Identifying Functional Flow Regimes and Fish Response for Multiple Reservoir Operating Solutions

Published in	Journal of Water Resources Planning and Management. 148.
Authors	Dalcin, Ana & Marques, Guilherme & Oliveira, Anielly G. & Tilmant, Amaury.
Publication year	2022
DOI	https://doi.org/10.1061/(ASCE)WR.1943-5452.0001567
Affiliations	Instituto de Pesquisas Hidráulicas (IPH), Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS 91501-970, Brazil   Instituto de Pesquisas Hidráulicas (IPH), Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS 91501-970, Brazil.   Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura (NUPÉLIA), Universidade Estadual de Maringá, Maringá, PR 87020-900, Brazil. Dept. of Civil and Water Engineering, Université Laval, Quebec City, QC, Canada G1V 0A6.
IAI Program	Inter-American Institute for Global Change Research (IAI) for financial support under SGP-HW program, project SGP-HW 091. CNPq for financial support through Grant 552 308549/2019-8. Professor Olavo C. Pedrollo and engineer Juliano S. Finck for discussions on the ANN approach.
IAI Project	SGP-HW 091
Keywords	Flow regime recovery Hydropower planning Environmental flows
	Identifying Functional Flow Regimes and Fish Responsefor Multiple Reservoir Operating Solutions.pdf

Abstract

Flow regulation through dams increases water and energy security for society but also threatens the natural equilibrium of river basins, leaving ecosystems and communities more vulnerable. While recovering flow regime dynamics to mitigate environmental impacts is a necessary goal, its effective implementation depends on the capacity to predict the expected outcomes to multiple competing users. Although such impacts can be measured between tangible economic uses, identifying the ecological trade-offs remains a challenge. To guide the design of environmental flows and support improved ecosystem restoration, we propose a methodology framework that builds an ensemble of flow regime options based on the naturalized flow regime range variability and quantifies the ecosystem response of each option in terms of migratory fish abundance with an artificial neural network model. The flow regime options with significant responses were called functional flow regimes because they provide conditions for the recruitment success of migratory fish species, which are vulnerable to flow dynamic synchronization. Our findings indicate that functional flow regimes may still produce relevant ecological responses even without fully recovering the natural flow regime. Specific levels of magnitude, frequency, duration, and timing of a flow regime can be combined to achieve a desired level of ecological response, while there is a clear threshold above which performance gains are smaller, indicating the presence of diminishing marginal performance gains when designing environmental flows. Knowing the trade-offs of different levels of flow regime recovery gives flexibility to the negotiation process between users and managers, leading to improved reservoir operation to meet multiple competing water needs.