Assessment of vulnerability of water resources to climate variability in Mara river basin, Kenya
Waithaka, Reuel Kamau
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Africa's water resources are at risk due to climate variability further aggravating the water scarcity and also ability to cope with other external pressures and calamities. Climate variability on intra-seasonal and decadal time scales has had significant impact on water resources. The main objective of the study is to assess the vulnerability of water resources to climate variability in Mara River Basin. To achieve this, study analysed rainfall, river flow and satellite imagery data. The rainfall data spanned from1980 to 2011 and satellite imagery from the years 1985- 2010. The study relied on secondary data (rainfall, temperature, river gauges measurements and satellite imagery) various empirical tools such as key informant interviews and field observation guides. Numerical tools for data analysis comprised descriptive statistics and non-parametric test. Satellite imagery were ana lysed by use ILWIS and Arc GIS software's and climatic data analysed through Microsoft excel. The study results showed great inter annual variability of rainfall and corresponding river flow. Temperature data trend line analysis showed an annual increase of 0.2oC. Rainfall showed an increase of 0.02mm/yr at Narok station while Ilkerin weather station showed a decreasing trend of 0.002mm/yr. The rainfall showed uneven distribution both in spatial and temporal scales with cyclic nature of high intensity followed by drought periods. The inter-annual variability in rainfall is more sporadic and unpredictable, and this affects water supply both to the ecosystem, domestic and agricultural use. The study predicts that this will have detrimental effect on the basin water resources at a local level and regional. Vegetation cover type and trend over time was utili sed as an indicator of water resources vulnerability. The analysis of NDVI, NDWI and LULC thematic maps from 1985-2010 provided compelling analysis of vegetation density and distribution in the basin. Forest/shrubland reduced by 38% while cropland/shrubland increased by 28% and surface water aerial coverage reduced by 10.7% within the same period. There is direct relationship between vegetation cover change and reduction of aerial coverage of surface water. Majority of the respondents interviewed were farmers (24.4%) planting mainly maize and pastoralists (45.5%). Drought and crop failure were the many effects of climate variability. The respondents (45.2%) experienced more than 5months of food deficiency. Majority associated the insufficiency to climate variability. Distance travelled to access water averaged 2-5km,while most of the water resources were seasonal (56.7%), apart from distance other challenges affecting water accessibility include ,dirty water and conflicts with neighbours. To overcome these challenges there is need to develop basin management strategies geared towards increased forest conservation. The need for education and awareness creation on crop diversification and investment in both household and community water harvesting strategies. There is need for integrated waters resources management especially on education on efficient water use mechanisms both for domestic and agriculture.