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Instream Flows for Recreation: A Handbook on Concepts and Research Methods
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Instream Flows for Recreation: A Handbook on Concepts and Research Methods
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Water Supply Protection
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Instream Flows for Recreation: A Handbook on Concepts and Research Methods
Date
1/1/1993
Author
Whittaker, Doug; Shelby, Bo; Jackson, William; Beschta, Robert - National Park Service
Title
Instream Flows for Recreation: A Handbook on Concepts and Research Methods
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There are a variety of methods for <br />examining flow - condition relationships, each <br />having advantages or disadvantages that depend <br />upon the circumstances of the river and the <br />opportunities or attributes in question. The next <br />chapter in the handbook, Exploring the Effects of <br />Flow on Resource Conditions, provides more <br />information on these methods and how they can <br />be used to develop flow - condition relationships. <br />Step 6: <br />EVALUATE FLOW NEEDS <br />FOR SPECIFIC OPPORTUNMES <br />This step develops the evaluative side of the <br />equation, providing information about the best <br />or preferred conditions or flows. The idea here <br />is to identify the conditions and flows (or flow <br />regimes) that are best for each particular <br />recreation opportunity. <br />There may be two or three parts to this <br />step, depending upon whether the evaluation <br />begins with flows or conditions. If the study <br />begins with conditions, those will need to be <br />evaluated first. After this, the preferred flows <br />(those that create preferred conditions or those <br />directly evaluated as preferred flows) can be <br />identified for important attributes of the <br />opportunity, which may involve one or a <br />combination of conditions. Finally, the range of <br />preferred flows for various attributes must be <br />integrated into an overall flow evaluation for a <br />specific opportunity. <br />As an example, think about an effort to <br />evaluate flows and conditions for a bank fishing <br />opportunity. It might begin with specific <br />evaluations of flow - dependent conditions such <br />as wadeability, turbidity, and water <br />temperatures at different flows. Researchers <br />would document the combinations of depth and <br />velocity best for wading (and thus determine <br />which range of flows provide preferred <br />combinations), as well as determine the flows <br />that provide preferable turbidity or temperature <br />levels for catching fish. <br />But this information alone is not sufficient. <br />Assume, for example, that after making these <br />initial evaluations, researchers discovered that <br />on this river lower flows provide better wading <br />and clearer water, but they also mean higher <br />temperatures, less active fish, and thus lower <br />fishing success. In contrast, higher flows and <br />14 <br />NOW <br />-2" <br />0 10 20 30 40 50 80 70 80 <br />Flow (x 1000 ds) <br />Figure 7. Example of an overall flow preference curve <br />for whitewater boating in the Grand Canyon. The <br />curve is based on evaluations by commercial guides <br />and private trip leaders. <br />corresponding lower temperatures bring better <br />fishing success, but increased turbidity at very <br />high flows eventually lowers that success, and <br />the higher flows are increasingly unwadable as <br />well. Taken singly, the preferred flow for each <br />condition may be very high or very low; taken <br />together, some medium range of flows appears <br />to provide the best overall evaluation. Only <br />when evaluations for all the important <br />conditions are integrated can an overall flow <br />preference be identified. In most cases no single <br />flow or narrow range of flows will provide <br />optimum conditions for every attribute of a <br />recreational opportunity. In order to fully <br />evaluate a range of flows, it is thus necessary to <br />examine flow needs through some sort of <br />optimizing filter. <br />The output from this step again depends on <br />whether effects are direct or indirect. For direct <br />effects, the ultimate goal is an incremental curve <br />that shows how recreation quality changes <br />through a range of flows. An example of such a <br />curve, which is also known as an overall flow <br />preference curve, is given in Figure 7. Readers <br />should note that this curveonly shows the "best" <br />flows for whitewater boating in Grand Canyon <br />and does not provide any information about best <br />flows for maintain the Canyon's fishery or its <br />beaches. <br />For indirect effects, information is generally <br />organized in more descriptive terms. The goal <br />in these cases is to evaluate alternative flow <br />regimes (or critical elements of those flow <br />regimes) rather than a simple range of flows. <br />
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