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'OOlh2 . -5- . II. METEOROLOGICAL STUDIES Proposal to Conduct Studies of Precipitation Frequenoy in the Colorado River Basin of Colorado and Other Upper Basin States. In the orderly development of expanded uses of water in the State of Colo- rado and for all the surrounding. states joined together to make up the Upper Division of the Colorado River System, it beoomes increasingly important that careful analyses be made of all existing data which pertain to the water which flows into and is diverted from the Colorado River. In addition to the rather extensive streamflow data, there have been com- piled during the past 70 years a rather sizeabls quantity of precipitation data. These, for the most part, have lain dormant. Up to the present time the planning decisions relative to expected flow of the Colorado River have been based almost exclusively on streamflow information. It is a fundamental fact, however, that the occurrence of preoipitation always precedes the collection of streamflow in any river. This oertainly implies that a thorough understanding of the pre- cipitation frequencies and their probability of occurrence should be studied in order to gain a more complete understanding of what may be expected in the way of subsequent streamflow in the Colorado River. Generally speaking, precipitation records used to date have consisted primarily of an arithmetic average of whatever period of record was available. Even with the use of only elementary statistical treatment it is possible to gain considerably more information from a series of precipitation records than this one single (and often misleading) piece of information. The following proposal of effort to be carried out on this general problem is divided into three separate steps, and further is divided into what could be conducted with data totally within the State of Colorado, and a somewhat further expansion of this into pertinent data from the additional Upper Colorado Basin States of Wyoming, New Mexico and Utah. While Arizona has some watershed areas contributing to the flow of the Upper Colorado Basin, the quantities contributed from this are rather negligible in an analysis of the entire flow of the Upper Colorado Basin. " The three steps are briefly summarized as follows: 1. A preliminary analysis of monthly and seasonal precipitation data for some Colorado stations having periods of record from 40 to 70 years, these data to be analyzed by hand computations.