Linderfelt, W.R., Williams, J.M., Turner, J.V., and Townley, L.R. (1996), Identifying zones of groundwater recharge and discharge in the shallow aquifer adjacent to the Swan River, Western Australia, in Wetlands for the Future, INTECOL's V International Wetlands Conference, Perth, 22-28 September, Programme and Abstracts, p.77.

The Swan River forms an estuary in contact with the Indian Ocean in the Swan Coastal Plain of Western Australia. The estuary is a dynamic and complex system with sea water intrusion, tidal and seasonal forcing the groundwater interaction. Nutrient loading to the river, which contributes to algal blooms, and other contaminant inputs are cause for concern over water quality along various stretches of the river. As a first step in identifying contaminant inputs to the river due to groundwater, we are mapping groundwater recharge and discharge zones along the river. It is conjectured that spatial variability of electrical conductivity (EC) observed in the shallow aquifer adjacent to the Swan River reflects zones of groundwater discharge to and recharge from the river which is brackish during the summer months. Given that high salinity groundwater is a gross indication of former brackish/saline river water, high ECs found in groundwater adjacent to the river are a useful tracer of former river water. By combining geologic data, soil-type information and the measured EC of water collected from springs, drains, bores and groundwater samplers along the river, groundwater recharge and discharge along the river can be delineated. The emerging pattern is one of lower EC water along the outside of river meanders where groundwater is discharging to the river, while higher EC water is seen along the inside of river meanders where river water may be flowing into the aquifers, especially during periods of high tide, increasing the interaction of the river water with sediments and groundwater adjacent to the river. Finally, seepage rates across the bed of the river are observed to vary in response to tides, showing the system to be dynamic and complex at small time scales.