Geology and ground-water resources of Outagamie County, Wisconsin

Abstract

Outagamie County is in east-central Wisconsin. It has no serious groundwater problem at present, but the county is important as a recharge area for the principal aquifers supplying water to Brown County and industrial Green Bay to the east. The county is covered by glacial drift and lake deposits of the Wisconsin stage of glaciation. In the northwestern quarter of the county these deposits rest upon Precambrian crystalline rocks; throughout the remainder of the county they are underlain by sandstone, limestone, dolomite, and shale of Cambrian and Ordovician age. ·where they are sufficiently thick, and where more productive formations are absent, glacial sand and gravel are an important source of ground water. The major sources, however, are the St. Peter sandstone, of Ordovician age, and the sandstones of the Upper Cambrian series. The Precambrian crystalline rocks, which underlie all the county, yield little or no water to wells. The regional dip of the Paleozoic bedrocks is 25 to 30 feet per mile eastward and southeastward. There are no major folds, but the thickness of each geologic unit may change from place to place because of predepositional or postdepositional erosion. There is no conclusive evidence of major faulting in the area. Ground water in Outagamie County occurs under both water-table (unconfined) and artesian (confined) conditions. The source of the ground water is precipitation which falls on the surface and percolates downward into the underlying permeable materials. Regional movement of ground water in the eastern third of the county is controlled by the bedrock structure, and the discharge is toward the east and south. Throughout the rest of the county the movement of water is controlled mainly by bedrock and surface topography, and the water moves toward the streams and bedrock valleys. Water-level :fluctuations follow definite patterns. Where the effects of pumping are at a minimum, water levels reach a high in April or May, decline through the summer months owing to natural discharge, and lack of recharge, and do not begin to recover until after the ground thaws in the spring. In areas of heavy pumping where this pattern is distorted, the lowest water levels occur in the early fall and recoveries begin in October or November after the period of heaviest pumping. Pumpage in the county was estimated to be about 9.0 million gallons per day (mgd) in 1951 and 1952. Nearly half of this was for industrial, commercial, and public-supply use along the Fox River. Wells, most of which are drilled by the cable-tool method, range in diameter from 3 to 16 inches and in depth from 10 or 20 feet to 804 feet. In the alluvium and glacial drift 1~- to 2¥2-inch driven wells are common. Pumping tests were made to determine the hydraulic characteristics of the aquifers at Seymour, Appleton, and Hortonville. The average coefficient of transmissibility at Seymour is about 18,000 gpd per foot; at Appleton it is about 19,000 gpd per foot. The coefficients of storage are 0.00022 and 0.00015 at Seymour and Appleton, respectively. Movement of ground water out of the county, assuming an average transmissibility of 18,000 gpd per foot, was calculated to be more than 10 mgd toward the southeast. The ground water differs greatly in chemical quality from well to well, but it is generally a very hard calcium magnesium bicarbonate water, some of it high in iron. To aid in determining the source of well waters, 22 chemical analyses were plotted on a logarithmic diagram to obtain characteristic patterns for waters from several geologic sources.