Abstract:
Galugur Kapur IX Sub district watershed is one of the upper watersheds in the Kotopanjang
hydropower reservoir which has the potential to trigger a reservoir sedimentation rate
increasement due to land clearing for plantations so that it will speed up the filling of dead bin of
reservoir significantly which will have an impact on the reduction of the planned service life of the
reservoir. The research objective is to analyze the potential for erosion in the Galugur watershed
using Geographic Information System (GIS) as an information of a watershed management policy.
The research approach method for erosion estimation is the Universal Soil Loss Equation (USLE)
method. The USLE method is influenced by four factors: rain erosivity factor (R), soil erodibility
factor (K), downhill length and slope factor (LS), and land utilization factor (CP). These erosion
estimation factors are then converted into four thematic maps, namely rain erosivity map (R), soil
erodibility map (K), downhill slope and length map (LS), land cover and management map (CP).
All thematic maps that have been generated are overlaid and will produce an erosion distribution
map. The main results of the study proved that erosion that occurred in the Galugur watershed
based on GIS was dominated by low category erosion approximately 43% of the total area of
5787,123 ha. Confirmed by the results of research that states that the Galugur watershed erosion
product will blend with the water flow from the upstream to the reservoir, so that the sediment in
the reservoirs will occur in large scale quantities. The reservoir sedimentations have the potential
to be a threat to the reduction in the service life of the Kotopanjang hydropower reservoir which is
designed to operate for 100 years.
