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<br />Next we consider what uses are to be made of the increased water. <br />If additional rainfall is desired on dry farm crops, it is comparatively <br />simple to consider the relationship between precipitation and crop yield <br />and arrive at the crop increase to be expected from each inch of additional <br />rainfall, and the value of a cloud~seeding operation. <br /> <br />There are benefits to agriculture :independent of precipitation <br />increase, which may prove more important than the precipitation increase. <br />One of these stems .from the fact that undeI1 the influence of cloud-seeding <br />a change in the character of precipitation ,seems to occur. Small drops of <br />gently falling rain replace heavy downpours. This factor has been responsi- <br />ble for increased wheat yields in the Pacific Northwest, where the amount <br />of yield has been out of proportion to the:amount of precipitation increase <br />produced by cloud-seeding operations. Haii suppression is a related cloud- <br />seeding by-product and future experience may prove that it is even a more <br />valuable result of cloud-seeding than precipitation increase. <br /> <br />If the need is for water in the form of streamflow for irrigation <br />or power generation, study is malie of the relationship be.tween precipitation <br />and stream flow. By using this relationship, it is possible to estimate what <br />each additional inch of precipitation would do to streamflow under a variety <br />of antecedent conditions. If the need for'additional streamflow exists in a <br />month when some precipitation falls as snoi< and some as rain, we take into <br />consideration the temperatures that would ~pply during cloud-seeding opera- <br />tions, to determine whether or not. the operations would result in increased <br />streamflow or produce an increased snowpac~ which would contribute to flooding <br />during a later melting season without increasing streamflow at the time re- <br />quired. The present flow in the river, the estimated precipitation for the <br />following months, and the estimated mean monthly temperatures in the basin <br />are all correlated to arrive at an estimate of the outflow of a drainage <br />area under study. <br /> <br />After the expected streamflow has been estimated and the amount of <br />increase due to seeding calculated, it is iPossible to arrive at the economic <br />value of the benefit. The ratio of benefits to cost will depend on more than <br />the amount of water made available throug~ cloud-seeding operations, since <br />the client t s ability to put the water to good use enters into the problem. <br />If his storage reservoir oapacities are too low or his plant generating ca- <br />pacities inadequate, the value of the additional water may not exceed the <br />cost of producing it. . <br /> <br />A final factor for stuqy grows oht of the. newness of cloud-seeding <br />, <br />and the amount of misunderstandingconcerping its potentialities and limita- <br />tions. No cloud-seeding operation can hope to be truly successful if there <br />is not a conviction on the part of most of the people in the area that they <br />can benefit. Co-ordination with local interests and proper public relations <br />are an important part of planning cloud-seeding operations. If the area to <br />be seeded is not the area which will eventually receive the benefits, as in <br />a snowpack operation designed to increas~ streamfiow that will be used a <br />considerable distance downstream, it beco~es increasingly important that <br />the people in the snowpack area understaqd the operation will not be carried <br />on to the point of causing damage to the~. <br /> <br />-24- <br />