Northeast Missouri Groundwater Province
Many of the bedrock formations found throughout southern Missouri are also found north of the Missouri River. The southern part of the Northeast Missouri groundwater province lies to the south of the freshwater-salinewater transition zone. Mississippian-, Ordovician-, and Cambrian-age strata in this area can supply from 10 to more than 1,000 gallons per minute of potable water, depending on depth. North of the transition zone water from deeper bedrock aquifers is generally too highly mineralized for most uses. Modest quantities of marginally potable groundwater are locally available in some of the shallow Mississippian strata where it is not overlain by Pennsylvanian strata. The Pennsylvanian strata have an overall low permeability and generally yield small quantities of marginal to poor quality water.
Glacial drift overlies the bedrock throughout much of this region. It is generally thickest in the northwestern counties of the province and thins toward the Missouri and Mississippi rivers. Thousands of shallow, large-diameter, hand-dug glacial drift wells once supplied many of the rural residents, but the development of rural public water supply districts has rendered most of these wells obsolete. The shallow glacial drift wells generally yielded less than three gallons per minute and relied on their large diameters for storage. Their shallow depths and poor construction made them very vulnerable to contamination from bacteria, animal wastes and agricultural chemicals.
In most places the glacial drift in this part of the state is not capable of supplying enough water suitable for a public water supply. Alluvial deposits consisting of sand and gravel underlying the floodplains of major rivers in this area can yield large quantities of good-quality water. Yields as high as 2,000 gallons per minute are possible from properly constructed wells in favorable areas of the major alluvial aquifers. Groundwater storage in the Northeast Missouri groundwater province is estimated at 66.7 trillion gallons, or about 13 percent of the state's usable groundwater.