HYDROCLIMATOLOGIC ANALYSIS OF A LAKE FOR EARLY WARNING LAKE LEVEL FORECASTING: CASE OF LAKE CHIUTA IN SOUTHERN MALAWI

Abstract

Lake Chiuta in Southern Malawi is a key water resource for the riparian community. The lake is a habitat to a diversity of fish species that sustain the peoples’ socio-economic livelihoods. Climate change and variability in the lake’s basin have been affecting the basin’s hydroclimatology, resulting in inflow variability and varying lake levels. The absence of an early warning tool for forecasting the lake levels has often resulted in delayed decision making for relevant interventions like scaling up or down of agricultural and fishing activities. This study was therefore aimed at analyzing the hydroclimatology of the lake in order to develop an early warning mechanism for lake level forecasting. The study analysed various components of Lake Chiuta’s water balance, to understand the role of climate forcing in lake level variation during 1960-2017. The study used hydroclimatic and historical satellite altimetry data. In the absence of discharge data from inflowing rivers, the monthly Water and Snow Model (WASMOD) was calibrated and validated in estimating catchment runoff using a runoff coefficient of 21.85%.The results show that the lake’s catchment had a mean annual rainfall of 879.9mm during 1960-2009 with an insignificant trend. On the other hand, temperatures and over-the-lake evapotranspiration had rising and significant trends during the period, with a mean over-the-lake evaporation of 130.87cm/year. Mean maximum and minimum temperatures were 23.69 ͦ C and 13.62 ͦ C respectively. Lake outflows were estimated to a mean of 74.19 mm/month with an insignificant trend. Inflows will fluctuate between 938mm and 1329mm resulting in a single full lake extent from 2009 to 2030 at a 95% statistical confidence interval.