The impact of land-use change on Cengklik Reservoir’s sedimentation rate

Abstract The Cengklik Reservoir is operated for irrigation of rice fields in 3 sub-districts in Boyolali Regency, namely Sambi, Ngemplak, and Nogosari. At the present time, the volume of the Cengklik Reservoir has decreased and resulted in dryness during the dry season. One of the main causes is due to the high sedimentation rate. This research was conducted to evaluate changes in land use that resulted in sedimentation in the Cengklik Reservoir. Erosion prediction in this study uses USLE (Universal Soil Loss Equation) analysis. The amount of sediment obtained uses the standard erosion data from USLE calculations, namely by multiplying the amount of erosion by the SDR and the area of River Basin. The potential for erosion and sedimentation used land use data for 10 years, from 2009 to 2019. Based on the research, the amount of erosion and sedimentation in the Cengklik Reservoir was fluctuated with the highest amount occurring in 2016, with erosion of 9,292 tones/ha/year and sedimentation of 4304,154 tons/year. In general, erosion and sedimentation have increased from 2009 to 2019. The classification of erosion in the Cengklik Reservoir according to this study was categorized as light erosion. The trap efficiency used in this study was calculated using formulae based on the research of Heinemann (1981) using the Brune method for small reservoirs with an area of less than 0.5 km2. In general, based on this study, the Trap Efficiency in Cengklik Reservoir was 95.254%.