Modeling Soil Erosion and Mapping its Risk in the Dura Watershed of the Upper Blue Nile Basin in North Western Ethiopia

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Date

2024-06

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Addis Ababa University

Abstract

Modeling soil erosion and mapping land use and land cover dynamics is critical for the estimation, management, and sustainability of current and future natural resources and improving the quality and quantity of agricultural products. It emphasizes soil erosion as a major environmental threat, causing significant economic losses and reduced agricultural productivity. The main objective of this study was to model soil erosion and map its risk in order to determine erosion vulnerability in the Dura watershed on the upper Blue Nile basin using the HEC_HMS model integrated with GIS and remote sensing. The impact of LULC change on the magnitude of surface runoff and soil erosion was assessed using MUSLE model and statistical tools in HEC-HMS. The effect of LULC change, on surface runoff, sediment load for the water and soil resources, and watershed management for sustainable Natural resource management was evaluated. The result showed that, forest area experienced a decline of 10.9% from 1993 to 2013, followed by a noteworthy recovery of 26.2% by 2023. Notably, bush land displayed the most substantial growth rate (84.9%) across the entire period, with a particularly sharp increase (45.5%) from 2013 to 2023. Agricultural land exhibited a peak in 2013, with a 46.4% increase from 1993, but then decreased by 23% by 2023. The area of bare land witnessed the most dramatic decline (95.8%) from 1993 to 2023, demonstrating a consistent decrease across each decade. Higher values indicate better agreement between model predictions and observations. These findings validate the suitability of the HEC-HMS model for runoff simulation. Notably, the upper sub-watershed exhibited higher surface runoff, soil erosion rates, and sediment yield compared to the lower sub-watershed in 1993. Specifically, SB1 experienced an erosion rate of 4.56 t/yr, which more than doubled to 11.76 t/yr by 2010. Similarly, SB2 witnessed a substantial increase from 8.27 t/yr in 1993 to 10.79 t/yr in 2010. The sediment yields for Sub-Basins 1, 2, and 3 were 45.15 t ha⁻¹ yr⁻¹, 28.9 t ha⁻¹ yr⁻¹, and 5.81 t ha⁻¹ yr⁻¹, respectively. In contrast, Sub-Basin 13 had a lower sediment yield of 0.031 t ha⁻¹ yr⁻¹. These results underscore the combined impact of land use/land cover changes, topography, rainfall patterns, and agricultural activities within the watersheds. Generally, LULC increases the watershed, decreases the traction power of rainfall, reduces soil loss and sediment yield in the watershed, increases the infiltration rate of the soil, reduces the magnitude of surface runoff. In order to enhance the quality and quantity of soil and hydrological components, it is important to expand reforestation efforts and consistently monitor shifting patterns. This will help identify areas that are particularly susceptible to erosion. By doing so, we can improve water absorption into the groundwater system, which will have positive impacts on agricultural productivity, water resources, and ecological sustainability in the surrounding area. Additionally, these efforts will also have social, economic, and environmental benefits, as they directly influence soil and water resources and watershed management in the Dura River watershed.

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Keywords

LULC Change, Mapping Land, MUSEL Model, Soil Erosion, Sediment HEC-HMS Model, GIS, Dura Watershed

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