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Simulation of groundwater flow in the glacial aquifer system of northeastern Wisconsin with variable model complexity

Scientific Investigations Report 2017-5010
By: , , and 
https://doi.org/10.3133/sir20175010

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Abstract

The U.S. Geological Survey, National Water-Quality Assessment seeks to map estimated intrinsic susceptibility of the glacial aquifer system of the conterminous United States. Improved understanding of the hydrogeologic characteristics that explain spatial patterns of intrinsic susceptibility, commonly inferred from estimates of groundwater age distributions, is sought so that methods used for the estimation process are properly equipped. An important step beyond identifying relevant hydrogeologic datasets, such as glacial geology maps, is to evaluate how incorporation of these resources into process-based models using differing levels of detail could affect resulting simulations of groundwater age distributions and, thus, estimates of intrinsic susceptibility.

This report describes the construction and calibration of three groundwater-flow models of northeastern Wisconsin that were developed with differing levels of complexity to provide a framework for subsequent evaluations of the effects of process-based model complexity on estimations of groundwater age distributions for withdrawal wells and streams. Preliminary assessments, which focused on the effects of model complexity on simulated water levels and base flows in the glacial aquifer system, illustrate that simulation of vertical gradients using multiple model layers improves simulated heads more in low-permeability units than in high-permeability units. Moreover, simulation of heterogeneous hydraulic conductivity fields in coarse-grained and some fine-grained glacial materials produced a larger improvement in simulated water levels in the glacial aquifer system compared with simulation of uniform hydraulic conductivity within zones. The relation between base flows and model complexity was less clear; however, the relation generally seemed to follow a similar pattern as water levels. Although increased model complexity resulted in improved calibrations, future application of the models using simulated particle tracking is anticipated to evaluate if these model design considerations are similarly important for understanding the primary modeling objective - to simulate reasonable groundwater age distributions.

Suggested Citation

Juckem, P.F., Clark, B.R., and Feinstein, D.T., 2017, Simulation of groundwater flow in the glacial aquifer system of northeastern Wisconsin with variable model complexity: U.S. Geological Survey Scientific Investigations Report 2017–5010, 52 p., https://doi.org/10.3133/sir20175010.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Foreword
  • Abstract
  • Introduction
  • Conceptual Model of the Groundwater System
  • Hydrogeologic Characteristics of the Groundwater-Flow System 
  • Model Construction
  • Model Calibration
  • Limitations of the Groundwater-Flow Models 
  • Summary and Conclusions
  • Acknowledgments
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Simulation of groundwater flow in the glacial aquifer system of northeastern Wisconsin with variable model complexity
Series title Scientific Investigations Report
Series number 2017-5010
DOI 10.3133/sir20175010
Year Published 2017
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Wisconsin Water Science Center
Description viii, 52 p.
Public Comments National Water-Quality Assessment
Country United States
State Wisconsin
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
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