The Grass Valley - Clark Canyon Cooperative Wildlife Management Unit (CWMU) lies east of Echo Reservoir. Although it is continuous, Chalk Creek cuts the Unit into a west and east sub-unit. On the west area the high point is around 7600 feet. The ridge line drops in a southwest direction too the shore of Echo Reservoir at about 5600 feet. To the north the Unit drops down into Echo Canyon, about 5800 feet before rising again to 7200 feet. Grass Valley Canyon cuts this west area and ranges from 5600 feet to 6400 feet. Then rises up to 7800 feet above Chappell Lake before dropping down again to Chalk Creek at 6000 feet. The east area is quite long and narrow with a high point around 7600 feet in the north and 7700 feet in the south. The most common elevation is 6300 feet but ranges from 5300 feet to 8000 feet with an elevation difference of 2700 feet. Fifty-one percent (51%) of the CWMU elevation ranges between 6300 feet and 7100 feet an elevation difference of 800 feet.Inter-Mountain Basins Montane Sagebrush Steppe (62) is the dominant land cover on the GrassValley - Clark Canyon-Moose Cooperative Wildlife Management Unit (CWMU). Closely behind and almost equal with the Sagebrush Steppe is Rocky Mountain Gambel Oak-Mixed Montane Shrubland (41). There are a number of areas particularly in the north part of the Unit that have areas of Rocky Mountain Aspen Forest and Woodland (22). To a lesser extent there are patches of Colorado Plateau Pinyon-Juniper Woodland (36) and Inter-Mountain Basins Big Sagebrush Shrubland (48). There are also a number of large patches of Agriculture (114) closer to riparian areas.One of the Grass Valley - Clark Canyon Cooperative Wildlife Mangement Unit (CWMU) nearest weather stations, ECHO DAM (422385), is about 1.2 km west from the west edge of the CWMU. ECHO DAM has sixty-seven (67) years of records, 1940 - 2007. During the FALL (September, October and November) the average precipitation is 3.88 inches, but it can be as high as 10.59 inches or as low as 0.47 inch. During the 91-day FALL period, 21 days will experience greater than or equal to 0.01 inch of precipitation, 11 days of greater than or equal to 0.10 inch, or 2 days of the greater than or equal to 0.50 inch of precipitation. Snowfall during the FALL averages 12.1 inches but can be as high as 41.5 inches. FALL temperature at ECHO DAM averages 46.5 degrees F. but can be as high as 97.0 degrees F. or as low as -21.0 degrees F. During the FALL, 54 days will be below freezing (32 degrees F.) and 3 days above 90 degrees F.