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).