Interactions between an ephemeral stream, Maules Creek and groundwater of the underlying aquifer are being studied using a combination of geological data, hydraulic data, stream water levels, fluid EC, temperature and resistivity imaging. Zones of groundwater discharge have been pinpointed largely based on temperature anomalies and EC variations. Zones where the stream appears to be recharging the aquifer were identified based on the geology and gradients in hydraulic head. Geological heterogeneity was found to be an important factor in controlling the occurrence of surface water flow and the exchange of water between stream and aquifer. However, anthropogenic effects in the form of groundwater extraction probably enhance the aquifer recharge from the creek.

Based on EC and temperature data, zones of groundwater discharge were detected in the upper part of the stream reach that was studied in August and October, 2006. Once water discharged into the creek it appears to be flowing for several kilometers between pools in a relatively thin (2-10 m) layer of sand and coarse gravel on top of more massive clayey layers as indicated by the resistivity imaging. However, the resistivity images also suggest that the clay is not laterally continuous with possible hydraulic connections to the aquifer below. Variations in the electrical conductivity downstream indicate a possible influx of groundwater with varying EC. It cannot be discounted that evapotranspirative concentration down the reach may also have some influence on the EC data. This needs to be quantified in order to use EC data to derive quantitative estimates of the exchange of water between the stream and aquifer. Further downstream, the stream is potentially recharging the regional aquifer as were inferred by downward hydraulic gradients and by inspecting the geological data. It is possible that this stream fed recharge is enhanced by drawdowns in the regional aquifer caused by extraction of groundwater.

So far, the results of this study are of a qualitative nature and actual fluxes needs to be established. Furthermore the results are obtained during low flow conditions and the dynamics of surface water groundwater interactions in relation to major precipitation and flooding events need to be studied in greater detail. The results of this study have implications for understanding the stream fed aquifer recharge and in turn for estimating the sustainable extraction of groundwater from the regional aquifer.