Managed Flow Regimes and Resource Values: Traditional versus Alternative Strategies

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(1) the data available for making choices; (2) the type of river system at hand; and (3) the legal and administrative environment in which decisions will be made. The type of data available is crucial. Informa- tion must be collected and organized to identi- fy different types of opportunities, as well as to identify possible thresholds for each (e.g., the optimum, the low end of the optimum range, and /or the low end of the acceptable range). As shown in this paper, flow evaluation curves and specified flow questions provide one method for accomplishing this. The nature of the river system is also impor- tant. For example, in a system with a water budget (a river where flows are captured in a large reservoir), providing higher flows (such as optimums) may mean providing fewer days of those or other flows. On the Dolores, for example, most rafting outfitters preferred a longer season at marginal whitewater levels in comparison to a shorter season (less than two weeks) at optimum levels. The Dolores, how- ever, is a river with nearly two- thirds of the water already sent out -of- basin, and this was a trade -off among lesser evils. On rivers where the water budget is less restricted, more opportunities and more triggers in a flow request structure will ensure greater diversity. Finally, choosing thresholds requires full consideration of the legal and administrative deci- sion environment. Different rivers have different legal status and different management priori ties. For example, a federally designated river (such as a segment in the National Wild and Scenic Rivers system, a national park, or a des- ignated wilderness) might warrant a "no degra- dation" standard. This would suggest protect- ing the full range of opportunities with multiple triggers for each. In contrast, manag- ing for such a high standard may not be possi- ble on a river segment below a dam, where much of the water is committed to other uses. Here recreation users might like the full range of opportunities available under a natural flow regime, but they also recognize that society has essentially decided to forgo some of those opportunities for other benefits such as hydro- electric, agricultural, or domestic uses. In these cases, a single flow per opportunity, fewer opportunities, less than optimal flows, or fewer days of flows are all possibilities. On some Fed- eral Energy Regulatory Commission relicens- ing projects, for example, providing weekend releases at a single flow for a single boating opportunity may be possible, whereas provid- ing a full range of flows through trigger or per- centage -based requests may be unrealistic. CONCLUSION 7 ' 4 � Different flow request structures, in combi- nation with different threshold decision rules, can create very different consequences for recreational opportunities or other resources. In general, one can think of the three struc- tures as a continuum, with fixed -time requests being the least like natural regimes, and per- centage -based requests being more like natur- al regimes in providing a diversity of flows. Trigger requests fall in between. Considering these newer request structures is an appropriate response to increased sophistication in the science of identifying relations between streamflows and resource values. Thirty years ago it was common for instream flow work to focus on determining a base flow for a single resource such as a game fish species. Today, scientists and a ncies focus on protecting flows for several resources, and the integration of flow needs for multiple val- ues (Schmidt et al. 1998). We believe this requires a paradigm shift among protection strategies, 242 an increase in complexity that may be analo- gous to the difference between checkers and chess. Alternative request structures are one issue in developing new strategies for dealing with this increased complexity. Several authors have explored the concep- tual basis of instream flow protection strate- gies, as well as the legal and administrative mechanisms used to implement them (Mac - Donnell and Rice 1989; Gillian and Brown 1999). In general, these strategies and mecha- nisms arose from large -scale societal decisions about which benefits to provide from rivers. In the past, society viewed rivers as sources of water for power, irrigation, domestic, or industrial use, and both human works and institutions were developed to provide those benefits (Reisner 1986). More recently, society has begun to recognize the benefits of instream flows for various purposes (as well as the costs of out -of- stream uses), and have begun adapt- ing or devele' n— new institutions to protect Rivers • Volume 7, Number 3 2000