Water resources of Lincoln and Union counties, South Dakota

Abstract

The water resources of Lincoln and Union Counties occur as surface and ground water. Sources of surface water include the Missouri River, the Big Sioux River, and various minor streams and lakes. The Missouri River, which forms the southern border of Union County, is the primary source of surface water in Union County. At a streamflow-gaging station on the Missouri River south of Union County, the discharge averaged 32,380 cubic feet per second during water years 1966-89. Near the study area, the Missouri River is used for municipal and domestic water supplies and for irrigation especially close to the river. The Big Sioux River, which forms the eastern border of Lincoln and Union Counties, is also an important surface-water source. At a streamflowgaging station on the Big Sioux River north of Lincoln County, the discharge averaged 523 cubic feet per second during water years 1972-89. Streamflow of the Big Sioux River and other minor streams in the study area is directly related to seasonal variations in precipitation and evapotranspiration. Dissolved-solids concentrations in water from these streams increase as stream discharges decrease. The flow of the Missouri River is less affected by seasonal variations in precipitation and evapotranspiration due to regulation (control) by upstream dams. Ten glacial aquifers and one bedrock aquifer were delineated in Lincoln and Union Counties. The area! extent of the glacial aquifers was determined to be 25 to 60 square miles for the Wall Lake, ParkerCenterville, Big Sioux, and Lower VermillionMissouri aquifers; 85 to 90 square miles for the Harrisburg, Upper Vermillion-Missouri, and Newton Hills aquifers; 130 square miles for the Shindler aquifer, and 180 square miles each for the Missouri and Brule Creek aquifers. The average thickness of the glacial aquifers ranges from 26 to 99 feet. Recharge to these aquifers mainly is from infiltration and subsequent percolation of precipitation. Recharge also occurs by leakage through till, by ground-water recharge from other glacial aquifers, by ground-water recharge from the Dakota aquifer, and by inflow from the Big Sioux and Missouri Rivers during high stages. The average depth below land surface to the top of the ParkerCenterville, Big Sioux, and Missouri aquifers ranges from 12 to 22 feet; the average depth below land surface to the top of the Hanisburg, Newton Hills, and Brule Creek aquifers ranges from 46 to 72 feet; the average depth below land surface to the top of the Wall Lake, Shindler, and Lower Vermillion-Missouri aquifers ranges from 103 to 106 feet; and the average depth below land surface to the top of the Upper Vermillion-Missouri aquifer is 162 feet. The buried aquifers are overlain by till and primarily are underlain by either till, Sioux Quartzite, Dakota Formation, Carlile Shale, or Niobrara Formation. Discharge from the glacial aquifers is by evapotranspiration where the aquifers are close to land surface; by withdrawals from domestic, stock watering, irrigation, and municipal wells; by discharge to other aquifers; and by outflow to the Big Sioux and Missouri Rivers. Reported maximum well yields are largest (1,000 gallons per minute or more) from the Big Sioux, Lower Vermillion-Missouri, and Missouri aquifers. Predominant chemical constituents are calcium, magnesium, sulfate, and bicarbonate in water from the glacial aquifers. Mean dissolved-solids concentrations in water samples from the aquifers ranged from 777 to 2,400 milligrams per liter, except for the Harrisburg aquifer which had a mean of 4,075 milligrams per liter and the Lower VermillionMissouri aquifer which had dissolved-solids concentrations of 340 and 1,820 milligrams per liter in water samples from two wells. The Dakota aquifer is a bedrock aquifer with an area! extent of 935 square miles, an average thickness of 216 feet, and an average depth below land surface to the top of the aquifer of 281 feet. The aquifer is overlain by Graneros Shale, the Lower VermillionMissouri aquifer, or the Missouri aquifer. The aquifer is underlain predominantly by several sandstones, shales, and dolostones of Cambrian, Ordovician, or Devonian age; by Sioux Quartzite wash; or by Sioux Quartzite. Discharge from the aquifer is by withdrawals from irrigation, municipal, domestic, and stock wells and probably by ground-water discharge to the Lower Vermillion-Missouri and Missouri aquifers. Reported well yields range from 10 to 1,200 gallons per minute. Predominant chemical constituents in water from the Dakota aquifer are calcium, sulfate, and bicarbonate. The water had a mean dissolved-solids concentration of 1,800 milligrams per liter. The total water use in Lincoln and Union Counties during 1985 was 14.66 million gallons per day. About 76 percent of the water used was for irrigation.