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.important question is whether increased snow depth and duration will worsen or extend winterkill occurrences. Some possible effects of widespread and prolonged application of precipitation management have been studied. Analysis has included studies of the effects of increased runoff on water temperature, the physical state of the streambed as it may affect spawn i ng and egg hatch, food supply for the fry, and the possible effect of cloud seeding agents on water qual ity. Other factors were considered as too far removed in their connection with precipitation management and too disturbed by other variables for meaningful analysis. The Skywater Programmatic FES discussion about effects on aquatic ecosystems and the more recent Sierra Ecology Project report on the workshop on lake and stream biota [17J are incorporated into this document by reference. Precipitation increases could significantly and/or adversely affect endangered and threatened species of animals and plants and their habitats. The site-specific investigations required for phase two of the proposed alternatives and for an operational cloud seeding scenario would include studies of likely effects on endangered and threatened species that may occur in the proposed project areas if such species are found. This process will begin with consultation with the Fish and Wildlife Service and State fish and game officials. Installation of instruments during the first phase (data collection/ cal ibration phase) of thE~ project would have no impact on these species because of the selection policy of avoidance of such sites. d. Impacts on the Human Envi ronment. - Increases in preci pitat i on usually estimated at behreen 10 and 15 percent per annum are not expected to generate new or incremental popul ation increases above those estimated in existing development scenarios for the Colorado River Basin. The two most commonly perceived driving forces for population growth in the Basin are the sunbelt phenomenon and devel- opment of coal and oil shale resources. Various studies of future resource requi rements in the Bas i n present the prospect of water shortages ranging from as early as 1990 to 2010 or 2020. Augmenta- tion of the Basin's water supply will be required by cloud seeding or other means if thi sneed is to be met. If additional water is not provided, the sector most capable of paying in the marketplace will outbid other sectors for a relatively diminishing supply of water. The agricultural sector w'ill lose its water to the mineral/energy development sector. Municipalities and residents will face rapidly increasing costs for new water supplies. Partial economic benefits were determined in 1979 using the most conservative estimates of water supply increases from cloud seeding (1,315,000 acre-feet) within the Upper Basin as input to WPRS's Colorado River Simulation System model. The results showed cloud seedi ng woul d produce est imated economi c benefits of at 1 east $80 million annually from the following sources: $29 million from increased hydroel ectri c capacity and power generation based on coal replacement cost at 20 mills per kilowatt-hour, $41 million from salinity reduction using an average value of $450,000 for each milligram per liter reduction 'in dissolved solids at Imperial Dam, 19