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Last modified
1/26/2010 12:28:30 PM
Creation date
10/11/2006 10:02:26 PM
Metadata
Fields
Template:
Water Supply Protection
File Number
8220.105.I
Description
Colorado River-Water Projects-Navajo-Environmental Studies
State
CO
Basin
Colorado Mainstem
Water Division
5
Date
10/1/2001
Author
BOR
Title
Navajo Dam EIS-Biological Assessment-Preliminary Draft
Water Supply Pro - Doc Type
EIS
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<br />New Mexico, San Juan County, and Utah, San Juan County. The San Juan River and its <br />100-year flood plain from the State Route 371 bridge in T.29N., R.l3W., section 17 <br />(New Mexico Meridian) to Neskahai Canyon in the San Juan ann of Lake Powell in <br />T.4l S., R.ll E., section 26 (Salt Lake Meridian) up to the full pool elevation. <br /> <br />Ryden (2000) reported on the present status of the fish in the San Juan. Only 19 wild (not <br />stocked) pikeminnows were located during SJRBRIP electro fishing surveys between 1991 and <br />I 996-most were found in the relatively short reach of river between the Mancos River <br />confluence and the Cudei Diversion Dam (RM 120-145). In addition to actual captures, 12 <br />pikeminnow were observed, mostly between the Four Comers and the Cudei Diversion. The <br />furthest upstream a pikeminnow was observed was near the Hogback Diversion (RM 160). <br />Larval and juvenile pikeminnows have also been collected, all downstream from a presumed <br />spawning area near River Mile 128 (referred to as the Mixer). Beginning in 1996, Colorado <br />pikeminnow were stocked near Shiprock and Mexican Hat (River Miles 148 and 53) and at least <br />some of these are surviving in the river (Ryden, 2000). <br /> <br />Habitat of the fish in the San Juan River includes a complex mix oflow-velocity habitats such as <br />eddies, pools, and backwaters adjacent to swifter run and riffle habitats. A natural hydrograph <br />(high spring flows. lower base flows) is important in maintaining the habitat and one of the main <br />effects of Navajo Reservoir under historic operations has been to reduce high spring flows while <br />increasing base flows. Miller and Ptacek (2000) and Holden (1999) discuss habitat types <br />seasonally used by the pikeminnow and should be referred to for specific information. Habitat <br />types used varies seasonally. During the pre-spawn period, pikeminnow use mainly slower <br />velocity habitats, including mouths of tributaries such as the Mancos River. During spawning, <br />higher velocity and often complex habitat areas are used. Following spawning the fish move into <br />simpler habitat complexes such as runs and pools, and runs provide fall and winter habitat. <br /> <br />Loss of habitat, competition from nonnative fish, water quality problems, and migration barriers <br />may all be factors in the fishes' decline. Reductions of water temperatures due to the operation <br />of Navajo Reservoir may also be a factor in reducing the range of the species, and habitat in the <br />lower river was lost when Lake Powell was filled. Larval fish that drift into Lake Powell may all <br />be lost due to predation. <br /> <br />Nonnative fish are common throughout the critical habitat reach and include channel catfish, <br />carp, fathead minnows, and other species. There are five major diversion structures between RM <br />142 and RM 178, which impede fish movement to varying degrees (Masslich and Holden, 1996); <br />and this may strongly influence the range of the pikeminnow which is a very migratory species. <br />There is potential that water contaminants may also affect the fish; these include selenium and <br />polycyclic aromatic hydrocarbons (P AH's). <br /> <br />The flow recommendations are specifically designed to create and protect habitats used by the <br />fish (Holden, 1999). Higher spring flows (> 10,000 cfs) generate new cobble sources, channel <br /> <br />17 <br />
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