Laserfiche WebLink
<br />Memo to Colorado Water Conservation Board Members <br />From: Peter Evans and Gene Jencsok <br />Date: October 17, 1995 <br />SUBJECT: Agenda Item 2, October 20, 1995 Board Meeting <br />Endangered Fish Recovery ISF Water Right - Colorado River (Mainstem) <br /> <br />Page 4 <br /> <br />habitat for adult squawfish and increase water temperatures during July to promote faster growth <br />among young squawfish in the 15 Mile Reach and downstream. Those recommendations were <br />based largely upon an analytical modeling technique which required that certain assumptions be <br />made to fill in gaps within our knowledge about the needs of the fish. Those assumptions, the <br />complexity of physical habitat in the 15 Mile Reach, and limitations in the modeling technique <br />produced many new questions and concerns about the flow recommendations and their use in <br />connection with the CWCB's instream flow protection authority. - <br />Because of these concerns, the CWCB recommended that the Recovery Program proceed <br />with studies to further refine the flow recommendations, and concluded that use of the flow <br />recommendations should be limited to the acquisition of water rights less than the recommended <br />amounts. In 1991, the Recovery Program engaged a senior scientist to review and evaluate the <br />various methodologies and data used by the FWS in developing its flow recommendations. The <br />Recovery Program was advised that, although the best available data and methodologies had <br />been used, geomorphologic/sediment transport and food web studies should also be undertaken, <br />and the Recovery Program is presently following those recommendations. The FWS has updated <br />and refined its earlier recommendations with a May 1995 report entitled Relationships Between <br />Flow and Rare Fish Habitat in the "15 Mile Reach" of the Upper Colorado River, <br />This new report presents a new approach for identifYing the flows needed during summer <br />and winter months and incorporates new information into the approach applied earlier for the <br />spring runoff months. The new approach for summer and winter months involves an <br />identification of habitat types preferred by the endangered fish and of the flow level at which the <br />total area of those habitat types is maximized. For the spring months, the recommended flow <br />levels are generally intended to maintain and enhance the year-round benefits provided by the <br />scouring and flushing of flood waters, rather than optimizing the availability of habitat during <br />those months. However, consideration was also given to maintenance and enhancement of <br />spawning habitat for razorback suckers, since they spawn during the spring months. <br />The FWS flow recommendations, which are summarized in an attachment to this memo, <br />are specified in terms of "mean monthly discharge" for years with "high," "above average," <br />"below average," and "low" levels of snowpack. The recommendations for April - July are also <br />specified in terms of volumetric increments for each 10-day period and in terms of an <br />instantaneous peak flows of at least 23,500 cfs in the wettest 5 years in each 20 year period, <br />between 20,500 - 23,500 cfs in the next 5 "above average" years, and between 12,900 - 20,500 <br />cfs in the remaining 10 years with "below average" to "low" snowpack. <br />The FWS report indicates that "because these populations are in danger of extirpation, the <br />management objective is to provide favorable if not optimum conditions that promote species <br />recovery. ...Therefore 'minimum' flows recommended in this report are something more than <br />that which will enable survival of individual fish: we define minimum flows for endanger~dfish <br />as those necessary for species recovery, i.e:,those that promote increases in population size:" <br /> <br />95C 1492 <br />