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<br />DJJ,Gl <br /> <br />VI. BENEFITS AND COSTS <br /> <br />The average annual water augmentation potential for cloud seeding 1n the <br />Upper Colorado River Basin was estimated to be 29300,000 acre-feet by the <br />Stanford Research Institute sponsored by the National Science Foundation. <br />An additional l,200,OOO-acre-foot yield was estimated for adjacent basins <br />since seeding storms over mountain ranges will increase precipitation and <br />runoff on both sides of the mountain crest. However. a more conservative <br />estimate made in a Reclamation-sponsored study conducted by North Pmerican <br />Weather Consultants is being used for CREST planning. The study used <br />20 years of precipitation. runoff, storm data. and a combination of meteoro- <br />logical and hydrological analyses to estimate runoff that could result from <br />cloud seeding. The meteorological information was factored into a numerical <br />model, the results of which were adjusted to fit historical data within each <br />subbasin examined. Final precipitation values were calculated as a function <br />of distance frc.wn the mountain massif of each subbasin. Runoff values were <br />calculated by developing precipitation/runoff relationships for each massif <br />and applying them seasonally by elevation to the precipitation quantities. <br />Runoff values were accumulated to represent the total additional water <br />available for each subbasin. <br /> <br />Based on this study, the potential augmentation in annual streamflow fran a <br />Basin-wide operational cloud seeding program is estimated to be 1,432,000 acre- <br />feet in the Upper Colorado River Basin and 298,000 acre-feet in the Lower <br />Colorado River Basin (fig. 3), and 533,000 acre-feet in adjacent basins of <br />Colorado, New Mexico, Wyoming, and Utah such as the Rio Grande, South Platte, <br />North Platte, Arkansas, Snake, and Wind River (fig. 4). The total increase <br />in water produced each year by a Basin-wide operational program 'o'Iould be <br />2,263,000 acre-feet. The annual streamflow augmentation fran the two-site <br />demonstration tests i!. estimated to be 340,000 acre-feet in the Colorado <br />River Basin and 70,000 acre-feet in the Rio Grande Basin (fig. 5). This <br />estimate is based on a randomized seeding program conducted in the San Juan <br />and White River subbasins which are preferred sites based on scientific and <br />logistic considerations. <br /> <br />Benefits of CREST and a follow-on Basin-wide operational program were deter- <br />mined by using the estimates of additional water supply in the Upper Basin as <br />input to Reclamation.s CRSS (Colorado River Simulation System) model. The <br />CRSS is a research model of the river, which reflects water availability; <br />salinity; demands on water by municipal, energy. and agricultural users; and <br />other water uses. The CRSS breaks down the Basin into various reaches or <br />subbasins. These reaches are then further broken down into sequence points <br />at which inflows, demands on water (diversions), and reservoirs are located. <br />The impact on river water supply and quality as a result of proposed changes <br />to the operation of the river system or alternative development schemes can <br />be analyzed with the model. In this study, a set of 15 historical hydrologic <br />sequences were used to simulate unmodified flow for the periOd 1983-2072. <br />The data from the North American Weather Consultants. study were used to <br />modify these sequences and to generate flows representative of those due to <br />weather modification. The estimated benefits were based upon the average of <br />the results from the 15 sequences. <br /> <br />19 <br />