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ARCHIE M, KAHAN of the main water production or seeding areas in the Colorado River Basin, The northern area is cup shaped and somewhat sheltered by upwind mountains, while the southern area is exposed to storms from the northwest through southwest. More favorable seeding events are expected in the southern area because of generally warmer temperatures, With the exception of the northwestern part of the northern area, runoff water yield from the area exceeds 10 inches annually. Evaluation wi1l primarily be directed toward determining the snowfall increase due to seeding, Given a normal occurrence of favorable seeding situations in the 4-year period (the winters 1969-1970 through 1972-1973), an indicated increase of about 10 percent or more should be statistically signifi- cant. Seasonal streamflow increases based on gage records are not expected to be statistically signifi- cant within a 4-year period but streamflow increase evaluations, including precipitation-runoff rela- tions, wilJ be an important part of the evaluations. Approximately 40 instrumented sites recording hourly precipitation, surface wind, and temp- erature wi1l be installed during the summer and early fall of 1969. These wilJ be located at approxi- mately 1,000 feet elevation differences in 10 or 12 watersheds that are representative of the project areas. Remote acquisition of data wi1l be provided where necessary and feasible although the project budget should limit communication facilities to only a few of these sites. Each of the representative watersheds wilJ be gaged by an existing or additional stream gage. This fall, three new gages have been installed by the USGS in likely watersheds ( at the western bottom of Berthoud Pass, wester'1 bottom of Wolf Creek, and southern bottom of Red Mountain Pass). Samples of falling snow wilJ be collected at four points and stored should silver analysis be- come desirable. Planned sampling period would not be less than 6 hours and may be as long as several days. , ~ A data network for recognition of favorable seeding situations and tactical seeding control wi1l be included. At least one project sounding station, possibly mobile between the areas, and several re- mote instrumented sites with radio communication in and around the project areas wilJ be installed. According to present plans, seeding wi1l mostly be done from 22 ground-based, remote con- trolled silver iodide generator sites located around the project areas, 6 for the northern area and 16 for the southern area. Some air seeding is planned. The operating period wi1l generally be October IS through May 11. Seeding the first season 1969-1970, wi1l be in the northern area. A random schedule wilJ be set in advance for a 4-year and long: er period. To balance the installation cost of the seeding and recognition systems between FY 1970 and FY 1971, the northern area equipment wi1l be installed in FY 1970 and the southern area the next fiscal year. A contract to be put out for bids in March 1969 wilJ be for the installation and operation of the seeding and recognition systems. Estimated costs over the 5-year period should exceed $2 milJion, mainly including the design contract at Colorado State University, the evaluation net work contract, the seeding contract, and com- prehensive evaluation contract or contracts. In addition to the Colorado River Pilot Project, we are planning a pilot project in the northern Great Plains in North Dakota. Others wm be undertaken as circumstances permit. The fact that pilot projects are being planned should not be misread as a justification for curtailment of. other needed re- search and experimentation. Although present budget limitations have forced some reduction in other activities, the need is clear for greatly expanded research and development if the crude technology pre- sently available is to be replaced in the future by truly otimum procedures. We have a lot left to learn but we are on our way to tap the "Rivers in the Sky". (graphs) -37-