Assessing Environmental Flows in the Central Valley Across Different Management Scenarios

Seasonal water flow patterns in Central Valley rivers within California's Sacramento-San Joaquin Delta watershed have been profoundly disrupted by dams, conveyance systems, and land use changes. These alterations have led to habitat degradation, declines in fish populations, and reduced ecosystem services. Environmental flows—quantities and qualities of instream water essential for ecosystem health—are critical for sustainable water management. However, implementing environmental flows in Central Valley rivers necessitates significant changes to current water management practices, with uncertain implications for other water uses. The COllaboratory for EQuity in Water Allocations (COEQWAL), a publicly funded initiative, seeks to improve understanding of California’s water future through participatory scenario planning. As part of COEQWAL, we investigate the impacts of water operation alternatives and climate scenarios on maintaining environmental flows based on Functional Flow targets, which represent flow regime components that support key ecosystem functions. We demonstrate that allocating specific monthly water volumes as an environmental water budget—tailored to river basin and water year type—can achieve these targets. Furthermore, we evaluate how climate warming influences the feasibility of achieving environmental flows under various water management scenarios. Our results highlight both the opportunities and challenges associated with managing environmental flows in California’s Central Valley rivers. They also provide valuable insights into the interplay between water management strategies and ecological outcomes, helping guide sustainable management practices for the future.