Relations among storage, yield, and instream flow

TLDR

Extensive literature documents relationships between reservoir storage capacity, water supply yield, and instream flow properties needed to support downstream ecosystems, yet studies evaluating the impact of reservoir operating rules on instream flow are limited and few general conclusions can be drawn. The study adapts the generalized WEAP model to explore general relationships among reservoir storage, instream flow, and water supply yield across diverse reservoirs and operating rules, introducing a seasonal ecodeficit/ecosurplus concept to evaluate regulation impacts. The authors use the generalized WEAP model, incorporating seasonal ecodeficit/ecosurplus metrics, to simulate reservoir operations and assess their effects on instream flow and water supply yield. Generalized relationships among these variables identify instream flow policies that, when combined with drought management strategies, can provide compromise solutions to ecological and human water negotiations for reservoirs of different sizes.

Abstract

An extensive literature documents relations between reservoir storage capacity and water supply yield and the properties of instream flow needed to support downstream aquatic ecosystems. However, the literature that evaluates the impact of reservoir operating rules on instream flow properties is limited to a few site‐specific studies, and as a result, few general conclusions can be drawn to date. This study adapts the existing generalized water evaluation and planning model (WEAP) to enable general explorations of relations between reservoir storage, instream flow, and water supply yield for a wide class of reservoirs and operating rules. Generalized relationships among these variables document the types of instream flow policies that when combined with drought management strategies, are likely to provide compromise solutions to the ecological and human negotiations for water for different sized reservoir systems. The concept of a seasonal ecodeficit/ecosurplus is introduced for evaluating the impact of reservoir regulation on ecological flow regimes.