Reconnaissance of ground-water quality, eastern Snake River basin, Idaho

Water-quality, geologic, and hydrologic data were collected for 165 wells in the eastern Snake River basin, Idaho. Water-quality characteristics analyzed include specific conductance, pH, water temperature, major dissolved cations and anions, and coliform bacteria. Ground water from aquifers in all rock units is generally composed of calcium, magnesium, and bicarbonate type and contains carbonate ions. Changes in area trends of ground-water composition probably are most directly related to variability in aquifer composition and proximity to varying sources of recharge, especially those related to man 's land- and water-use activities. In the uplands subareas, median values for selected ground-water characteristics from current analyses are 2000 mg/l hardness; 7.6, pH; 200 mg/l alkalinity; 13C; 0.2 mg/l fluoride; 15 mg/l silica; 0.51 mg/l nitrite (as nitrogen); less than 1 colony per 100 milliliters of water coliform bacteria; 0.02 mg/l phosphorus (total); and 25 mg/l hardness; 7.7, pH; 180 mg/l alkalinity; 11C; 0.4 mg/l fluoride; 26 mg/l silica; 1.2 mg/l nitrite plus nitrate; less than 1 colony per 100 milliliters of water coliform bacteria; 0.01 amg/l phosphorus; and 283 mg/l dissolved solids. Ground-water quality in most of the study area meets recommended standards or criteria for most uses. (USGS)