South East Queensland
18.4 Discharge to surface water

Supporting information

a. Overall

This line item represents the groundwater discharge into surface water within the South East Queensland (SEQ) region.

b. Groundwater – surface water interaction

This process occurs in the SEQ region, but the volume could not be quantified in a way that is complete, neutral and free from material error due to the lack of both data and a suitable quantification approach.

When modelling the interaction between the surface water and groundwater within an area, typically only the net flow is able to be estimated. Due to the limited development of groundwater resources outside of the groundwater management areas described in line item 2.1 Water table aquifers; modelling of this flux has not been developed sufficiently to estimate the flow. The magnitude of this flow is currently unknown.

In general, groundwater levels higher than surface water levels indicate groundwater discharge into surface water and vice versa. Surface water groundwater interaction is vital for the health of rivers. In some areas high groundwater levels are important to maintain water in the streams either providing base flow to rivers or diminishing river leakage to groundwater. Whereas in other areas, discharges from surface water storages are used to replenish groundwater supplies (Department of Environment and Resource Management 2009). The rate of groundwater recharge and discharge to surface water varies across the SEQ region.

The groundwater–surface water interactions are important flows within the region. Individually, these flows would be considered material to the water balance for each store.