D.T. Febrianti, M. Bisri, D. Sisinggih, C. Aina
Indonesia's increasing population has intensified the demand for food production, thereby elevating the need for reliable irrigation water. The Krisak Reservoir, located in Wonogiri Regency, serves as a crucial infrastructure for supporting agricultural water supply. However, upstream water availability remains a key challenge. This study evaluates the upstream inflow to Krisak Reservoir using CHIRPS rainfall datasets and simulates the water balance to assess its capacity in meeting downstream irrigation demands. Inflow discharge was estimated using the F.J. Mock model over a 20-year period (2004-2023) with 15-days intervals. Additionally, average discharge was assessed under three reliability scenarios - dry (Q80: 0.13 m3/s), normal (Q50: 0.27 m3/s), and wet (Q20: 0.53 m3/s). The water balance simulation over a 20-year period revealed a near-equal distribution of surplus (49%) and deficit (51%) events based on long-term CHIRPS data. Scenario-based analysis showed that only 42% of periods resulted in surplus, while 58% experienced deficits, particularly under dry conditions. These results highlight the vulnerability of the existing water supply system and reinforce the strategic importance of Krisak Reservoir in regulating flow and ensuring water availability during critical periods. The application of satellite-based rainfall data and hydrological modelling proves effective for supporting adaptive and sustainable water resource planning in irrigated agricultural regions. © 2026 Published under licence by IOP Publishing Ltd.
Water Resources Engineering Departement, Universitas Brawijaya, East Java, Malang, Indonesia; Integrated Graduate School of Medicine Engineering and Agricultural Science, University of Yamanashi, Yamanashi, Japan
