The study of the effects of Mau Catchment Degradation on the Flow of the Mara River, Kenya

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Journal of Environment and Earth Science
The Mara River is the lifeline of the Trans boundary Mara basin across Kenya and Tanzania.The basin is considered one of the more serene sub-catchments of the Lake Victoria Basinand ultimately the Nile Basin. The basin traverses the famous Maasai Mara and SerengetiNational Parks in Kenya and Tanzania respectively. The basin also contains forests, largescalefarms, smallholder farms, pastoral grazing lands, as well as hunter gatherers and fishers.There is growing concern however, regarding land degradation in the basin, particularlydeforestation in the headwaters, that is affecting the natural resource base and the river flows.Scientific studies are required to advise on policy issues, and to plan appropriate mitigationmeasures. This study utilizes remote sensing and geographical information system (GIS)tools, and hydrological and ground-truth studies to determine the magnitude of the landuse/cover changes in the Mara River Basin, and the effects of these changes on the riverflows over the last 30 years. The results of the studies indicate that land-use/cover changeshave occurred in the basin. In 1973, for example, rangelands (savannah, grasslands andshrublands) covered 10,989 km2 (79%) of the total basin area. The rangelands have now beenreduced to 7,245 km2 (52%) by 2000. The forest areas have been reduced by 32% over thesame period. These changes have been attributed to the encroachment of agriculture, whichhas more than doubled (203%) its land area over the same period. To investigate the effectsof land cover change on river flow, stream flow was generated from derived land coverthematic maps of 1973 and 2000 using the same rainfall and evaporation data of 1983 to 1992period. The other model input datasets for topography and soils were held constantduring the two runs. The differences in the generated hydrographs could only be associated tochanges in land cover, which was the only variable. The percentage difference between themean annual stream flows of the two hydrographs was negligible at 0.01%. This studytherefore concludes that land cover changes in the basin have changed the day to dayflow characteristics of the river but the annual flow volumes remain unaffected. There isneed for urgent action to stem the land degradation of the Mara River Basin, includingplanning and implementing appropriate mitigation measures.