Temporal Variations in Rainfall and Temperature and their Effects on the River Discharge in the Mara River Basin

Abstract

The Mara River basin is one of the important transboundary resources in Eastern Africa that not only serve Kenya and Tanzania where it is located as one of the waterheads but also serve the lower countries of Sudan and Egypt. Variations in weather conditions, especially rainfall and temperature in the basin have impacts beyond the basin. The environmental processes that relate to variation in weather conditions include river flow regimes, vegetation cover, agro-calendar and wildlife. This paper looked at how variations in rainfall and temperature affect the river discharge in the Mara basin in order to determine the nature of rainfall and temperature variations in relation to river discharge in the basin. Observed long-term daily rainfall, temperature and river discharge covering 1983 – 2014 period, are used in time series analyses to measure periodicity and trend in rainfall, temperature and river discharge. The relationship between river discharge and the weather elements is determined using linear correlation analysis and multiple regression procedures at ? = 0.05. The results of the data analysis reveal that, the long-term variations in temperature, rainfall and river discharge are such that temperatures are tending toward increase while rainfall and river discharge are tending towards decline. Further, variations in rainfall and temperature conditions indicate un-seasonality in the timing and duration of monthly variations. The variations in rainfall, temperature and discharge series are statistically not significant (Mann Kendall trend test). The relationship between variations in rainfall and temperature with river discharge is that rainfall has stronger linear correlation with river discharge than temperature and therefore declining trends in rainfall are causing reduction in river discharge in the Mara basin. Measures should, therefore, be taken to reduce activities in the basin that are likely to impact on rainfall and temperature such as deforestation and encroachment on the water towers.