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<br />1850 <br /> <br />J <br /> <br />TABLE 5 (cont'd) <br /> <br />CAPACITY, ACTIVE STORAGE, AND STORAGE CHANGE <br />OF MAJOR COLORADO RIVER BASIN RESERVOIRS <br />DURING WATER YEAR 1979-80 <br />(ThousandS of Acre-feet) <br /> <br /> Active <br /> St orage <br /> Gross Usable * Sept. 30, <br /> Capacity Capacity 1980 <br />Lower Basin <br />Lake Mead 28,537 26,159 23,637 <br />Lake Mohave 1,818 ' 1,810 1,445 <br />Lake H3.vasu 648 619 559 <br /> Subt otal 31,003 28,588 25,641 <br />Total, Both 60,345* <br />Basins 64,931 * 54,524 <br /> <br />Change <br />During <br />Year <br /> <br />+ 1,395 <br />+ 17 <br />11 <br /> <br />+ 1,401 <br /> <br />+ 3,579 <br /> <br />* Includes 4,132,000 acre-feet of flood control storage space <br />which must be evacuated by January 1 of each year. <br /> <br />The Water and Power Resources Service has assumed that the amount <br />of water that percolates into the areas adjacent to Lake Powell is not <br />lost but has gone into ground water storage or "bank storage". It is <br />the residual resulting from a hydrologic balance of Lake Powell inflow, <br />outflow, change in surface storage, and evaporation. Evaporation and <br />a portion of the inflow must be estimated; thus, the estimated bank <br />storage is subject to wide variation and possible error. The 1980 <br />year-end bank storage in Lake Powell was estimated to be 11.2 maf, <br />representing an increase in bank storage from 1979 of about 0.3 maf. <br /> <br />Water Uses <br /> <br />Colorado River Basin depletions in the Upper Basin are classified <br />by the Water and Power Resources Service as inbasin consumptive uses, <br />transbasin diversions, and reservoir evaporation. Irrigated agriculture <br />is responsible for most of the inbasin consumptive uses. The quantity <br />of these uses is estimated by applying unit water use factors to <br />estimates of the land areas being irrigated. The Water and Power <br />Resources Service's estimates of Colorado River water depletions <br />above Lee Ferry for the 1980 water year are: <br /> <br />-5- <br />