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Last modified
7/14/2009 5:02:34 PM
Creation date
5/18/2009 12:42:12 AM
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UCREFRP
UCREFRP Catalog Number
8239
Author
McAda, C. and K. Fenton.
Title
Relationship of Fish Habitat to River Flow in the Gunnison River.
USFW Year
1998.
USFW - Doc Type
Project number 47,
Copyright Material
NO
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Executive Summary <br />This study described relationships between fish habitat and river flow in the <br />Gunnison River. These relationships will be used in conjunction with data collected <br />in a variety of other studies to make flow recommendations for operation of the <br />Aspinall Unit in the upper Gunnison River. The Aspinall Unit is a series of three <br />reservoirs (Blue Mesa, Morrow Point, and Crystal) that were completed by the <br />Bureau of Reclamation between 1966 and 1976. These reservoirs have had a <br />significant impact on timing and magnitude of river flows within critical habitat for two <br />endangered fishes -Colorado squawfish Ptychocheilus lucius and razorback <br />sucker Xyrauchen texanus. Reopera#ion of the Aspinall Unit will contribute to <br />recovery of these two species in the Gunnison River. <br />We used a combination of airborne videography and mapping of surface <br />habitats to quantify surface area of 11 macro-habitat types at 5 study sites under 7 <br />river flows. These flows ranged between a low of 981 cfs (the lowest flow in the <br />Gunnison River during the study) to a high of 15,800 cfs. In addition to habitat <br />mapping, cross-channel bed profiles were surveyed annually at each study site to <br />monitor changes in the river channel. Habitat mapping was also supplemented with <br />staff gauges placed at important bottomland sites to determine when over-bank <br />flooding occurred. The. study extended over a 4-yr period that saw peak flows of <br />20,500 cfs in 1993, 6,040 in 1994, 17,300 in 1995, and 7,670 in 1996. <br />Maintenance and restoration of flooded-bottomland habitats is an important <br />component of the Recovery Program. In the Gunnison River, most of this <br />bottomland habitat occurs near Delta, Colorado. Over-bank flooding in the Delta <br />area began at flows as low as 6,000 cfs, with considerable flooded habitat available <br />at 8,000 cfs. Area of flooded habitat increased as discharge increased; however, <br />low-velocity deep-water habitats were maximized at about 13,000 cfs in the primary <br />floodplain study site. <br />A base-flow recommendation already exists for the lower Gunnison River. A <br />minimum of 300 cfs is required to provide a migration corridor in a 2.3-mi-long reach <br />between the Colorado River and the Redlands Diversion Dam where a fish passage <br />structure has recently been completed. Combined with a 750 cfs water right held by <br />Redlands, that recommendation translates into a base flow of about 1,050 cfs in the <br />Gunnison River above the dam. The lowest flow we studied approximates the base <br />flow mentioned above and that flow provided a mixture of habitats preferred by <br />Colorado squawfish -pools, eddies, and slow runs. <br />Maintaining habitat complexity necessary for a healthy river environmen# <br />requires regular scouring and bar building along the river channel. In this study, <br />some scouring and deposition occurred in all years, but major channel modifications <br />occurred more often in high-runoff years than in low-runoff years. Further, material <br />v <br />
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