Demise of Uley-Wanilla Basin (Short Version)
Water was first extracted from the Uley-Wanilla Basin for our public water supply in 1949.
The map below is from the Southern Basins Prescribed Wells Area Water Allocation Plan, showing the location and extent of Uley-Wanilla Basin in the year 2000.
The graph below shows the yearly water extraction from 1949 to 2011.
As a result of all this extraction over that time period the area of the basin has shrunk from 37 sq.km to 14.3 sq.km (60% shrinkage).
Bar graph (below) showing yearly extractions from Uley-Wanilla Basin.
More importantly the maximum amount of yearly extraction by SA Water (formerly EWS) has plummeted from close to 2,827 ML/y to about 250 ML/y.
While most of the extraction that has resulted in Uley-Wanilla being so depleted occurred before 2000, the proposed WAP (Water Allocation Plan) makes no mention of closing this basin off to allow recovery.
Diagram showing a Uley-Wanilla cross-section of one of SA Water pumping bores.
This will only occur slowly because of the reduction in recharge caused by over-extraction in the past, and any reduction in natural run-off caused by natural climate variation.
EPWAG believes that the “people’s WAP” should require the complete cessation of water extraction from Uley-Wanilla until such time that its sustainable level of extraction recovers. Should pumping machinery at the Basin need to be switched on for maintenance purposes then the pumped water should be returned directly to the Basin.