Canberra
18.3 Discharge to landscape

This process occurs in the Canberra region, but the volume could not be quantified due to the lack of data and a suitable quantification approach. In Canberra the recharge is due largely to rainfall, while discharge generally is to streams and evapotranspiration. Recharge of groundwater and discharge to surface water in fractured rock aquifers is usually localised and as such difficult to calculate. Broad-scale movement of water through an upland fractured system with local flow system is generally limited. During the 2012–13 year, Canberra region experienced a total annual rainfall of  692 mm which was below average compared to its long-term annual average rainfall of 800mm (Figure C3 Graph of total monthly rainfall for the Canberra region). Recharge and discharge from fractured rock aquifers is closely linked to recent rainfall history. As such, it would be expected that the groundwater recharge and consequently discharge from landscape to be lower in 2012–13 than an average year.

The Australian Capital Territory Government, Environment and Sustainable Development Directorate uses an estimate of 74 GL of groundwater recharge each year as a guide when setting limits for ground water extractions; approximately 10% of this recharge is available for abstraction annually.