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0031~9 Page 48 V. SUMMARY AND CONCLUSIONS The primary objective of this study was to project the probable future uses of additional flows in the Colorado River due to vegetation manipulation in the river's headwater area. Consequently, the most obvious parameter to be varied was river flow. However, additional parameters were also of interest, initially because it was thought that the uses made of increased run-off might vary as water demands grew over time and with differences in such factors as climate and the institutions which govern water allocation. A. Hydrologic Aspects The anticipated runoff increase for climatic conditions equal to those in I ~ each of the years for which records were available varies from 49,000 acre-feet to 106,000 acre-feet, with a mean of 82,000 acre-feet. The increase in each year is distributed over the period April 15 to June 15. The effects of enhancing streamflows through vegetation manipulation are I summarized in Table V-l. Under existing institutional arrangements, and under current demand conditions, they were to increase outflow (over 80 percent of the increase flowed unused into Mexico ), to increase evaporation modestly, and to alleviate Lower Basin shortages and increase storage slightly. Under full development conditions, the increased flows were more evenly divided between outflow, evaporation, storage, and (to a lesser extent) alleviating Lower Basin shortages. Removing institutional constraints did change this conclusion. Enhanced flows continued to be almost entirely undiverted under current demand conditions. Under full development conditions, however, increased flows were distributed roughly equally between evaporation, outflow, and alleviation of shortages in the Upper and Lower Basins, respectively. Under these