Ground-water pumpage in Camas Prairie, Idaho, for irrigation and municipal supplies totaled nearly 9,500 acre-feet in 1977. Declines of pressure head in the artesian aquifer have ranged from 3 to 12 feet since 1974 when increased ground-water pumping began. A comparison of water-level measurements made in September 1957 and September 1977 shows declines of more than 30 feet in places in the artesian aquifer. Camas Prairie aquifers are recharged by percolation from streams and by precipitation on the valley floor. Estimated mean annual recharge to the artesian aquifer is 37,000 acre-feet. Vertical recharge from the artesian aquifer to the overlying water-table aquifer is estimated to be 20,000 acre-feet annually. Declines in artesian pressure caused by increased irrigation pumping will result in a reduction of recharge from the artesian aquifer to the water-table aquifer. Yields from irrigation wells in the prairie ranged from 400 to slightly more than 2,000 gallons per minute. Flows in Camas Creek in the 1977 drought year averaged 9,400 acre-feet, compared with 138,000 acre-feet in a normal year. Surface and ground waters sampled in the basin were either a sodium or calcium bicarbonate type water. Dissolved-solids concentrations ranged from 61 to 284 milligrams per liter. (Woodard-USGS)
