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<br />e <br /> <br />e <br /> <br />e <br /> <br />INSTREAM FLOW QUANTIFICATION - LITTLE DRY CREEK <br />April 5, 1993 <br />PAGE 19 <br /> <br />e <br /> <br />DISCUSSION <br /> <br />The habitat vs. flow relationships for the CGV IFIM site warrant some discussion. The <br />fathead minnow curve is a typical adult curve in that once the bottom of the channel is wetted, <br />increases in flow cause a rapid increase in habitat up to a point where additional flow does not <br />increase habitat. This curve starts to asymptote at about 3.5 cfs. The creek chub curves also <br />are quite typical in their appearance; the adult curve starts to asymptote at about 3 cfs where the <br />juvenile curve is fairly flat but has a peak at about 2.2 cfs. The relationships for the four life <br />stages of white sucker also are fairly typical in appearance; an adult asymptote at about 1.6 cfs <br />and low peaks for the other three life stages in the 1.2 to 1.6 cfs range of flows. <br /> <br />The CRY IFIM site exhibits very similar results. This is not surprising in that the habitat <br />at both sites was very similar and the channel geometry and flow regime are also very similar. <br />The flow vs. habitat relationships for the three species are similar in shape to the ones in CRY <br />(discussed above). For both the fathead minnow and creek chub adults the asymptote is initiated <br />at approximately 3.8 cfs. For the creek chub juveniles, the peak in habitat occurs at about 2.6 <br />cfs. The white sucker relationships are somewhat different in that a minor asymptote occurs at <br />about 1.6 cfs and another one (a more sustained asymptote) occurs at about 3.4 cfs. As for the <br />other three life stages; fry and juveniles peak at approximately 1.9 cfs and the spawning curve <br />asymptotes from 1.3 to 2.2 cfs and then peaks at about 3 cfs. <br /> <br />e <br /> <br />Referring back to the life history discussion above, creek chubs and white suckers spawn <br />during the spring season while the fathead minnows spawn when water temperatures are between <br />65 and 85 degrees (F). Adults of all three species are obviously present in the system year- <br />round. The spring spawning species have fry and juveniles present in the stream during the <br />early summer months on into the fall. It is necessary to keep this information in mind when <br />drawing conclusions from the habitat vs. flow relationships. <br /> <br />RECOMMENDATION SYNTHESIS <br /> <br />Given the nature of these fish species in that none are state or federally listed as <br />threatened or endangered, nor are any of them designated as species of special concern by the <br />Colorado Wildlife Commission, an optimum level of flow protection is not necessary. All of <br />the fish species are quite common in Colorado streams similar to Little Dry Creek. The <br />Division of Wildlife, particularly the Central Region, has a great deal of interest in preserving <br />urban corridors such as this one because they are relatively rare in urban areas. Most urban <br />streams like Little Dry Creek are severely impacted by the urbanization that has occurred in and <br />around them - impacts from construction, storm runoff, channelization, nutrient concentrations, <br />and diversion. The upper reaches of Little Dry Creek through Greenwood Village and Cherry <br />Hills Village down to about Downing Street are essentially in the natural state. The fish <br /> <br />e <br />