Aquifers - DNR · Aquifers Groundwater is contained in and moves through aquifers. An aquifer is a permeable geologic formation of rock, sand or gravel that can absorb, contain and

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Aquifers Groundwater is contained in and moves through aquifers. An aquifer is a permeable geologic formation of rock, sand or gravel that can absorb, contain and conduct significant quantities of water under the ground. Nearly all of the geologic formations in Missouri are capable of storing and discharging varying amounts of groundwater. Missouri's groundwater resources vary greatly across the state. They are closely tied to the geology of the various regions. Missouri’s groundwater resources have been separated into seven provinces. The boundaries of the groundwater provinces are drawn based on several factors including aquifer characteristics, groundwater quality changes, and aquifer boundaries. You will find that the groundwater resources of Missouri are not evenly distributed. Descriptions of the groundwater provinces follow the map below.

Map of Missouri’s Groundwater Provinces

Northeast Missouri

Groundwater Province

Salem Plateau

Groundwater Province

West -Central Missouri

Groundwater Province

Springfield Plateau

Groundwater Province

St. Francois Mountains

Groundwater Province

Southeast Lowlands

Groundwater Province

Mississippi and Missouri River

Alluvial Aquifer

Areas with similar limestone

strata as the Springfield

Plateau Groundwater

Province, but not consid-

ered a part of it.

Northwest Missouri

Groundwater Province

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Missouri’s Groundwater Provinces Mississippi and Missouri River Alluvial Aquifer The alluvial aquifers beneath the floodplains of the Mississippi and Missouri rivers are some of Missouri's most valued water resources and are widely used for municipal water supply and agricultural irrigation. The volume of water stored in the Mississippi and Missouri River alluvial aquifer varies somewhat, but is estimated to contain about 1 percent of the state’s groundwater.

Northeast Missouri Groundwater Province Groundwater storage in the Northeast Missouri groundwater province is estimated to contain about 13 percent of the state's groundwater. Cambrian-Ordovician, Mississippian, Pennsylvanian, Glacial Drift and Alluvial aquifers underlie this province.

Northwest Missouri Groundwater Province In northwest Missouri there are no high-yield, potable bedrock aquifers available. The Northwest Missouri groundwater province is estimated to contain about 2 percent of Missouri's groundwater. Pre-Pennsylvanian, Pennsylvanian and Glacial Drift aquifers underlie this province.

St. Francois Mountains Groundwater Province

There are few places in Missouri where it is more difficult to develop a groundwater supply than the St. Francois Mountains groundwater province. This is a beautiful part of Missouri, with steep, rounded mountains and narrow valleys. Although the igneous rock formations in this area are very scenic, they are poor water producers. These rocks are nearly impermeable except where they are fractured. It is estimated that this province contains less than 0.2 percent of Missouri’s water. The St. Francois and Ozark aquifers underlie this province.

Salem Plateau Groundwater Province All but a very few communities and essentially all of the rural residents in this province rely on groundwater. About 45 percent of Missouri’s groundwater is in this region. There are two major aquifers that underlie this region, the St. Francois aquifer and the Ozark aquifer.

Springfield Plateau Groundwater Province The Springfield Plateau groundwater province occupies the southwestern part of the state and a small region of central Missouri south of the Missouri River. Although similar limestone strata occur along the Mississippi River in St. Louis, Jefferson, St. Genevieve, Perry and Cape Girardeau counties, they are not considered to be in the Springfield Plateau province because of the great distance separating them. This province is estimated to contain about 24 percent of the groundwater in Missouri. There are three aquifers that underlie this region; The St. Francois, Ozark and Springfield Plateau aquifers.

Southeast Lowlands Groundwater Province About 15 percent of the state’s groundwater is found in this southeastern corner of Missouri. The St. Francois, Ozark, McNairy, Wilcox and Southeast Lowlands Alluvial aquifers underlie this province.

West – Central Missouri Groundwater Province Groundwater in the West-Central Missouri groundwater province is typically difficult to obtain. This province is estimated to contain less than 0.2 percent of the state’s water resource. The Pennsylvanian Bedrock aquifer and Alluvial and Glacial Drift aquifers underlie this province.

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Aquifer Recharge

Diffuse Groundwater Recharge Recharge is the primary method through which water enters an aquifer. Groundwater recharge is an important process for sustainable groundwater management. Groundwater recharge can be broadly categorized into two types—diffuse recharge and discrete recharge. Diffuse recharge is the relatively slow infiltration of water from the Earth’s surface into the groundwater system. Diffuse recharge is generally slow, and consists largely of water moving downward through soil materials and weathered rock, through permeable sand and gravel or small cracks and crevices in bedrock. Diffuse recharge can occur almost anywhere that the soils or surficial materials are permeable enough to allow water movement. This type of recharge occurs in the glacial drift areas of northern Missouri as well as the alluvial plain of the Bootheel and nearly all points in between. The more permeable the surficial materials and shallow bedrock are, the greater the recharge.

In diffuse groundwater recharge, the amount of precipitation an area receives may not be as important as when and where precipitation occurs. For example, an intense summer rainstorm occurring for a brief time generally provides less groundwater recharge and more runoff than a gentle, prolonged rain lasting an extended period in the spring or fall of the year; even though the rainfall amounts are the same in both events. The slope of the terrain, the type of soil, and the amount of vegetation are also important factors to consider when determining the efficiency of a region to have significant diffuse recharge to underlying aquifers. Diffuse recharge typically provides a relatively small volume of recharge per unit area, but since it occurs over broad regions it ultimately supplies very large quantities of groundwater recharge. There are large regions where almost no groundwater recharge occurs, and much smaller areas where rather large amounts of recharge take place. Estimates as to how much of the total water available from rainfall actually becomes diffuse recharge range from a low of less than one inch per year in low permeability glacial drift and Pennsylvanian shales to more than 8 inches in sandy alluvium in the Southeastern Lowlands. Although these values seem low, if the total area of the state is considered, the resulting volume of diffuse groundwater recharge is large. Assuming a statewide average diffuse recharge of 4 inches, diffuse recharge supplies about 4.85 trillion gallons of recharge per year, enough water to supply each of Missouri’s 6.1 million residents 100 gallons of water per day for nearly 22 years1.

The alluvial plain of the Missouri Bootheel has sandy soils that allow diffuse recharge to

occur.

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Discrete Groundwater Recharge Another more spectacular type of recharge occurs in many areas of the state, especially in southern Missouri. This type of recharge, called discrete recharge, occurs in Missouri in areas where the dissolution of limestone and dolomite bedrock has occurred. Discrete recharge is the localized, concentrated movement of water from land surface into the subsurface. It typically occurs where karst groundwater recharge features have developed.

Losing streams are karst features that concentrate movement

of water from land surface to the subsurface.

Sinkholes act as natural funnels, collecting and channeling

underground the runoff that occurs within their catchment

areas.

Most Missouri caves are wet, with permanent cave streams.

Water in caves results primarily from discrete recharge.

The volume of water emerging from a spring is influenced by

discrete recharge.

References

Statistics about groundwater have been taken from the following publication:

Miller, Don E., and Vandike, James E., 1997, Missouri State Water Plan Series Volume II, Groundwater Resources of Missouri, Missouri Depart-

ment of Natural Resources' Division of Geology and Land Survey, Water Resources Report No. 46, 210 p.

1. See page 2

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For more information: DNR Youth Education and Interpretation P.O. Box 176 Jefferson City, MO 65102-0176 1-800-361-4827 or (573) 522-2656 office e-mail: [email protected] http://dnr.mo.gov/education

Glossary of Terms

Alluvial plain: A level or gently sloping flat or a slightly undulating land surface resulting from extensive deposition of alluvial materials by running water.

Alluvium: Material consisting of silt, sand, clay, and gravel in varying proportions deposited by rivers. May be deposited at any point where the river overflows its banks or where the velocity of a river is checked; for example, where it runs into a lake.

Bootheel: An area of Southeast Missouri where the Missouri-Arkansas border dips southward forming a rectangular-shaped extension of the state, so called because its shape in relation to the rest of the state resembles the heel of a boot.

Diffuse recharge: Groundwater recharge that trickles slowly through soil layers over a widespread area.

Discrete recharge: Groundwater recharge that flows rapidly through soil layers via sinkholes.

Dissolution: Dissolution occurs when water passing through soluble rocks produces underground cavities and cave systems.

Glacial drift: Sediment transported or deposited by glaciers or the water melting from a glacier.

Groundwater provinces: Distinctive geographical regions identified by their groundwater properties and the geological formation that makes up the aquifer.

Groundwater: Water that flows or collects beneath the earth’s surface in saturated soil or aquifers.

Karst: An area of limestone terrane characterized by sinkholes, caves, springs, and losing streams.

Permeability: The property of a material to let liquid or gas pass through itself. (see pervious)

Pervious: The ability of a material to allow liquid or gas to pass through itself. (see permeable)

Recharge: A hydrologic process where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer.

Runoff: The part of precipitation not absorbed by soil that appears as liquid water in surface streams, lakes and rivers.

Slope: The steepness of the land downward or upward. Ground that has a natural incline, such as the side of a hill.

Surficial materials: Materials produced by weathering, sediment deposition, biological accumulation, volcanic and human activity that has been deposited on the land surface.