Linderfelt, W.G., Turner, J.V., Townley, L.R., Bartle, G.A., Watson, G.D., and Woodbury, R.J. (1997), Interaction between shallow groundwaters and saline surface water in a seasonal estuary: The Swan River System, Progress report (1996-1997) prepared for the Western Australian Estuarine Reseach Foundation, CSIRO Land and Water, 19pp., August. [Confidential]

The Swan and Canning Rivers in Western Australia are seasonally and tidally forced systems which form an estuary in contact with the Indian Ocean. Eutrophication in the upper reaches of the estuary in past years has prompted an investigation into the conditions favourable for algal blooms and the mechanisms and processes responsible for nutrient loading to the estuary. Our study examines to what extent shallow groundwater interacting with the Swan River contributes to nutrient availability in the river. Findings to date suggest that groundwater discharge to the Swan River is small in comparison to the total river flow. However, nutrient concentrations within the sediments adjacent to and underlying the river are very high relative to concentrations in the river such that even low groundwater discharge rates can introduce significant nutrient mass to the river. Both seasonal and tidal forces increase the complexity of the system and in many cases may act to increase the presence and availability of groundwater-derived nutrients in the river and estuary system.