18.4 Discharge to surface water
This line item refers to the volume of water that naturally discharges from the water table aquifer and underlying aquifers to the surface water system. This process occurs in the Canberra region, but the volume could not be quantified due to the lack of both data and a suitable quantification approach. In Canberra the recharge is due largely to rainfall, while discharge generally is due to streams and evapotranspiration. Groundwater levels in the Australian Capital Territory are linked closely to recent rainfall within the region. As rainfall occurs, groundwater aquifers gradually recharge and discharge groundwater into the surface water system, increasing flow into creeks and rivers. The 2011–12 year was considerably wetter than an average year. As such, it would be expected that the groundwater recharge and consequently the discharge to surface water would be comparatively larger in 2011–12.