Cambrian-Ordovician Aquifer

The aquifer is composed of three separate units, starting with the lowermost Cambrian-age Jordan Sandstone.  The Ordovician-age dolomite and sandstone of the Prairie du Chien Group and the St. Peter Sandstone at the top complete the aquifer.  The Cambrian-Ordovician aquifer is a widespread and dependable source of water for high-capacity wells, and it is used extensively by municipalities and industries in the eastern half of the state.  Wells that require large amounts of water typically tap the full thickness of the aquifer, while other wells may tap only the upper strata. Often called the “Jordan aquifer,” much groundwater also comes from the Prairie du Chien, thus “Cambrian-Ordovician aquifer” is a more accurate name.  Typical well depths in this aquifer range from 300 to 2,000 feet.     Wells that are properly developed in the Cambrian-Ordovician aquifer yield from several hundred to over 1,000 gpm. The best water quality is found in northeast Iowa, nearest the areas of outcrop and recharge. In western and southwestern areas, as the depth to the aquifer increases the dissolved mineral content increases to undesirable levels.  The main area of aquifer recharge is in southern Minnesota and northern Iowa, via vertical leakage from overlying aquifers. Subsurface flow is then to the southeast, with discharge to the Mississippi Valley.

Cambrian - Ordovician Aquifer

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  For further information:  Iowa’s Groundwater Basics by Jean C. Prior, et al, Iowa Dept. of Natural Resources, Iowa Geological Survey Educational Series 6, 83 pages.