Spatial Analysis of Erosion and Land Degradation Leading to Environmental Stress: The Case of Lake Hawassa Catchement
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Date
2009-06
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Addis Ababa Universty
Abstract
Land degradation mainly soil erosion and deforestation are principal environmental problems exacerbating environmental stress and food insecurity in developing countries including Ethiopia. Ethiopia loses about 1.5 billion tons of soil per year, and about 1.5 million tons of grain, as a result of soil erosion. The present study is aimed at analyzing erosion hazard and vegetation degradation, which is leading to environmental stress in Lake Hawassa Catchment. Satellite images of Landsat TM 1986 and ETM+ 2005, 30m resolution SRTM-DTED, and data on land use and conservation practices collected from field and secondary sources such as; agro-meteorological and livelihood data, were major data types used for the study. Data analysis were undertaken using GIS and Remote Sensing techniques involving satellite image processing, identification of erosion hazard areas using USLE model and finally estimating the degree of environmental stress using multi-criteria weighted overlay analysis of rainfall variability, erosion hazard, vegetation index and livelihood system. The result of the study indicates that nearly 8% of the catchment, particularly the escarpments in Shamena_Hurufa, Boricha_Bushulo and Lalima sub-catchments are highly and severely degraded with long and wide gullies. Further more, the overlay analysis of land degradation, rainfall variability, vegetation index and the livelihood system indicated that 15% of the catchment is found with high degree of environmental stress; while 35 % is in the range of moderate stress. Similar to the results of erosion hazard, the western and northwestern parts of the catchment especially Boricha_Bushulo, Shamena_Hurufa, Lalima and Shashemene_Toga sub-catchments are with in a moderate to high environmental stress regime. Environmental stress areas are found both on the escarpment and on the plain. The underlying factors causing this stress could be different and thus need further investigation using other techniques. Therefore, in order to reverse the adverse effects of environmental degradation and stress in the catchment, appropriate conservation and rehabilitation measures, community based integrated watershed management initiatives and alternative livelihood approaches should be promoted and implemented.
Key Words: Environmental stress, Erosion hazard, Vegetation index, Universal Soil Loss Equation.
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Keywords
Environmental stress, Erosion hazard, Vegetation index, Universal Soil Loss Equation