Surface-groundwater Modelling Studies OfCoastal Lakes On The East Coast Of South Africa.

Abstract

The lakes and estuaries of the extensive coastal plain along the east coast of Southern Africa are an important water resource for social, ecological and industrial purposes. The rapid developments in the region are placing a huge burden on the sustainable utilization of the water resources. Recognition of the environment in sustaining the water resources is contained in new legislation and placing a demand for greater understanding of the dynamics and utilization of these resources. Numerical groundwater modelling of the primary aquifer and the interaction with the lake systems is being investigated to determine the water balance of the lakes, the flow dynamics of the aquifers and the interactions between the groundwater and coastal lakes systems. Three dimensional numerical finite difference modelling of the groundwater system has been used to examine the regional flow patterns around the shallow coastal lakes and to simulate their fluctuating level under natural and disturbed conditions. TheUSGS model, Modflow, together with several conceptual modules containing codes for simulating the lakes and rivers have been obtained and applied to several lakes in the Richards Bay area of South Africa. The model calibration and simulations of conditions controlling the utilization of Lake Mzingazi for municipal and industrial use are described. The calibrated parameters for the one lake have been applied directly to simulations of other ungauged lake system where there is no information for detailed calibrations. The model simulations have been used to assess the water balance components to determine the relative importance of the local primary aquifers in sustaining the lake under different land use conditions during periods of flooding and drought. Transactions on the Built Environment vol 40 © 1999 WIT Press, www.witpress.com, ISSN 1743-3509