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000482 29 v. CONCLUSIONS AND RECOMMENDATIONS A. CONCLUSIONS A large mass of data have been prepared in readily available form for computer analyses. These data have been by no means exhaustively treated in this study. The availability of these "refined!' climato- logical data makes it possible to use the probabi- listic approach for short term (less than one year) forecasts of precipitation events. In nearly all of the precipitation data included in this report I the mean or average values are higher than the median values. This positive skew- ness is typical of preCipitation data. particularly in semi-arid areas. This difference between the mean and me<lian values means that in most cases the amounts of precipitation that will be received 50 per cent of the time will be less than the average amounts. Therefore, the average amounts are somewhat mis- leading because they will not be received 50 per cent of the time. Major storms are significant contributors to runoff from the Upper Colorado River Basin. These major storms can be identified from existing pre- cipitation stations shortly after they occur. The primary moisture sources of precipita- tion in the Upper Colorado River Basin have been identified as being from the northern Pacific in the winter, southern Pacific in the fall, and from the Gulf of Mexico in the summertime. B. RECOMMENDATIONS Further research should be accomplished to explore different levels of "drop outs" as a means of adjusting observed precipitation data to give ob- served runoff. Studies such as the one described in this report for the Gunnison River would be of value, not only for the development of prediction equations for seasonal runoff, but also as a means for obtaining a better understanding of the physical processes involved in the rainfall-runoff relation- ship. It is desirable to have additional observing stations for precipitation at elevations higher than 6000 feet ros!. Because of the high evapotranspira- tion amounts for elevations below 6000 feet msl in the Upper Colorado River Basin, additional stations belOW 6000 feet would be of questionable value. In view of the importance of major storms t particularly in the fall, it would be desirable to conduct "bucket surveys" for major storms occur- ring in the fall of the year. Such "bucket surveys" would give a better measure of the total quantity of precipitation that falls. This information should be valuable in making estimates of runoff to be ex- pected during the following spring season. It is recommended that short-term planning make use of the data that can be obtained from the occurrence of major storms as they happen. For example, if a major storm occurs in the fall of the year, it is quite likely that additional runoff can be expected the following spring. Conversely, if no major storm occurs in the fall of the year, it is likely that the amount of runoff to be expected the following spring will be relatively low. This con- cept should be of value in planning for the rrmoff. Any future plans for attempting to increase precipitation by artifical means must necessarily consider the moisture source, and any operational plans must be based on the primary sources of preCipitation available. This means, for example, that attempts at increasing precipitation in the wintertime should exploit the availability of mois- ture from the Pacific northwest. Conversely, any attempt at weather modification that would plan to use moisture from the same region in the summer- time would likely be foredoomed to failure. Any plan which would not recognize the di fferences between moisture sources in any season would not represent proper planning. It is recommended that the present study be considered only a beginning of a better under- standing of the precipitation occurrences in the Upper Colorado River Basin. Future work on this subject will be of considerable value in gaining a better understanding of the hydrologic process that effect the economy of the Upper Colorado River Basin.