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5. Strategy a. Scientific i. Reservoir catchments vs. rainfed agriculture. - Precipitation enhancement may ease water shortages and stabilize natural water supplies by providing additional water in two ways. It can be used to increase the amount of water stored in reservoirs; either surface or underground, manmade or natural. The water would then be available to draw on when and where needed for use by munici- palities, industries, irrigated agriculture, and for the genera- tion of hydroelectricity. The sophisticat1ed water management system of Thailand allows for weather modification use over most months when the appropriate weather conditions suitable for seed- ing exist. Timing and targeting of the rainfall are not critical because the added precipitation is caught by a large catchment basin and stored in a reservoir for use until needed. Precipitation enhancement can also be used to serve the water needs of rainfed agriculture by direct application of precipita- tion on croplands. However, the practicability of this approach depends on the availability of seedable clouds when and where the water is needed and the technical ability to target the rainfall induced by cloud seeding. Timing of the precipitation is impor- tant because the water needs of crops are very time specific and becomes critical for soils that have poor moisture storage capa- city. Because of these factors it is recommended that the first priority be given to a demonstration project to increase reservoir storage by seeding over a scientifically and econrnnically appropriate catchment area. A demonstration project iln a reservoir catchment area would achieve definitive results in the shortest time because of the higher frequency of seeding opportunities, the better capa- bilities to measure rainfall and streamflo'~ and a firmer basis for estimating benefits from additional water produced by the seeding operations. Inasmuch as the clouds throughout Thailand are physi- cally similar from a seedability standpoint, the results from the demonstration project should be able to be extended to other areas in Thailand through properly focused transferability studies. Taking into account the expected utility al1d benefits of addi- tional water, availability of storage to handle additional water, availability of logistical support facilit'les, size of the catch- ment area, availability of precipitation and streamflow historical data and measurement capabilities, and location with respect to scientifically-suitable control basins, thla catchment area of the Bhumipol Reservoir is recommended as the target basin for the demonstration project. The Bhumipol Reservoir is a multipurpose project on the Ping River, one of the majolr tributaries of Thailandls most important and largest river basins - the Chao Phraya Basin. The reservoir provides protection against flood 44 ~ ~ . r