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Abstract

Two aquifers are extensively used by residents of small communities and rural areas in northern Searcy County, Arkansas. The Mississippian Boone-St. Joe aquifer is generally the less productive and the shallower of the two. Ground-water yields for the Boone-St. Joe range from 0.5 to 75 gpm with a median yield of 5 and a mean of 9.8 gpm. Well depths range from 100 to 754 feet with a median depth of 350 feet and a mean of 360 feet. Confined conditions are indicated by the greater depths, whereas the Boone-St. Joe aquifer is unconfined when exposed at the surface. Underlying the Boone-St. Joe aquifer is an aquifer zone composed of sands, sandy limestones, and/or dolomitic limestones below the Chattanooga Shale and above and including the Everton Formation. This aquifer can be composed of one or more of the following units: upper Everton, St. Peter, Clifty, Sylamore, Lafferty, St. Clair and/or Plattin. The range in yields for this aquifer is 1 to 80 gpm with a median yield of 9 and a mean of 17 gpm. Well depths range from 200 to 875 feet with a median and mean depth of 570 feet. A statistical correlation was found among well yields (gpm), regolith thickness, depth of well, and cave intersection by the well. The results indicate that greater yields can be obtained in areas of thicker regolith. Cave presence was also found to enhance yields. A strong relationship between cave presence and deeper regolith was observed. These three relationships demonstrate increased weathering, and thus water flow along fractures. The effect of joints closing off at depth produced a strong relationship between shallower wells and greater yields within the Boone-St. Joe aquifer.

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