| Abstract: | Starting from a simplified version of the water balance equation, it is shown how the levels and outflows from a open lake can be related to the magnitude and statistical characteristics of the annual net basin supply series, which is defined as the net inflow arising from tributary inflows, rainfall on the lake surface and the lake evaporation. Using the models, estimates are derived for the response time for several large open lakes in Africa and Asia. Also, the observed net basin supply series for three major lakes (Victoria, Malawi and Toba) are investigated in detail. It is suggested that, on an annual basis, the assumption of a random normally distributed series of net basin supply can provide a reasonable first guess for the equilibrium response of a lake and for the likely range of variation of levels. These estimates are likely to be useful in water resources assessments and for investigations of the effects of land use and climate change on lake levels. The effects of departures from this simplified approach are discussed and are illustrated with some practical examples. © 1998 John Wiley & Sons, Ltd. |
