Water resources - Availability - Victoria
Basin & Surface Water Management Area: Campaspe River
Introduction
This section presents information about surface water quantity and sustainability. For simplicity of communication, sustainability measures are based on assessing the level of water use and/or allocation with the quantity of water required to fulfil a sustainable flow regime (environmental water provision) - this has been expressed as a sustainable yield.
Vital statistics:
| Mean Annual Run-Off (Natural) (ML/yr) | 305,000 |
|---|---|
| Mean Annual Outflow (Natural) (ML/yr) | 305,000 |
| In-stream commitment (Total available flow - imported water - sustainable yield) (ML) | 184,000 |
| Sustainable Yield - Developed Yield (ML) | 0 |
| Divertible Yield (ML/yr) | 121,000 |
| Developed Yield (ML/yr) | 121,000 |
| Sustainable Yeild (ML/yr) | 121,000 |
| Yield, Security of Supply | |
| Current Development Category | FULL DEVELOPMENT |
| Diversion (ML/yr) | 121,000 |
| Total Available Water | 305,000 |
PLEASE NOTE:
Mean Annual Flow:
The mean annual flow (MAF) for the Campaspe River Basin has been determined as the sum of the average annual diversions, the Mean Annual Outflow (MAO, estimated under current levels of surface water development), the evaporation from the storages, and river transmission losses. The evaporation from storages and river transmission losses were estimated using the existing Resource Allocation Model of the water supply system. The estimated evaporation from Lake Eppalock and the Upper Coliban storages is 18 GL/year. River transmission losses were estimated to equal 3 GL/year.
The calculation of the mean annual flow can be summarised as follows:
MAF = MAO (current) + avg annual diversions + evaporation from storages + river transmission losses.
Mean Annual Outflow:
The flow in the Campaspe River Basin increases downstream. The flow is therefore greatest at the outlet of the Basin and represents both the Mean Annual Runoff and the Mean Annual Outflow (for undeveloped conditions). (Refer to the estimation of the Mean Annual Runoff). This assumes negligible river losses relative to the total outflow from the basin.
The Mean Annual Outflow (MAO) under current levels of surface water development has been determined using a water resource allocation model of the water supply system. The model was run at the 1993/94 level of development, which represents the average diversion that is permitted to take place in accordance with the Murray Darling Basin Cap.
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 conversion process, initiated in Victoria in the early 1990s, has involved a comprehensive assessment of the developed water resource. The developed resource or yield of water supply systems has been established using simulation models of the various supply systems. Within the Murray Darling Basin, the system yields are determined at the 1993/94 levels of development, which is consistent with the Murray Darling Basin Cap on diversions.
The Murray Darling Basin Cap arrangements require that the average diversion within the basin does not exceed the 1993/94 levels of development. Inherent in this cap arrangement is the requirement to meet downstream flow needs.
Therefore the average volume of water that is currently available for diversion represents the surface water development in 1993/94. This defines the developed yield of the basin and is also equal to the average surface water allocation.
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 Victorias River Basins" (Alexander and Haydon 1986). An essential component of the study involved the determination of the incremental costs of future water resource 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:
- Only streams carrying large flows in relation to the total annual basin yield and having a salinity of less than 1600 EC units (1000 mg/l) were investigated for possible storage sites.
- The yield estimation method is based on 95% supply security (a one in twenty year failure to supply unrestricted demands), an urban demand pattern and retention of 20% of storage capacity for dead storage and drought security carryover.
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 (equivalent to around $3300/ML in 1996),were not included in the estimate of divertible yield as these were considered to be uneconomical.
Two potential dam sites have been identified in the Campapse River Basin, providing a net increase in system yield of 2.66 GL. The effective cost of both storages exceeds $3,300/ML and have therefore been assessed as uneconomical. For this reason the divertible yield has been reported as equal to the developed yield.
How has flow regime changed in Campaspe River?
Change in Flow Regimes:
The hydrology of the Campaspe River Basin is significantly changed due to its regulation. There are four major storages in the basin. Lake Eppalock is located on the Campaspe River and was completed in 1962. Malmsbury, Lauriston and Upper Coliban Reservoirs are in the south-east of the Basin on the Coliban River and have storage capacities of 18,000 ML, 20,000 ML, and 31,500 ML respectively.
The impounding of winter and spring flows and releases during summer have resulted in an extreme inversion of the seasonal flow pattern.
The impact of regulation on the river reach immediately downstream of Lake Eppalock can be summarised as follows:
- Currently 75% to 80% of the flow occurs during summer and autumn, due to releases to the irrigation sector downstream. Under natural flow conditions, only 6% of the flow occurs during this period.
- June is now the lowest flow month, with flows reduced to zero in some years. March is the highest flow month, with the total monthly flow representing 24% of the average annual flow.
In the headwaters of the Coliban River, the three reservoirs store and divert water to supply Bendigo and the surrounding region. The impact of the reservoirs has been to reduce the total flow downstream. The mean annual flow has been reduced by almost 50% from 76,200 ML to 39,400 ML. The seasonality of flows has not been significantly modified.
Trade and Transfer - a bit of give and take:
Water use efficiency and optimisation strategies within existing infrastructure (eg. water supply efficiency, precision irrigation and scheduling, water recycling, trading and pricing) are part of the modern water resource development planning tool kit. Recognising that water is a finite resource, the States and Territories have developed water allocation systems where security and reliability are assigned to entitlement, trading is provided so water can be moved to high value uses and the choices of individuals are maximised.
Measurement Stations in Campaspe River
Summary surface water measurement station statistics
| Name | Stream gauge ID | Mean annual flow (ML/yr) | Mean annual flow (mm) |
|---|---|---|---|
| Stream guage 406202 | 406202 | 189,038 | 55 |
| Stream guage 406200 | 406200 | 39,384 | 139 |
| Stream guage 406225 | 406225 | 91,255 | 44 |
Modelled unimpaired stream-flow sites in Campaspe River
Over 300 sites across Australia were modelled to predict the unimpaired (natural) stream-flow. The long time series of stream-flow data are important for both research and management of Australia's hydrological and ecological systems. A simple conceptual daily rainfall-runoff model was used to extend the stream-flow data.
The model estimates stream flow from daily runoff and potential evapotranspiration data. The parameters of the model are first calibrated against the available stream-flow data. The optimised parameter values are then used to estimate monthly stream flow from 1901 - 1998.
For further information please refer to : Project Report - Stream Flow Study
Table: Summary unimpaired stream flow sites statistics:
| Station Name | Mean annual runnoff | Mean annual rainfall (mm) |
|---|---|---|
| AXE CK AT LONGLEA | 72 | 608 |
| CAMPASPE R AT REDESDALE | 144 | 800 |
Further information
- Victoria Water Resources Assessment 2000 Technical Report
- report from the study of streamflow data and modelled streamflow
- Link to data available for download on the:
- extension of unimpaired monthly streamflow data and regionalisation of parameter values to estimate streamflow in ungauged catchments (NLWRA 2000)
- Surface Water Management Areas
- Link to the Map Maker to make a map using this information.
Key
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