Adaptive (re)operations facilitate environmental flow maintenance downstream of multi-purpose reservoirs

TL;DR

This study examines how adaptive release strategies from multi-purpose reservoirs can balance environmental flow needs with other water uses, demonstrating that prioritizing environmental flows can meet ecological goals without major trade-offs.

Contribution

It introduces a decision framework analyzing the impact of release order on environmental and sectoral benefits in multi-purpose reservoirs.

Findings

Prioritizing environmental flows enhances ecological outcomes.

Releasing for demand first can compromise environmental flow targets.

Simple changes in release order can improve environmental compliance.

Abstract

Multi-purpose reservoirs support socioeconomic development by providing irrigation, domestic water supply, hydropower, and other services. However, impoundment of water impacts instream aquatic ecosystems. Thus, the concept of minimum environmental flows (MEFs) was established to restore the benefits of naturally flowing rivers by specifying minimum flow rates to be maintained downstream of dams.But varying legislative contexts under which multi-purpose reservoirs operate may not always necessitate MEF releases. To what extent the release of MEF affects other sectoral benefits remains an open-ended and possibly a site-specific inquiry. A related issue is - how does the order in which releases are prioritized influences sectoral performances? We analyse these issues for the Nagarjuna Sagar reservoir, one of the largest multipurpose reservoirs in southern India. We formulate two versions of a multi-objective decision problem. PF_MEF formulation prioritizes MEF releases over releases for water demand satisfaction, followed by hydropower releases. PF_nMEF formulation follows the regional legislative rule releasing first for demand satisfaction, followed by hydropower and MEF releases. Results thus indicate that prioritizing MEF releases improves can meet MEF requirements without significant compromises in other objectives. We hypothesize that similar investigations may reveal how simple modification of release order may improve ability of other reservoirs to meet environmental goals.