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<br />l'lil <br />11, <br /> <br />,~ <br /> <br /> <br />Environmental Effects <br /> <br />~ <br /> <br />ABOUT 1930, the Upper Colorado River Basin began to enter a <br />dry period. If it continues WOSA could raise the average river <br />flow to near that of its recorded history (1896-present). The <br />variation in precipitation from one year to the next is inuch <br />greater than the shift WOSA will bring, but over many years <br />WOSA will affect the plants and animals of the Upper Basin, <br />however slightly. <br /> <br />il <br /> <br />I <br /> <br />~I, <br /> <br />Effects on Animal Life <br /> <br />Identifying subtle long-term effects in biological communities <br />that face very different environmental stresses from one year to <br />the next is difficult. Even if long-term changes can be identified, <br />long-term cyclic changes in the weather occur naturally, and <br />would be expected in the future. If we cannot predict precise <br />environmental effects for WOSA, at least we can describe the <br />natural environmental stresses caused by winter snow and show <br />how WOSA might influence them. <br />Changes in the temperature and the amount of moisture <br />available will encourage some kinds of vegetation and dis- <br />courage others. In turn, changes in vegetation will encourage <br />some kinds of wildlife and discourage others. With the long- <br />term average increase in snowfall that WOSA will bring, we <br />can expect a gradual shift of plants to lower elevation. We will <br />see the timberline retreat to lower elevations over a period of <br />many years. Mountain sheep and goats that winter in the tundra <br /> <br />37 <br /> <br />SNOWPACK, CLOUD-SEEDING, AND THE COLORADO RIVER <br />Flood damage can be reduced by effective forecasting and <br />flood warning that gives people time to prepare. The weather, <br />climate, precipitation, snowpack and streamflow information <br />needed for proper evaluation and control of the WOSA program <br />are the same kinds of information needed for flood forecasting <br />and warning. The WOSA program could provide flood warning <br />and forecasting at little additional cost. With adequate fore- <br />casting and warning, the average saving in flood damages would <br />more than offset any losses resulting from the WOSA program if <br />it observed the precipitation limits for flood and avalanche <br />hazard control. <br />Flooding in the Lower Basin due to snowmelt runoff in the <br />Upper Basin is virtually impossible because of the vast storage <br />capacity in Lake Powell and Lake Mead. <br />36 <br />fI <br />