Managed Flow Regimes and Resource Values: Traditional versus Alternative Strategies

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2000 by S.E.L. & Associates Managed Flow Regimes and Resource Valued Traditional versus Alternative Strategies Doug Whittaker Confluence Research and Consulting 6324 Red Tree Circle Anchorage, Alaska 99516 USA Bo Shelby Department of Forest Resources Oregon State University Corvallis, Oregon 9:331 USA ABSTRACT: Research shows that varied flow regimes provide a diversity of aquatic species and life stages, create and maintain a diversity of channel features, and provide a diversity of "niches" for recreational activities. Requests for water, however, typically specify distinct flows to be provided at specific times. Resulting "managed flow requests," often with a single flow identified per resource value, impose a relatively coarse and static managed floe regime that removes beneficial variation. There is a need for alternative request structures that substantially protect the diversity provided by natural regimes and yet alloy some out -of- stream use. In this paper, we review the traditional managed flow request and two alternatives, exploring their ability to produce the range and quality of resource values provided by natural flow regimes. By applying data from a case study of recreational flow needs on Colorado's Dolores River, we illustrate three alternative flow management request structures (1) fixed time requests, (2) trigger requests, and (3) percentage- based requests. Results suggest that each type has advantages and disadvantages for protecting the diversity of high quality recreational opportunities, providing water for out -of- stream uses, or being administratively feasible. Discussion focuses on the appropriateness of different flow request structures for rivers with different characteristics. Trigger and percentage -based requests are offered as promising alter- natives that are more likely to mimic natural regimes and thus protect important diversity. These new alternatives suggest a paradigm sluft in flow protection strate- gies, a logical response to increased sophistication in the science of identifying rela- tions between flows and resource values. KEY WORDS: Flow protection strategies, flow requests, recreation flows, water rights claims. BACKGROUND C onsiderable research has focused on developing relations between flows and resource values such as fisheries, channel maintenance, and recreational quality. Fish- eries biologists, for example, have document- ed many links between flows and ecological quality (Petts et al. 1995), and have developed flow - habitat models that can be used to iden- tify minimum and optimum flows for various fish species and life stages (Bovee 1996). Simi- larly, fluvial geomorphologists have explored the relations between flows and a variety of channel features and shown how high flow events are often necessary to create and main- Rivers • Volume 7, Number 3 Pages 233 - 244 233 �L