On small scale water chemistry distribution within a spring complex near Madison, Wisconsin

Abstract

Spring waters were sampled at the discharging points and analyzed for EC and major anions in three small spring complexes located near Madison, Wisconsin. The purpose of this study was to elucidate a meter-scale spring water chemistry variation at the time of discharge, which may shed light on underground flow paths of the spring water.
The major anion concentrations (Cl^－ and NO₃^－) showed strong effect of land use such as road salts in the urban watershed and N-fertilizer applications in agricultural fields. The STDs of Cl^－ in an urban watershed and NO₃^－ in an agricultural watershed were 27.4% and 39.9% of their average concentrations, respectively. It was found that the major anion concentration in each spring complex has large spatial variations even within a meter-scale separation.
Based on the hydrogeology and land use of the watersheds, the large chemistry variation observed could be caused by the solutes from different source areas, that converge towards a small discharge zone with little mixing and discharge into close but different points in the same spring complex.
Acquisition of more detailed information on hydrogeology and water quality is required to better understand the causes of the observed large variation of chemistry within a single spring complex.