Effect of land use land cover change on stream flow in Azuari watershed of the Upper Blue Nile Basin, Ethiopia

Land use land cover (LULC) dynamics is an important environmental issue due to its effect on hydrologic processes. This study investigated the effect of LULC change on stream flow in the Azuari watershed of the Upper Blue Nile Basin, Ethiopia. Three periods of satellite images (1991, 2006, and 2020) of the area were considered and the ERDAS image processing tool was used for the LULC classification based on the supervised classification algorithm. The Soil Water Analysis Tool (SWAT) was employed for streamflow simulation in the three periods. Agricultural land, forest, shrubland, woodland, and grassland were identified to be the major LULC types in the watershed. Over the study periods (1991-2020), the agricultural land was observed to increase by 19.86% while forest, shrubland, woodland, and grassland decreased by 34.11%, 42.09%, 38.51%, and 4.16%, respectively. With the LULC change, the monthly wet period streamflow increased by 5.81%, whereas the monthly dry period flow decreased by 3.34%. The trends of monthly, mean annual, wet and dry seasons, 1-day and 7-day maximum, and minimum flows were assessed using the statistical Mann-Kendall test. Only the 1-day and 7-day minimum flow exhibited a significant declining trend. In conclusion, the results revealed that a good understanding of the extent of LULC change on the stream flows can help planners and policymakers develop effective land management strategies for reducing adverse effects on the hydrology of the watershed.