Basin-scale optimal trade-off between human and environmental water requirements in Hsintien Creek basin, Taiwan

Abstract

Reallocating water resources to satisfy human and environmental water requirements in a balanced manner within a basin constitutes a challenge task in water resources management. This study aims to develop a basin-scale multi-purposes operation model coupled with a multi-criteria optimization framework to investigate values of coordinated releasing rules for maintaining streamflow variability at different river reaches. The proposed approach is applied to the Hsintien Creek basin (northern Taiwan) to explore four management scenarios. The results indicate that the no-environmental-flow scenario is most favorable to human benefits. But severe hydrologic alteration at all reaches leads to the worst overall performance of 0.521, which is a multi-criteria index based on normalized human-benefit and environmental objectives and ranges between 0 and 1. The current rule releasing minimum environmental flows at some reaches receives an improvement at those reaches and has a slightly improved overall index of 0.530. Sustaining minimum environmental flows at all reaches does not provide a further overall improvement of 0.530 since mitigation of hydrologic alteration at those reaches is offset by deterioration of human benefits. The best overall performance of 0.620 is achieved by the basin-scale optimization for deriving the coordinated operation rules and time-varying environmental flow releases that lead to the most compromising alternative between conflicting human and environmental objectives.