OCR Text |
Show ing (excluding those reservoirs built solely for flood control) : Reservoir capacity Usable Total (ratio to annual capacity Regulation1 regulation flow) Number (acre-feet) (percent) (acre-feet) Less than- 0.05 415 19,000,000 200 38,000,000 .05 to .19 343 55,000,000 120 66,000,000 .20 to .49 210 61,000,000 70 43,000,000 .50 to .99 167 45,700,000 45 21,000,000 1.0 to 1.49 68 43,500,000 31 13,000,000 1.5 and over 64 49,000,000 20 10,000,000 Totals 1,267 273,000,000 270 191,000,000 1From figure 1. 2Average. Thus, it is computed that an annual amount of about 190 million acre-feet of water supply is made available by means of the existing reservoir capacity. This quantity, reduced by an estimated net loss of 10 million acre-feet by evaporation (mostly in the western States), is 13 percent of the total flow of the rivers of the United States (1.4 billion acre-feet). The percentage varies in different river basins. The figures for some typical major drainage basins are: Drainage Basin Total flow of regulated storagef (percent) Ohio (excluding Tennessee-Cumberland) 1 Tennessee-Cumberland 17 Colorado* 50 fExcluding flood-control reservoirs. *Not including Glen Canyon reservoir now under construction. Water control by storage follows a law of diminishing returns. Each successive increment of control desired takes a larger amount of reservoir storage space than the preceding increment. The net effect is illustrated by figure 2. Storage capacity equal to a year's flow can regulate almost 45 percent of the flow, but |
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Original book: [State of Arizona, complainant v. State of California, Palo Verde Irrigation District, Coachella Valley County Water District, Metropolitan Water District of Southern California, City of Los Angeles, California, City of San Diego, California, and County of San Diego, California, defendants, United States of America, State of Nevada, State of New Mexico, State of Utah, interveners] : |