Numerical rainfall-runoff model of Cimanuk Watershed before and after the operation of Jatigede Reservoir

Abstract Cimanuk watershed is one of the watersheds in West Java that has critical land. Critical land resulted in a Cimanuk watershed becomes a flood and drought. The management of Cimanuk Watershed water availability is done by regulating water supply from the Cimanuk River with the contruction of Jatigede Reservoir. The watershed hydrological process is the relationship between inputs in the form of rainfall, process, and output in the form of runoff. The process of converting rainfall into runoff is very complex, therefore, simplifying the rainfall-runoff model approach is needed. Hydrologic Engineering Center-hydrologic Modeling System (HEC-HMS) is one of the models for simulating rainfall into runoff. The purpose of the study is to simulate the availability of water surface at Cimanuk Hulu watershed using HEC-HMS hydrological modeling system based on before and after the operation of Jatigede reservoir. The results showed that the calibration of the model produced an NSE value of 0,640. On the other hand, the best validation results was in 2018 with NSE of 0,576 with the peak discharge value before the operation of the reservoir was of 456,8 m 3 / s , and after modified with the presence of Jatigede Reservoir, peak discharge became 131,9 m 3 / s .