Abstract
Land degradation and sedimentation has been increasingly a crucial problem in upper Wabe-Shebele catchment, south eastern Ethiopia over the last two decades. Nevertheless, so far no detail research has been conducted to assess such problem. Therefore, the present study was conducted at Melka Wakena Catchment of Upper Wabe Shebelle Watershed to identify the trends of land use and land cover change and its effects on hydrology and land degradation. To achieve the objectives of the study different data sources such as satellite images, climate and rivers gage data; soil sample data were collected and analyzed using relevant corresponding up to dated software. Based on pre-defined criterion, available satellite images for the years 1986, 2011, and 2015 were analyzed using ERDAS, ENVI and ArcGIS softwares. The study catchment stream flow and soil erosion information were computed using SWAT model. MUSLE was employed to assess the amount of sediment yields and rate of soil loss existed in the study area. The study showed that significant land use and land cover changes were recorded during the past nearly three decades. This change has been directly affecting the hydrology and sedimentation of the catchment. The annual surface runoff varied between 45.65 mm and 332.29 mm. The amount of surface runoff was generally increased from 1990 to 2010, whereas decreased until 2013 before beginning the increasing trend. The result of the sediment yield analysis showed that there was a general increasing trend from 1992 to 2010 and then declined up to 2013 before it started the rising trend. From the simulated results, it was observed that the long-term mean soil loss was 20.22 t/ha. Sustainable integrated watershed management practices should be practically implemented throughout the landscape of the catchment from upper to down streams. Above all, dam buffer area needs to be demarcated and protected from the current settlement: cultivation and over grazing.
Highlights
Land degradation signifies the temporary or permanent decline in the productive capacity of the land resources ecosystem such as soil, water, vegetation, rocks, air, climate, relief [1]
The present study was conducted at Melka Wakena Catchment of Upper Wabe Shebelle Watershed to identify the trends of land use and land cover change and its effects on hydrology and land degradation
modified Universal Soil Loss Equation (MUSLE) was employed to assess the amount of sediment yields and rate of soil loss existed in the study area
Summary
Land degradation signifies the temporary or permanent decline in the productive capacity of the land resources ecosystem such as soil, water, vegetation, rocks, air, climate, relief [1]. Sedimentation as an ecological and environmental phenomenon is increasingly affecting the sustainable development of human societies in the Ethiopian highlands [5] Such land degradation and soil erosion from high lands of the country have attributed to increased soil nutrient loss (on-site effect) and sedimentation of dams and lakes (off-site effect) [6]. Predictions of long-term impacts of land-cover change on streamflow are important to study different environmental conditions For this purpose Soil and Water Assessment Tool (SWAT) is one of the most suitable models for simulating water and sediment yields under land use and management scenarios [11]. This study aims to assess the influence of land-use change on the stream flow through GIS and remote sensing techniques coupled with the SWAT model
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