The Willunga Basin is a groundwater resource being stressed by groundwater abstraction for agricultural purposes. The Southern Vales Water Resources Committee, in conjunction with MESA, DENR and SA WATER, are developing groundwater management strategies to ensure the long term sustainability of the irrigated agriculture industries which the basin's groundwater resource supports. Resource sustainability is dependant on groundwater extraction not consistently exceeding groundwater recharge. Most components of the water budget for the basin are unknown and therefore the sustainable yield of the basin cannot be quantified at this time. However, groundwater levels are declining in the vicinity of high groundwater use. This indicates extraction is exceeding recharge in the areas of high groundwater extraction. Given the current level of knowledge of the hydrodynamics of the basin, it is inadvisable to increase extraction from the basin at this time. Further work is proposed to quantify major components of the water balance. This work is aimed at defining a sustainable yield for the basin.