Groundwater Flow Models of Northeastern Illinois a case study

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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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