Water use in South Dakota during 1985 is estimated to have been 674 million gal/day. This is a slight decrease from the 1980 estimate of 690 million gal/day. Of the total use, 63% was from surface-water sources and 37% was from groundwater sources. About 75% of the total water use was for agriculture, 16% was for domestic and commercial use, 8% was for industrial and mining use, and 1% was for thermoelectric and geothermal uses. Of the total used, 361 million gal/day were consumed and 313 million gal/day were returned to the surface- and groundwater system. Water use by agriculture, the largest user, was mostly for irrigation. Total use was 516,000 acre-ft (460 million gal/day) for irrigation of 397,000 acres. Non-irrigation use, mainly for livestock, was 47.1 million gal/day. About 12% of the total use was by public-water suppliers. Seventy-five percent of the deliveries by public-water suppliers were for domestic use by 78% of the population. In addition to offstream use, instream use was substantial because of hydroelectric-power generation by the four dams on the Missouri River. During 1985, 60,500 million gal/day were used to generate 6,095 gigawatt-hr of electricity.
