Assessment of Climate Change and Hydrological Responses of the Mara River Basin, Kenya/Tanzania

Mara River Basin (MRB) is endowed with diverse cultural heritage and pristine biodiversity. Climate change is predicated to exacerbate land degradation and reduction in the fauna and flora affecting livelihood and the Mara-Serengeti ecosystem. We employed past and projected climate scenarios from sixteen Global Circulation Models (GCMs) outputs and historical records to better understand the climate dynamics and its implication on the hydrological system of the MRB. Nine of the sixteen GCMs showed positive correlation (< 0.5) with the monthly observed rainfall over a control period (1961 - 1990). Five of them were selected for future climate and hydrological impact assessment using delta and direct downscaling methods for the A1B, A2 and B1 greenhouse gas emission scenarios. On average, the dry season rainfall was observed to increase 2- 6% in the 2050s (2046 - 2065) but showed a variable change (-1-11%) towards the end of the 21st century (Figure 1). Temperature is expected to increase by 3 - 4 degrees Celsius by the end of the century. Results also showed that Mara river flow will experience significant changes in all scenarios with extents depending on the choice of GCM and downscaling technique (Figure 2). Findings of the study point to a higher impact of climate change in the basin, hence incorporating the negative and positive aspects in strategic planning may promote sustainable development in MRB. Figure 1. % change of the 2050s and 2080s rainfall from the control period at Bomet, Keekorok GL and Buhemba TC of the MRB for the A1B, A2 and B1 SRES scenarios using the Delata and Direct downscaling mehtods. Figure 2. Annual average runoff based on downscaled rainfall and temperature data for the MRB. The trend of each model hydrograph was plotted with the corresponding R2 Value. Average of the five GCMs was also included.