
Gippsland V69 UA - Gippsland (Middle Tertiary Aquifer) 5,873 50 50
Gippsland V70 UA - Gippsland (Lower Tertiary Aquifer) 4,568 150 300
Lachlan V11 Alexandra 30 10 3
Lachlan V12 King Lake 90 20 100
Lachlan V13 Wandin Yallock 40 20 40
Lachlan V14 Lancefield 40 20 20
Lachlan V54 Moolort 600 5 40
Lachlan V55 Ascot 272 5 20
Lachlan V56 Spring Hill GSPA 253 5 20
Lachlan V57 Bungaree 200 5 20
Lachlan V58 Glengower 510 65 60
Lachlan V59 Bullarook 325 75 90
Lachlan V60 Tourello 270 48 80
Lachlan V66 UA - Lachlan 86,500 5 200
Murray V35 Mullindolingong 235 0 25
Murray V36 Barnawartha 1,800 25 55
Murray V37 Murmungee 750 5 20
Murray V38 Goorambat 250 10 50
Murray V39 Katunga GSPA 2,100 25 40
Murray V40 Kialla 750 25 40
Murray V41 Nagambie 90 25 40
Murray V42 Campaspe GSPA 958 25 40
Murray V43 Shepparton GSPA 6,741 0 30
Murray V44 Ellesmere 60 5 9
Murray V45 Bridgewater 1,800 25 55
Murray V46 Salisbury West 430 10 40
Murray V47 Balrootan 422 100 75
Murray V48 Berrook 240 60 140
Murray V49 Murrayville GSPA 1,184 150 110
Murray V50 Telopea Downs 730 75 120
Murray V51 Lillimur 590 40 70
Murray V52 Neuarpur GSPA 810 40 75
Murray V53 Boikerbert (Apsley) 730 125 80
Murray V77 UA - Murray (Watertable Aquifer)) 71,213 20 60
Murray V78 UA - Murray (Middle Tertiary Aquifer) 34,000 80 50
Murray V79 UA - Murray (Lower Tertairy Aquifer) 30 250 100
Otway highlands V65 UA - Otway Highlands 1,374 5 200
Otways V22 Newlingrook 325 0 100
Otways V23 Gerangamete 380 60 250
Otways V24 Gellibrand 88 8 100
Otways V25 Warrion 400 30 5
Otways V26 Colongulac 450 30 15
Otways V27 Paaratte 1,321 120 100
Otways V28 Glenormiston 100 30 50
Otways V29 Nullawarre GSPA 561 60 50
Otways V30 Yangery GSPA 290 40 50
Otways V31 Portland 4,000 200 400
Otways V32 Condah 950 100 50
Otways V33 Heywood 800 70 30
Otways V34 Lake Mundi 700 0 300
Otways V74 UA - Otways (Watertable Aquifer) 19,738 50 30
Otways V75 UA - Otways (Middle Tertiary Aquifer) 18739 100 15
Otways V76 UA - Otways (Lower Tertiary Aquifer) 16845 120 100
Port Phillip V15 Nepean 100 5 100
Port Phillip V16 Frankston 140 5 40
Port Phillip V17 Moorabbin 130 5 75
Port Phillip V18 Cut Paw Paw 60 50 100
Port Phillip V19 Deutgam 50 5 28
Port Phillip V20 Merrimu 14 5 4
Port Phillip V21 Jan Juc 80 20 55
Port Phillip V71 UA - Port Phillip (Watertable aquifer) 2,547 30 50
Port Phillip V72 UA - Port Phillip (Middle Tertiary Aquifer) 2,870 60 50
Port Phillip V73 UA - Port Phillip (Lower Tertiary Aquifer) 1,830 100 50
Westernport V9 Lang Lang 265 5 125
Westernport V10 Corinella 110 5 75
Westernport V61 Koo-wee-rup / Dalmore Groundwater Conservation Area 746 25 50
Westernport V64 UA - Westernport 1,234 50 50

Background

Groundwater allocation, or licensing, is undertaken by the Rural Water Authorities. In Victoria there are four Rural Water Authorities. These are:

Licensing for groundwater bores under the jurisdiction of Sunraysia Rural Water Authority is undertaken by Wimmera Mallee Water. Hence, data was collated on groundwater allocations from the three Rural Water Authorities presently issuing groundwater extraction licenses.

Groundwater licenses are issued for groundwater extraction according to:

Before an extraction licence is issued the bore must be constructed in accordance with current bore construction standards and have a bore construction license.

The Rural Water Authorities maintain records of all extraction licences within the GMUs in Victoria. Within these areas there are stricter controls on groundwater extractions than in UAs. In the UAs licences are issued where groundwater of the yield and quality required is extractable, provided that no environmental or other reasons are found to prevent the licence from going ahead. The issuing of an extraction licence does not guarantee that it will be possible to extract the volume from the aquifer. More than one bore is often required to extract the required volume from an aquifer.

Information Available from Rural Water Authorities

The information collated from Rural Water Authorities included:

Groundwater allocations and use types can be categorised as formal, informal and other, as indicated in Table 5. Most high yielding bores are formally licensed with an 'allocated' volume for extraction.

Table 5. Information Available From Rural Water Authorities On Use Types For Licensed and Other Allocations/Uses

Level 1 Use types

Formal allocations

(allocated volume for each licence)

Informal allocations

(bore construction licence given, but not a formally acknowledged allocation volume)

Other

(known extractions, but not licensed, and allocation volume unknown)
Urban/Industrial

Domestic/Urban/ Mineral Waters

Industrial including:

  • Agricultural industry;
  • Aquatic industry/ Fisheries ;
  • Dairy.

Commercial

Power Generation

 -

Urban (National Parks Facilities, Fire/drought supply bores)

Mine dewatering
Rural Stock and domestic bores, from Victorian Groundwater Database. -
Irrigation Irrigation (Level 2 information supplied by diversion inspectors and from field surveys) - -
In-Situ Environmental Other (salinity, dewatering) - Other (salinity, dewatering)

Table 5 above clearly shows that the Level 1 use types are documented in current licensing procedures, but not all of the Level 2 use types are known. If Rural Water Authorities are going to be required to keep this type of information, a protocol on licensing information needs to be developed.

The allocation information used in The Audit is indicated in Table 6 below. It is evident from the table that individual licence records for each GMU do not extend as far back as 1996. Of the Rural Water Authorities only Wimmera Mallee Water had records for individual license allocations for 1996; for all other authorities, only total allocation volumes were known.

Table 6. Availability Of Allocation Information From The Rural Water Authorities

Rural Water Authority Information source 1995 1996 1997 1998 1999
Goulburn-Murray Water

End of Financial Year Reports

(reported as total volumes only)

 X X X
Individual licenses from GMW database

X

(by GMU)

X

(by GMU)
Southern Rural Water Total licence volumes in GMU X X X X
Individual licences from SRW database

X

(by GMU)
Wimmera Mallee Water Individual licences from WMW database (by GMU) X X X X

Methodology Used

The most comprehensive data set available for allocations was for the 1999/2000 year. Total allocation volumes were known for 1996/1997 for each GMU, and these were apportioned on the basis of the use information for 1999/2000. It was assumed that the relative proportions of total use accounted for by the different use types had not changed in the last 4 years, so that current percentages of use (e.g. 69% irrigation) could be used to proportion the total licensed volumes for each GMU for 1996/97. Allocations for the region managed by Wimmera Mallee Water were determined using data provided by Wimmera Mallee Water for 1996/1997.

Accuracy of Estimates

The allocation information provided for the Audit is rated as a category B classification, with a medium reliability (+/-25 %). This rating is based on the definition provided for the Audit which specifies category B information as information based on approximate analysis and limited surveys, with some measured data and some interpolation/extrapolation to derive the data set.

Groundwater Abstraction

Groundwater abstraction data has only recently been collected by the Rural Water Authorities, and only in limited areas. The information types currently available are listed for the different Rural Water Authorities in Table 7 below. The accuracy of the information is also noted, which in most cases is very low and should be regarded as unreliable for many of the GMUs.

Table 7. Source Of Use Information For Each Rural Water Authority (as at November 1999)

Rural Water Authority Total No. of GMUs^

No. of GMUs with Metered Use Information

(Accuracy: +/-10%)

No. of GMUs with Field Survey Information or Field Inspections

(Accuracy: +/- 25%)

Estimated Use from Allocation volumes

(Accuracy: +/-50%)
Goulburn- Murray Water 18 + 3 co-managed with SRW

0

(6 GMUs currently being metered)

2 - field survey

7 - field inspection

4 - irrigated area information (GIS analysis undertaken by GMW)

 8
Southern Water 35 + 3 co-managed with GMW

1 - Koo-wee-rup / Dalmore GCA

(metering program is in place currently for priority GMUs)

2 - field survey

(most GMUs either currently surveyed or about to be surveyed)

 35
Wimmera Mallee Water 7*

3

(approximately 25% of bores are metered in these GMUs)

 4 - field inspection 0

* The Berrook GMU lies within Sunraysia Rural Water Authority jurisdiction but is managed by Wimmera Mallee Water.

^ There are 3 GMUs which lie on the boundary of GMW and SRW regions. Of the three GMUs, Ascot and Kinglake are managed by GMW, and Bungaree is managed by SRW. Licensing of the three areas is jointly undertaken according to the agreed licensing policy for the GMU.

Programs are in place to remedy the problem of data accuracy. Priority is being given to GMUs where allocations and abstractions are greater than the sustainable yield. In priority areas, field surveys have been undertaken to give an initial estimate of usage in the GMU. This is being followed up with metering programs for priority GMUs (with some already implemented), and subsequent metering of other GMUs over the next few years.

The metering programs currently being implemented will mean that more detailed information will be available in the future. Even as the Audit has progressed, more information has progressively been made available to increase the accuracy of the results.

Selection of Key Monitoring and Major Abstraction Bores

Key Monitoring Sites

Representative monitoring sites for each GMU were chosen on the basis of the:

Between one and five bores were selected for each GMU. Reduced water level records are given for the selected bores, incorporating bores for each zone within the GMU as appropriate.

Major Abstraction Bores

The number of abstraction bores was identified from information obtained from:

Major abstraction bores were selected on the basis of:

Between one and five bores were selected for each GMU. Abstraction volumes for the bores were given by Rural Water Authorities, or estimated based on the ratio of allocation to abstraction volumes for the GMU.

Groundwater Level Change Assessment

Groundwater level trends were assessed from the representative bores for the GMU. Trend assessments were done by eye, with comments about:

Groundwater Salinity Determination

Groundwater salinity was determined from information on salinity levels from all monitoring bores in the GMU. The minimum and maximum salinities were determined from the range of salinity levels in the GMU. The median value was determined from salinity information obtained from representative bores, which were assumed to be typical of salinity levels in the GMU.

Sustainable Yield

Sustainable yields have been estimated for all GMUs in Victoria, in the context of the Permissible Annual Volume (PAV) project undertaken for the Department of Natural Resources and Environment by Sinclair Knight Merz. The methods used to determine sustainable yields varied across the State according to the characteristics of the aquifers being investigated.

Recharge sources to aquifers were identified and quantified using one or more of the following methods:

In most cases, because of the lack of usage data and, in many cases bore hydrograph data, the sustainable yield has been determined as a percentage of rainfall, with adjustments made to take account of environmental requirements to the extent possible given currently available information. Allowances for aquifer storage, river recharge/discharge, aquifer throughflow, well interference, seawater intrusion and pressure/head loss were incorporated into the methodology. The most commonly considered issues were baseflow to river systems and the intrusion of seawater. No leakage component between aquifers has been allowed for, either from or to aquifers.

The requirements of groundwater dependent ecosystems (GDEs) have not generally been considered explicitly in this process of estimating sustainable yields, as their requirements are as yet poorly understood. However, in estimating sustainable yields for groundwater management units, efforts have been made to avoid significant interference with GDEs.

Most of the sustainable yields were calculated in 1998. Several GMUs have had their sustainable yield estimates updated since that time, particularly those for which Basic Groundwater Management Plans (BGMP) have been developed. One of the main objectives for a BGMP is that further data is gathered to refine the sustainable yield estimate in 3 to 5 years time. NRE are currently looking to provide estimates on GDE requirements in GMUs so that more accurate estimates of sustainable yields can be made. As the requirements of GDEs are evaluated, current government policy will allow for variation of the sustainable yield if the prospect of a detrimental impact emerges (e.g.seawater intrusion, which may result in aquifer salinisation).

It should be noted that the derived estimates of sustainable yield are relatively subjective. Until there is more substantial data on usage it will not be possible to derive water balances for the GMUs, and determine the recharge that provides the basis for sustainable yield. Similarly, the lack of information about the requirements of GDEs has meant that some fairly broad assumptions about these requirements have had to be made. Because of these, and other uncertainties such as the impact of climate variability and the likely impacts of plantation forestry on sustainable yields, a conservative approach has been adopted in the estimation of sustainable yields for GMUs.

Categorisation

Categorisation of the GMUs was based on the volumes allocated and abstracted relative to the sustainable yields of the GMUs (expressed as a % of the sustainable yields). These percentages were then used to categorise the GMUs as follows:

Category 1: Low level of development: 0-30%

Category 2: Medium level of development: 31-70%

Category 3: High level of development: 71-100%

Category 4: Over allocated/used resource: > 100%.

Management Goals and Objectives

Specific management goals and objectives for groundwater in Victoria are to:

The management goals and objectives for each GMU are detailed in the individual GMU reports. This includes information on priority issues and management responses derived from:

The management goals for 2020 and 2050 were predominantly based on comments from Rural Water Authorities, along with Rural Water Authority policy guidelines on information requirements for Category 3 and 4 GMUs, and the Audit descriptors for Category 3 and 4 resources.

Assessment of Joint Groundwater and Surface Water Use

Joint Water Use

For the purposes of the Audit, an assessment of total water use (surface plus groundwater) within a SWMA is required. This assessment of joint water use (for all GMUs and SWMAs) has been undertaken on the following basis:

These assumptions given above clearly indicate the limitations of this assessment. In particular, the areally based apportionment of groundwater use to the various SWMAs is likely not to be a true representation of the actual situation, which will very much depend on the location of demand centres within each SWMA relative to the location of groundwater sources.

Current Status of Conjunctive Management in Victoria

Groundwater is the minor player in the supply of the State's water, with some 11% of total water use being drawn from groundwater resources. However, it is now being increasingly recognised that, in many areas, groundwater substantially contributes to the baseflow of surface streams, and that groundwater use can impact upon the availability of surface water resources (and vice versa).

The Water Act 1989 prescribes in considerable detail the setting up of Groundwater Supply Protection Areas (GSPAs), and the development of Groundwater Management Plans for these areas. On the other hand, it is silent on the question of Streamflow Management Plans (SMPs), which are developed in an informal arrangement between NRE and the rural water authorities. Part of the function of SMPs is to apportion the baseflow between consumptive use and the environment.

Ideally, where there is a significant interaction between surface and groundwater systems, there should be some integration of groundwater and surface water planning and management processes.

The only conjunctive management of surface and groundwater resources currently in place in Victoria is in relation to 'on-farm' water allocations in some locations, where total water use cannot exceed a set allocated volume, regardless of the source of the water. Goulburn Murray Water currently has such a policy in place in some irrigation districts, particularly in those areas covered by salinity management plans, where infiltration of water to the groundwater can cause rising water tables and, subsequently, increased land salinisation. The implementation of the policy is still in its infancy and the data required to enforce this policy is currently not readily available (pers. comm. D Morrison (GMW) October 2000).

While current SYs for some GMUs take into consideration baseflows to rivers and lakes, and have reduced SYs to allow for the maintenance of these surface water flows, these allowances have been made on the basis of very limited information. The impact of groundwater use on river baseflow needs to be monitored to determine whether the assumptions that have been made are correct, and what management actions are required in order to ensure that surface water resources are not impacted upon by the extraction of groundwater resources.

Impediments to Conjunctive Management of Surface and Groundwater Resources

Impediments to the conjunctive management of surface and groundwater resources are:

Priorities for Conjunctive Management

Rural water authorities have identified streams that they consider require investigation as a matter of priority because of their potential interaction with groundwater systems. These are listed in Table 8, along with the GMU that impacts on those streams. Monitoring is required in these situations to determine the connection between surface water and groundwater.

Table 8. Surface Water Bodies Requiring Further Investigation Into Possible Conjunctive Management

RWA Surface water body GMU Comments/Concerns raised by RWAs
SRW Freestone Creek Wa De Lock
Moorabool River Bungaree
GMW Upper Ovens River (above junction with Buffalo River) Murmungee
Kiewa River and tributaries Mullindologong
Yea River Possible recharge to aquifer upstream of Nagambie GMU Macquarie Perch endangered, large number of dams; small reduction in base flow may affect water quality; possible demand for groundwater by subdivision.
King Parrot Creek Possible recharge to aquifer upstream of King Lake GMU Possible demand from irrigation and subdivision; Murray cod endangered; high diversion from stock and domestic bores.
Seven Creeks Possible recharge source to aquifer upstream of Nagambie GMU Endangered Trout Cod; possibility of irrigators increasing demand on groundwater as surface water capped.
Loddon River above Cairn Curran Reservoir Recharge to aquifer upstream of Moolort GMU Fish threatened; high value vegetation; low base flows which should be protected.
Nariel Creek Recharge to upper Murray River and possibly to Mullindolingong GMU
Delatite River Possible recharge to aquifer upstream of Alexandra GMU

For the purposes of the Audit, a further assessment was made of the priorities for considering conjunctive management of surface and groundwater resources. The results of this assessment are shown in Table 9. The listed priorities are based on the categorisations of the various GMUs and SWMAs relative to current use, and on the degree of physical connection between surface water and groundwater systems. Of the 63 GMUs in Victoria, 44 are physically connected to surface water resources.

Having prioritised GMUs and SWMAs in relation to the need for conjunctive management, the next steps would involve specifying and prioritising particular river reaches and the aquifers connected to those particular reaches. Information currently available indicates that most aquifers are connected either in part to a river reach, or have variable connection along a stream's length (see Appendix 2 for further information). More detailed information would be required prior to any conjunctive use policy or management process being put in place. This would include information on the physical processes and connections between surface water and groundwater systems, on the impacts that high use of groundwater or surface water has on the other resource, and an estimate of the joint 'sustainable yield' for the combined systems. As each case differs from the next, management strategies would need to be tailored to particular situation.

Planning for Conjunctive Management

One possible way of integrating surface and groundwater planning processes would be to amend the legislation to include provision for 'Water Management Plans'. Such Plans would specify (inter alia) how the groundwater baseflow would be shared between groundwater users, surface water users and the environment.

An available option would be to declare a zone of a fixed width adjacent to a stream, in which groundwater extraction is treated as if it were a stream diversion. At present there are zones defined for some streams in Victoria where this is the case. However, these zones are generally applied to a relatively narrow strip adjacent to the stream and are determined somewhat arbitrarily. Water Management Plans could also allow for the allocation in any particular season to be 'biased' towards either groundwater or surface water, depending on the state of each resource at the time.

Any conjunctive use policy or management process put in place would require much more detailed information on the physical processes and connections between surface and groundwater than is currently available. Considerable work would be required to provide this understanding and such investigations are outside the scope of the Audit.

Table 9. Prioritisation of GMUs and SWMAs for Conjunctive Management

GMU Level of connection with SWMA
SWMA Priority SWMA High Medium Low Nil
High Werribee

Deutgam

Merrimu

 - - Cut Paw Paw
Barwon

Gerangamete

Gellibrand

 Bungaree - -
Corangamite

Gerangamete

Warrion

Colongulac

 - - Paaratte
Broken -

Katunga GSPA

Goorambat

Shepparton GSPA

Kialla GSPA

 -
Goulburn -

Katunga GSPA

Alexandra

Campaspe GSPA

Shepparton GSPA

King Lake

Kialla

Nagambie

 -
Campaspe Campaspe GSPA Ellesmere Shepparton GSPA
Loddon

Campaspe GSPA

Ascot

Bridgewater

Bungaree

Moolort

Ellesmere

Salisbury West

Spring Hill GSPA

 Shepparton GSPA

Glengower

Bullarook

Tourello
Avon Wa-de-lock - Sale GSPA Seacombe Rosedale
Thomson-Macalister

Denison GSPA

Wa-de-lock

 - Sale GSPA

Seacombe

Rosedale
Medium Mitchell Wy Yung - Sale GSPA -
Yarra Wandin Yallock Moorabbin King Lake -
Moorabool - Bungaree - -
Hopkins

Ascot

Nullawarre GSPA

Yangery GSPA

 - -

Glenormiston

Tourello
Ovens Murmungee Barnawatha - -
Lower Latrobe Denison GSPA Moe Sale GSPA

Seacombe

Rosedale
Low Bunyip Lang Lang

Moorabbin

Frankston

 Nepean Koo-wee-rup / Dalmore GCA
Millicent Coast Lake Mundi - -

Neuarpur GSPA Telopea Downs

Lillimur (Kaniva)

Boikerbert
Kiewa Mullindolongong - - -
Glenelg Lake Mundi

Portland

Condah
Otway

Gellibrand

Nullawarre GSPA Colangulac

Newlingrook

 - Jan Juc Paaratte
South Gippsland Leongatha Giffard Corinella

Seacombe

Rosedale

Tarwin
Maribyrnong Lancefield Cut Paw Paw
Portland Yangery Heywood -

Portland

Condah

No physical connection

(all categories of SWMA and GMUs)

 East Gippsland - - - -
Snowy - - - -
Tambo - - - -
Avoca - - - -
Mallee - - -

Murrayville

Berrook

Telopea Downs
Wimmera - - - Balrootan
Mitta Mitta - - - -

* Text Colours for GMU & SWMA current use categorisations:

Category 4 = Red; Category 3 = Pink; Category 2 = Green; Category 1 = Blue

Development Potential

Demand Trends

For the purposes of predicting likely future demands, total demand for water has been considered at an SWMA scale and as comprising three sub-components; namely urban domestic, industrial/commercial and irrigation. Rural domestic and stock demand was included in the urban domestic component. In making predictions, a distinction has been made between future demand and future use, with demand being considered to be the unrestricted demand for water, and use being the amount of water that could realistically be supplied to meet forecast demand, after various constraints on supply have been taken into account.

The first step involved predicting future demands in each SWMA. Average rates of economic growth for each SWMA, representative of the next 20 years (i.e. out to the year 2020), were derived from the MONASH model (Adams et al 1994). This model is a general equilibrium simulation of the Australian economy that was first developed in the late 1970s. It accounts for 115 different commodity inputs, and has been used widely in Australia as a tool for practical policy analysis by academics, government and the private sector. Factors such as land capability, population trends and social issues are embodied in the growth rate projections.

Specifically, MONASH consists of equations describing:

Demand and supply equations for private sector agents are derived for the solution to an optimisation problem (cost minimisation, utility maximisation etc), which are assumed to underlie the behaviour of the agents in conventional neo-classical economics. The agents are assumed to be price takers, with producers operating in competitive markets.

The MONASH model was run to project growth rates of real value added (or output) and employment for 61 industries in 11 regions (Statistical divisions) in Victoria for the period 1996-97 to 2019-2020. In most cases these Divisions correspond relatively well with SWMA boundaries. However, in some situations it was necessary to adjust results (using an areal weighting technique) to derive growth estimates for SWMAs.

The economic growth rates obtained from the MONASH model were subsequently converted to baseline water demand forecasts using the method employed by the Australian Academy of Technological Sciences and Engineering in a recent study of Water and the Australian Economy (AATSE 1999). This method requires the estimation of a set of generic 'water use coefficients' that relate the level of economic activity (value added) to the amount of water consumed.

For this study the method used to establish these relationships involved the following steps:

As noted above, total demand has been considered as comprising three distinct sub-sectors - urban domestic, industrial/commercial, and irrigation. Unfortunately, the MONASH model provides forecasts only for the industrial, commercial and irrigation sectors. Forecasts of growth rate for the urban domestic component were therefore made using household and population forecasts published by the Victorian State Government (Department of Infrastructure 1996, 1999).

The adopted growth rates are summarised in Table 10. These estimates indicate that the highest rates of growth exist in the industrial/commercial and irrigation sectors.

Table 10. Estimated Rates of Growth in Water Demand (percent per annum)

No. SWMA Urban Domestic Industrial/Commercial Irrigation
North of the Great Dividing Range (Murray-Darling Basin)
1 Upper Murray -Eastern Tributaries 0.482 2.855 2.513
2 Mitta Mitta River 1.298 2.950 2.452
3 Kiewa River 2.708 2.761 2.590
4 Ovens River 0.734 2.813 2.401
5 Broken River 0.843 2.943 2.451
6 Goulburn River 1.060 2.752 2.520
7 Campaspe River 1.486 2.881 2.406
8 Loddon River 0.974 2.843 2.216
9 Avoca River 0.173 2.847 2.506
10 Mallee 0.851 2.850 2.432
11 Wimmera-Avon Rivers 0.107 2.857 2.161
South of the Great Dividing Range
1 East Gippsland 1.325 2.798 2.591
2 Snowy 1.325 2.798 2.591
3 Tambo 1.325 2.798 2.591
4 Mitchell 0.715 2.807 2.572
5 Avon 0.419 2.798 2.591
6 Thomson/Macalister 0.608 2.783 2.570
7 LaTrobe 0.510 2.776 2.669
8 South Gippsland 1.797 2.662 2.654
9 Bunyip 0.978 2.823 2.499
10 Yarra 0.289 2.784 2.310
12 Maribyrnong 0.995 2.877 2.304
13 Werribee 2.045 2.931 2.431
14 Moorabool 2.051 2.846 2.438
15 Barwon 1.053 2.762 2.543
16 Corangamite 0.548 2.764 2.618
17 Otway 0.920 2.740 2.611
18 Hopkins 0.427 2.744 2.616
19 Portland -0.254 2.778 2.653
20 Glenelg -1.013 2.794 2.627
21 Millicent Coast -0.459 2.770 2.230

The derived growth rate data was then used to estimate unrestricted water demand assuming a compound growth function:

where UDi = projected demand in year 'i'

UDo = initial demand in 'year zero'

r = rate of growth in demand

n = number of years since 'year zero'.

It should be noted that these forecasts are for total demand within a SWMA, which could potentially be met from either surface or groundwater sources. In the absence of any other information, it was necessary to assume that the derived growth rates would continue through to the year 2050.

Based upon the figures obtained, total demand for water in Victoria is expected to increase at a rate of approximately 2.3% p.a. However, a number of factors will act to constrain this growth. These factors are discussed below.

Constraints to Development

There are a number of constraints on further growth in water use in each of the SWMAs and GMUs which mean that forecast use in 2020 and 2050 may be less than forecast demand. These are:

Unfortunately, sustainable yield determination for SWMAs is a complex task, requiring detailed environmental assessments and, given the time frame of the Audit, many simplifying assumptions have had to be made. As a consequence, for the various SWMAs a number of different methods have been adopted for determining sustainable yield. For SWMAs located north of the Divide within the Murray Darling Basin, further increases in water use are not permitted under the Murray Darling Basin Cap and sustainable yields have been set at 1993/94 modelled levels of usage (as per requirements under the Cap). Therefore, there is no potential for further increases in water use within these SWMAs. However, in these SWMAs there is nevertheless still significant potential for further water-based economic development via the trading of water entitlements and the freeing up of water via efficiency gains, both in distribution systems and in on-farm water use.

Similarly, south of the Divide, there are a number of SWMAs where sustainable yield has been set at current allocation levels as an interim measure pending the completion of detailed environmental studies (the Snowy, Tambo, Mitchell, Avon, Thomson-Macalister and Latrobe Rivers) and/or Streamflow Management Plans the Yarra and Moorabool Rivers). The current potential for further increases in water use in these SWMAs is therefore dependent on the 'gap', if any, between current usage and the estimated sustainable yield (i.e. the current allocation). Once the various studies and investigations have been completed, there may be identified opportunities for further increases in use within these SWMAs. As is the case for SWMAs in the Murray Darling Basin, there are also current opportunities in these southern SWMAs for further increases in water-based economic activity via water trading and efficiency gains.

In relation to the determination of sustainable yields for GMUs there are several limitations. These include:

Because of these limitations a conservative approach has been taken in the estimation of sustainable yields for GMUs, which have been based on the Permissible Annual Volume work undertaken for NRE (SKM 1996, Woodward-Clyde 1999).

While further increases in use are limited in GMUs where current allocations are close to or at the sustainable yield, as is the case for surface water, further water-based economic development is possible via increases in water use efficiency (nearly 70% of groundwater is used for irrigation) and water trading. A moratorium on the issuing of further licenses is currently in place for the highly developed GMUs, until further information on the resource is available to quantify the sustainable yields more accurately, and the actual current use. As estimates of sustainable yield are reviewed based on the additional information being gathered, there may be additional opportunities identified for further increases in use in some GMUs.

The majority of Victoria's surface water sources are considered to be of a high quality, with the exception of the Avoca, Lake Corangamite and Hopkins SWMAs where further increases in surface water use are constrained by the salinity of the resource. However, conjunctive use of high and low quality water sources, and promising research into 'halophytes' (crops that prefer brackish water) provide potential opportunities for utilising poorer quality water. There is also scope for the development of industry not dependent upon high quality water.

Groundwater resources across Victoria have varying standards in water quality. Of the approx. 800 GL available in the GMUs in Victoria, 68% have less than 1500 mg/L TDS. A further 27% have less than 5000 mg/L TDS which is of a quality generally suitable for stock and irrigation purposes. Resources outside of the GMUs are more saline, and are hence less likely to be used in the future. Fifty percent of the groundwater outside of GMUs is greater than 5000 mg/L TDS, with 28% of this greater than 14,000 mg/L TDS. Consequently there is currently a lack of demand for these resources, as higher quality resources still remain unutilised. The Otways is the most likely area for future development outside of current GMUs, as there is water of less than 5000 mg/L TDS available in parts of this Province, and current demands for water are high. There is also geothermal development potential for some of the aquifers in this Province.

For the purposes of forecasting likely surface water use in 2020 and 2050, it was necessary to first evaluate the feasibility of developing new sources of supply, and to estimate the likely costs associated with potential new sources of supply.

The price of water charged to a consumer is determined by the commercial cost of supply and pricing policies. Pricing considerations may act to reduce (through subsidies) or increase the price for supply incurred by the end consumer. Pricing effects have not been considered in this study; rather, the estimated economic cost of recovery has been used.

Costs associated with developing a water resource differ between groundwater and surface water sources. Groundwater costs are comprised of a bore development cost and subsequent licensing fee. In contrast, the principal costs for surface water development are the capital cost of construction, treatment (if necessary), and delivery and distribution of the water. Comparing costs, groundwater is in many cases the cheaper option, although it is most often used for local supply at the point of extraction.

Surface Water

A state-wide investigation into potential dam sites for further surface water development was completed by the Rural Water Commission in 1986 (Alexander and Haydon 1986). The sites identified in this study are still relevant today. Of the 143 potential dam sites identified, 73 were selected for detailed analysis. Site locations were restricted to high yielding streams with a salinity less than 1600 EC (1000 mg/L). Annual yields from these potential new storages were computed, together with estimated capital costs.

For the purposes of forecasting likely use in 2020 and 2050, estimates of the costs of supply from the potential new storage sites were made. The capital costs were based upon the estimates provided by Alexander and Haydon (1986), indexed to 1996. Water treatment and supply costs were extracted from annual reports provided by each of the water authorities. Distribution costs were based upon detailed pipe costings for the Northern Adelaide Plains network.

Desalination was also considered as a potential opportunity for fresh water supply. Currently no large scale desalination processes are in operation in Australia. However, the economics of such plants are becoming more favourable when considered as part of a large scale industrial process. The cost of desalination technology varies significantly, being dependent upon the type of technology (ie. reverse osmosis or thermal desalination), raw water quality, site infrastructure requirements, raw water source, and the cost of energy. Based upon these factors it is difficult to accurately estimate the cost of desalinated water. However estimates made for Western Australia range from $1,000 to $1,500 per megalitre.

Groundwater

The identification of areas for potential groundwater development in GMUs was based on the Permissible Annual Volume work undertaken by Sinclair Knight Merz for NRE in 1996. The initial work was based on existing developed groundwater resources, where demands were high. Further areas have been listed since 1996. Around 90% of the licensed volume of groundwater is used within these GMUs, and further development in these areas is expected over the next 50 years.

Resources in shallow aquifers of good quality water are already being harvested across the State. Other good quality resources that lie in the Highlands of Victoria will not be developed for various reasons, particularly because of the costs involved. Aquifers in fractured rock systems such as those in the Highlands (which generally have high quality water) typically have uneconomical yield rates. Deeper aquifers in some locations (e.g. the Gippsland and Otway Basins) are currently being utilised for industrial and urban supplies where the users find it economically feasible to invest in the infrastructure required to ensure security of supply.

Groundwater extraction costs were computed for the various GMUs across the State. These costs were based on depth of the GMU, its transmissivity (or aquifer yield), geology (hard or soft rock) and aquifer type.

Costs vary considerably for groundwater production bores depending on the geology, depth of the aquifer, the nature of the use and the yields required. A windpump for stock and domestic use may cost around $20,000 with annual maintenance costs of $1000 per annum. An industrial purpose geothermal bore of depth 500m, such as in the Otway Province on the western coast of Victoria, could cost around $1,000,000, plus annual maintenance costs. Most bores have a minimum lifespan of around twenty-five years, with current construction techniques possibly giving even longer lifespans. This again is dependent on the groundwater quality. High yielding bores will pay for themselves over the lifespan, but if the bore requires refurbishment or replacing these costs can be significant. These are some of the issues faced by groundwater users in Victoria.

Groundwater users are also subject to licence fees. Groundwater licensing costs are split into three components:

Costs of groundwater licenses have increased over the last 5 years with the implementation of user-pays systems and full cost recovery by water authorities. The costs vary across the different Rural Water Authorities and will also vary across the GSPAs where costs will be tailored to enable the recovery of groundwater monitoring and management costs.

Groundwater is rarely used off site and infrastructure is generally privately owned, unlike surface water infrastructure which has historically been government owned. As such, the groundwater industry has been price-driven for a lot longer than surface water supplies. For many groundwater users though, who are users of small volumes of water, there is a sensitivity to the price rises which are required to cover the costs of proper groundwater management.

For the purposes of modelling, costs of groundwater development were determined on a GMU basis and applied to each SWMA that the GMU lies within. Individual bore costs within GMUs were determined based on the costs of construction, development, maintenance and use of a bore, as described above. These costs were summed, and expressed on a $/ML basis, using an estimate of the average yield of the aquifer in the GMU. Due to significant variability in geology, depth to water, yield, and the type of bore construction (according to the use of the water), the cost estimates for individual bores are highly variable within a GMU, as well as between GMUs. The final cost estimates should therefore be considered to be indicative of the order of magnitude of groundwater extraction costs across a GMU, rather than a realistic estimate of actual costs in specific situations.

Annualised Costs

All costs (surface and groundwater) were expressed as a fixed annualised recovery cost per megalitre of water supplied ($/ML/yr). Once-off capital costs were annualised across the design life of the infrastructure using a discount rate of 8%; an acceptable discount rate for financial evaluation. It should be noted that the cost estimates assume full utilisation of the resource over the entire design life of the structure. In reality the resource may only be partially utilised in the early part of its life. Hence, full cost recovery is not being achieved during the first few years of use. This is further complicated because the time taken to achieve full cost recovery depends upon the assumed growth rate of demand and the initial consumption. These factors mean that the adopted estimates are likely to be slightly underestimated. However, the error is considered small, particularly given the limitations of the raw data.

Forecast Use

Water use was forecast for each SWMA across Victoria for the years 2020 and 2050. The forecasts are based upon the projections of unrestricted demand, adjusted for the developmental constraints discussed above. It is assumed that new demands will be met through the use of additional resources - i.e. no account is taken of the potential for future demands to be met via efficiency savings or via water trading.

The forecasting process can be summarised as follows:

The demand and supply process was conceptualised on a SWMA basis, and a computer model was developed to forecast average annual consumption and yield development up to the year 2050. Several model parameters were used to characterise water demand and the available water resources. These parameters are summarised in Table 11.

Water use, the demand that can be reasonably met by available supply sources, is computed according to the flow chart illustrated in Figure 3. Initially, the unrestricted demand is computed according to a compound growth function (as outlined above). This value represents an upper limit on future use. Water to meet new demands is first allocated from already developed sources and a cost is computed. Water sources are then sequentially selected to meet demands on the basis of an acceptable water quality and least cost. In the common situation that a particular user group sources its water from multiple resources, one cost is still assumed to apply to all users, and this is computed as a yield-weighted cost. The cost remains constant throughout the use of a particular supply source. However, when it is necessary to augment the water supply system by adding a new source, the cost rises to account for the development costs of the new resource. In this situation, the price rise is used to compute the degree to which the initial estimate of unrestricted demand is likely to be constrained by cost. This computation is made by applying a consumer response model that incorporates the arc elasticity of demand. This has the effect of constraining consumption to those users willing to pay the higher price for water (see Figure 4).

Table 11. Model Inputs

No Parameter Units Description
Water demand inputs
1 Initial Demand; UDo ML/yr Water consumption recorded in 1996/97.
2 Desired water quality EC Maximum salinity acceptable for the intended use.
3 Growth rate of demand: r % p.a. Estimated average rate of growth between 1996 and 2050.
4 Arc elasticity of demand: e - A measure of the consumer response to a price change. By definition, it is the ratio of the percentage change in water demanded to the corresponding percentage change in price.
Water supply inputs
1 Average annual yield ML/yr The average yield that can be sustainably harvested from the nominated source.
2 Annualised cost $/ML/yr Annual recovery cost estimated assuming a discount rate and design life of the infrastructure.
3 Water quality EC The salt concentration of the water source.

In the extreme case, the response model may predict an overall decline in demand if the price rise is very high. It is argued that if the cost of system augmentation is so great as to cause such a decline, the new resource would in fact not be developed at that time. Instead, demand would remain at the existing level of development until some time in the future, when consumers would be willing to pay the cost of further resource development. Clearly, it is difficult to determine at what time in the future consumers would support this development. However, it is likely to be a function of the growth in demand and proportional to the price increase incurred. On this basis, the model determines the likely delay in system augmentation by computing the immediate decline in water use caused by the price increase and simulates the time taken for it to return to system capacity based on the adopted growth rate. This is illustrated by the dashed curve in Figure 4.

Figure 3. Water Use Forecasting Algorithm

Figure 4. Hypothetical Projection of Water Use

The model sequentially allocates water to meet user (restricted) demand on a year by year basis. Urban domestic users receive priority of water over industrial/commercial users and, similarly, industrial/commercial users receive priority over irrigation users. Hence, low priority users may be progressively excluded from a particular resource required by higher priority users.

This modelling process is repeated annually for each of the SWMAs until the year 2050.

In interpreting the results of this modelling exercise, a number of limitations must recognised:

The impact of water trading and improvements in water use efficiency could be incorporated in the model via the assumed growth rates. However, these impacts are extremely difficult to forecast and any attempt to estimate them is likely to be subjective. No attempt has therefore been made to allow for them in this assessment. [Note that in the State Overview Report a distinction is made between development potential in terms of the potential for further increases in water use ('volumetric development potential'), and development potential in terms of the potential for further increases in water-based economic activity ('economic development potential')].

Figure 5. Example of the Spatially Inexplicit Limitation of the Model

In addition, the model develops water resources sequentially, rather than simultaneously. While this is generally true for the development of large surface water storages which can be used to supply extensive regions, it is not the case for most groundwater resources which usually only supply relatively local consumers.

These factors operate to spatially distort the 'picture' of future groundwater use, although it is considered that the forecast total demand across the State is likely to be a reasonable indication of the likely future development of the total groundwater resource.

Because of the difficulties associated with forecast future groundwater use, a second approach was used to obtain more realistic forecasts of groundwater use within the various SWMAs. This was based on work undertaken for NRE (Read Sturgess and Associates 1997). This work split demand across urban (domestic and industrial), irrigation and rural (domestic and stock) uses, which is a slightly different break up of use types compared with those used for the MONASH model. Demands were predicted for each GMU over the 50 year period, for each of the three consumer groups. The adopted growth rates are based on a series of scenarios run for each of the three consumer groups, using a stepped linear growth rate for the periods 1999 to 2020 and 2021 to 2050. The final growth rates adopted were the best fit with current trends and represent an average demand scenario. Average growth rates over 50 years for irrigation and rural use were estimated to be 1.30% and 1.25% per annum respectively. For urban use, it was decided to adopt a stepped linear growth rate, with the growth rate over the first 20 years (1999 to 2020) being 1.25% per annum, after which it slows to 0.70% per annum (2021 to 2050).

As expected, the overall growth rate in total groundwater use across the State predicted by Read Sturgess was comparable to that predicted using the spatially inexplicit modelling approach. The Read Sturgess model forecasts for GMUs were used to determine forecast use within the various SWMAs by areally splitting results for GMUs across the relevant SWMAs.

It should be noted, however, that in predicting future groundwater demands, one missing factor is the ability to foresee which GMUs will break away from a steady growth pattern to one of 'explosive' growth to full allocation due to the attributes of that area (e.g. soil type, climate) suddenly being in demand for particular enterprises. It is believed that all GMUs will be fully developed in 50 years, and that most growth will occur in 'agribusiness' style enterprises, and not small family farm operations.

Additional minor limitations in the modelling approach include:

Categorisation in 2020 and 2050

The various SWMAs and GMUs were categorised according to the forecast use of these resources in 2020 and 2050 as a proportion of their respective sustainable yields.

Data and Information Gaps

As resources become more fully utilised, the need for data and information to ensure their effective management and sustainable use increases. Priorities include the following:

Surface and Groundwater Monitoring

Water Use

Environmental Water Requirements

Improved 'Process' Understanding

Data Management

Future Research and Development

Priorities for further data and information to ensure the effective and sustainable management of Victoria's surface and groundwater resources are identified in the Section on 'Data and Information Gaps' above.

Many of the identified information gaps are being addressed by projects currently underway within NRE and by the current research programs of the Cooperative Research Centres (CRCs) for Catchment Hydrology and for Freshwater Ecology.

It is clear that the sustainable management of Victoria's land and water resources requires 'clever' spatially integrated solutions within catchments - so that, for example, high water using species can be located so as to maximise the their salinity mitigation benefits while minimising adverse impacts on surface and groundwater yields. One of the more critical needs is therefore for analytical tools that allow for the integrated assessment of the impacts of management initiatives on land and water resources across catchments and over time. The modelling 'toolkit' being developed by the CRC for Catchment Hydrology, which will comprise an integrated suite of existing and new models aimed at providing such a predictive capability, should prove useful in this regard.

References

Adams, P. D., Dixon, P. B. and McDonald, D (1994) MONASH forecasts of output and employment for Australian industries: 1992-3 to 2000-01, Australian Bulletin of Labour, v 20, n.2.

AATSE (1999) Water and the Australian Economy, A joint study project of the Australian Academy of Technological Sciences and Engineering and the Institution of Engineers, Australia, April, 1999.

Alexander, D.P. and Haydon, S. R. (1986) 'Long Run Incremental Costs of Annual Regulated Flow in Victorian River Basins', unpublished report prepared by the Rural Water Commission for the Department of Water Resources.

Department of Infrastructure (1996) Victoria in Future - The Victorian Government's population projections for the State's Local Government Areas, 1996-2021, Department of Infrastructure, Research Unit, Victoria.

Department of Infrastructure, (1999). Towns in Time: Data, Department of Infrastructure, Research Unit, Victoria.

DCE (1991) Water Victoria, The Next 100 years, Department of Conservation and Environment, 1991.

Gehrke, P.C., Brown, P., Schiller, C.B., Moffatt, D.B. and Bruce, A.M. (1995) River Regulation and Fish Communities in the Murray-Darling River System, Australia. Regulated Rivers Research and Management 11: 363-375

Goulburn Murray Water (GMW) (Sep. 1997) Murray-Darling Basin Water Audit Report 1996/97, Victoria, Murray-Darling Basin Commission.

Goulburn Murray Water (GMW) (1997) Annual Report 1996/97.

Read Sturgess and Associates (1997), 'Investment analysis of groundwater activities', Unpublished report prepared for the Department of Natural Resources and Environment, April 1997.

SKM (1996) 'Permissible Annual Volume Reports', Series of unpublished reports prepared by Sinclair Knight Merz for the Department of Natural Resources and Environment.

SKM (1997) 'Investment analysis for groundwater management', Unpublished report prepared for the Department of Natural Resources and Environment, August 1997.

White, L. and Ladson, A. (1999) Index of Stream Condition Reference Manual. April 1999, Melbourne.

Woodward-Clyde (1999) 'Permissible Annual Volume Reports', Series of unpublished reports prepared by Woodward-Clyde for the Department of Natural Resources and Environment.

Appendix 1

1. Estimation of Sustainable Yield using the Hydrology Sub-Index of Index of Stream Condition

The Index of Stream Conditions (ISC) is an approach developed for the broad level assessment of stream condition. The method consists of calculated stream condition scores for five sub-indices - water quality, aquatic life, physical form, streamside zone and hydrology. The hydrology sub-index has been used in the assessment of sustainable yields for this Audit.

The hydrology sub-index relies on a formula referred to as the Amended Annual Proportional Flow Deviation (AAPFD) that was developed by NSW Fisheries. The formula calculates the degree of change to the natural flow regime (Gehrke et al. 1995) and is given below.

where

N is the period of record (years);

Cij is the actual flow for month i of year j;

is the average monthly flow for year j, ie. .

A rating table has been developed to relate the AAPFD score to stream condition. This rating table is shown in Table A1.1.

Table A1.1. Rating Table For The Index Of Stream Condition (ISC) Relating AAPFD Scores To ISC Catchment Condition Ratings (after White and Ladson 1999)

AAPFD ISC Rating
<0.1

(excellent condition)

10
> 0.1-0.2 9
>0.2-0.3 8
>0.3-0.5 7
>0.5-1.0 6
>1.0-1.5 5
>1.5-2.0 4
>2.0-3.0 3
>3.0-4.0 2
>4.0-5.0 1
>5.0

0

(very poor condition)

The AAPFD formula was used in reverse to estimate the sustainable yield of an SWMA. The sustainable yield was determined by calculating the total volume of water that can be extracted from the river system (during May to November) such that the degree of change to the natural flow regime is not 'unacceptable'' as defined by the achievement of a rating of no less than 5 for the Hydrology sub-index of the Index of Stream Condition (ISC). The change in the natural flow regime was achieved by subtracting a monthly diversion from the monthly flow for the period of available natural flow record. The monthly diversion volumes were determined as a proportion of the natural flow monthly volumes and were restricted to the period May to November, inclusive. The application of this diversion pattern maximises the total volume of water that can be diverted.

The sustainable yield was reported as the maximum average annual volume of water that can be diverted while maintaining an AAPFD score of no less than 5.

Appendix 2

Table A2.1 indicates the surface water systems (river reaches, lakes and other surface water bodies) that the various GMUs are connected to. The degree of physical connection between surface and groundwater systems will vary spatially and temporally, with river flows dictating whether reaches will be discharging to groundwater, or receiving recharge from groundwater (commonly referred to as baseflow) during low flow periods.

Extensive investigations are required for each river reach, the nature of which will vary according to the type of aquifer system it is connected to, before any policy or management process can be put in place to conjunctively manage the total water resource.

Table A2.1. Groundwater Connections With Surface Water Bodies, Listed By GMU

GMU Physical Connection with Surface Water Systems
Wy Yung Connected to Mitchell River, with parts recharging aquifer (5788 ML/yr) and other parts discharging to the river (939 ML/yr). Relationship with river not well known. In drought, irrigators resort to groundwater when in fact it is already depleted due to discharge to river. A minimum level for groundwater needs to be set to ensure that extractions do not compromise baseflow in the River.
Seacombe None
Sale GSPA Possibility of saline water recharging the aquifer from the Gippsland Lakes if groundwater levels drop below sea level.
Wa De Lock Discharge to the Macalister, Thomson and Avon Rivers occurs in zones 1 & 2, although it has not been quantified. In zone 2, in low flow periods Freestone Creek is dependent on groundwater and the integrated management of surface and groundwater resources is required.
Denison GSPA River recharge of around 1752ML/yr occurs from Rainbow Creek and along the upper part of the Thomson River.
Moe Recharge of approx. 2263 ML/yr occurs to the aquifer from the LaTtrobe River in the Willow Grove and Narracan Creek. In the south-west portion of the GMU, discharge to LaTrobe River of approx. 526 ML/yr occurs.
Leongatha Aquifer discharge to Tarwin River of around 3500 ML/yr, with most annual recharge discharging to river if not extracted from the groundwater system.
Tarwin Seawater intrusion is an issue for this GMU.
Lang Lang Seawater intrusion is an issue for this GMU.
Corinella Discharge to Bass River of 146 ML/yr.
Alexandra Discharge to Goulburn River of 1241 ML/yr.
King Lake Discharge to Pheasant Creek of 170 ML/yr.
Wandin Yallock Groundwater connection with Wandin Yallock Creek (at approx. the same level, so it is a variable recharge/discharge relationship depending on river levels) and Stoney Creek which recharges the aquifer at 584 ML/yr.
Lancefield None
Nepean Seawater intrusion is an issue for this GMU.
Frankston River recharge and discharge to the aquifer is thought to be in equilibrium throughout the GMU. Allowance was made in the groundwater sustainable yield estimates for the prevention of seawater intrusion.
Moorabbin None
Cut Paw Paw None
Deutgam River recharge and discharge in this area nearly equates to a zero net recharge, with 292 ML/yr river recharge and 438 ML/yr discharge to the local Werribee River and other deltaic streams.
Merrimu Groundwater discharge to the Lerderderg River (in parts) and to the Werribee River. The volume of water discharging to these rivers is minimal at around 13 ML/yr.
Jan Juc Discharge to streams including Anglesea River and Salt Creek, totalling 420 ML/yr. Sea water intrusion is also an issue in this GMU
Newlingrook The Gellibrand River is strongly connected with this aquifer, with nearly 14% of the river flow contributed by groundwater (41,650 ML/yr). Any extractions close to the river should be monitored carefully to ensure that baseflow is not reduced and that the stream does not start losing water to the groundwater, instead of vice versa.
Gerangamete Flows in Boundary Creek would be affected by groundwater extractions, and springs in the area may also be affected if the sustainable yield is totally extracted
Gellibrand Strong connection with Ten Mile, Porcupine, Yahoo and Love Creeks (tributaries of the Gellibrand River), to the extent that he sustainable yield for groundwater will not be allocated to users to ensure that environmental flows within local creeks are maintained.
Warrion Discharge to lakes and rivers, including: rivers (5500 ML/yr), Lake Corangamite (20,600 ML/yr), Eastern Terminal Lakes (11,000 ML/yr), Lake Colac (11,000 ML/yr)
Colongulac Groundwater discharges to springs on edge of lava flows, which in some areas comprise wetlands, and also the lakes, including Purrumbete, Gnotuk and Bullen Merri. Groundwater also discharges to Bostock Creek and other streams at 55 ML/yr.
Paaratte None
Glenormiston None
Nullawarre GSPA Groundwater discharges to the sea and possibly to local streams and land surfaces. Seawater intrusion is the main issue for this GMU.
Yangery GSPA None
Portland None
Condah None (groundwater used for town supply at Macarthur)
Heywood Approximately 10,000 ML/yr is assumed to discharge to rivers, streams, wetlands and along drainage lines.
Lake Mundi Groundwater extraction is limited in this GMU to avoid impacts on local wetland systems which may be dependent on the shallow watertables. Drawdowns of 1m max. were used to determine sustainable yield, to ensure the wetlands were not affected.
Mullindolingong Much of the groundwater in this GMU discharges to the Kiewa River, with 6752 ML/yr in zone 1 and 7136 ML/yr in zone 2. As such, the sustainable yield for this GMU has been set conservatively to ensure that baseflow in the Kiewa River is maintained.
Barnawartha The Indigo and Stockyards Creeks are both gaining and losing streams in the lower and upper reaches of the rivers. The net recharge to the aquifer is zero, with both recharge and discharge equalling 2847 ML/yr.
Murmungee Groundwater discharges to Ovens River, Buckland River and Buffalo River (in total 52,000 ML/yr), supplying approx. 3% of total annual river flow. In drought years groundwater extractions must be monitored to limit impacts on local rivers and depletion of the aquifer.
Goorambat Recharge from the Broken River is estimated at 910 ML/yr. Neither recharge nor discharge from the aquifer to Broken Creek has been taken into account.
Katunga GSPA The GMU receives 6531 ML/yr in river recharge from the Murray River, Broken Creek and Goulburn River. The strong connection clearly indicates the need for conjunctive management of resources in this area.
Kialla Goulburn River recharges aquifer at approx. 302 ML/yr.
Nagambie River recharge of 493 ML/yr from Goulburn River and Hughes Creek
Campaspe GSPA The Campaspe River both recharges and receives discharges from this aquifer in different areas. In the old Diggora GMU 1774 ML/yr of recharge occurs to the aquifer. In the old Echuca South region recharge to the aquifer is 329 ML/yr There is considerable connection between surface water and groundwater in this area.
Shepparton GSPA The objective of the Groundwater Management Plan (this is actually a Salinity Management Plan in essence) "is to ensure that the groundwater resources of the Plan area are managed in an equitable manner", and under S40, that "...consideration be given to the need to protect the environment including riverine and riparian environment...". As such, this region is managed so as to consider all water resources and environmental impacts in the area.
Ellesmere Campaspe River recharges aquifer at approx. 427 ML/yr.
Bridgewater (Loddon) Recharge from Laanecoorie-Serpentine Rivers of around 2526 ML/yr with discharge to streams of around 913 ML/yr. The Loddon River forms a zero flow boundary alongside this GMU indicating no connection to this river in this area.
Salisbury West Groundwater recharge from Loddon River and Bullock Creek, totalling 1862 ML/yr with another 482 ML/yr discharging to the Loddon River in other reaches.
Balrootan (Nhill) None (town supply for Nhill)
Berrook None
Murrayville GSPA None
Telopea Downs None
Lillimur (Kaniva) None (town supply for Kaniva)
Neuarpur - GSPA None
Boikerbert (Apsley) None (town supply for Apsley)
Moolort Recharge of 2142 ML/yr is assumed to come from two storages, Tullarook and Cairn Curran, with some discharge to the Loddon River of 158 ML/yr.
Ascot None
Spring Hill GSPA Some groundwater discharge at edge of lava flows to streams, springs and lakes, although it has not been quantified.
Bungaree Groundwater is likely to discharge to streams, lakes, springs and swamps, although there is little information to quantify the connection or rates of flow.
Glengower None (deep leads)
Bullarook None (deep leads)
Tourello None (deep leads)
Koo-wee-rup Dalmore G/W Conservation Area Seawater intrusion is an issue for this GMU.
Rosedale None
giffard None

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