Assessment of Land Use/Land Cover Change Impact on Stream Flow Using SWAT Model (The Case Study of Katar Catchment)

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Water is a precious and finite resource and must be managed in sustainable way to meet human as well as environmental needs. Land use land cover change has an impact for alteration of watershed hydrology. In the last 24 years Katar catchment experienced land use/land cover change. The Katar watershed, which is the major contributor of runoff for Lake Ziway is very sensitive to land use and land cover change. The basin is undergoing land use change due to intensive cultivation and urbanization as a result of population growth which has an impact on hydrologic response of the basin. This study quantified basin runoff volume using SWAT model and assessed the effect of land use/land cover change on the stream flow. Geographic Information system (GIS) was integrated with SWAT model to carry out the study. Arc GIS10.4.1 and Erdas IMAGINE2014 were used to process soil raster data set and prepare land use/cover map from Land sat image acquired in 1995 and 2015 respectively. Land use classification was performed using supervised classification system and accuracy assessment was done using confusion matrix. Classification result indicated expansion of agricultural and settlement lands. Using the two land use/cover map SWAT model was set up and run and the default simulation was compared with the observed data. Then sensitivity analysis was made on monthly basis using 20 flow parameters where only six parameters were identified as influencing the flow. The model calibration was done from 1991 to 1999 and validation period from 2000 to 2004. The calibration and validation results showed good match of simulation with observation with Nash-Sutcliff efficiency 0.84 and 0.6 xiv coefficient of determination (R 2 ) 0.87 and 0.62 for calibration and validation respectively. The result showed that the mean wet monthly flow increased by 17.21% (from 50.38m 3 /s in1995 to 59.05m 3 /s in 2015) and the mean dry monthly flow decreased by 41.69% (from 22.43m 3 /s in 1995 to 13.08m 3 /s in 2015). Generally the study result indicated flow during wet season increased whereas during dry season decreased. The SURQ contribution increased whereas GWQ decreased from 1995 to 2015 as a result of expansion of agricultural and settlement area. The study results showed change in flow with change in land use/cover.



Land Use/Land Cover, SWAT, Katar Catchment, Stream Flow