Information Sheet- Karnup and Dandalup Groundwater
Background
The Karnup and Dandalup groundwater scheme options are separate, but adjacent schemes, situated approximately 55 kilometres south-east of Perth and 20 kilometres north-east of Mandurah. They cover a surface area of about 300 Km2.
The towns of Serpentine, Keysbrook and North Dandalup are situated in the eastern part of the area and the new residential land development area, Keralup (formerly known as Amarillo), is in the western part of the area.
There are a large number of environmentally sensitive wetlands and vegetation in this area. The local area has been mainly cleared for pasture with sheep and cattle. There are some small market gardens as well. There is also some remnant bushland near the wetlands.
The area is hydrogeologically complex. There are three main aquifers in this area, the Superficial, the Leederville and the Yarragadee. The scheme proposal is to access the superficial and the confined aquifers.
The water quality is bordering on brackish and has some colour and turbidity. It would require treatment and may need to be blended with better quality sources.
The superficial groundwater has salinity ranges in the order of 200 to 1500 mg/l, but is predominantly less than 500 mg/l. The Leederville groundwater has salinity ranges in the order of 500 to 3000 mg/l but is predominantly 1000 mg/l. Water for drinking generally should be less than 1000 mg/L and preferably be below 500 mg/l.
Current Situation
Conceptual water source planning has been undertaken. There are potentially significant social and environmental impacts of the proposed groundwater extraction. In addition, the brackish nature of the water is a significant issue for public water supply.
Source protection is an important issue and this would need to be resolved with the Department of Water.
The Future
The scheme configuration is for a series of approximately 90 shallow (~40 metres) and medium depth (~100 metres) bores into the Superficial and Leederville aquifers. The water would be collected, treated and pumped into the IWSS water grid.
The requirements for integration of this source into the IWSS water grid have not been determined at this stage. Development of this source to meet local area future demand would minimise the extra cost of integrating this source into the water grid.
Sustainability Considerations – addressed in planning
Economic | Social and Cultural | Environmental |
| Variable salinity in Leederville aquifer, may lead to additional treatment costs in the future. | Access to the land to locate bores, pipes and possible tanks may lead to protracted negotiations. | Potential lowering of the water table in sensitive areas may affect the extent and duration of wetlands and the flora and fauna which depend upon them. |
| Standard groundwater scheme, similar to many others the Corporation owns. | There are nearly 900 existing private bores in the area. Pump rates of these bores may alter causing concern and loss of water to landowners. | |
| Potentially, a cost effective water source for local use. | Landowners in the area may object to the local groundwater being used for Perth water supplies. |
Potential source yield
The potential source yield is up to 22 gigalitres per year. This is unproven and significant investigation would need to be undertaken.
Potential cost
Costs have not been estimated, but would be typical of other Water Corporation groundwater schemes and would be in the order of $1.00 per kilolitre or less based on supply to local area demands.
If the scheme needs to be connected to the water grid and transferred long distances into other areas, then integration costs will need to be added. This may double the cost of the scheme.
Key
Potential source yield (in 50 year planning horizon)
Potential cost (2007 $)