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

• Published in: Journal of water resources planning and management 2022-06, Vol.148 (6)
• Main Authors: Dalcin, Ana Paula, Marques, Guilherme Fernandes, Galego de Oliveira, Anielly, Tilmant, Amaury
• Format: Article
• Language: English
• Subjects: Aquatic ecosystems; Artificial neural networks; Economics; Ecosystem restoration; Ecosystems; Energy security; Environmental impact; Environmental restoration; Fish; Fish migration; Migratory species; Natural flow; Neural networks; Reservoir operation; River basins; Security; Synchronism; Synchronization; Technical Papers; Threatened species; Tradeoffs; Water demand; Water resources management
• ISSN: 0733-9496; 1943-5452
• DOI: 10.1061/(ASCE)WR.1943-5452.0001567

AbstractFlow 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.