The Impact of Global Warming on the Optimization of Water Allocation in Dams: A Case Study of the Way Apu Dam, Maluku

Abstract

Global warming has altered the hydrological regime of tropical archipelagic regions and subjected dam infrastructure to operational stresses that were not anticipated at the design stage. This paper evaluates the impact of global warming on the optimization of water allocation at the Way Apu Dam in Buru Regency, Maluku Province, which serves 10,000 hectares of premium irrigation, a raw water supply of 0.505 m³/s, hydropower generation, and flood control. The study combines three approaches: (i) climate projection modelling for 2025–2050 using the five IPCC AR6 emission scenarios (SSP1-1.9 through SSP5-8.5) against a 30-year observational baseline from the Namlea Meteorological Station; (ii) hydrological data quality analysis of the Way Tina Station record for 2013–2023 through Grubbs–Beck, RAPS, Spearman, and t-tests; and (iii) development of a nonlinear water allocation optimization model solved with the Generalized Reduced Gradient (GRG) algorithm and implemented in a web-based application. The projections indicate that under the worst-case SSP5-8.5 scenario in 2050, mean temperature rises by 1.65 °C to 28.45 °C, annual rainfall increases by 5.6% to 2,270.9 mm but with an increasingly skewed seasonal distribution, rice productivity in the Wayapo Valley declines by 11.0% to 4.63 tonnes per hectare, 63.67 hectares of the Namlea coast are inundated, the climate vulnerability index reaches 0.382, and annual economic losses reach IDR 46.0 billion. Under normal conditions, GRG optimization yields an allocation efficiency of 65.1% with a total annual release of 173.02 million m³ (irrigation 95.29; domestic 0.24; hydropower 77.50 million m³), energy output of 6,546.9 MWh per year, and an annual deficit of 92.94 million m³ concentrated in October–December. Climate scenario simulations show irrigation reliability falling from 98–100% under a wet pattern to 70–75% under a dry pattern, while raw water supply is maintained above 95%. Sensitivity analysis reveals an allocation elasticity with respect to inflow of 1.2–1.5, and improving irrigation efficiency from 65% to 75% expands service coverage by 12–15%. The study concludes that global warming does not invalidate the feasibility of the Way Apu Dam, but shifts its operational optimum such that static rule curves must be replaced by adaptive operation informed by seasonal forecasting.