2.3.2.4 Water balance

The only source of potential rainfall recharge to the Eromanga Basin is via the Innamincka Dome, which lies over the Innamincka Ridge. No other Eromanga Basin units crop out in the Cooper subregion. Some limited recharge via diffuse infiltration of sporadic rain water, flood waters or streamflow through Quaternary and Cenozoic cover sequences may occur, although this is likely to be effectively zero, as a result of extremely low rainfall and high evaporation (Cresswell et al., 2012; Love et al., 2013). The most significant source of groundwater to the Eromanga Basin sequence in the Cooper subregion is inflow from areas outside the subregion.

Groundwater recharge to the Cooper Basin sequence can only occur through vertical leakage from adjacent aquifers or cross-formation flow.

Natural leakage or natural discharge to surface takes place at springs and areas of seepage, as well as in lakes, which are abundant around the margins of the Central Eromanga Basin (Love et al., 2013; Radke et al., 2000). Figure 15 highlights groundwater discharge to the surface at Lake Blanche.

Surface water is present in ephemeral drainages and terminal salt lake systems in the subregion. The drainage network is active following large rain events in the headwaters, and is subject to spectacular flood flows. Springs are the only recognised groundwater contribution to the surface water system in the southern Cooper Basin.