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LJ <br />CHAPTERTHREE Affected Environment <br />the annual snowpack is at its maximum and/or temperatures aze at a minimum in the two worst <br />winters out often. Winter concentration azeas aze defined as that part of the winter range where <br />densities are at least 200 percent greater than surrounding winter range density, the average five <br />1 winters out of ten. These ranges are paramount to the survival of the herd during severe winters <br />when other habitats can not be used (CDOW 1998). Summer range is that part of the range <br />where 90 percent of the individuals aze located between spring green-up and the first heavy <br />snowfall. <br />The Piceance Basin portion of the study azea is within CDOW Data Analysis Unit D-7 (White <br />River DAU), while the azea from the drainage divide south to the Colorado River is within DAU <br />D-41 (CDOW 1998). DAU D-7 has 1,969 squaze miles of winter range, 256 squaze miles of <br />winter concentration azea, and 627 square miles of severe winter range. DAU D-41 contains 453 <br />' square miles of winter range, 167 square miles of winter concentration azeas, and 218 squaze <br />miles of severe winter range. Severe winter range is considered to be critical habitat. <br />Piceance Site <br />The Piceance Site includes winter range and severe winter range for mule deer. It is used <br />extensively by deer during the winter months, with the heaviest use occurring from September <br />through February, during which time the greatest mortality occws (not including harvest) <br />(Prenzlow 1998). Snow depth continually decreases from Ryan Gulch northwazd along Piceance <br />Creek. Mule deer tend to follow the decreasing snow line and congregate north of Horse Draw. <br />During late March through late April, deer tend to drift north as winter snows accumulate, and to <br />concentrate on south and south-west facing slopes along Piceance Creek. Beginning in late April <br />to eazly May, agricultural meadows containing grasses and forbs along Piceance Creek are used <br />heavily. These agricultural grasses and forbs comprise >_ 66% of mule deer spring forage <br />(Hartmann 1983). This succulent forage provides the first opportunity for deer to begin reversing <br />' their negative energy balance (Garrot et al. 1987). BLM biologists conducted field surveys to <br />determine on-lease deer use report that on April 22, 1998, the peak spring concentration along <br />Piceance Creek north of Horse Draw was at a minimum of 143 individuals. During the fall and <br />spring migration (September-October, April-May) the Piceance Site has concentrated deer <br />movement especially between the ridge line and Piceance Creek. <br />1 The Piceance Site represents approximately 2 percent of total available severe winter range in <br />Game Management Unit (GMU) 22. The Piceance site is used heavily by mule deer because of <br />less snow, southerly aspects, available thermal cover, and accessibility to native and agricultural <br />vegetation in the spring. <br />Pipeline <br />All of the pipeline corridor from the Piceance Site to the lower part of Barnes Ridge is winter <br />range, and most of the length between the Piceance Site to one mile south of the second Piceance <br />' Creek crossing (about Milepost [MP] 15) is also severe winter range (CDOW 1998). The azea <br />from fames Ridge to the East Fork of Pazachute Creek (MPs 19 to 34.5) is summer range. All <br />of the pipeline corridor from Davis Point to the Pazachute Site is in winter range, most of which <br />is also severe winter range and/or winter concentration areas (CDOW 1998). <br />~Idlife 3-33 <br />