Managed Flow Regimes and Resource Values: Traditional versus Alternative Strategies

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INFORMATION PROVIDED BY FLOW- RECREATION STUDIES Many studies have used social science theo- ries and techniques to analyze evaluative information about environmental conditions and recreational experiences (e.g., Shelby et al. 1988; Vaske et al. 1993; Roggeribuck et al. 1993; Shelby et al. 1996; Symmonds et al. 2000). Sev- eral studies have also applied this work to recreation user evaluations of instream flow levels, typically employing normative or atti- tudinal scales (e.g., Moore et al. 1990; Shelby et al. 1992a; Whittaker et al. 1993; Shelby and Whittaker 1995), but sometimes employing "willingness to pay" metrics (e.g., Daubert and Young 1981; Loomis 1987; Roach et al. 1999) or professional judgment suitability criteria (Hyra 1978). These studies suggest that recre- ation users (particularly whitewater boaters) are often sensitive to flows and can evaluate flow quality for specific types of recreation opportunities (Shelby et al. 1992b; Whittaker et al. 1993; Shelby and Whittaker 1995). These studies also consistently suggest there is an incremental relation between flows and recre- ation quality, often taking the form of an inverted U- shaped curve. For example, Figure 1 shows two "flow evaluation curves" for raft- ing and canoeing opportunities on the Upper Dolores, based on mean ratings for a range of flows (Shelby and Whittaker 1995). In each case, certain median flows are rated more acceptable, but very low and very high flows are rated less acceptable. Curves based on mean evaluations provide a good starting point for understanding the relation between flow and quality, but it is also important to identify points along the curve and show ho i- they relate to specific trip attrib- utes (Shelby et al. 1992b). "Specified flow eval- uations' are responses to questions that ask users to identify minimum or optimum flows for specific opportunities. These can be used to identify critical threshold flows along the flow W Rafts a w 4 Q MARGINAL LINE w Open Canoes v 2 o y °o ^ °oo ^000 ry000 0 ", °000 FLOW IN CFS FIGURE 1. Flow evaluation curves for canoeing and rafting on the Upper Dolores River, Colorado (from Shelby and Whittaker 1995. evaluation curve (Shelby and Whittaker 1995). "Specified flows" for rafting and canoeing on the Upper Dolores are provided in Table 1. They identify the following points along the curve (1) low end of the range (the minimum flow to use the river for transportation); (2) low end of optimum range (lowest flow that provides whitewater); (3) the peak of the curve (optimum, or the flow the largest num- ber of boaters rate as high quality); and (4) high end of the range (when it crosses the marginal line for canoes; highest available flows for rafts). We have rounded the flows to simplify discussion. There could be other spec- ified flows, depending on the particular inter- ests of a study. Taken together, the curves and specified flows illustrate another consistent research finding: flow needs often differ for opportuni- ties defined by different craft types, skill lev- els, or type of experience desired (Shelby et al. 1992a; Whittaker et al. 1993; Shelby and Whit- taker 1995). When research shows such needs, it becomes important to develop flow man- agement requests that provide the appropri- ate range of high quality opportunities. TABLE 1 Specified flows for two types of opportunities and two types of craft on the Dolores River. Specified Flow Rafts Canoes Low end of boatable range for scenic trips 800 300 Low end of optimum range for whitewater trips 1,000 800 Optimum flow for whitewater trips 2,500 1,300 High end of optimum range for whitewater trips b n/a 2,000 a Small rafts (14 feet long or less). b The study did not collect information defining the high end of the optimum range. These flows are professional judgment estimates provided for illustrative purposes. D. Whittaker and B. Shelby 235 1 i d 4 1 , i ,