Prepared in cooperation with the Lansing Board of Water and Light

Delineation of Contributing Areas to Selected Wells 

in Ingham County, Michigan

Open-File Report 2014–1054

U.S. Department of the Interior

U.S. Geological Survey

Delineation of Contributing Areas to 

Selected Wells in Ingham County, Michigan

By Carol L. Luukkonen

Prepared in cooperation with the Lansing Board of Water and Light

Open-File Report 2014–1054

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014

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Suggested citation:

Luukkonen, C.L., 2014, Delineation of contributing areas to selected wells in Ingham County, Michigan: 

U.S. Geological Survey Open-File Report 2014–1054, 11 p., http://dx.doi.org/10.3133/ofr20141054

ISSN 2331-1258 (online)
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................1

Previous Studies ...................................................................................................................................1

Description of Study Area ............................................................................................................................3

Geologic Setting....................................................................................................................................3

Hydrogeologic Setting .........................................................................................................................3

Groundwater Withdrawals..................................................................................................................3

Groundwater-Flow Simulation.....................................................................................................................3

Spatial and Temporal Discretization..................................................................................................4

Hydraulic Properties.............................................................................................................................4

Water Levels and Streamflow ............................................................................................................4

Steady-State Model Results ...............................................................................................................4

Delineation of Contributing Areas......................................................................................................7

Model Assumptions and Limitations ........................................................................................................10

Summary and Conclusions.........................................................................................................................10

References Cited..........................................................................................................................................11

Figures

1. Location of the Tri-County regional model area, participating communities, 

and the nine-township area surrounding Lansing, Michigan...............................................2

2. Summary of model budget for 2011–12 pumping conditions, 

Tri-County region, Michigan .......................................................................................................5

3. Relation between observed and simulated water levels and streamflow, 

Tri-County model, Michigan........................................................................................................6

4. Simulated 10-year time-of-travel areas for selected production wells in the 

nine-township area, Tri-County region, Michigan ..................................................................8

5. Simulated 40-year time-of-travel areas for selected production wells in the 

nine-township area, Tri-County region, Michigan ..................................................................9

Tables

1. Base-flow estimates at eight U.S. Geological Survey (USGS) streamgaging 

stations in the Tri-County region ................................................................................................5
iv

Conversion Factors and Datums 

Multiply By To obtain

meter (m)

Length

foot (ft) 0.3048

mile (mi) 1.609 kilometer (km)

square centimeter (cm2

)

Area

square foot (ft2

) 929.0

square foot (ft2

) 0.09290 square meter (m2)

square mile (mi2

) 2.590 square kilometer (km2) 

liter (L) 

Volume

gallon (gal) 3.785

gallon (gal) 0.003785 cubic meter (m3) 

million gallons (Mgal) 3,785 cubic meter (m3

)

cubic foot (ft3

) 28.32 cubic decimeter (dm3) 

cubic foot (ft3

) 0.02832 cubic meter (m3) 

meter per day (m/d)

Flow and recharge rate

foot per day (ft/d) 0.3048

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

gallon per day (gal/d) 0.003785 cubic meter per day (m3

/d)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3

/s)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

meter per day (m/d)

Hydraulic conductivity

foot per day (ft/d) 0.3048

Vertical coordinate information is referenced to the North American Vertical Datum of 1929 

(NVGD 29).

Horizontal coordinate information is referenced to the Michigan State Plane Coordinate System, 

South Zone.

Altitude, as used in this report, refers to distance above the vertical datum.
Delineation of Contributing Areas to Selected Wells in 

Ingham County, Michigan

By Carol L. Luukkonen

Abstract

A groundwater-flow model that was constructed in 2009 

was updated to reflect recent (2011–12) pumping conditions in 

the Tri-County region, which consists of Clinton, Eaton, and 

Ingham Counties, Michigan. As part of local wellhead protection area programs, areas contributing water to local production wells must be periodically updated, because groundwaterflow paths depend in part on the stresses, such as groundwater 

withdrawals, to the groundwater-flow system. For this current 

(2013) study, withdrawals from selected city of Lansing 

production wells were updated, and simulated heads and 

flows under the new pumping conditions compared favorably 

to previously measured values. Results of flow simulations 

indicate that 10-year time-of-travel contributing areas cover 

approximately 19.4 square miles, and 40-year time-of-travel 

contributing areas cover approximately 39 square miles. 

Introduction

The Tri-County region, which consists of Clinton, Eaton, 

and Ingham Counties, covers 1,697 square miles (mi2) in the 

south-central part of the Lower Peninsula of Michigan (fig. 1). 

A groundwater-flow model developed in 1996 (Holtschlag 

and others, 1996) was refined in 2009 (Luukkonen, 2009) in 

cooperation with the Tri-County Regional Planning Commission and local communities in order to better represent the 

groundwater flow system in the Tri-County region. Participating communities included Alaiedon Township, Bath Township, Delhi Township, Delta Township, city of East Lansing, 

city of Eaton Rapids, city of Lansing, city of Williamston, 

Eaton Rapids Township, Lansing Township, Michigan State 

University, Meridian Township, Oneida Township, Vermontville Township, Village of Dimondale, Watertown Township, 

Williamstown Township, and Windsor Township. The 2009 

study helped to improve understanding of the regional hydrologic system in the Lansing area, and the groundwater-flow 

model continues to be used for planning and protection of the 

water supplies in the Lansing area. As part of local wellhead 

protection area programs, areas contributing water to local 

production wells need to be periodically updated, because 

groundwater-flow paths depend in part on the stresses to the 

groundwater-flow system. Different pumping rates or pumping locations will change the groundwater-flow patterns in the 

modeled area and result in different zones of contribution and 

areas contributing recharge to the pumping wells; therefore, 

for this current (2013) study, prepared in cooperation with the 

Lansing Board of Water and Light, withdrawals from selected 

production wells were updated to reflect 2011–12 pumping 

conditions, simulated heads and flows under the new pumping 

conditions were compared to previously measured values, in 

part to ensure boundary conditions of the original model were 

still appropriate, and contributing areas to production wells 

were delineated.

Purpose and Scope

This report briefly describes the 2009 Tri-County regional 

groundwater-flow model and the simulation of 2011–12 pumping conditions. Simulated water levels and streamflow under 

the new pumping conditions were compared to observed water 

levels and streamflow used in the 2009 model and a new set 

of water levels and flow from more recent measurements from 

2006–9. These updated pumping conditions were used with 

particle-tracking analysis to determine 10- and 40-year timeof-travel contributing areas to selected production wells. The 

limitations of the model for assessing groundwater levels and 

flow and for delineating contributing areas are described. 

Previous Studies

Several previous studies contributed to the development of the 2009 model. A report by Holtschlag and others 

(1996) documents how the 1996 regional groundwater-flow 

model was developed and used to determine contributing areas for most production wells in the Tri-County 

region. Two reports describe refinement of the grid spacing 

of the original 1996 model and the results of additional 

groundwater-flow simulations in the north Lansing area 

(Luukkonen and others, 1997a, b). Finally, a report by 

Luukkonen (2009) describes additional refinements to the 

1996 model and subsequent simulations investigating the 

groundwater flow system in the Tri-County area.
2 Delineation of Contributing Areas to Selected Wells in Ingham County, Michigan

Base map from the Michigan Resource Information System,

Michigan Department of Environmental Quality, Easting and 

Northing Coordinates referenced to Michigan State Plane 

System, South Zone.

400,000

350,000

450,000

500,000

550,000

600,000

NORTHING, IN FEET

IONIA COUNTY

CLINTON COUNTY

SHIAWASSEE COUNTY

LIVINGSTON 

INGHAM COUNTY

JACKSON COUNTY

EATON COUNTY

1,850,000 1,900,000 1,950,000 2,000,000 2,050,000 2,100,000

EASTING, IN FEET

COUNTY

300,000

Lansing

East Lansing

Williamston

Eaton Rapids

Dimondale

Grand Ledge

Oneida

Township

Williamston

Township

Vermontville

Township

Michigan State

University

Delhi Twp

Alaiedon Twp

Meridian Twp

Delta Twp

Eaton Rapids 

Twp

Windsor Twp

Watertown 

Twp

Bath Twp

Dewitt Twp

Lansing Twp

EXPLANATION

Nine-township area

2009 Tri-County regional

 model boundary

10 20

10 20

0

0

MILES

KILOMETERS

M I C

H I G

A

N

Lansing, Michigan.

Figure 1. Location of the Tri-County regional model area, participating communities, and the nine-township area surrounding 
Groundwater-Flow Simulation 3

Description of Study Area

In this report, the “nine-township area,” which is in and 

surrounding the city of Lansing, Michigan, consists of Alaiedon, Bath, Delhi, Delta, Dewitt, Lansing, Meridian, Watertown, 

and Windsor Townships (fig. 1). The nine-township area is the 

principal area of municipal groundwater withdrawals in the 

Tri-County region. Groundwater is withdrawn primarily from 

the Saginaw aquifer, which consists of water-bearing sandstones 

within the Grand River and Saginaw Formations of Pennsylvanian age. Aquifers in the glacial deposits and other bedrock 

units are important groundwater sources in some places. The 

primary geologic, hydrogeologic, and water-use characteristics that affect groundwater flow in the Saginaw aquifer are 

described in the following sections. More detailed information 

is available in Luukkonen (2009). 

Geologic Setting

In the Tri-County region, Pennsylvanian rocks form the 

uppermost bedrock unit. The Pennsylvanian rocks are thickest in the west-central part of Clinton County and generally 

thin to the south. They are absent in the extreme eastern part of 

Ingham County. Discontinuous lenses of sandstone, shale, coal, 

and limestone in the Pennsylvanian bedrock units have been 

formally subdivided into two formations. The uppermost Grand 

River Formation consists of massive, coarse-grained sandstones; all remaining Pennsylvanian rocks are considered part 

of the underlying Saginaw Formation (Mandle and Westjohn, 

1989). The assignment of formation is not precise, however, 

because no lithologic differences or stratigraphic horizons mark 

a change from one formation to the next (Westjohn and Weaver, 

1996). Jurassic red beds separating Pennsylvanian rocks from 

overlying glacial deposits in some areas of the Lower Peninsula 

are either entirely absent or only marginally present in the TriCounty region (Westjohn and others, 1994). For the purposes 

of this study, all deposits between the top of the Pennsylvanian 

rocks and the land surface were assumed to be glacial deposits. 

The glacial features in Michigan are the result of ice 

advances during late Wisconsin time (35,000 to 10,000 years 

before present). The glacial deposits are absent in a small area 

near the city of Grand Ledge; the thickest glacial deposits are 

in the northwestern part of the study area. These deposits are 

generally not regionally continuous; hydrogeologic properties 

vary across the study area (Mandle and Westjohn, 1989). 

Hydrogeologic Setting

Glacial deposits form the uppermost aquifer in the TriCounty region. Groundwater flow in the glacial deposits is generally from south to north, away from topographic divides and 

toward surface-water bodies. Aquifers in the glacial deposits are 

composed primarily of coarse alluvial and outwash materials. 

Till is present over much of the region and is generally not a 

source of water to wells (Vanlier and others, 1973). 

The Saginaw aquifer is in water-bearing sandstones in the 

Grand River and Saginaw Formations. The Saginaw aquifer can 

be thought of as an aquifer system consisting of three sandstone 

units separated by an upper interbedded-series unit and a lower 

shale unit (David Westjohn, U.S. Geological Survey, oral commun., 2005). Division of the Saginaw aquifer into these units 

is uncertain in some areas because of incomplete or missing 

well-log data, heterogeneities within the units, and varying 

thicknesses of these units in the formation. Most groundwater 

flow in the Saginaw aquifer is from south to north, although 

some is toward local pumping centers. Flow between aquifers in 

the glacial deposits and the Saginaw Formation is limited where 

confining units are present that consist of: (1) a lower till unit 

in the glacial deposits, (2) an upper shale unit in the Saginaw 

Formation, or (3) both types of confining units.

Groundwater Withdrawals

Groundwater is the principal source of water supply for 

the Tri-County region and the majority of communities rely on 

groundwater from the Saginaw aquifer; in 2010 about 

95 percent of municipal withdrawals were from the Saginaw 

aquifer (Andy LeBaron, 2012, Michigan Department of Environmental Quality, written commun.). Domestic, agricultural, 

and industrial supplies may be from the Saginaw aquifer or 

glacial deposits. Groundwater withdrawals in the 2009 model 

totaled 45.3 Mgal/d (million gallons per day) and represented 

2006–7 conditions. For this study, simulated groundwater 

withdrawals for 88 Lansing production wells in the central 

part of the model area were updated to reflect 2011–12 pumping conditions (Bill Maier, 2013, Lansing Board of Water and 

Light, written commun.), with about equal numbers of wells 

with increasing and decreasing pumping rates; other municipal 

withdrawals were unchanged from the 2009 model. Groundwater withdrawals totaled 46.1 Mgal/d in the updated steady-state 

model. Pumpage generally increased for wells in the western 

and northern parts of the wellfield and decreased for wells in the 

southeastern part.

Groundwater-Flow Simulation

The U.S. Geological Survey modular three-dimensional 

finite-difference numerical groundwater-flow model MODFLOW-2000 (Harbaugh and others, 2000) was used to simulate 

groundwater flow in the Tri-County region. The steady-state 

model area consists of Clinton, Eaton, and Ingham Counties 

along with parts of Ionia, Shiawassee, Jackson, and Livingston 

Counties (fig. 1). Simulated pumping rates for 88 city of Lansing wells were updated to reflect more recent conditions; all 

other model values and boundary conditions were not changed 

for the current study. A brief description of the model, hydraulic 

characteristics, and water-level and streamflow data and the 

comparison between model simulated and observed water levels 

and flow are described below. For a more detailed description of 

the model construction see Luukkonen (2009).
4 Delineation of Contributing Areas to Selected Wells in Ingham County, Michigan

Spatial and Temporal Discretization

The model area covers about 3,500 mi2 and is approximately 61 miles (mi) long (north-south) and 58 mi wide 

(east-west). The model consists of 338 rows and 307 columns 

of grid cells that vary in size. In the central part of the model 

area, each cell is approximately 660 by 660 feet (ft). Cell spacing increases outward from the central part of the model area 

in each direction by a factor of 1.2 to a maximum grid spacing 

of about 1,330 ft. 

Three units were determined to represent the glacial 

materials. The uppermost glacial unit (layer 1) was thickest 

for deposits adjacent to rivers to minimize problems associated with model convergence of calculated water levels. The 

remaining glacial materials were subdivided equally to create 

layers 2 and 3.

The Saginaw Formation materials were divided into an 

uppermost shale unit overlying three aquifer units that are 

separated by an interbedded-series confining unit consisting 

of shale and sandstone lenses and a lowermost shale unit. The 

uppermost shale confining unit (layer 4) is thickest in Clinton County and the northern part of Eaton County. The shale 

unit is absent in parts of Lansing and is thinnest over most of 

southern Ingham and Eaton Counties. The uppermost sandstone aquifer unit (layer 5) is thickest in the central Tri-County 

region and northern Clinton County. The interbedded-series 

confining unit (layer 6) is thickest in the eastern, western, 

and northern parts of the Tri-County region. The intermediate 

sandstone aquifer unit (layer 7) is thickest in central and northern parts of the Tri-County region. The lower shale confining 

unit (layer 8) is thickest in the central and northern parts of 

the Tri-County region. The lowermost sandstone aquifer unit 

(layer 9) is thickest in Ingham and Eaton Counties. The lowermost model layer (layer 10) represents the material underlying the Saginaw aquifer and was included because well logs 

indicate that some wells may be completed below the bottom 

of the Saginaw aquifer. 

Hydraulic Properties

Estimates of hydraulic conductivity ranged from 

12.7 to 107.2 feet per day (ft/d) for the glacial aquifer units 

(model layers 1, 2, and 3). Horizontal hydraulic conductivity estimates are highest in the central and eastern parts of 

the model area and lowest in the northern and southern parts 

of the model area. Vertical hydraulic conductivity estimates 

ranged from 0.0001 to 0.027 ft/d. 

The estimated horizontal hydraulic conductivities for the 

shale (layer 4) are highest in the southern model area and lowest in the central and northeastern model area and ranged from 

0.0004 to 0.435 ft/d. The estimated horizontal hydraulic conductivity of the sandstone (layers 5, 7, and 9) equaled 11 ft/d, 

and the vertical hydraulic conductivity estimate equaled 

1.1 ft/d. The sandstone transmissivity estimates vary according 

to the sandstone thickness and are highest in the central and 

northern model area and lowest in the southern model area. 

Horizontal hydraulic conductivity estimates for the interbedded series (layer 6) and the lower shale (layer 8) equaled 

0.1 ft/d and 0.01 ft/d, respectively. The horizontal hydraulic 

conductivity for the bottom bedrock unit was estimated to be a 

constant value of 8 ft/d, and the vertical hydraulic conductivity 

was estimated to be 0.1 times the horizontal value, or 0.8 ft/d. 

Streambed hydraulic conductivity was estimated to be 4.6 ft/d. 

Water Levels and Streamflow

Simulation results with the updated pumping rates were 

compared to water-level and streamflow data used for calibration of the 2009 model and to more recent water-level and 

stream flow data. Within the Tri-County region, water-level 

data used for calibration of the 2009 model consisted of 

2,775 water-level measurements from well logs (Holtschlag 

and others, 1996). Measurements in the upper layer were 

not restricted to a particular time period; however, measurements in the lower layer were restricted to the period 1984–92 

because of local trends in the historical groundwater-level 

data associated with changes in pumping conditions. Streamflow data used for calibration of the 2009 model consisted 

of base-flow estimates at 10 continuous-record streamgaging 

stations and 25 partial-record streamgaging stations. Daily 

mean streamflows from streamgaging stations were disaggregated into surface runoff and base flow components by use 

of a streamflow partitioning technique (Rutledge, 1993). The 

average base flow component was assumed to represent the 

average groundwater discharge. Some more recent water-level 

data are available from well logs from the Michigan Department of Environmental Quality Wellogic database (Michigan 

Department of Environmental Quality, 2013). These additional 

water level and streamflow data representing more recent 

conditions (2000–9) were compiled as an additional check 

on model results. These water-level data consisted of 2,284 

water-level measurements obtained from well logs for wells 

installed from 2005–9 in the glacial deposits and 2006–9 in the 

Saginaw aquifer; streamflow data (table 1) consisted of baseflow estimates at 8 continuous-record streamgaging stations 

determined using flows from 2000–5.

Steady-State Model Results

In the steady-state model, the amount of water recharging the ground-water system is assumed to equal the amount of 

water discharging from the ground-water system; changes in 

storage do not occur. Water may enter the system as recharge 

from precipitation, seepage from lakes and rivers, and as inflow 

from outside the study area. Water may leave the ground-waterflow system as seepage into lakes and rivers, outflow from the 

study area, and as withdrawals by wells. The model budget 

indicates that the majority of flow out of the model is to rivers 

and the majority of inflow is from recharge (fig. 2). 
Groundwater-Flow Simulation 5

Table 1. Base-flow estimates at eight U.S. Geological Survey (USGS) streamgaging stations in the Tri-County region.

[Streamflow data from 2000–5 were used to estimate base flow by use of a streamflow partitioning technique (Rutledge, 1993)]

USGS gagingstation number Station name Drainage area Period of record Base flow(cubic feet 

per seond)

04111379 Red Cedar River near Williamston 163 1975–89, 2001–13 75.1

04111500 Deer Creek near Dansville 16.3 1954–2013 7.2

04112000 Sloan Creek near Williamston 9.34 1954–2013 2.7

04112500 Red Cedar River at East Lansing 355 1903, 1931–2013 152.2

04113000 Grand River at Lansing 1,230 1901–6, 1934–2013 664.5

04114000 Grand River at Portland 1385 1952–82, 1988–2013 786.7

04114498 Looking Glass River near Eagle 280 1944–96, 2001–13 131.0

04111000 Grand River at Eaton Rapids 661 1950–82, 1995–2013 430.2

Storage Wells Constant 

head Recharge River leakage

800

200

400

600

0

-200

-400

-600

-800

Volume of water, in million gallons

EXPLANATION

Into model

Out of model

region, Michigan

Figure 2. Summary of model budget for 2011–12 pumping conditions, Tri-County 
6 Delineation of Contributing Areas to Selected Wells in Ingham County, Michigan

Model fit is evaluated by comparing the magnitude and 

distribution of the differences (residuals) between observed 

and simulated water levels and flows. Simulated water levels 

and flows can be plotted against observed values, and the 

deviation from the 1:1 line gives one indication of model fit. 

Simulation results for the refined 2009 10-layer model using 

2011–12 pumping conditions were compared to observations 

used in the development of the 1996 model and to a second set 

of water-level and streamflow observations from 2000–9. The 

agreement between observed and simulated groundwater levels 

and streamflow was similar for both sets of calibration data 

(fig. 3). 

1996 model calibration data values 1996 model calibration data values

Recent (2005−9) data values Recent (2000−5) data values

1100

1000

900

800

600

700

600 700 800 900 1000 1100

Simulated water levels, in feet above NGVD29

Observed water levels, in feet above NGVD29

1100

1000

900

800

600

700

600 700 800 900 1000 1100

Simulated water levels, in feet above NGVD29

Observed water levels, in feet above NGVD29

140

100

80

60

0

20

0 20 60 80 100 140

Simulated discharge in cubic feet per second

Observed discharge, in cubic feet per second

40 120

40

120

120

80

60

40

0

-20

0 20 60 80 100

Simulated discharge in cubic feet per second

Observed discharge, in cubic feet per second

40 120

20

100

National Geodetic Vertical Survey Datum of 1929)..

Figure 3. Relation between observed and simulated water levels and streamflow, Tri-County model, Michigan, (NGVD 29, 
Groundwater-Flow Simulation 7

As described in Holtschlag and others (1996), observation weights were based on the assumed accuracy in the 

measurement. Measurements from the Wellogic database 

were estimated to be accurate within ± 7 ft, 90 percent of the 

time. Measurements at monitoring wells were estimated to 

be accurate within ± 2 ft, 90 percent of the time. Using the 

water levels and streamflow from the 2009 study, the sum 

of squared weighted residuals (SSWR) for heads decreased 

from 16,170 in the 1996 model to 10,452 in the 2009 model 

and equaled 10,387 in the 2009 model with 2011–12 pumping 

conditions; the mean water-level residual is 4.6 ft. The SSWR 

for streamflow measurements increased slightly from 350 in 

the 1996 model to 415 in the 2009 model and equaled 391 

under the new pumping scenario. This comparison indicates 

that (1) the model conceptualization and boundary conditions 

are still appropriate with the updated pumping conditions, 

and (2) the differences between observed and simulated water 

levels and flows are not great enough to require recalibration 

of the model before estimating contributing areas.

Delineation of Contributing Areas

The particle-tracking program MODPATH (Pollock, 

1994) can be combined with MODFLOW-calculated flow in 

each cell to determine the zone of contribution to a pumping 

well within a given time frame. The zone of contribution to 

a pumping well is defined as the land-surface projection of 

the three-dimensional volume of water flowing to the pumping well (Morrissey, 1989). That three-dimensional volume 

includes the surficial contributing recharge area and any 

subsurface zones of contribution. The contributing area for 

each pumping well is defined here as the combination of areal 

extent of the areas contributing recharge and of the zones of 

contribution projected up to the land surface. An estimated 

porosity of 15 percent was previously used for particletracking simulations (Holtschlag and others, 1996) and, in the 

absence of any additional information, was used for all layers 

in the 2009 model.

A total of 24,000 hypothetical particles were placed on 

the sides of the cells in the Saginaw aquifer layers containing 

the 88 Lansing-area production wells with updated pumping 

rates. These particles were tracked backward using the steadystate model along flow paths through the groundwater-flow 

field until they reached a top cell face (representing the land 

surface) in the upper model layer or until a specified amount 

of time elapsed. Consequently, the position of the particle at 

the end of the simulation represents the location at the water 

table where the particle enters (recharges) the groundwaterflow system or the location where water would flow to the 

well in the specified amount of time. Groundwater withdrawals of 46.1 Mgal/d representing 2011–12 conditions were specified for this simulation. Surface areas contributing recharge as 

well as subsurface zones of contribution were determined for 

10 and 40 years using the 2009 model with the modified withdrawals. Under 2011–12 pumping conditions, the areal extent 

of the 10-year time-of-travel wellhead-contributing areas 

encompasses about 19.4 mi2 (fig. 4); the areal extent of the 

10-year time-of-travel areas under 2007 pumping conditions 

encompassed about 19.2 mi2. Contributing areas were generally larger in the western and northern parts of the wellfield 

and smaller along the eastern side of the wellfield. The areal 

extent of the 40-year time-of-travel areas encompasses about 

39 mi2 under 2011–12 pumping conditions (fig. 5).
8 Delineation of Contributing Areas to Selected Wells in Ingham County, Michigan

INGHAM COUNTY

EATON COUNTY

CLINTON COUNTY

Lansing

410,000

390,000

430,000

450,000

470,000

490,000

1,890,000 1,910,000 1,930,000 1,950,000 1,970,000 1,990,000

Base map from the Michigan Resource Information System,

Michigan Department of Environmental Quality, Easting and 

Northing Coordinates referenced to Michigan State Plane 

System, South Zone.

10 MILES

10 KILOMETERS

5

0 5

0

EASTING, IN FEET

NORTHING, IN FEET

EXPLANATION

10-year time of travel areas

 under 2011−12 pumping conditions

10-year time of travel areas

 under 2007 pumping conditions

96

96

96

96

96

69

69

69

69

69

127

127

127

127

496

496

99

127

496

99

96

96

43 43 43

43

69

69

Figure 4. Simulated 10-year time-of-travel areas for selected production wells in the nine-township area, Tri-County region, Michigan.
Groundwater-Flow Simulation 9

96

96

96

96

96

69

69

69

69

69

127

127

127

127

496

496

99

127

496

99

96

96

43 43 43

43

69

69

INGHAM COUNTY

EATON COUNTY

CLINTON COUNTY

Lansing

410,000

390,000

430,000

450,000

470,000

490,000

1,890,000 1,910,000 1,930,000 1,950,000 1,970,000 1,990,000

Base map from the Michigan Resource Information System,

Michigan Department of Environmental Quality, Easting and 

Northing Coordinates referenced to Michigan State Plane 

System, South Zone.

10 MILES

10 KILOMETERS

5

0 5

0

EASTING, IN FEET

NORTHING, IN FEET

EXPLANATION

Simulated 40-year time of travel areas

 for selected production wells

Figure 5. Simulated 40-year time-of-travel areas for selected production wells in the nine-township area, Tri-County region, Michigan.
10 Delineation of Contributing Areas to Selected Wells in Ingham County, Michigan

Model Assumptions and Limitations

The groundwater-flow model was developed to simulate the regional groundwater-flow system in the Tri-County 

region. Hydraulic properties represented in each layer were 

assumed to be horizontally isotropic; that is, within a cell, 

hydraulic properties are the same in the north-south direction 

as in the east-west direction. Hydraulic properties do vary 

from location to location; however, each grid cell represents 

the average hydraulic properties in the volume of aquifer 

represented by the cell. Vertical variations in aquifer properties 

within layers and any variations in head or flow within each 

layer are not simulated in the model. Local flows over distances smaller than the dimensions of the grid cell also cannot 

be accurately simulated. Additional geologic and hydrologic 

data, as well as finer discretization of the model, would be 

needed to simulate flow systems in smaller areas. The accuracy of layer surfaces and hydraulic conductivity estimates 

are limited by the available data at well and boring locations. 

Additional control and accuracy could be achieved by inclusion of more data points. 

Small withdrawals from domestic wells were not 

included because of the difficulty in obtaining reliable data 

and the limitations in representing small-scale flow systems 

(systems considerably smaller than simulated as part of this 

study). However, domestic groundwater withdrawals and the 

unaccounted-for effects are probably small at the scale of the 

model. 

The base of the model is assumed to be impermeable. 

External boundary conditions, which are based on natural 

hydrologic conditions and are distant from the Tri-County 

region well fields, are assumed to have minimal effect on 

water levels and flow in the interior of the model. The model 

may not accurately represent the groundwater-flow system for 

any predictive simulations involving groundwater withdrawals 

near the model boundaries.

The location and size of the areas contributing recharge 

to wells are affected by the hydrogeologic characteristics and 

boundary conditions of the groundwater-flow system, as well 

as the location, depth, and discharge rate of each simulated 

well. Thus, the simulated areal extent of the areas contributing recharge and zones of contribution are dependent on the 

estimated values for the hydraulic characteristics, such as 

transmissivity and riverbed conductance, and on the pumping 

rates of the individual wells. In reality, the size and location of 

the zone of contribution could change over time as a function 

of annual or seasonal variations in pumping rates or pumping 

locations. In addition, the zone of contribution could change 

in size or location with changes in recharge rates or in the way 

the groundwater-flow system is represented. 

The accuracy of particle-tracking simulations is limited 

by the accuracy of the numerical model on which the simulations are based, the estimates of the effective porosity of the 

flow system, and the accuracy of the cell flow velocities in 

approximating the local groundwater-flow velocities. Actual 

effective porosity may differ from location to location and 

from layer to layer. Lower effective porosities in the system would tend to increase the rate that particles move and 

increase the size of the contributing areas to the wells. Particle 

tracking simulates the advective movement of groundwater, 

so the effects of diffusion, dispersion, and chemical reactions 

are not considered. Therefore, particle tracking, by itself, is 

not sufficient for simulating all aspects of the transport of 

dissolved chemicals in the groundwater-flow system. Under 

steady-state conditions, the water discharging from a pumped 

well is a blend of water of different ages or traveltimes. In 

each specified time-of-travel simulation, it is assumed that 

model pumping rates and pumping locations remain constant 

indefinitely and that the water withdrawn by each simulated 

well may represent water that has entered as recharge or that 

already was in the zone of contribution when the well began 

pumping. Simulations of transient processes (with changes in 

recharge and/or pumping) may affect the size and shape of the 

areas contributing recharge (Reilly and Pollock, 1996). 

Summary and Conclusions

A groundwater-flow model that was constructed in 2009 

was updated to reflect recent (2011–12) pumping conditions 

in the Tri-County region, which consists of Clinton, Eaton, 

and Ingham Counties, Michigan. The Saginaw aquifer, which 

consists of water-bearing sandstones in the Grand River and 

Saginaw Formations of Pennsylvanian age, is the primary 

source of groundwater for Tri-County residents. As part of 

local wellhead protection area programs, areas contributing 

water to local production wells need to be periodically updated 

because groundwater-flow paths depend in part on the stresses 

to the groundwater-flow system. Different pumping rates or 

pumping locations will change the groundwater-flow patterns 

in the modeled area and result in different zones of contribution and areas contributing recharge to the pumping wells. 

Therefore, for this current (2013) study, withdrawals from 

selected production wells were updated to reflect 2011–12 

pumping conditions, simulated heads and flows under the new 

pumping conditions were compared to measured values, and 

contributing areas to production wells were delineated.

Contributing areas to wells (defined for this study as 

the combination of the areal extent of the areas contributing 

recharge and of the zones of contribution projected up to the 

land surface) were delineated for selected Tri-County region 

production wells by using particle-tracking analysis. Groundwater withdrawals for 2011–12 totaled 46.1 Mgal/d. Results 

of flow simulations indicate that 10-year time-of-travel areas 

cover approximately 19.4 mi2, and 40-year time-of-travel areas 

cover approximately 39 mi2. 
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Luukkonen—Delineation of Contributing Areas to Selected Wells in Ingham County, Michigan—Open-File Report 2014–1054

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20141054