Laserfiche WebLink
<br />. <br /> <br />. <br /> <br />Hypothesis 7, Higher spring flows and a natural hydrograph will <br />increase flooded areas in spring for adult razorback sucker and <br />Colorado squawfish use in both the Colorado and Gunnison rivers <br />and will improve quality of young-of-the-year habitat. <br /> <br />Hypothesis 8, Higher spring flows and a natural release pattern <br />from the Aspinall Unit will improve the ability of the Gunnison <br />and Colorado rivers to clean spawning substrate, to maintain <br />sand and silt substrate in nursery areas, and to maintain <br />natural channel characteristics. <br /> <br />Hypothesis 9. Reproductive success of humpback chub in Black <br />Rocks and Westwater Canyon will be enhanced by high spring <br />flows from the Gunnison River. Survival of young chubs will <br />improve under a more natural flow regime. <br /> <br />Test flows will be released from the Aspinall Unit to more closely mimic a <br />natural hydrograph (i.e, higher spring flows, and lower fall and winter <br />flows). These flows will be released over a five year period to allow <br />investigators to monitor the response of endangered fish populations, and <br />the quantity and quality of the various habitat types important to the <br />endangered fishes. Spring flows are the most important component of a <br />natural hydro graph and will determine the flows during the remainder of <br />the year, Spring flows during the test period will fall into two <br />categories--optimal and suboptimal, Based on previous investigations it <br />is believed that optimal spring runoff occurs when maximum annual flow <br />from the Gunnison River exceeds 12,000 cfs (measured at the USGS stream <br />gage near Whitewater, CO [09152500]); suboptimal flow occurs when maximum <br />annual flow is less than 8,000. The studies will test these flows by <br />releasing suboptimal spring flows for two years and optimal flows for <br />three years, Flows during the rest of the year will cover the range of <br />flows that occurred during the same periods prior to construction of <br />Aspinall to allow assessment of available habitats (including nursery <br />habitat) at the various flows, More specific details on flows are being <br />developed in a separate document, Because it is impossible to predict how <br />much water will be available during the course of the five-year study, <br />researchers will meet with USBR and WAPA early each spring to determine <br />the release pattern for the coming year. <br /> <br />Researchers from the Fish and Wildlife Service, Bureau of Reclamation, <br />Utah Division of Wildlife Resources and Colorado Division of Wildlife <br />developed studies to address each of the hypotheses listed above--some of <br />these studies will address the same hypotheses, but in different river <br />reaches or using different but compatible methodologies. Seven tasks were <br />developed for FY 93. A table describing the estimated schedule for <br />studies to evaluate each of the hypotheses is attached, <br /> <br />As already mentioned, the study is planned to last five years. One more <br />year will be required to consolidate the studies and produce a summary <br />report with flow recommendations that will lead to the Biological Opinion. <br />Each investigator will be responsible for annual reports on their <br />activities. However, the Service will be responsible for an annual report <br />on the general progress of the individual studies as relates to the <br />Biological Opinion. The Service will be responsible for general oversight <br /> <br />4 <br />