Assessment of Cause of Water Level Change of Lake Kivu and its impact at downstream

Abstract

The Kivu Lake level is subjected to high fluctuations during the recent years. The aim of this research was to identify the causes for the fluctuations in Lake Level. SWAT model was used to generate water balance components of Lake catchment. The results, using the reference period 1976 to 1990, indicate that the mean annual rainfall over the lake is 1266 mm and the mean annual evaporation from the lake is 583 mm. When compared with lake level changes, there is imbalance of 21 %. Adding this amount to the calculated evaporation, it was possible to reconstruct the inflow variation into the Lake from 1976 to 1990 and the water balance of the lake. Sensitivity analysis shows that the discrepancy in the balance is most likely due to water abstraction from the lake as some of water is used for domestic supply around the lake and minor abstracts In this research, the water balance of Lake Kivu is carried out using the SWAT rainfall runoff model. The inflow from the catchment into the lake has been generated using SWAT model. Evaporation is estimated using Penman formula. Rainfall over the lake is estimated from the catchment rainfall employing the two classes 'A' gauging stations around the lake as weather generating stations to fill the gaps in the other rain stations. Finally the main cause for high Lake level fluctuation is found to be the rainfall variability analyzed with hydrological components in their variability trends especially in the second rainy season in October, November and December ,