Assessing basin-wide soil erosion in the Citarum watershed using USLE method

Abstract

Citarum is the largest watershed in West Java, which is home to 25 million people. In such a large and populated watershed, land conversion is an inevitability. This condition directly encouraged an increase in erosion rates, which impacted increasing sedimentation rates in rivers, lakes, and dams. This research aimed to assess the spatial characteristics of soil erosion in the Citarum Watershed using the USLE method. The results showed that 45 % of the land in the Citarum watershed was in class I erosion hazard with an erosion rate of ≤15 tons/ha/year, 18 % in class II (15–60 tons/ha/year), 26 % in class III (60–180 tons/ha/year), 5 % in class IV (180–480 tons/ha/year), and the remaining 6 % in class V (>480 tons/ha/year). Total annual erosion in the Citarum watershed reaches 80.1 million tons, of which 52 % is contributed by the Middle Citarum Watershed (42.0 million tons/year), 26 % is the Upper Citarum Watershed (21.2 million tons/year), and the remaining 22 % contributed by the Lower Citarum Watershed (17.0 million tons/year). The proposed control measures for erosion hotspot locations throughout the watershed, which include structural and nonstructural approaches, are also proposed.