Priortization of micro-watersheds for conservation intervention and restoration measures using gis and remote sensing technologies: a case of upper bilate watershed, snnpr, Ethiopia.

Abstract

Watershed prioritization has gained importance in natural resources management, especially in the context of watershed management. RUSEL model and Morphometric analysis has been commonly applied to prioritization of micro watersheds. In the present study, prioritization on the basis of RUSEL model and morphometric analysis of watersheds has been performed for the Upper Bilate watershed. Eighteen micro-watersheds were delineated and designated as MWSD-1 to MWSD-18 for prioritization purposes. A particular micro-watershed may get top priority due to various reasons but often, the severity of land degradation is taken as the basis. A methodology, based on RUSLE and Morphometric analysis, has been applied using remotely sensed data, ASTER DEM together with other ancillary data in a ArcGIS10.3 environment. The analysis shows that RUSLE model and Morphometric analysis helps to categorize micro-watersheds into different levels of erosion risk and identify areas that require priority to conservation measures in relative to others. In both RUSEL model and morphometric analysis, and the resultant ranks, the micro-watersheds have been classified into five categories in relation to their priority for soil conservation measures: very high, high, moderate, low and very low. Based on the RUSLE model, the potential average annual soil loss of each micro-watershed in the watersheds ranges from 0.15-2985 t/ha/year with a mean annual soil loss of 16.08t/ha/year. The result showed that Micro-watersheds (MWSD-3, 6, 8 and 16) estimated very high soil loss (16.03-44.17t/ha/year) and fell under high soil erosion classes. About 21.03% of the micro-watersheds fall in below the annual average soil loss of the entire watershed. Based on Morphometric analysis, different prioritization ranks were ascribed following the computation of compound factors. It is found that micro-watersheds (MWSD-8 and 6) and micro-watersheds (MWSD- 10) are categorized in the class of very high and very low priority respectively and about 38.47% of micro-watersheds are classified in the categories of very high and high priority. With reference to the integration of the two methods of prioritization, microwatersheds (MWSD-3, 6, 8 and 16), and (MWSD- 5, and 11) can be classified in the class of very high and high priority class respectively. By contrast, micro-watersheds (MWSD- 13, 17 and 18) and microwatersheds (MWSD- 10) are categorized in the class of low and very low priority respectively. About 40.22% of the watershed falls in the categories of very high and high priority. As a result the critical micro-watersheds which are under very high and high category were selected and prioritized to be intervened for conservation and other rehabilitation measures.