18.4 Discharge to surface water
The volume reported (72,148 ML) represents annual average groundwater discharge (baseflow) to watercourses in the Adelaide region. This volume included annual baseflow from groundwater to watercourses within the Western Mount Lofty Ranges Prescribed Water Resources Area (PWRA) (70,655 ML) and baseflow at the Yaldara gauging station on the North Para River (1,493 ML).
Hydstra database and Western Mount Lofty Ranges Prescribed Water Resources Area Water Allocation Plan.
Groundwater discharge to surface water in the Western Mount Lofty Ranges PWRA was summed from the annual baseflow figures detailed in the Western Mount Lofty Ranges PWRA Water Allocation Plan.
The stream gauge for the North Para River at Yaldara (A5050502) was deemed the only streamflow site with a significant baseflow component outside the Western Mount Lofty Ranges PWRA. Baseflow was calculated for this site using a Lyne and Hollick filter (Grayson et al. 1996) with a filtering factor of 0.925 and daily flow records for 1 July 1975–30 June 2010.
Assumptions, limitations, caveats and approximations
- Baseflow at the gauging stations captured all the surface water—groundwater interactions in the catchment.
- Baseflow identified by the Lyne and Hollick filter was entirely due to contributions from groundwater.
- Long-term baseflow represents the flux during the 2012–13 year.
- Groundwater discharge to connected surface water was the dominant process in the Western Mount Lofty Ranges.
- Surface water—groundwater interactions outside the Western Mount Lofty Ranges PWRA and the catchment for Yaldara gauge are negligible.