Statistical analysis of specific-capacity data for a dolomite aquifer

Abstract

Correlation and regression analyses were made to determine if significant relationships exist between geohydrologic conditions and the specific capacities of 135 dolomite wells in Du Page County, Illinois. Geohydrologic conditions considered include the character and thickness of glacial drift and bedrock units penetrated by wells and the structure of the dolomite at well sites. The dolomite aquifer under investigation consists of Silurian and Ordovician rocks which are encountered at an average depth of 100 feet. It commonly exceeds 100 feet in thickness and is overlain mostly by glacial drift. Significant correlations were found between specific capacities and (1) the thickness of the dolomite aquifer, (2) stratigraphic units penetrated by wells, and (3) the thickness of reef and associated strata at well sites. Other correlations probably exist, but they are too subtle and complex to permit detection. Frequency graphs of specific capacity per foot of penetration are given. These graphs show the role of individual units uncased in wells as contributors of water. Probable ranges of specific capacities and yields of wells in undeveloped areas are estimated on the basis of frequency graphs, aquifer thickness and areal geology maps, and water-level data.