Managing for Water Supply and Ecological Flows

Presentation (pdf document)

Brian Joyce¹, Mark P. Smith², Richard Vogel³, Jack Sieber¹, Stacey Archfield³, and Colin Apse⁴

¹ Stockholm Environment Institute, Somerville, MA, 617/627-3786, jack.sieber@sei-us.org, brian.joyce@sei-us.org
² The Nature Conservancy, Boston, MA, 617/542-1908, msmith@tnc.org
³ Tufts University, Dept. of Civil and Environmental Engineering, Medford,
MA, 617/627-3211, Richard.Vogel@tufts.edu, sarch@usgs.gov
⁴ The Nature Conservancy, New Paltz, NY, 845/255-9051, capse@tnc.org

Several New England states are developing in-stream flow and water level standards to protect aquatic resources and other water quality criteria. This process presents challenges, because many communities are heavily dependent upon the water resources of rivers and lakes for which ecological standards are being defined. Balancing these water resource demands is critical to human and environmental sustainability and is the focus of this project. This project utilizes a decision support system to provide an efficient and effective means of balancing human and environmental water needs under changing environmental conditions. We have adapted the existing Water Evaluation And Planning (WEAP) model to allow water managers to optimize multiple objectives by simultaneously maximizing the use of water storage capacity, the use of drought management measures, and to adaptively meet variable ecological flow needs based on real-time environmental conditions. By providing a tool for adaptively managing the quantity and timing of reservoir releases, actively managing human water demands through the use of drought management measures, we demonstrate how water supply reservoirs can be managed under variable environmental conditions to substantially maintain the reliability of the water supply yield while more consistently meeting ecological flows requirements. Our results demonstrate the general relationships between reservoir operating rule, storage volume, watershed inflows, and desired releases for environmental flow needs. We also evaluate which environmental flow policies lead to the most favorable tradeoffs between ecological and human uses of water and how the nature of these tradeoffs varies with the storage ratio of the reservoir system.