MATERIALS AND METHODS

Description of Gumara Watershed

The Gumara watershed is found in the North-West part of Ethiopia in the Amhara National Regional State, South Gondar Zone at 624 km north of Addis Ababa (Figure 1). This watershed is situated in the eastern part of the Lake Tana sub-basin. Astronomically, the watershed lies between 110 34’ 41.41” N and 110 56’36.95” N latitude to 370 29’ 30.48” E and 380 10’ 58.01” E longitude (Figure 1). Gumara watershed has an undulating topography ranging from 1755 m a.s.l. near Lake Tana to 3700 m a.s.l. at mount Guna (Figure 2a). The topography of the area has an important contribution to the surface runoff and soil erosion processes (Yibeltal, 2020). The steep slope in the upper part and gentle slope in the downstream characterizes the watershed (Figure 2b). The area is dominated by unimodal rainfall mainly concentrated from June to September. The mean annual total rainfall ranges from 1257 to 1544 mm. Based on the 2018 land use land cover classification, cultivated land constitutes the largest share of the watershed with 97.5% (1509 km2). Grazing and forest land comprise 1.4% (22 km2) and 1.2% (19 km2), respectively. Gumara watershed experienced large-scale land use/cover dynamics. Cultivated and settlement land expanded by 21.99% whereas forest, shrub, grassland, and wetland declined by 85%, 91%, 76%, and 73% over the period 1985–2016, respectively (Wubie et al., 2016) . Although there is a decline in natural vegetation, there is an expansion of some exotic tree species like eucalyptus on privately owned farm plots. The major means of livelihood in the area is subsistence-mixed agriculture (crop and livestock production).

Methods

Study site selection

Before the start of the research in the watershed, sub-watersheds were identified. Watershed development practices (WDP) have been started on degraded watersheds and the assessment was ideal to meet the community engaged in SWC efforts. Therefore, selecting erosion hotspot watersheds were taken as a tool to identify sample sub-watersheds. A hydrologic analysis tool soil and water assessment (ArcSWAT, Version 2009) model was applied to identify hotspot watersheds based on sediment yield output. The SWAT model used different input data such as digital elevation model (DEM) for watershed delineation, land use and soil data, weather data (Rainfall, minimum and maximum temperature, humidity, sunshine hour) and streamflow data to predict the streamflow. DEM, Land use, soil, weather and streamflow data were found from the USGS webpage, Ministry of water energy and irrigation, and Ethiopian meteorology agency, respectively.
Therefore, the SWAT model output provides the amount of soil loss in the watershed. Based on the given values greater than 65 t ha-1 yr-1 of sediment loss were considered for the research. Although a greater number of sub-watersheds had soil loss greater than 65 t ha-1yr-1, the research gave priority to those watersheds having access to roads and their proximity to agriculture offices. Besides, since the watersheds lie under the four districts, due consideration was given to include agriculture officers as a source of information assuming that different modes of watershed implementation approach employed. Finally, the four selected watersheds located under the four districts (Farta, Fogera and Dera) were, Girbi, Gena-mechawocha, Tankua Gebriel and Wanzaye (Figure 3).