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`+� "• T - sue' similar daily flow fluctuations based on power <br />demand. Surveys showed that rafters and jetboaters <br />preferred fluctuations of less than 3,000 cfs per <br />day, but could tolerate 6,000 to 9,000 cfs. Current <br />operations <br />fluctuate <br />�7 <br />` 1 s - <br />Far Left. Rafters pushing a boat into the Colorado <br />River in Grand Canyon after overnight flow <br />t <br />fluctuations left it "high and dry." Flow comparison <br />surveys of experienced boaters helped define <br />fluctuation tolerances. <br />z <br />Inset: The Snake River through Hells Canyon has <br />`+� "• T - sue' similar daily flow fluctuations based on power <br />demand. Surveys showed that rafters and jetboaters <br />preferred fluctuations of less than 3,000 cfs per <br />day, but could tolerate 6,000 to 9,000 cfs. Current <br />operations <br />fluctuate <br />�7 <br />` 1 s - <br />12,000 c15 <br />in some <br />in some <br />t <br />seasons. Inset: <br />Consequences <br />are greater for <br />1l " <br />larger boats. <br />I <br />Far Right. Lava Falls in Grand Canyon <br />at about 35,000 cfs. Experienced boaters t <br />are often knowledgeable about the flows <br />that produce different types of recreation <br />opportunities. Flow comparison studies <br />draw on this accumulated knowledge. <br />t r <br />Right: A commercial jetbaat runs Wild <br />Sheep Rapid in Hells Canyon at 9,000 <br />cfs. Flow comparison surveys were used to <br />develop overall flow evaluation curves for <br />rafts and jetboats (below). Minimum flow <br />needs were similar, but higher flows are <br />better for rafts than jetboats. <br />Evaluatiosi <br />AccdptWe 4 <br />3 <br />Unacceptable 2 r <br />1L <br />0 <br />Rafts <br />.I a ilsuyt% <br />10,000 24,000 00,000 10,000 50,000 <br />US from He1MS Cwwoo Dam <br />Flows and Recreation: 25 <br />A Guide for River Professionals <br />r <br />i <br />