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now <br />6,000 <br />5,000 <br />4,000 <br />3,000 <br />2,000 <br />1,000 <br />0 Fu.u.. F Y.0 4. �i 4 -r <br />10/1 11/1512/30 013 3/29 5/13 6/27 8/11 9/25 <br />Date <br />Figure 5. Annual hydrograph (mean daily flows) for <br />Alaska's Gulkana River. Hydrographs provide key <br />information for instream flow studies. <br />river system in question is regulated, as well as <br />a discussion of the changes from natural flow <br />resulting from any water development projects. <br />This includes a discussion of operational <br />constraints for any projects. <br />Step 5: <br />DESCRIBE FLOW - CONDITION <br />RELATIONSHIPS <br />This step establishes the link between <br />various flow levels (the hydrology of the river) <br />and the conditions that create recreation <br />opportunities. However, this is the descriptive <br />side of the equation: the information generated <br />here should ideally show how conditions change <br />with different flows or flow regimes, not <br />evaluate those different conditions. <br />In many studies, particularly those focusing <br />on long -term or indirect effects of flow on <br />channel features or vegetation, this step is at the <br />center of the effort. In these cases, examining <br />the flow - condition link is a prerequisite for <br />evaluating those specific conditions. In other <br />cases this step may be partly bypassed because <br />the flows themselves can be evaluated. For <br />example, it is often possible to have boaters <br />directly evaluate flows for certain recreation <br />attributes such as boatability or whitewater <br />without bothering to learn the details of how <br />different flows affect specific whitewater or <br />boatability conditions (e.g., water depth or <br />velocity). The more researchers know about the <br />flow - condition link, the better they can <br />understand any subsequent evaluations, and the <br />13 <br />more likely that "generalized" methods can be <br />developed. Almost any study should provide at <br />least a qualitative analysis of that relationship. <br />Output from this step comes in one of two <br />forms, depending upon the type of conditions <br />under examination. For conditions directly <br />affected by flows, information should show how <br />conditions will change through a range of flows <br />(incremental relationships). One basic example <br />of this relationship might show how depths in <br />riffles change through a range of flows. A more <br />complex example of a flow - condition relation- <br />ship is given in Figure 6, showing how increases <br />in flow decrease the number of times rafts run <br />aground in shallow areas. In this case, the <br />condition of interest (number of "hits ") depends <br />on more basic conditions affected by flow (depth <br />and perhaps velocity), but it still refers to a non- <br />evaluative and measurable variable. Similar <br />curves could be developed for floaters' rate of <br />travel, size and frequency of rapids, availability <br />of gravel bars for fishing or camping, or other <br />attributes of a trip. <br />For conditions that are more indirectly <br />affected by flows, incremental relationships may <br />be more difficult to develop. In these cases, <br />changes are typically longer term and /or subtle <br />and researchers must often take a step back to <br />gain perspective. In most cases, the goal is to <br />link different flow regimes with the trends in <br />various conditions. A common example of this <br />type of analysis would be a relationship between <br />average peak flows and the creation or <br />maintenance of channel features such as beaches, <br />sloughs, or riffles. <br />Number of Hits <br />14 <br />12 <br />10 <br />/OD 750 800 850 900 950 1000 <br />Flow in cfs <br />Figure 6. An incremental curve shows the <br />relationship between flows and a measurable resource <br />condition (in this case, the number of hits reported by <br />rafters). Data come from Colorado's Dolores River. <br />