D. Anggraini, S. Wahyuni, H. Siswoyo, C. Aina, Y. Wijayanti
Accurate estimation of water availability is crucial for sustainable water resource management, especially in irrigation-dependent infrastructures such as the Pacal Reservoir in Bojonegoro, Indonesia. This study evaluates the use of CHIRPS (Climate Hazards Group Infrared Precipitation with Station Data) satellite-based rainfall estimates, calibrated with ground observations, to simulate the water balance in the reservoir's upstream catchment. Inflow was estimated using the F.J. Mock water balance model, which converted rainfall data into discharge over a 20-year period (2004-2023) at 10-day intervals. The results indicate that inflow during dry years (Q80) ranged from 0.001 to 4.356 m3/s, in normal years (Q50) from 0.069 to 6.050 m3/s, and in wet years (Q20) from 0.296 to 11.338 m3/s. Long-term simulations showed a near balance, with 49% of periods experiencing a water surplus and 51% a deficit, while reliability-based analysis produced a similar pattern (48% surplus, 52% deficit). These findings demonstrate the viability of CHIRPS data for hydrological assessments in data-scarce tropical catchments, and provide a valuable reference for adaptive and informed reservoir operation planning under variable climatic and hydrological conditions. © 2026 Published under licence by IOP Publishing Ltd.
Water Resources Engineering Department, Faculty of Engineering, Universitas Brawijaya, Malang, Indonesia; Integrated Graduate School of Medicine Engineering and Agricultural Science, University of Yamanashi, Yamanashi, Japan; Civil Engineering Department, Faculty of Engineering, Bina Nusantara University, Jakarta, Indonesia
