Examining Observed and Future Rainfall and Lake Water Levels at Jinja during March to May Season

Abstract

This study aimed at examining observed and future projected rainfall and lake water levels at Jinja during March to May season. The study used observed daily rainfall for the period (1985 to 2016) obtained from Uganda National Meteorological Authority using the Jinja meteorological station. The projected rainfall amounts included data that is got from a model MPI-ESM, downscaled using RCA regional model for a period of 30 years from 2016-2090 for two RCP 4.5 and 8.5 scenario while Water level data was collected from Ministry of Water and Environment particularly from the Department of water from the gauging station placed at Jinja from 1985 to 2015. The projected water levels were computed from rainfall projections for the two scenarios. The results indicated that monthly rainfall for Jinja district was found to be variable during the March-May (MAM) season with maximum amounts of rainfall received in May and the lowest amounts recorded in March. Mann-Kendall results indicated positive trends in April, May and the MAM seasonal averages and a negative trend in March but the trends were not statistically significant. Total monthly averages of lake water levels indicated that the area experiences variable lake water levels within the March-May (MAM) season with maximum lake water levels received in May and the lowest were recorded in April. Mann-Kendall results on lake water levels at critical value (α =0.05) indicated positive trends in April and May, while results for March and MAM seasonal averages depicted negative trends in water levels. Result from regression analysis indicated a moderate positive linear relationship between rainfall and lake water levels. Both Mann-Kendall and regression results for projected water levels under RCP4.5 and RCP8.5 showed positive trends in projected water levels which is statistically significant and negative trends in projected rainfall which is not significant under both scenarios.