Morphometric Analysis and Watershed Prioritization in Relation to Soil Erosion of Dabus Watershed, Abbay River Basin, Ethiopia

Abstract

Environmental deterioration is currently one of the most important challenges, culminating in the extinction of ecosystems and the loss of vital natural resources. Prioritization is a strategy of organizing the multiple watersheds in a catchment in the order of treatment and soil conservation measures to be performed out. The identification of essential watersheds or the prioritization of sub-watersheds was required for effective and long-term watershed management programs and natural resource allocation. Morphometric analysis is a key to understand the hydrological process of a drainage basin and is a means of mathematically quantifying different aspects of hydrological characteristics of a river basin. Traditional morphometric parameter determination methods are time consuming, extremely expensive, and tedious. However, development of Geographical Information System (GIS) and remote sensing technology makes the procedure easier, cheaper, and faster. The present study aims to prioritize watershed based on morphometric analysis and soil erosion susceptibility in Dabus river Catchment(DRC), located in Upper Blue Nile basin, Ethiopia using geospatial data. For this study, the Digital Elevation Model (DEM) data with spatial resolution 12.5mx12.5m and Topographic map of the study area was obtained from Ethiopian basin development authority(EBDA). The DEM data was used to determine the stream network and delineate the Sub-watershed along the watershed border. The fundamental parameters (stream order, stream number, stream length, basin area, basin perimeter, and elevation) were retrieved using GIS software. All geomorphometric parameters were acquired and computed using fundamental geomorphometric parameters and DEM data. Based on computed fundamental parameters using DEM data and ARC GIS software, the derived parameters were determined using mathematical formulae and methodologies that have already been devised. The combined use of remote sensing and GIS might aid in quantifying rate of soil erosion at different levels and in identifying regions that may be at danger of erosion. Fourteen DRC sub-watersheds were prioritized and ranked based on their susceptibility to soil erosion employing morphometric parameters. Morphometric characteristics influencing soil erosion were employed as ranking criteria, with compound values derived for final prioritizing. The compound parameter values for each sub watershed were calculated to generate the final priority classifications, which were classified as Very high, high, Medium, and Low. As per analysis result, the sub-watershed SW1, SW7 and SW10 with a covering total area of 2390.75 km2 ,2555.77 km2 and 1642.71 km2 respectively received the very high priority classes where as SW3, SW4, SW 6 and SW 13 covering total area 2213.87 km2 , 1899.07 km2 , 949 km2 and 865 km2 received high priority classes. To reduce soil erosion risk appropriate immediate management measures must be implemented for very high and high-priority rank sub-watersheds Likewise, the sub-watersheds in the Medium priority classes SW11 (458.82Km2 ) and SW5 (552.22km2 ) indicate a moderate land degradation area. Sub watersheds in low priority classes SW2 (333.44km2 ), SW8(164.89km2 ), SW9(328.72 km2 ) and SW14 (334.16km2 ) imply low soil erosion.