This Hydrologic Atlas is one of series describing the 39 watershed units in Minnesota. The 1,750 sq mi in the Rock River watershed are glaciated upland plain including all of Rock County and parts of Pipestone, Murray, Lincoln, Nobles and Jackson Counties. The average annual water budget shows 25.8 inches precipitation, 3.1 inches surface runoff and 22.7 inches evapotranspiration. Water use in million gallons for 1970 was 3 ,333 ground water and 274 surface water. Domestic supplies accounted for 37 percent livestock 37 percent, and industrial 26 percent of total use. All 18 municipalities use ground water, mostly from glacial drift, seven use water from Precambrian aquifers. Precipitation recharges ground water through glacial deposits. Water-table and potentiometric maps and section show ground-water movement. Highest streamflow results from snowmelt and spring rains followed by recession in flow through summer, fall, and winter. Surface water and ground water are both very hard. Surface water and water from surficial and shallow drift aquifers generally range from 450 to 1,000 mg/liter dissolved-solids concentrations. Water from deep drift and from bedrock generally exceeds 1,000 mg/liter dissolved-solids concentration except where Precambiian quartzite aquifers underlie pre-Wisconsin drift. (Woodard-USGS)
