Abstract:
Soil erosion has become a globally challenging issue that poses a serious threat to agriculture
and natural resources, particularly in developing countries like Ethiopia. Estimating the
magnitude of soil loss and understanding the spatial distribution of erosion-prone areas is
critical to plan and effectively implement soil conservation measures with limited resources.
This study was conducted in Gununo watershed, where soil erosion is threatening the
sustainability of agricultural production and environmental systems, to estimate mean annual
soil loss, to identify high erosion risk areas and to prioritize erosion hotspot subwatersheds in
Gununo watershed in order to plan and implement evidence-based and site-specific
conservation measures. The RUSLE (Revised Universal Soil Loss Equation) model integrated
with GIS and remote sensing was used. Primary and secondary input data sets were collected
from various sources to analyze RUSLE parameters in the ArcGIS 10.8 environment. The
overall analysis was carried out by multiplying input factors together in a raster calculator to
quantify soil loss of the entire watershed. The findings revealed that the annual soil loss ranged
from 0 to 359.99 t ha-1
yr-1 with a mean annual value of 22.31 t ha-1
yr-1
. The result indicated
that 36.06% of the study area is categorized under moderate to very severe erosion classes,
which contributed 72.21% of the total soil loss. Zonal statistics result showed that, both bare
land and cultivated land were found to be more vulnerable land use classes of the watershed
jointly contributing about 72.77% of the total soil loss. Furthermore, the study indicated that
the central west and northeast parts of the watershed are highly prone to erosion. The result
signified that about 52.9% of the eroded materials including soil and nutrients are transferred
to the outlet of Gununo watershed. Besides, the estimated sediment yield ranged from 0 to 42.5
t ha-1
yr-1 with a mean value of 12.02 t ha-1
yr-1
. The RUSLE model was highly sensitive to the
C factor followed by LS factor. Based on mean annual soil loss, the subwatersheds SW-4, SW 5, SW-7, SW-8, SW-3, SW-9, SW-6, SW-2, SW-10, and SW-1, are given 1 to 10 sequential
priority levels. The mean annual soil loss of six subwatersheds (SW-4, SW-5, SW-7, SW-8, SW 3, and SW-9) covering an area of 57.45% of the total landmass, exceeded the maximum tolerable
soil loss rate and were considered as hotspot area of the watershed that need priority in
intervention.
