2. Understanding the Effect of Land Use Land Cover (LULC) Dynamics on the Streamflow of Gelda Watershed, Abay Basin, Ethiopia

Globally, land cover has drastically changed over the last five decades, especially in tropical regions like the Nile basin. Changes in land use and land cover (LULC) have affected the streamflow in the highlands of Ethiopia. Remote sensing data and Geographical Information System (GIS) were used to understand the effect of LULC change dynamics on the streamflow of the Gelda watershed that drains into Lake Tana of the Abay Basin. The Landsat images from 1984, 2000, and 2016 were extracted and analyzed using ENVI and ArcGIS software. Land cover maps were classified using Maximum Likelihood Algorithm classification technique in ENVI 5.3 platform. In the Gelda watershed five major LULC classes (grazing land, agricultural land, forest land, bush land, and built-up area) were found. The streamflow of the watershed was evaluated using SWAT (Soil and Water Assessment Tool) model. During the study period, it was found that 32.8% of the bush land, forest, and grazing land was changed to agricultural land. This has resulted in streamflow change over the years. The monthly stream flow modeling showed a very good agreement between measured and simulated flows. The results show an increase in the peak flow during the wet months and a decrease in low flows during the dry months. The model results showed that the streamflow characteristics were changed due to the LULC changes during the study period (1984–2016).