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<br />. <br /> <br />.. ~. . .1 <br />~.'.:).~~:i <br /> <br />. <br /> <br />"'~'~~~ <br /> <br />j <br /> <br />. <br /> <br /><- <br /> <br />Introduction <br /> <br />In the Summer of 2000, students in Western State College's Field Geology class (GEOL <br />450) had the opportunity to study the hydrology of a section of West Antelope Creek. <br />West Antelope Creek is located just northwest of Gunnison in the foothills of the West <br />Elk Mountains (Figure 1). It is located in Township 50 north, Range 2 west, bpt no <br />Section lines are shown for this part of the quadrangle. The reach that we surveyed is <br />immediately northwest of the boundary between National Forest and Bureau of Land <br />Management (BLM) land. <br /> <br />West Antelope Creek is part of the Gunnison River watershed and contains several old <br />beaver dams that have been breached or destroyed (Figure 2). Aerial photographs from <br />1977 (Figure 3) show some ponds from these beaver dams. The ponds are no longer <br />filled, so it appears that the beavers (Castor canadensis) died or migrated out of this <br />section of West Antelope Creek within the last 23 years. <br /> <br />West Antelope Creek is of particular importance because it supports a population of <br />Colorado River cutthroat trout (Oncorhynchus clarki pleuriticus). Genetic analysis <br />indicates that this is a genetically pure Colorado River cutthroat trout and may be the <br />only remnant population of trout native to the upper Gunnison River as no others have <br />been confirmed (Arthur Hayes, Bureau of Land Management, personal communication). <br />West Antelope Creek provides an important refuge for this species and channel instability <br />may threaten the continued existence of this population. Flow in the stream was <br />measured by the Field Geology class and was found to be quite small (between 1 and 2 <br />cubic feet per second) and the potential exists for the creek to run dry in sections. We <br />hypothesize that the beaver ponds may have provided refuge for the trout during low- <br />flow periods. <br /> <br />The purpose of this hydrologic survey is to provide a benchmark of the physical <br />condition of the channel, floodplain, and terraces of a section of West Antelope Creek <br />that contains abandoned and breached beaver dams, and to look for evidence of <br />instability in the channel (i.e. excessive erosion or deposition). This survey could be used <br />to monitor changes in the following years. The survey was performed on June 6-8. 2000 <br />as part of Geology Field Camp for students in the Geology Program of the Department of <br />Natural and Environmental Sciences at Western State College of Colorado. It is expected <br />that the class will return to West Antelope Creek in the upcoming years to survey <br />changes that have occurred. The hydrologic survey included: <br /> <br />· Establishment of benchmarks, <br />· Cross.,.section profiles, <br />· Longitudinal profiles, <br />. Discharge measurements, <br />. Pebble counts (bed-material size). <br /> <br />2 <br />