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Commonly ASked Questions About Springs - Minnesota Dept. of Health Page 2of3 springs along the north shore of Lake Superior and along the Mississippi and St. Croix River Valleys are generally of this type. .. . .. . . . ......' ..........,.~ . ..:..c.-. ... Fig. 2 PERENNIAL SPRINGS drain a large land surface area and flow continuously throughout the year. INTERMITrENT SPRINGS flow only during certain times of the year when rainfall or snowmelt Is sufficient to recharge the soli and groundwater. TUBULAR SPRINGS are most commonly associated with limestone channels and cavern, and volcanic lava tubes. The water is contained in caves or solution cavities in the limestone, or hollow "tubes" formed by cooling lava. Cavities or tubes may range from microscopic In size to large openings measuring many tens of feet across. Large tubular springs In some parts of the United States flow over a million gallons per minute. The large springs of southeastern Minnesota are tubular springs. SEEPAGE SPRINGS are formed when groundwater slowly seeps out of the ground. Seepage springs usually occur In sand, gravel, or organic materials and generally are found In depressions or valley bottoms. Seepage springs are different from artesian springs because they are not necessarily confined (contained below a dense layer of clay or other material) and usually have low flows. THERMAL SPRINGS are springs that rele~se groundwater warmer In temperature than groundwater In the surrounding watershed area. Examples of thermal springs are warm springs, hot springs, mudpots, and geysers such as those at Yellowstone National Park. Thermal springs are most commonly found In areas with a recent history of volcanic activity. Springs and Artesian Wells Springs are often confused with flowing artesian wells. An artesian well Is a hole or boring that has been drilled Into a water-bearing formation or "aquifer" that Is under pressure. The water In an artesian well rises above the top of the aquifer (water-bearing formation) until the pressure Is equalized. In a flowing artesian well, the water rises above the ground surface and the water flows out of the well casing to equalize the pressure. Are Springs Sources of Safe Water? Usually not.. Water quality from springs may vary from year to year and even minute to minute. The Minnesota Department of Health (MDH) routinely sampled springs for coliform bacteria and nitrate-nitrogen In the 1960's and 1970's. Coliform bacteria Indicate the possible presence of disease-causing organisms. Elevated nltrate- nitrogen levels typically result from sewage, animal wastes, or nitrogen fertilizers. Water samples were collected statewide from springs at various times of the year. The results Indicated that 85 to 90 percent of the sampled sprln~s were contaminated with coliform bacteria or nitrate at one or more times. http://www.health.state.mn.us/divs/ehlwells/waterquality/springs.html 2f7/2007