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<br />inches) cause elk to move to more exposed winter range, and <br />snow depths in excess of 70 centimeters (28 inches) usually <br />prohibit the use of an area by elk. The southern exposure <br />areas favored for calving are not affected by the receding <br />snowline and provide ample habitat (15). <br /> <br />Small mammal populations undergo very wide fluctuations <br />based on a number of complex factors which are only partially <br />understood. A study of pocket gophers in the San Juan Mountains <br />found an'increase in litter size in response to severe winter <br />conditions. The same study found a decrease in deer mouse <br />and chipmunk populations after a winter of deep snows (15). <br />A study of eastern cottontail rabbit in Illinois determined <br />that weather factors, in general, are not highly correlated <br />with cottontail popula~ions (6). <br /> <br />The Project Skywater Final Environmental Impact Statement <br />concluded that: "The potential impact of widespread or pro- <br />longed application of precipitation management will probably <br />involve occasional episodes of circumstances resulting in temporary <br />declines in small mammal populations. There appears to be <br />little likelihood that such applications will significantly <br />affect the range of diversity of small mammal species." (18) <br /> <br />2.3.3 Aquatic Impacts. Both beneficial and nonbeneficial <br />impacts to the aquatic ecosystem have been identified from <br />the effects of weather modification. Possible physical changes <br />in aquatic systems as a result of a successful snow augmentation <br />program are: increased flow volumes as a result of additional <br />melt water, changes in salinity and siltation, lowering of <br />water temperatures due to increased snowmelt, and mortality <br />occurrence associated with increased snow cover (2). <br /> <br />2-12 <br />