Impact of Land use/Land Cover change on the Stream flow: (Case Study of Megech River Watershed, Abay River Basin, Ethiopia)

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Date

2020-09

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Addis Ababa University

Abstract

T he main goal of this study is to identify the impact of land use/ land cover changes on the hydrology of Megech Watershed S pecifically, the study was analyzed the histor ical land cover changes at (2000, 2010 and 20018 years) that have occurred in the ca tchment and its impact on stream flow of watershed because the recent input data gives more accurate results. Population growth, deforestation and higher demand for farm lands have eff ect on natural resource of the M egech river catchment of A bbay River basin. Assessing the problem and finding solution at catchment level is use full to minimize the effect of the problem. Decision support tools are need ed for successful assessment for impact of land use on stream flow and application of soil and water conservation measures at upstream of watershed . Land cover change analysis has shown that the settlement (town) area has increased from 2.21% to 9.13%, agricultural land increased from 46.3% to 70.49% and forest area has been decreased from 6.43% to 0.8% between 20 00 2018 years . In this study the effect of land use and land cover changes on stream flow was observed. Soil & water assessment tool (SWAT model set up were run to evaluate the impacts of land use changes o n stream flow using three land cover year s of 2000, 2010 and 2018. Sensitivity, calibration, validat ion and uncertainty analysis were also conducted using sequential uncertainty fitting version 2 (SUFI 2) in SWAT CUP (C a libration and U ncertainty pr ogram ) using stream flow historical data. Model calibration and v al idation were conducted for land use 2000, 2010 and 2018 years by using measured (gauged) data near to watershed by using SWAT CUP. For 2000 land use, calibration from 1999-2001 and validation from 2002-2003, for 2010 land use, calibration from 2008-2010 & validation from 2011-2013, for 2018 land use, calibration from 2014-2016 & validation from 2017-2019 years was conducted. The Results from calibration for three land use show acceptable range (0.82, 0.63 and 0.71 for NSE and 0.82, 0.79 and 0.74 for R2) between observed and simulated stream flow respectively. The results of validation were also acceptable range (0.66, 0.78 and 0.75 for NSE and 0.71, 0.84 and 0.78 for R2) respectively. The mean monthly stream flow for both dry and w et season were decreased by 3.31 m 3 /s and 1.88 m 3 /s due to land use/land cover changed in the catchment from 2000 2018 years respectively.

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Keywords

SWAT, SWAT-CUP, LULC change, Arc-GIS, Stream flow

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