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Groundwater Flow Models of Northeastern Illinois
a case study for building MODFLOW models with GIS
PROJECT FRAMEWORK
Abstract
The Chicago metropolitan area of northeastern Illinois is
experiencing rapid population growth, particularly in the
suburban counties surrounding the city of Chicago. The
population of one of these suburban counties, Kane County,
is predicted to increase by as much as 36 percent by the
year 2020. At this growth rate, five townships within Kane
County are projected to experience local water shortages by
2020, prompting Kane County to fund a joint study by the
Illinois State Water Survey and Illinois State Geological
Survey of the water resources of Kane County. Managers
and policy makers require a study that organizes the data,
evaluates the system, improves understanding, and
establishes a framework for follow-up analyses. This effort
is assisted by the use of GIS and database technologies,
which provide efficient tools for building a knowledge base
for this study and translating geohydrological data into
model-ready formats. Examples are provided for several
procedures to efficiently manage, interpolate, and reformat
MODFLOW data using ArcGIS 8.X.
Figure 1. The model domain includes the active regional
aquifer model (light gray) and local deep aquifer model
(dark gray).
The management of water resources in
northeastern Illinois is complicated by
international and interstate agreements,
hydraulically coupled aquifer systems, natural
and anthropogenic contamination, surface water
– groundwater interaction, and conjunctive use of
multiple resources. The net effect of these
complications is that withdrawals from Lake
Michigan cannot be increased beyond current
rates, and the withdrawals from the deep bedrock
Figure 2. Conceptual geological model of aquifers in northeastern Illinois
aquifers may already be at their maximum.
Urban planners have concluded that the region’s
Flux & Head Watershed Withdrawal Surface Water Existing Non- Existing Digital
Measurements
Climate Data
Boundaries Data Properties digital Maps Maps growing population will need to investigate the
shallow aquifers as a source of water to meet
Digitizing & Assembling
Mass Balance Models
USGS Stream
Well Cell &
Transient
Stream to
River Cell
Interpolation & Smoothing growing demands
Coding System
Data Conversion
Pattern Recognition* K/T/S
Pattern & Rates The initial efforts of the project have focused on
Recharge (R)
Boundary Conditions Model Grid Structure
assembling the data and information of previous
Pattern & Rates
studies in a unified format to provide the
Groundwater Flow Model: MODFLOW 2000
framework for analyses. A series of databases
Using GIS
Platform and GIS files are being created for storage,
(ArcGIS 8.x)
Calibration Processing: UCODE
No
retrieval, and processing of these data (Figure 3).
The end product of this initial step is a geologic
Calibration Targets
Head and Flux
Optimum Parameter
Values (R/K/T/S)
and hydrologic data set extensive enough to
permit modeling on an interstate basis, while
Yes
detailed enough to support site-scale models.
Optimum GW Flow Model Parameter Sensitivity
Rather than commit to a single model code or
* Lin, Y-F., and M.P. Anderson, 2003. A Digital Procedure for Ground Water Recharge and Discharge Pattern Recognition and
grid, this study has emphasized the use of GIS in
Rate Estimation, Ground Water 41(3), p.306-315 cataloging, analyzing, and adapting the data, as
Figure 3. Flow chart of the regional modeling process: 1) gray boxes well as procedures and scripts for translating
indicate the processing applications; 2) The dashed box contains
processes and data in a GIS compatible format.
geohydrological data into model-ready formats.
Yu-Feng Lin, Doug Walker, Scott Meyer
yflin@uiuc.edu, ddwalker@uiuc.edu, smeyer@uiuc.edu
DATABASE INTEGRATION
Several procedures have been developed to efficiently manage, interpolate, and reformat hydrogeological data
using ArcGIS 8.2 and 8.3. Figure 4 illustrates the process employed for integrating geologic information
collected from various states in different formats. We then apply procedures and scripts for translating
geohydrological data into digital and model-ready formats (e.g., Figure 5).
Silurian
Maquoketa
St. Peter
Prairie du Chien
St. Lawrence
Ironton-Galesville
Eau Claire
Mt. Simon
Precambrian
Figure 4. An example of information unified under a GIS platform
for re-interpolation based on MODFLOW grids. The bedrock
elevation information includes GIS contours in different coordinate
systems (IL and IN), contours manually digitized from paper maps
(MI), USGS DEM data (SW WI) and interpolated point elevations
from previous studies (SE WI and Lake Michigan). Figure 5. SURFER interpolation of nine major bedrock structural
surfaces as a preliminary step in compiling a geologic regional
model.
GIS and other database tools have been used in organizing data and information of various types to create a
knowledge base for this study and future studies. These data include an extensive database of groundwater
withdrawals in Illinois, complete for the period from 1980 to present, presently being augmented with data for
the pre-1980 period for the Kane County area (Figure 6). Low-flow data for 20 streams within the regional
model domain have been assembled to assure that the calibrated regional model predicts reasonable rates of
natural groundwater discharge to streams. Two hundred and two sets of shallow aquifer pumping test data in
the Kane County area have been identified. High-quality pumping test data will be reinterpreted in later stages
of the project to determine aquifer and aquitard hydraulic properties for use in local-scale groundwater flow
modeling of the shallow aquifers. The above data will be in GIS and Microsoft Access compatible formats.
(a) (b) Figure 6. Groundwater withdrawal database
integration using GIS application: (a) deep
aquifer withdrawal locations, and (b)
shallow aquifer withdrawal locations. The
data sources were from various state
agencies. The shallow aquifer accounting
region was selected by the watershed areas
contributing to Kane county and the
adjacent watersheds to those areas.
Kane County
Deep Aquifer Accounting Region
Shallow Aquifer Accounting Region
Illinois State Water Survey
2204 Griffith Drive, Champaign, IL 61820, USA
GROUNDWATER MODEL
The groundwater flow models for this study will use a nested modeling strategy, with a regional-scale model of
the entire set of aquifers; a local-scale model of only the deep bedrock aquifer system (Figure 3); and local-
scale models of the shallow aquifer system in selected areas of interest. The regional model provides the
boundary conditions for constructing local-scale models in three dimensions, including local-scale models of
shallow aquifers in Kane County. The regional model will be a multilayer groundwater flow model of the entire
aquifer system from the Precambrian crystalline basement to ground surface. A local-scale, multilayer
groundwater flow model will be constructed of the deep bedrock aquifer system. Local-scale shallow aquifer
models will be constructed on an as-needed basis to support water resources planning at the county level.
The models generally will consist of the unconsolidated glacial drift and the upper 50 to 100 feet of the
fractured dolomite and shale bedrock; model domains will extend to natural hydrologic divides around Kane
County.
(a)
Model Approximate Dimension
• Regional deep aquifer model:
• approximately 360 miles by 360 miles
• grid spacing varies from 16 miles to 1/2 mile. N
N
• model size is approximately 44,000 cells for each
layer or 880,000 cells for all 20 layers.
Z
• Local deep aquifer model Y X
• approximately 60 miles by 90 miles (6 counties) X:Y:Z = 1:1:100
• grid spacing varying from 1/2 to 1/4 mile.
Figure 7. Grid structure of regional
• Local shallow aquifer models: groundwater flow model in (a) whole
(b) domain, and (b) near field with finer
• grid density of approximately 1/2 to 1/16 mile. grid resolution.
Key elements of database for surface water -
groundwater (SW-GW) interaction
• Length, perimeter from USGS National Hydrography
Dataset (NHD)
• Stream width inferred from drainage area using GIS
scripts.
• Streambed conductivity from published estimates, and
from well tests near streams
• Determination of river type or drain type using stream
seasonality from Q7,10
• Discharge from baseflow analysis of streams (flux targets
for calibration)
Figure 8. Surface water features from NHD in shallow • Database of predevelopment head
aquifer accounting region (Figure 6).
Conclusion
This project will provide a framework for managing groundwater resources in Kane County, Illinois through
collection, management, and analysis of data; conceptual and numerical modeling of aquifers; and evaluation
of aquifer yield. Evaluation of the consequences of management options will also be examined based on this
framework. The studies will produce a series of models and databases that will be maintained for use in
assessing management options and will provide a framework for model updates and additional studies.
ArcGIS 8.X and MODFLOW were chosen as the data management platform and groundwater flow modeling
package, respectively, to optimize the research process in different stages and to amalgamate data from
various sources.
Acknowledgment
U.S. Geological Survey - Wisconsin District Office, Wisconsin Geological and Natural History Survey, Indiana
Geological Survey, Indiana Department of Natural Resources, Michigan Department of Environmental Quality,
Illinois State Geological Survey, and Kane County Water Resources Department.
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