Modelling the water and salt balance in a shallow lake

Abstract The effects of changing land-use in the catchment have influenced the ecology of Lake St. Lucia and become particularly evident during severe drought. Ameliorative measures and future management of the lake system demand careful planning if they are to be effective. Mathematical models of the several components of the lake system have been devised. Thus, there are separate models for handling the lake catchment, the swampy delta of the main feeder river, the groundwater inflow, the dynamics and salinity regime of the estuary and the salinity and water level changes in the lake itself. These can be interlinked for the testing of various remedial measures. The formulation and calibration of the models are described. Simulations of the behaviour of the system show clearly the effects of climatic fluctuations and human interference on the ecology of the system as reflected in the salinity levels at various parts of the lake.