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<br />ABSTRACT <br /> <br />..' <br /> <br />A workshop group of six scientists evaluated the possible effects of a weather modification <br />pilot project upon hydrologic processes, including sediment and nutrient inputs, withinCalifor- <br />nia's American River Basin. The group considered effects upon three elevation zones within the <br />basin: a 1220- to 1530-m (4000- to 5000-ft) zone affected primarily by rainfall, a rainfall/snowfall <br />zone between 1525 and 1680 m (5000 and 5500 ft), and a snowfall zone above 1680 m (5500 ft). <br />Background information on the area's climatic and physical conditions is presented, followed by <br />an analysis of potential changes in precipitation, macronutrients, particulate matter, heavy <br />metals, and other constituents. The group proposed research and monitoring needs and con- <br />cluded that an average 5- to 7.5-percent precipitation increase (10 to 15 percent increase reduced <br />by 50 percent randomization) over the life of the research program will not significantly alter the <br />current nutrient and particulate matter systems, assuming reasonable weather modification <br />suspension criteria are observed. The greatest possibility for degradation of the environment may <br />occur in the 1220- to 1525-m (4000- to 5000-ft) zone under bare soil conditions in which rainfall <br />intensity, duration, and amount could be significantly increased as a result of cloud seeding. <br /> <br />-; <br /> <br />JOt <br />, <br /> <br />~ <br /> <br />IV-l <br />