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 (70,655 ML) and baseflow at the Yaldara gauging station on the North Para River (1,493 ML) as shown in the following table.
|Underground water management zones||Baseflow (ML)|
|Lower South Para (inc. Lower Gawler River)||1,351|
|Middle South Para River||3,784|
|Upper South Para River (Adelaidean)||1,538|
|Upper South Para River (Kanmantoo)||660|
|Little Para Reservoir||209|
|Lower Little Para River||87|
|Upper Little Para River||1,407|
|Kangaroo Creek Reservoir||1,330|
|Inverbrackie Creek Kanmantoo||305|
|Inverbrackie Creek Adelaidean||567|
|Mount Bold Reservoir||2,644|
|Hindmarsh Fractured Rock||6,484|
|Hindmarsh Tiers Sedimentary||1,372|
|Southern Fleurieu North||4,013|
|Southern Fleurieu South||7,673|
|Western Mount Lofty Ranges Subtotal||70,655|
|North Para River at Yaldara||1,493|
Groundwater discharge to surface water was summed from the annual baseflow figures stated in the Draft Water Allocation Plan for the Western Mount Lofty Ranges PWRA (70,655 ML) and baseflow at the Yaldara gauging station on the North Para River (1,493 ML).
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 to 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 2010–11 year.
- Groundwater discharge to connected surface water was the dominant process in the Western Mount Lofty Ranges.
- Surface water–groundwater interactions outside the draft Western Mount Lofty Ranges PWRA and the catchment for Yaldara gauge are negligible.
This item corresponds to 16.3.2 Groundwater discharge to connected surface water reported in the 2010 Account. There was no change to the volume reported in the 2010 Account. The restated comparative year volume is 72,148 ML.