Towards an understanding of human impact upon the hydrology of Lake Naivasha, Kenya

Abstract

The water balance of Lake Naivasha, has been calculated from a model based upon the long-term meteorological data of rainfall, evaporation and river inflows. The lake is Kenya’s second Ramsar site because of its international importance as a wetland, but supplies drinking water to Nakuru and irrigation water to the nationally important industries of horticulture and power generation. Groundwater flows into and out of the lake are estimated from the model’s success in predicting water level fluctuations over the same period. The most accurate predictions of lake level were derived from the data sets of river discharges known to be from the most-reliable time period and gauging stations. The model estimated a current annual abstraction rate of 60 × 106 m3 ann−1, a figure perhaps six-times higher than that calculated as a ‘safe’ yield in the 1980s. There is an urgent need to accurately measure all abstractions and provide consistent, reliable, hydrological and meteorological data from the catchment, so that a ‘safe’ yield may be agreed upon by all stakeholders and sustainable use of the lake waters achieved.