Known springs in Missouri (Missouri Department of Natural Resources)
Missouri Springs
Geology
The majority of Missouri springs originate in the dolomitic rock mass that makes up the majority of the Ozarks (Vineyard et al, 1982). Dolomite, also referred to as dolostone, is a sedimentary rock with calcium magnesium carbonate (CaMg(CO3)2) as its primary constituent. Dolomite forms through the chemical alteration of limestone. As result, dolomite and limestone have similar properties (Unklesbay and Vineyard 1992). This rock mass is believed to have originated during the Ordovician age, which took place approximately 490-445 million years ago (Spencer 2011; University of California 2011). This dolomite mass is highly permeable and is one to two thousand feet deep, allowing it to store an exceptional amount of precipitation for later discharge (Vineyard et al, 1982).
Karst
These Ozark springs are often the most visible karst topography feature. Karst systems include a wide variety of unique geologic features such as caves, losing streams (streams that lose water as they flow downstream), and sinkholes. Over many years, these features have been formed by the dissolving of the softer sedimentary rock underlying the Ozark region. In addition to dolomite, limestone (composition CaCO3) is dissolved by rainwater. This rainwater filters through years of leaf litter (that is primarily oak); through this filtration, the water becomes slightly acidic. Unsurprisingly, this acidic water is able to dissolve the basic carbonate compounds. As more and more of the rock is dissolved, substantial passageways form. These passageways form a specific subset of springs, tubular springs (Unklesbay and Vineyard 1992).
Classification
The most generally accepted method of spring classification focuses exclusively on flow rate, though there are more sophisticated systems that account for aquifer type, hydraulic characteristics, and temperature and chemical characteristics of the spring as well.
2Magnitude | Discharge |
First | >100 cfs (cubic feet per second) |
Second | 10-100 cfs |
Third | 1-10 cfs |
Fourth | 100 gpm (gallons per minute)-1cfs |
Fifth | 10-100 gpm |
It is also helpful to understand the distinctions based on flow characteristics. Springs can be subdivided into three classes based on the opening they issue from: seepage (or filtration) springs, fracture springs, or tubular springs. Seepage springs are characterized by the filtering of water through many small openings in a permeable surface. This definition is intentionally vague, allowing “Any considerable area in which water is seeping to the surface” (Vineyard et al, 1982) to be classified as a seepage or filtration spring. Examples of this permeable material include sand and gravel as well as highly fractured rock. These are widespread within the state and are most common at the base of hills or bluffs. Fracture springs are observed when the point of discharge is a jagged opening (ie fracture) in the rock. These can occur naturally as a result of seismic activity (Differing fault characteristics and activity can allow fracture springs to be divided into more subcategories) or other more mundane geologic process. (For example, a tree root grows downward above an aquifer surrounded by a thin layer of impermeable rock. Over time, the root splits the rock and a fracture spring is created). Fracture springs can also be “man-made,” so to speak, when a layer of impervious rock is broken to allow water to pass. In a tubular spring, water is discharged from a smooth, rounded opening in rock, most commonly dissolved into limestone (Vineyard et al 1982). These water passages can be found in dolomite as well. As mentioned earlier, tubular springs can extend into a deep, complex cave system (Unklesbay and Vineyard 1992). For more information about the geology of springs, caves, and karst systems, visit the Geology of Missouri page at https://pages.wustl.edu/mnh/geology-and-geological-history .
Springs in each of these three categories can also be categorized as either artesian or nonartesian. In an artesian spring, the water “discharge(s) with noticeable vigor,” according to Vineyard et al (p. 11, 1982). Artesian springs meet the classic image of water welling up from the earth, while nonartesian springs are more discreet, with water oozing out. The vast majority of seepage springs are nonartesian. Finally, springs are either warm, hot, or nonthermal depending on their temperature. According to Vineyard et al (1982), springs with a temperature approximately similar to the atmosphere are nonthermal, with anything between the average atmospheric temperature and 980C being classified as warm springs and anything with a temperature greater than 980C being a hot spring. All springs in Missouri are classified as nonthermal (Vineyard et al 1982).
Concerns
As mentioned in the section on karst, springs recharge primarily through rainwater that has been filtered through the surrounding surfaces. Unsurprisingly, then, pollution in the watershed of the spring greatly impacts the water quality of the spring. People have long worked to protect springs by limiting the human impact on the area surrounding them, and this strategy has changed little over time. In part because of this constancy, the efficiency of this method has been called into question. Doerfliger, Jeanin, and Awahlen studied the methods used to define different areas that are to be protected in their 1999 publication on water vulnerability of karst aquifers. They came to the conclusion that GIS (geographical information systems) should be used to evaluate the susceptibility of different layers of the karst system, and these evaluations should be used to readjust contamination zones according to both their vulnerability and their importance to the local area, both ecologically and economically. On the whole, it was found that the restrictions were overly lax and needed to be reformed to do more to protect these resources (Doerfliger, Jeanin, and Awahlen 1999).
Flora
The vegetation of Missouri springs is known for enhancing the geologic beauty. This vegetation is, generally speaking, unique to the spring ecosystem because of the cooler water temperature. While the most recognizable species of vegetation is water cress (Nasturtium officinale), the other most common species include water milfoil (Myriophyllum heterophyllum) and water starwort (Callitriche heterophylla). A wide variety of algae species (including green algaes Nitella and Chara and red algae Batrachospernum) can be found, and mosses and liverworts can also be seen, either in the spring itself as a mat or in the area immediately around the spring (Vineyard et al 1982). However, the flora of springs varies with differing dissolved mineral contents, according to Boyer and Wheeler (1989). Although the study was conducted in Britain, the chemical composition of springwater in the investigation sites corresponds to the composition of Missouri springs. It was found that calcium ions, Ca2+, and bicarbonate ions, HCO3–, had the greatest impact on total growth as well as type of growth, with the net mass and the overall height being greater in springs with higher concentration of these two ions (Boyer and Wheeler 1989). Given that both limestone and dolomite are calcium carbonate compounds, it follows that springs from these two rock sources will have a greater amount of flora.
Fauna
While springs are not known for their biodiversity, the richness of the habitat is often underestimated. In addition, many species in Missouri are found only in this habitat. These species have become highly specialized, sometimes being found in just one spring or stream. (Some of these species also originate in the subterranean passages feeding tube springs.) The majority of the fauna are invertebrates; however, vertebrates, most often fish and salamanders are often found. Among the more common invertebrates are flatworms, several classes of small crustaceans (including scud, Amphipoda), crayfish, a fairly wide variety of snails, and several insects of different classes. Although there are relatively few vertebrate species that live exclusively in spring waters, salamanders (most notably the Ozark hellbender) and many fish species thrive in spring-fed streams. Mottled and banded sculpin are both common to many springs and spring-fed streams, and trout (rainbow and brown) are often stocked in the cool water of Ozark streams (Vineyard et al 1982).
References
Vineyard, J., Feder, G., Pflieger, W., and Lipscomb, R., 1982. WR29: Springs of Missouri, Missouri Department of Natural Resources, Division of Geology and Land Survey in cooperation with U.S. Geologic Survey and Missouri Department of Conservation, 212pp
Doerfliger, N., Jeanin, P., and Zwahlen, F, 1999. Water vulnerability assessment in karst environments: a new method of defining protection areas using a multi-attribute approach and GIS tools (EPIK method). Environmental Geology, 39 (2), 165-176.
Boyer, M., and Wheeler, B., 1989. Vegetation Patterns in Spring-Fed Calcareous Fens: Calcite Precipitation and Constraints on Fertility. Journal of Ecology, 77 (2), 597-609.
Spencer, C., 2011. Roadside Geology of Missouri, Mountain Press Publishing Company, Missoula, MT. 273pp
Unklesbay, A., and Vineyard, J., 1992. Missouri Geology: Three Billion Years of Volcanoes, Seas, Sediments, and Erosion, University of Missouri Press, Columbia and London. 189pp
University of California Museum of Paleontology. “The Ordovician Period.” University of California-Berkeley, 6 July 2011. Web. 7 Oct. 2015. <http://www.ucmp.berkeley.edu/ordovician/ordovician.php>