17.3 Leakage to groundwater
Groundwater recharge from surface water (equivalent to surface water leakage to groundwater) could not be quantified in a way that is complete, neutral and free from material error. Groundwater recharge from surface water, in particular rivers, is an important process on the coastal plains throughout the Adelaide region. In the Mount Lofty Ranges, groundwater frequently contributes to the baseflow component of streamflow and recharges deeper aquifers (Harrington 2004).
Rivers and their tributaries flowing west from the Mount Lofty Ranges across the Adelaide Plains typically start as contiguous-gaining streams then change to contiguous-losing streams after they cross the Eden–Burnside or Para Faults, recharging the Quaternary aquifers. The majority of the smaller watercourses terminate in this zone. Rivers that reach the coast return to being contiguous-gaining streams just before they discharge to the Gulf St Vincent (Sinclair Knight Merz 2011; Turner et al. 1996).
While groundwater recharge from surface water is an important process, insufficient information is available to estimate the magnitude of the impact to the groundwater balance.