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Last modified
7/14/2009 5:02:35 PM
Creation date
5/22/2009 5:30:16 PM
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UCREFRP
UCREFRP Catalog Number
9433
Author
Anderson, R.
Title
Riverine Fish Flow Investigations.
USFW Year
2002.
USFW - Doc Type
Federal Aid Project F-288-R5,
Copyright Material
NO
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<br />4 <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />The Cross Mountain Ranch is the landowner for most of the river at Sevens and Lily <br />Park. The BLM is the primary landowner at Duffy. In general, each site on the Yampa River <br />has distinctly different fish and habitat characteristics. Duffy is located in Little Yampa Canyon <br />and has some deep pools with large boulders that provide cover. Duffy is low gradient and the <br />primary habitat during the base flow period is shallow pools. Sevens is also low gradient and <br />primarily with shallow, low-velocity habitats at typical base flows. Sevens appears to have <br />higher riffle composition and pools are mid channel and exposed. The channel gradient is high <br />at Lily Park and substrate for most of this site is cobble and boulders. Faster flowing habitats <br />(runs and riffles) dominate in Lily Park. The Lily Park site was added because of poor native <br />fish composition at Duffy and the habitat of this site appears much more similar to the Colorado <br />River in the IS-Mile Reach than the other two Yampa sites. <br /> <br />Peak flows recorded at the Maybell gage were fairly similar for the years 1998, 1999 and <br />2000, at 10,040 cfs, 9,980 cfs and 9,830 cfs, respectively. Peak flows in these three years are <br />near the magnitude of the median peak flow of9,980 cfs for the 86 year period of record (Figure <br />2). Peak flow in 2001 was 7,650 cfs, which has been exceeded in 77% of the years during the <br />period of record. The peak flow in 1997 was 16,400, and has been exceeded in only 5% of the <br />period of record (Figure 2). <br /> <br />Impacts oflow flows are one of the primary objectives of this study. There are several <br />ecological problems associated with low flows, which will be addressed in the discussion <br />section. Instream flows are founded on the principle of a relationship between low flows and <br />detrimental conditions to the fish population. In a prior flow study on the Yampa River, Modde <br />et al. (1999) used a cross section methodology (modified R2Cross) to identify habitat availability <br />for endangered fish at low flows on the Yampa River. The result was a recommendation that 93 <br />cfs be used as a reference flow for future stream flow studies and the significance of the 93 cfs <br />was that it signals the beginning of severely degraded conditions. The 93-cfs reference flow was <br />deliberately not presented as an instream flow recommendation since instream flows are <br />typically based on a community perspective for protecting habitat and nearly always indicate a <br />flow that should not be violated. Some authors (Modde et al1999) felt that endangered fish can <br />survive the severely degraded conditions that exist at flows below 93 cfs at least for a short term, <br />and were not concerned with flow needs for non-endangered native fish. <br />
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