Simulation of Ground-Water Flow, 

Contributing Recharge Areas, and GroundWater Travel Time in the Missouri River 

Alluvial Aquifer near Ft. Leavenworth, 

Kansas 

By Brian P. Kelly 

Prepared in cooperation with the 

U.S. Army Corps of Engineers, 

and the 

U.S. Army 

Scientific Investigations Report 2004–5215 

U.S. Department of the Interior

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

Gale A. Norton, Secretary 

U.S. Geological Survey

Charles G. Groat, Director 

U.S. Geological Survey, Reston, Virginia: 2004 

For sale by U.S. Geological Survey, Information Services


Box 25286, Denver Federal Center


Denver, CO 80225


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Although this report is in the public domain, permission must be secured from the individual copyright owners to repro-


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Suggested citation: 

Kelly, B.P., 2004, Simulation of ground-water flow, contributing recharge areas, and ground-water travel time in the Missouri River alluvial aquifer near Ft. Leavenworth, Kansas: U.S. Geological Survey Scientific Investigations Report 2004– 

5215, 70 p. 
iii 

Contents 

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


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


Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4


Study Area Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4


Hydrogeologic Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4


Physiography and Drainage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4


Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5


Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5


Bedrock and Valley Walls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5


Alluvial Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5


Hydrology and Conceptual Ground-Water Flow Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5


Hydraulic Properties of the Aquifer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5


Aquifer Boundaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12


Rivers and Lakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12


Potentiometric Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14


Alluvial Valley Walls and Bedrock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14


Upstream and Downstream Aquifer Boundaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14


Well Pumping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14


Ground-Water Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15


Simulation of Ground-Water Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15


Model Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15


Boundary and Initial Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21


Parameters and Model Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22


Hydraulic Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24


Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24


Quasi-Steady-State and Transient Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31


Sensitivity Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36


Model Limitations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38


Contributing Recharge Areas and Ground-Water Travel Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44


Pumping- and River-Stage Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45


Iatan Power Plant Well Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47


Weston Well Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47


Leavenworth Well Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53


Ft. Leavenworth Well Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59


Individual wells of the Ft. Leavenworth Well Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59


Hydrologic Controls On Contributing Recharge Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60


Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66


References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

iv 

Figures 

1–9. Maps showing— 

1. 	 Location of well fields, rivers, streams, drains, and lakes in the study area. . . . . . . . . . . . . . . . . . . . .2


2. 	 Location of ground-water contamination sites in the Missouri River 


flood plain at Ft. Leavenworth, Kansas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3


3. 	 Lithologic sections of the Missouri River alluvial aquifer in the study area.. . . . . . . . . . . . . . . . . . . . .6


4. 	 Thickness and extent of the Missouri River alluvial aquifer in the study area. . . . . . . . . . . . . . . . . 13


5. 	 Generalized potentiometric surface map of the Missouri River alluvial


aquifer in the study area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16


6. 	 Thickness of model layers 1 through 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17


7. 	 Parameter zones for recharge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25


8. 	 Parameter zones for model layers 1 through 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26


9. Location of wells in the study area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33


10–15. Graphs showing—


10. 	 Average daily river-stage altitude at St. Joseph, Kansas City, and Sharps Station, 


Missouri, from March 26, 2001, to July 25, 2002. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37


11. 	 Precipitation between March 26, 2001, and July 25, 2002. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38


12. 	 Simulated and observed ground-water levels from April 5, 2001, to 


July 25, 2002, for 13 wells in the study area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39


13. 	 Composite scaled sensitivities for the quasi-steady-state and transient 


calibration simulations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43


14. 	 One-percent scaled sensitivities for selected parameters for the quasi-steady-state


calibration simulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44


15. One-percent scaled sensitivities for selected parameters for the transient 


calibration simulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45


16–18. Maps showing—


16. 	 Simulated contributing recharge areas for each well-pumping/river-stage scenario . . . . . . . . 48


17. 	 Simulated ground-water travel time for each well-pumping/river-stage scenario . . . . . . . . . . . 54


18. 	 Simulated ground-water travel times between FTL-10, FTL-11, and FTL-69 and the 


Ft. Leavenworth well field. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61


Tables 

1.	 Parameter names, types, layer number, zone number, and final value. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22


2.	 Horizontal hydraulic conductivity, transmissivity, and storage data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30


3.	 Horizontal hydraulic conductivities for clay, silt, sand, and gravel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31


4.	 Water-level measurement error sources and maximum error values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32


5.	 Well numbers and simulated and observed ground-water altitudes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34


6.	 Volumetric budget for quasi-steady-state calibration simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36


7.	 Well field, well number, well name, well layer, row, column, and pumping rates used for the 


steady state and transient simulation ground-water flow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46


8.	 Contributing recharge areas for all well fields and all well-pumping/river-stage scenarios. . . . . . . . . 53


9.	 Contributing recharge areas for individual Ft. Leavenworth wells for each well-pumping/


river-stage scenario. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

v 

Conversion Factors and Datum


Multiply By To obtain 

Length 

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi) 

Area 

square meter (m2) 10.76 square foot (ft2) 

square kilometer (km2

) 0.3861 square mile (mi2) 

Volume 

cubic meter (m3

) 0.0008107 acre-foot (acre-ft) 

Flow rate 

meter per day (m/d) 3.281 foot per day (ft/d) 

cubic meter per second (m3

/s) 35.31 cubic foot per second (ft3/s) 

cubic meter per day (m3/d) 35.31 cubic foot per day (ft3/d) 

cubic meter per day (m3/d) 264.2 gallon per day (gal/d) 

cubic meter per day per square gallon per day per square mile 

kilometer [(m3

/d)/km2] 684.28 [(gal/d)/mi2] 

cubic meter per second (m3/s) 22.83 million gallons per day (Mgal/d) 

cubic meter per day per square million gallons per day per square mile 

kilometer [(m3/d)/km2] 0.0006844 [(Mga/d)/mi2] 

Hydraulic conductivity 

meter per day (m/d) 3.281 foot per day (ft/d) 

Transmissivity* 

meter squared per day (m2

/d) 10.76 foot squared per day (ft2/d) 

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: 

°F = (1.8 x °C) + 32 

Altitude, as used in this report, refers to distance above the National Geodetic Vertical Datum of 

1929 (NGVD of 1929)—a geodetic datum derived from a general adjustment of the first-order 

level nets of both the United States and Canada, formerly called Sea Level Datum of 1929. 

*Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times 

foot of aquifer thickness [(ft3/d)/ft2]ft. In this report, the mathematically reduced form, foot 

squared per day (ft2/d), is used for convenience.
Simulation of Ground-Water Flow, Contributing Recharge 

Areas, and Ground-Water Travel Time in the Missouri 

River Alluvial Aquifer near Ft. Leavenworth, Kansas 

By Brian P. Kelly 

Abstract 

The Missouri River alluvial aquifer near Ft. Leavenworth, 

Kansas, supplies all or part of the drinking water for Ft. Leavenworth; Leavenworth, Kansas; Weston, Missouri; and cooling 

water for the Kansas City Power and Light, Iatan Power Plant. 

Ground water at three sites within the alluvial aquifer near the 

Ft. Leavenworth well field is contaminated with trace metals 

and organic compounds and concerns have been raised about 

the potential contamination of drinking-water supplies. In 2001, 

the U.S. Geological Survey, U.S. Army Corps of Engineers, and 

the U.S. Army began a study of ground-water flow in the Missouri River alluvial aquifer near Ft. Leavenworth. 

Hydrogeologic data from 173 locations in the study area 

was used to construct a ground-water flow model (MODFLOW-2000) and particle-tracking program (MODPATH) to 

determine the direction and travel time of ground-water flow 

and contributing recharge areas for water-supply well fields 

within the alluvial aquifer. The modeled area is 28.6 kilometers 

by 32.6 kilometers and contains the entire study area. The 

model uses a uniform grid size of 100 meters by 100 meters and 

contains 372,944 cells in 4 layers, 286 columns, and 326 rows. 

The model represents the alluvial aquifer using four layers of 

variable thickness with no intervening confining layers. 

The model was calibrated to both quasi-steady-state and 

transient hydraulic head data collected during the study and 

ground-water flow was simulated for five well-pumping/riverstage scenarios. The model accuracy was calculated using the 

root mean square error between actual measurements of 

hydraulic head and model generated hydraulic head at the end 

of each model run. The accepted error for the model calibrations 

were below the maximum measurement errors. The error for the 

quasi-steady-state calibration was 0.82 meter; for the transient 

calibration it was 0.33 meter. 

The shape, size, and ground-water travel time within the 

contributing recharge area for each well or well field is affected 

by changes in river stage and pumping rates and by the location 

of the well or well field with respect to the major rivers, alluvial 

valley walls, and other pumping wells. The shapes of the simulated contributing recharge areas for the well fields in the study 

area are elongated in the upstream direction for all well-pumping/river-stage scenarios. The capture of ground water by the 

pumping wells as it moved downgradient toward the Missouri 

River caused the long up-valley extent of the contributing 

recharge areas. Recharge to the Iatan and Weston well fields 

primarily is from precipitation and surface runoff from the surrounding uplands because the contributing recharge area does 

not intersect the Missouri River for any well-pumping/riverstage scenarios. Recharge to the Leavenworth and Ft. Leavenworth well fields is from precipitation, surface runoff from the 

surrounding uplands, and the Missouri River because the contributing recharge area intersects these boundaries for all wellpumping/river-stage scenarios. 

Particle tracking analysis indicated ground water from the 

three contaminated sites was captured by the Ft. Leavenworth 

well field for all well-pumping/river-stage scenarios. Groundwater travel times to the Ft. Leavenworth well field for average 

well-pumping/river-stage scenario ranged from about 33 years 

for the closest contamination site to about 71 years for the farthest contamination site. Ground-water flow was induced below 

the Missouri River by the Ft. Leavenworth and Leavenworth 

well fields for all well-pumping/river-stage scenarios. 

Introduction 

The Missouri River alluvial aquifer in the Ft. Leavenworth, Kansas, area supplies all or part of the drinking water for 

Ft. Leavenworth, Kansas; Leavenworth, Kansas; and Weston, 

Missouri. Ft. Leavenworth is located in Leavenworth County, 

and occupies 5,634 acres on the west bank of the Missouri River 

(fig. 1). Currently (2003), Ft. Leavenworth has five operating 

water-supply wells in the Weston Bend meander loop of the 

Missouri River flood plain that pump 1.5 million gallons per 

day and are a reliable source of drinking water. Cooling water 

is supplied for the Kansas City Power and Light, Iatan Power 

Plant from the Iatan well field. 

The United States Army Installation Restoration Program 

(IRP) under the Defense Environmental Restoration Program is 

for investigation and cleanup of hazardous waste at Department 

of Defense sites. Previous IRP investigations have discovered 

contaminated sites (Solid Waste Management Units) at Ft. 

Leavenworth (Ecology and Environment, Inc., 2000). Each 

Solid Waste Management Unit is referred to as a Ft. Leaven-
2 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas
Introduction 3

worth site (FTL). The presence of ground-water contamination 

at three former fire training areas, (FTL-10, FTL-11, and FTL69) within the river bend (fig. 2), and inundation of the existing 

supply wells by the Missouri River during the flood of 1993, 

have raised concerns about the future reliability of the existing 

drinking water supply at Ft. Leavenworth. 

In 2001, three large public-water-supply well fields in the 

study area were supplied by the Missouri River alluvial aquifer, 

and to a lesser extent, the adjoining alluvial aquifer of the Platte 

River. These are the only aquifers in the study area that can supply large quantities of ground water for public and industrial 

use. Ground-water contamination at FTL-10 and FTL-11 and 

potential ground-water contamination by diesel fuel at FTL-69 

pose a potential threat to the existing public-water-supply well 

field and other nearby public-water-supply well fields. Therefore, in 2001, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army Corps of Engineers and the U.S. Army, 

began a study of ground-water flow in the Missouri River alluvial aquifer near Ft. Leavenworth.

The overall objective of this study was to characterize 

ground-water flow in the Missouri River alluvial aquifer in sup-
4 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

port of the IRP at Ft. Leavenworth, Kansas. Specific objectives 

of the project were: 

1.	 Determine simulated ground-water levels and the direction 

of ground-water flow in the Missouri River alluvial aquifer 

at Ft. Leavenworth under steady state and transient conditions. 

2.	 Determine the travel time and the simulated zone of contribution to the existing public-water-supply well fields 

under several combinations of pumping and river-stage 

conditions. 

3.	 Simulate ground-water flow direction and travel time from 

FTL-10, FTL-11, and FTL-69 to the Ft. Leavenworth well 

field for average yearly well pumping and average annual 

river stage and rainfall conditions. 

Area FTL-10 operated from the 1950s to 1980, and area 

FTL-11 operated from 1980 to 1989. Both areas were used to 

store drummed flammable and hazardous waste materials 

before their use in fire training areas. During fire training exercises, the waste material was placed on the ground and burned. 

Soil samples from previous investigations between 1989 and 

1999 at FTL-10 indicate the presence of arsenic, beryllium, and 

1,1-dichloroethylene. Ground-water samples at FTL-10 

detected benzene, toluene, ethyl benzene, trichloroethylene, 

dichloroethane, carbon tetrachloride, arsenic, and nickel. Soil 

samples from FTL-11 obtained in 1992 indicate the presence of 

Di-n-octylphthalate, a semi-volatile compound, barium, cadmium, and mercury. Analysis of ground-water samples indicated the presence of chromium, lead, iron, manganese, and 

sodium. Area FTL-69 was built in the 1950s and was used to 

house diesel generators for nearby radio transmitters. A 30,000-

gallon diesel fuel storage tank was buried to the south of the 

building. The building was abandoned in the early 1970s and 

the tank was removed in July 1991. Diesel contamination was 

detected under the floor slab of the building at FTL-69 in February 1999 during demolition (Ecology and Environment, Inc., 

2000). 

Purpose and Scope 

The purpose of this report is to describe the development, 

calibration, and results of a ground-water flow model of the 

Missouri River alluvial aquifer near Ft. Leavenworth, Kansas. 

The simulated results of five pumping-rate and river-stage scenarios are presented and include low pumping rates, average 

river stage; high pumping rates, average river stage; average 

pumping rates, average river stage; average pumping rates, low 

river stage; and average pumping rates, high river stage. The 

contributing recharge area (CRA) to each well field and related 

ground-water travel times at various distances from each public-water-supply well field are presented for each scenario as 

well as ground-water flow direction and travel time from FTL10, FTL-11, and FTL-69 to the well fields for average yearly 

well pumping and average annual river stage and rainfall conditions. For this report, the Missouri River alluvial aquifer 

includes the alluvial aquifer adjacent to the Platte River in the 

study area. 

The International System of Units is used in this report. 

However, locations along the Missouri River are identified by 

river miles to allow readers to easily identify Missouri River 

locations. Data collected for this study during 2001 and 2002 

include hourly water levels from 13 monitoring wells installed 

in 2001, rates of ground-water pumpage from public-water-supply well fields located in the study area, daily rainfall amounts, 

and concurrent river stages for the Missouri and Platte Rivers. 

Study Area Description 

The approximately 202-km2 (square kilometer) study area 

(fig. 1) extends from approximately 10.3 km (kilometers) north 

of the Leavenworth-Atchison County line in Kansas near Missouri River mile 418 to approximately 4.8 km south of the 

mouth of the Platte River in Missouri near Missouri River mile 

388. The study area is bounded by the Missouri River alluvial 

valley walls on the east and west. Part of the alluvial valley of 

the Platte River is included. Parts of Atchison and Leavenworth 

Counties in Kansas and Platte County in Missouri lie within the 

study area. The boundary of the study area is the boundary of 

the ground-water flow model. The southern boundary overlaps 

the northern boundary of a ground-water model constructed for 

the Missouri River alluvial aquifer in the Kansas City metropolitan area (Kelly, 1996). Land use in the study area is row-crop 

agriculture or undeveloped land. Small parts of the flood plain 

at Ft. Leavenworth and the Iatan Power Plant are industrial. 

Hydrogeologic Framework 

Water-level data for the Missouri River alluvial aquifer 

were collected from 13 monitoring wells installed at the beginning of the study, wells with historical water-level data obtained 

from the U.S. Geological Survey National Water Information 

System (NWIS), and well installation forms from the Kansas 

Department of Health and Environment and Missouri Department of Natural Resources. Hydrogeologic data from numerous 

geologic and hydrologic investigations within the study area 

also were compiled. The description of the hydrogeologic 

framework of the study area is based on a literature review of 

the following reports: Fischel, 1948; Fischel and others, 1953; 

Emmett and Jeffery, 1969; Gann and others, 1973; Hasan and 

others, 1988; Kelly and Blevins, 1995; Kelly, 1996; and Ecology and Environment, Inc., 2000. 

Physiography and Drainage 

The Missouri River alluvial valley is flat within the study 

area. However, highway embankments, levees, and some construction activities have raised the surface of the alluvial valley 

in developed areas. Total relief within the study area is about 24 
5 

m (meters), with the highest elevations about 250 m above 

National Geodetic Vertical Datum (NGVD) of 1929 in the north 

and adjacent to the valley walls, and the lowest elevations about 

226 m above NGVD of 1929 in the southeast and near the Missouri River. The major tributary to the Missouri River within 

the study area is the Platte River, but numerous smaller streams 

and constructed agricultural drains and ditches also drain into 

the Missouri River. Low-lying areas collect surface runoff during wet periods and standing water may remain for some time 

where soils are poorly drained. 

The Missouri River is too small to have eroded the valley 

in which it flows (Grannemann and Sharp, 1979). Changes in 

discharge, sediment load, and base level during glacial and 

interglacial stages have caused the width, meander wavelength, 

and meander length of the Missouri River valley to be larger 

than that typically formed by a river the size of the present-day 

Missouri River. Consequently, the Missouri River is an underfit 

stream. 

Climate 

The humid continental climate of the study area is characterized by large variations and sudden changes in temperature 

and precipitation. The average high temperature in July, the hottest month of the year, is 26 °C (degrees Celsius), and the average high temperature in January, the coldest month, is 2.3 °C 

(Hasan and others, 1988). Average annual precipitation ranges 

from about 0.86 m in the north to about 0.89 m in the east of the 

study area. About 70 percent of precipitation falls during the 

growing season from April to October (Bevans and others, 

1984). 

Geology 

The Missouri River and Platte River flood plains are 

underlain by alluvial deposits of Quaternary age consisting of 

clay, silt, sand, gravel, cobbles, and boulders (Emmett and Jeffery, 1969; Kelly and Blevins, 1995). These deposits form the 

alluvial aquifer discussed in the “Hydrology and Conceptual 

Ground-Water Flow Model” section. The nature and extent of 

the alluvial deposits have been greatly influenced by glacial 

processes that caused numerous changes in discharge, sediment 

load, and the course of these rivers with time. The present 

course of the Missouri River approximates the southern-most 

limit of continental glaciation. Previous investigations of the 

geology and geologic history of the study area include Fischel 

(1948); Fischel and others (1953); Hasan and others (1988). 

Bedrock and Valley Walls 

The Pennsylvanian age shale, limestone, sandstone, siltstone, conglomerate, coal, and clay define the bottom and walls 

of the alluvial aquifer. The altitude of the bedrock surface 

underlying the alluvial aquifer, as determined from existing 

Hydrology and Conceptual Ground-Water Flow Model 

borehole and well data, is bowl- or pan-shaped in cross section 

with steeply sloping sides and a flat bottom (fig. 3). Typical 

depth to bedrock is between 25 and 30 m. 

Alluvial Deposits 

The uppermost fine-grained clays, silty clays, and clayey 

silts are recent (Holocene) alluvial deposits and the lower 

coarse sands, gravels, cobbles, and boulders are Wisconsinian 

age alluvial deposits of glacial origin (Hasan and others, 1988). 

Although grain size typically increases with depth, this grainsize distribution in locally heterogeneous deposits can be 

reversed. Lithologic sections for five locations in the study area 

were developed from existing well-cutting descriptions and 

borehole log data to illustrate the shape of the alluvial aquifer 

and the extent and lithology of the alluvial deposits. 

Lithologic sections A-A’, B-B’, C-C’, D-D’, and E-E’ (fig. 

3) show the alluvial deposits of the Missouri River. The typical 

grain-size distribution includes several meters of clay and silt at 

the surface, a thick layer of sand and gravelly sand in the middle, and a thin layer of sandy-gravel, gravel, and boulders at the 

base of the aquifer. 

Hydrology and Conceptual Ground-Water 

Flow Model 

Ground-water flow in the Missouri River alluvial aquifer 

is affected largely by the hydraulic properties of the aquifer 

material, the areal extent and thickness of the aquifer, the stage 

of the Missouri River and its major tributaries, and water flow 

across the boundaries of the aquifer. These properties were used 

to construct a conceptual model of ground-water flow that 

describes the internal and external boundaries of the groundwater flow system, the inflow and outflow of water at each of 

these boundaries, and the effect each boundary has on groundwater flow in the aquifer. The conceptual model identifies the 

hydrologic processes that need to be simulated in a properly 

constructed numerical ground-water flow model. 

Hydraulic Properties of the Aquifer 

Ground water exists in the small openings between the particles of clay, silt, sand, and gravel that make up the alluvial 

deposits of the aquifer. The percent of the total volume of the 

aquifer occupied by these openings, or pores, is called the 

porosity. Typical porosity values for alluvial deposits are 40 to 

70 percent for clays, 35 to 50 percent for silts, 25 to 50 percent 

for sands, and 25 to 40 percent for gravels (Freeze and Cherry, 

1979). 

The total maximum volume of ground water in the fully 

saturated Missouri River and Platte River alluvial aquifer in the 

study area can be estimated by multiplying the saturated volume 

of the aquifer by the porosity. Assuming the aquifer is saturated 
6 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas
Hydrology and Conceptual Ground-Water Flow Model 7 
8 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 
Hydrology and Conceptual Ground-Water Flow Model 9 
10 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 
Hydrology and Conceptual Ground-Water Flow Model 11 
12 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

from land surface to bedrock and an average porosity of 30 percent in the saturated aquifer volume of 4.29 x 109 m3

 (cubic 

meters), the volume of water in the alluvial aquifer in the study 

3 area is approximately 1.29 x 10 9 m . 

The porosity determines the total volume of water the 

aquifer can hold but does not determine how much water may 

be obtained from the aquifer for use. The specific yield, the storage coefficient in an unconfined aquifer, is a measure of the 

ratio of the volume of water that will drain because of gravity to 

the total volume of saturated aquifer. For this alluvial aquifer 

the specific yield usually is between 0.15 and 0.2 (Emmett and 

Jeffery, 1969). The maximum volume of water that can be 

obtained from an unconfined aquifer is estimated by the product 

of the saturated volume and specific yield of the aquifer. Using 

a fully saturated aquifer from land surface to bedrock and a specific yield of 0.2, the maximum volume of water available from 

the alluvial aquifer in the study area is approximately 8.58 x 108 

m3. The aquifer is confined by a clay layer in some areas. In 

these areas the volume of available water is determined by the 

storage coefficient. The storage coefficient is about 0.001 for 

this aquifer under confined conditions (Emmett and Jeffery, 

1969). 

The hydraulic conductivity is the capacity of the aquifer to 

transmit water and is measured as the volume of water at the 

existing kinematic viscosity that will move in unit time under a 

unit hydraulic gradient through a unit area at a right angle to the 

direction of flow. Reported horizontal hydraulic conductivity 

values for the aquifer as measured by aquifer tests in the study 

area are between 1 m/d (meter per day) and 300 m/d (Ecology 

and Environment, Inc., 2000). Transmissivity is the rate at 

which water of the prevailing kinematic viscosity is transmitted 

through a unit width of an aquifer under a unit hydraulic gradient, and equals the hydraulic conductivity multiplied by the 

thickness of the aquifer. Reported transmissivity values are 

between 5 m2

/d (meter squared per day) and 7,400 m2/d (Fischel, 1948; Emmett and Jeffery, 1969). The thickness and 

extent of the alluvial aquifer in the study area are shown in figure 4. The greatest aquifer thickness is about 40 m, but average 

thickness is about 25 m. 

recharge is zero and the alluvial valley walls and the bedrock 

base where the rock is of very low permeability compared to the 

permeability of the alluvial aquifer. 

Rivers and Lakes 

The fluctuation of river stage in the Missouri and Platte 

Rivers has a large effect on ground-water levels in the study 

area. Bean Lake, Horseshoe Lake, and other smaller lakes and 

ponds also affect ground-water levels. An increase in river stage 

with respect to the altitude of the potentiometric surface causes 

water to flow from the river into the aquifer and the altitude of 

the potentiometric surface to increase. A decrease in river stage 

with respect to the potentiometric surface causes water to flow 

from the aquifer into the river and the altitude of the potentiometric surface to decrease. The magnitude of the change in the 

potentiometric surface altitude in response to river stage fluctuations depends on the magnitude of the change in river stage, 

the length of time the river remains at the current river stage, the 

hydraulic properties of the aquifer material, and the distance 

from the river to the point of interest (Grannemann and Sharp, 

1979). The potentiometric surface increases or decreases in altitude in response to increases or decreases in river stage more 

rapidly in areas closer to the river because of the time required 

for the change to propagate into and through the aquifer. Therefore, the area of the aquifer that is affected by an increase or 

decrease in river stage depends on the length of time that the 

river stage remains at the new altitude. Changes in the altitude 

of the potentiometric surface at distant locations from the river 

are the result of long term river-stage changes typically caused 

by seasonal high and low flows or long-term river-stage management. 

The Missouri River has large streambed hydraulic conductivities. The bottom of the river channel is below the top of the 

potentiometric surface, and therefore river stage changes have a 

large effect on ground-water flow. The Missouri River streambed deposits typically are composed of sand and gravel and 

the channel bottom penetrates through the silt-clay cap and into 

the sand and gravel in the middle depths of the aquifer (fig. 3). 

Thus, the Missouri River is well connected hydraulically to the 

Aquifer Boundaries 

The Missouri River alluvial aquifer is bounded at the top 

by the water table, laterally by the alluvial valley walls, and at 

the base by bedrock. The Missouri River alluvial aquifer 

extends for hundreds of kilometers upstream and downstream 

from the study area and arbitrary boundaries were established at 

the upstream and downstream edges of the study area. Water 

flows into or out of the aquifer through the river beds of the Missouri and Platte Rivers and at pumping wells. The potentiometric surface is defined by the level to which water will rise in 

tightly cased wells from a reference level. In an unconfined 

aquifer the potentiometric surface is the water table and is the 

boundary where recharge from precipitation enters the aquifer. 

No-flow boundaries include the potentiometric surface where 

underlying alluvial aquifer. 

The Platte River, and other smaller streams, have less 

affect on ground-water flow than the larger Missouri River. 

These rivers have smaller streambed hydraulic conductivities 

and locally, the bottoms of the river channels can be above the 

top of the potentiometric surface. Streambed deposits of the 

Platte River typically are composed of finer grained sand, clay, 

and silt compared to streambed deposits of the Missouri River, 

and the bottom of the channels intersects the finer grained alluvial deposits located at shallower depths. Thus, these rivers are 

poorly connected to the underlying alluvial aquifer, but can 

have some effect on ground-water flow. 

Numerous smaller streams and drainage ditches are 

present in the study area. During most of the year the bottom of 

these streams are above the top of the potentiometric surface 
Hydrology and Conceptual Ground-Water Flow Model 13
14 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

and have less affect on ground-water flow than larger streams. 

These smaller streams and ditches have low or intermittent discharges that supply small amounts of recharge to the aquifer 

during the year. However, these smaller streams may affect 

ground-water flow locally during floods when they supply 

recharge to the aquifer or during periods when the potentiometric surface rises above the stream stage and the aquifer drains 

into the streams. 

Bean Lake and Horseshoe Lake are oxbow lakes. Lake 

bottom deposits of oxbow lakes typically are composed of clays 

and silts of low hydraulic conductivity. Lakes recharge the aquifer when the potentiometric surface is below the lake level, but 

drain the aquifer when the potentiometric surface is above the 

lake level. This recharge volume typically is small, however, 

because of the low hydraulic conductivity of the lake bottom 

deposits. Water levels in other small lakes are affected by 

increases or decreases in the potentiometric surface altitude that 

cause a corresponding increase or decrease in lake water levels. 

These lakes may be areas of increased recharge because they 

collect surface runoff. 

Potentiometric Surface 

The potentiometric surface is the boundary across which 

recharge from precipitation flows into the aquifer. Areally distributed recharge occurs when the rate of precipitation or snow 

melt exceeds the rate of evapotranspiration from the soil and 

water flows into the aquifer. During periods of high rates of 

recharge, the potentiometric surface altitude increases because 

the aquifer is gaining water. When recharge rates are low, the 

potentiometric surface altitude decreases as water drains out of 

the aquifer. 

Total annual precipitation for the area ranges from 0.86 to 

0.89 m and occurs mainly during the growing season between 

April and October (Hasan and others, 1988). Recharge has been 

estimated in two previous studies to be between 2 and 25 percent of precipitation (Fischel and others, 1953; Hedman and 

Jorgensen, 1990). Recharge to the alluvial aquifer in the study 

3 area from precipitation is about 4.045 x 107

 m per year, assuming about 0.2 m of recharge per year (22.5 percent of 0.89 m 

precipitation). 

Topography generally has little affect on the areal distribution of recharge, although low-lying areas in the study area may 

have larger recharge rates caused by collected runoff. Rather, 

the vertical hydraulic conductivity of soils directly controls the 

rate of infiltration in most areas. Aquifer recharge is greater 

beneath ponded areas or soils with larger vertical hydraulic conductivities than beneath soils with a smaller vertical hydraulic 

conductivities. Therefore, soil variability affects the areal distribution of recharge to the aquifer. 

Alluvial Valley Walls and Bedrock 

The alluvial valley walls form the lateral boundary of the 

alluvial aquifer. Bedrock forms the lower boundary of the alluvial aquifer. Ground-water flow between the alluvial aquifer 

and bedrock has not been quantified. However, bedrock units 

have estimated hydraulic conductivities between 0.003 and 3 

m/d and very slow rates of water flow (Gann and others, 1973). 

This range of hydraulic conductivity is between 10 and 10,000 

times lower than the range for the alluvial aquifer. Consequently, flow between the aquifer and the valley walls and bedrock is considered to be low in comparison to the total flow of 

ground water in the aquifer. 

Upstream and Downstream Aquifer Boundaries 

The Missouri River alluvial aquifer extends the length of 

the Missouri River. The alluvial aquifer of the Platte River also 

extends beyond the study area. The upstream and downstream 

boundaries of the study area are not physical hydraulic boundaries, but were chosen based on the study objectives and area of 

interest. Ground water flows into the system through the 

upstream boundaries of the study area and flows out of the system through the downstream boundaries of the study area. The 

ground-water flow rate across the boundary depends on the 

direction of ground-water flow with respect to the boundary, the 

hydraulic conductivity of the material at the boundary, the gradient of the potentiometric surface at the boundary, and the 

thickness of the aquifer at the boundary. When the direction of 

ground-water flow is parallel to the boundary, no ground water 

crosses the boundary. The upstream and downstream boundaries were chosen to be located at some distance from the area 

of interest to minimize their effect on the study results. 

Well Pumping 

In 2003, three public-water-supply well fields (Weston, Ft. 

Leavenworth, and Leavenworth) and one industrial well field 

(Kansas City Power and Light, Iatan Power Plant) were in operation in the study area. Water pumped from the alluvial aquifer 

in the study area by public-water-supply well fields in 2003 

totalled 21,439 m3

/d (cubic meters per day) (7,825,235 m3 per 

year) (S. Wood, U.S. Army, written commun., 1997; D. 

Masoner, City of Weston, Missouri, written commun., 2000; D. 

Murphy, City of Leavenworth, written commun., 2000; H. 

Sweet, Kansas City Power and Light, Iatan Power Plant, written 

commun., 2000). Recharge from precipitation supplies about 

4.045 x 107

 m3 of water per year to the aquifer; the volume of 

stored water available for use at any one time is about 8.58 x 108 

m3

. Therefore, about 19 percent of annual recharge supplied to 

ground water from precipitation and a maximum of about 0.9 

percent of the ground water stored in the aquifer was withdrawn 

in 2003 by public-water-supply well fields. However, the actual 

percent of ground water removed was less because wells 

located close to the Missouri River can obtain a large part of 

their water from recharge induced from the river. 

Withdrawal of water from the aquifer by well pumping 

creates cones of depression on the potentiometric surface 

around each well or well field and causes ground water to flow 
------ ------ ------ ------

Simulation of Ground-Water Flow 15 

W is a volumetric flux per unit volume 

and represents sources or sinks, or 

both, of water, such as well discharge, 

leakage through confining units, 

streambed leakage, recharge, and 

water removed from the aquifer by 

drains, per day; 

Ss is the storage coefficient of the porous 

material, per meter; and 

t is time, in days. 

The flow equation was solved by the Link-AMG method 

(Mehl and Hill, 2001), a method for solving matrix equations 

using an algebraic multigrid solver. 

Three-dimensional simulation of ground-water flow in the 

alluvial aquifer was necessary to accurately determine the 

hydraulic-head distribution beneath the larger rivers and around 

the multiple well fields in the study area. Discharge from the 

aquifer to rivers may vary according to river size or depth of the 

streambed. Ground-water flow may be divided into smaller 

flow subsystems because of the degree of interaction between 

ground water, the well fields, and the larger and smaller rivers 

in the study area. Three-dimensional simulation also is necessary in the analysis of ground-water travel times and the contributing recharge area around each pumping well field because 

of the vertical flow of ground water caused by well pumping. 

Also, pumping from the well fields located near the Missouri 

River can induce recharge from the river and cause groundwater flow beneath the river. 

Model Description

 The modeled area is 28.6 by 32.6 km and contains the 

entire study area shown in figure 1. The model uses a uniform 

grid size of 100 m by 100 m and contains 372,944 cells in 4 layers, 286 columns, and 326 rows. The irregular shape of the 

study area reduced the number of active cells in the model to 

toward the wells. A cone of depression generally has the shape 

of an inverted cone with the lowest part centered at the pumping 

well. Most water recharging the Missouri River alluvial aquifer 

comes from surface recharge from precipitation or recharge 

from the Missouri River. 

Ground-Water Movement 

In the absence of pumping, ground-water flow within the 

alluvial aquifer typically is away from the valley walls, toward 

the Missouri River, and down the river valley (Emmett and Jeffery, 1969; Kelly and Blevins, 1995). A sudden increase in river 

stage can temporarily reverse the direction of ground-water 

flow near the river. Flooding, irrigation, well pumping, and 

dewatering during construction also can alter ground-water 

flow directions. Historic water levels, average historic water 

levels when more than one measurement was available for a 

particular well, and average water levels of wells with multiple 

or continuous measurements obtained during this study were 

used to develop a potentiometric surface map to illustrate the 

general flow of ground water down the river valley and toward 

the Missouri River (fig. 5). 

Simulation of Ground-Water Flow 

Ground-water flow was simulated for the Missouri River 

alluvial aquifer using the three-dimensional finite-difference 

ground-water flow model MODFLOW-2000 (Harbaugh and 

others, 2000). MODFLOW-2000 is a modified version of 

MODFLOW (McDonald and Harbaugh, 1988) that incorporates the use of parameters to define model input, the calculation of parameter sensitivities, and the modification of parameter values to match observed heads, flows, or advective 73,132, with 20,412 active cells in layer 1; 19,723 active cells 

in layer 2; 18,622 active cells in layer 3; and 14,375 active cells transport using the observation, sensitivity, and parameter-estimation processes described by Hill and others (2000). 

The equation used in the computer model to describe 

in layer 4. The regular grid spacing facilitated data input from a 

Geographic Information System (GIS) and analysis of model 

ground-water flow is: 

∂ ∂ ∂ -----⎛Kxx∂h⎞ + -----⎛Kyy∂h⎞ + -----⎛Kzz ∂h⎞ – W = Ss∂h 

∂x⎝ ∂x⎠ ∂z⎝ ∂y⎠ ∂z⎝ ∂z⎠ ∂t 

where 

Kx, Ky, and Kz 	 are the values of hydraulic 

conductivity along the x, y, and z 

coordinate axes and are assumed to be 

parallel to the major axes of hydraulic 

conductivity, in meters per day; 

h 	 is the potentiometric head, in meters; 

output by the GIS, and the grid size minimized errors in flowpath analysis that would be caused by a large grid size (Pollock, 

1994; Zheng, 1994). 

The model represents the alluvial aquifer using four layers, 

numbered 1 to 4, of variable thickness with no intervening confining layers. Layer thicknesses are shown in figure 6. Layer 1 

corresponds to the upper part of the aquifer where clays, silts, 

and finer-grained sands are dominant. The thickness of layer 1 

is adequate to account for the anticipated range of water-level 

variation within the aquifer during ground-water flow simulation and was modeled using both confined- and unconfinedaquifer hydraulic properties. Layers 2 and 3 correspond to the 

middle part of the aquifer where sand and gravelly sands predominate. These layers were not anticipated to dewater during 

the simulations and were modeled using confined aquifer 
16 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas
Simulation of Ground-Water Flow 17
18 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas
Simulation of Ground-Water Flow 19
20 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas
hydraulic properties. Layer 4 corresponds to the deep parts of 

the aquifer where gravels and sandy gravels are present and also 

was modeled using confined-aquifer hydraulic properties. 

Boundary and Initial Conditions 

Boundaries include rivers and lakes, the potentiometric 

surface, alluvial-valley walls and bedrock, edges of the study 

area, and pumping wells. The ground-water flow model simulates each of these boundaries as a specified head boundary, a 

specified flow boundary, a head-dependent flow (mixed boundary) condition, or a free-surface boundary (Franke and others, 

1984). A specified-head boundary is used where the hydraulic 

head is maintained at a specified value as a function of time and 

position and ground-water flow across the boundary varies with 

respect to the difference in head between the boundary and the 

aquifer. A specified-flow boundary is used where the volume of 

water that flows across the boundary is a function of time and 

position and head varies as a function of flow. A headdependent flow mixed boundary is used where the volume of 

flow across the boundary varies as a function of head at the 

boundary and varies as head varies. A free-surface boundary is 

used where the position of the boundary is not fixed but varies 

with time. 

The Missouri and Platte Rivers, Bee Creek, and Bean, 

Iatan, Mud, and Horseshoe Lakes are represented in the model 

as head-dependent flow boundaries. For each cell in the model 

where a river or lake affects ground-water flow, the altitude of 

the river or lake stage must be assigned. Flow into or out of the 

aquifer at each of the cells where a river or lake is simulated is 

a function of the river or lake stage with respect to the altitude 

of the potentiometric surface, the hydraulic conductivity of the 

streambed or lakebed material, the cross-sectional area of flow 

between the river or lake bed and the aquifer, and the altitude of 

the potentiometric surface with respect to the altitude of the 

streambed or lakebed (McDonald and Harbaugh, 1988). 

River stage in the Missouri and Platte Rivers was recorded 

hourly at nearby gaging stations at St. Joseph, Kansas City, and 

Sharps Station (fig. 1). The river stage used in each simulation 

was assigned by interpolation of the specified river stage 

between gaging stations along the midline of each river to each 

model cell that contained a river. River stage in the Platte River 

was interpolated along the midline of the river between the gaging station at Sharps Station and the Missouri River stage at the 

Platte River mouth. River stage in the ungaged Bee Creek was 

estimated using Missouri River stage at the mouth of Bee Creek 

and the slope of the land surface and interpolated along the midline of Bee Creek to the edge of the study area. 

The shallower parts of the Missouri River channel located 

near the banks of the river correspond to the clay and silt found 

in layer 1 of the model. The channel bottom of the Missouri 

River intersects the sand and gravel found in the middle of the 

aquifer that corresponds to layer 2 of the model. Therefore, the 

bottom of the Missouri River was placed in layer 1 for model 

cells near the banks of the river and in layer 2 for model cells 

Simulation of Ground-Water Flow 21 

representing the deeper main channel of the river. The channel 

bottoms of the smaller Platte River and Bee Creek are within 

layer 1 of the model because they are shallower than the bottom 

of the Missouri River and intersect the shallower clay and silt in 

the upper parts of the aquifer. The effect on ground-water flow 

by lake stage in Bean, Iatan, Mud, and Horseshoe Lakes is similar to the effect of river stage on ground-water flow, and is simulated in the model with the same equation used for the rivers. 

The lake beds intersect the clay and silt of the upper parts of the 

aquifer and were placed in layer 1 of the model. 

Numerous small ungaged streams and drainage ditches are 

in the study area. These streams can supply small amounts of 

recharge to the aquifer during runoff events and drain the aquifer when the potentiometric surface intersects the stream beds. 

Drainage ditches were constructed to drain agricultural land but 

can provide small amounts of focused recharge during periods 

of high rainfall. These ditches do not receive water from the 

uplands. Because recharge from these ungaged streams and 

ditches is considered to be small compared to drainage, they 

were simulated in the model as drains. Drains are headdependent flow boundaries but, unlike the simulated rivers, 

cannot supply water to the aquifer. Water was removed from the 

aquifer by the drains at a rate proportional to the difference 

between the head in the aquifer and the altitude of the bottom of 

the drain and the hydraulic conductivity of the drain bottom 

material (McDonald and Harbaugh, 1988). Rivers, streams, 

drainage ditches and lakes are shown on figure 1. 

The potentiometric surface, the upper boundary of the alluvial aquifer, was simulated in the model as a free-surface 

boundary and is the boundary across which areally distributed 

recharge enters the aquifer. Recharge to the model is applied to 

the top-most active cell in each vertical column and is varied 

temporally as a function of precipitation. Recharge is estimated 

to be between 2 and 25 percent of precipitation. Precipitation 

was recorded hourly with a rain gage located at Ft. Leavenworth 

between March 28, 2001, and September 26, 2002. 

The alluvial valley walls and bedrock were simulated in 

the model as no-flow boundaries, a form of the specified flow 

boundary. The rate of water flow between the alluvial aquifer 

and the valley walls and bedrock has not been quantified. However, the hydraulic conductivities of the alluvial valley walls 

and bedrock are between 1 and 4 orders of magnitude less than 

hydraulic conductivities in the alluvial aquifer. Therefore, simulating the alluvial valley walls and bedrock as no-flow boundaries is reasonable because the amount of flow is a negligible 

percentage of the total flow. 

Several boundaries of the model do not represent actual 

physical or ground-water flow boundaries of the alluvial aquifer, but are located where the alluvial aquifers of the Missouri 

and Platte Rivers intersect the model boundary. The locations of 

these boundaries were extended as far as practical from areas of 

well pumping to limit boundary effects on model results within 

the anticipated CRAs. Also, the orientation of each boundary 

was set parallel or sub-parallel to the estimated direction of 

ground-water flow at the boundary. This orientation further limits the effects of these boundaries on model results. These 
22 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

boundaries were simulated in the model as general head boundaries, a form of the head-dependent flow boundary that allows 

flow to enter or exit the model proportional to the difference 

between the water level in the model and the water level 

assigned to the boundary multiplied by a conductance term that 

limits the rate of flow (McDonald and Harbaugh, 1988). Water 

levels along the boundary were assigned to each general head 

boundary cell based on the river stage at the boundary plus the 

average gradient of the land surface from the river to the alluvial 

walls multiplied by the distance from the river. 

Pumping wells are internal boundaries of the model where 

water was removed from the model at a specified rate equal to 

the discharge of each well. The total volume of water withdrawn annually from the aquifer by pumping of public-watersupply and industrial wells was obtained from each water supplier when available. The total annual volume of water removed 

from the aquifer by other wells in the study area was obtained 

from the Missouri Department of Natural Resources (2001). 

The depth of each pumping well in the model was based on the 

altitude of the screened interval, when known, or model layer 4 

when the altitude of the screened interval was unknown. 

Parameters and Model Zones 

Parameters are used in the model to represent various 

hydraulic properties of the aquifer. Groups of cells in each layer 

in the model are assigned zones, and a parameter value is associated with each zone or group of zones. These properties 

include horizontal hydraulic conductivity, vertical hydraulic 

conductivity, porosity, specific storage, specific yield, and 

recharge rate. Lithologic descriptions recorded during the 

installation of wells and boreholes are the most numerous and 

have the greatest areal extent of all data types in the study area. 

The distribution of clay, silt, sand, and gravel within the aquifer 

was used to determine parameter zones among model cells for 

horizontal hydraulic conductivity, vertical hydraulic conductivity, porosity, specific yield, and specific storage. The distribution of clay, silt, sand, and gravel within the top layer of the 

model was used to determine zones for recharge rate as a percent of rainfall. Nomenclature for parameter zones are based on 

the type of parameter, the layer number, and the zone number 

(if more than one zone per layer). For example, the zone designation L3-Z1 denotes the 1st zone in layer 3. The layer number 

and zone number nomenclature is used for hydraulic conductivity parameter names. Parameter names, types, layer and zone 

numbers, and final values, units, and comments are listed in 

table 1. Recharge zones are shown in figure 7. Zones for each 

model layer are shown in figure 8. 

Some parameters represent hydraulic properties that are 

not distributed using zones. These properties include streambed 

Table 1. Parameter names, types, layer number, zone number, and final value. 

[m/d, meter per day; --, not applicable; -, no data available] 

name 

Parameter Zone 

Final 

Parameter parameter

type 

Layer 

number number value Unit Comment 

L1-Z1 Horizontal hydraulic conductivity 1 1 0.5 m/d Porosity is 0.45. 

L1-Z2 Horizontal hydraulic conductivity 1 2 5.0 m/d Porosity is 0.4. 

L1-Z3 Horizontal hydraulic conductivity 1 3 10.0 m/d Porosity is 0.35. 

L2-Z1 Horizontal hydraulic conductivity 2 1 .5 m/d Porosity is 0.45. 

L2-Z2 Horizontal hydraulic conductivity 2 2 5.0 m/d Porosity is 0.4. 

L2-Z3 Horizontal hydraulic conductivity 2 3 10.0 m/d Porosity is 0.35. 

L2-Z4 Horizontal hydraulic conductivity 2 4 50.0 m/d Porosity is 0.35. 

L2-Z5 Horizontal hydraulic conductivity 2 5 80.0 m/d Porosity is 0.3. 

L3-Z1 Horizontal hydraulic conductivity 3 1 10.0 m/d Porosity is 0.45. 

L3-Z2 Horizontal hydraulic conductivity 3 2 50.0 m/d Porosity is 0.35. 

L3-Z3 Horizontal hydraulic conductivity 3 3 120.0 m/d Porosity is 0.35. 

L4-Z1 Horizontal hydraulic conductivity 4 1 30.0 m/d Porosity is 0.4. 

L4-Z2 Horizontal hydraulic conductivity 4 2 120.0 m/d Porosity is 0.35. 
Simulation of Ground-Water Flow 23 

Table 1. Parameter names, types, layer number, zone number, and final value.—Continued 

[m/d, meter per day; --, not applicable; -, no data available] 

Parameter Parameter Layer Zone 


name type number number 


Final 

parameter 

value Unit Comment 

Ratio of horizontal to vertical 


VK1 hydraulic conductivity 1 -- 5 - --


Ratio of horizontal to vertical 


VK234 hydraulic conductivity 2, 3, 4 -- 1 - --


Transient ground-water 


SS1 Specific storage 1 -- .0014 - flow simulation only. 


Transient ground-water 


SY1 Specific yield 1 -- .01 - flow simulation only. 


Transient ground-water 


SS2 Specific storage 2 -- .0013 - flow simulation only. 


Transient ground-water 


SS3 Specific storage 3 -- .0012 - flow simulation only. 


Transient ground-water 


SS4 Specific storage 4 -- .0014 - flow simulation only. 


MRV11 River conductance 1 1 .004 m/d --


MRV12 River conductance 1 2 .004 m/d --


MRV13 River conductance 1 3 .004 m/d --


MRV21 River conductance 2 1 .0085 m/d --


MRV22 River conductance 2 2 .0085 m/d --


Small streams simulated 


STREAMS Drain conductance 1 -- .001 m/d using drain package. 


DRAINS Drain conductance 1 -- .000001 m/d 	 --

Factor to convert gallons per 

minute to cubic meters per 

WELLS Well pumping rate -- 5.3 day. 


Recharge as a 


RECH1 percent of precipitation 1 1 .05 -- --


Recharge as a 


RECH2 percent of precipitation 1 2 5 -- --


Recharge as a 


RECH3 percent of precipitation 1 3 8.5 -- --


Recharge as a 


RECH4 percent of precipitation 1 4 8.5 -- --


PLATTE Streambed conductance 1 -- .001 m/d --


BEE Streambed conductance 1 -- .001 m/d --


Bean Lake Bean Lake simulated using 


BEAN lakebed conductance 1 -- .001 m/d river package. 

--

--

--

-- --

-- --

-- --

-- --

24 

Table 1. 

Final 

Parameter Zone parameter 

name number number 

Iatan Lake Iatan Lake simulated using 

IATAN lakebed conductance 1 river package. 

Mud Lake 

MUD lakebed conductance 1 m/d river package. 

Horseshoe Lake 

HORSE lakebed conductance 1 m/d 

GHB1 1 2.0 

GHB2 2 50.0 

GHB3 3 100.0 

GHB4 4 100.0 

Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

Parameter names, types, layer number, zone number, and final value.—Continued 

[m/d, meter per day; --, not applicable; -, no data available] 

Parameter Layer 

type value Unit Comment 

0.001 m/d 

Mud Lake simulated using 

.001 

Horseshoe Lake simulated 

.001 using river package. 

General head boundary m/d 

General head boundary m/d 

General head boundary m/d 

General head boundary m/d 

conductances, drain conductances, well pumping rates, and rate 

of flow across general head boundaries. Each of these properties 

is distributed within the model using the row and column 

number of each cell. 

Hydraulic Properties 

Hydraulic conductivity or transmissivity data are available 

for 16 locations within or near the study area (table 2). However, locations for which lithologic data are known are more 

numerous and have the widest distribution within the study 

area. Aquifer tests conducted during previous investigations to 

determine hydraulic conductivity or transmissivity typically 

were performed in wells where the lithology and altitude of the 

screened interval were known. 

Hydraulic data were used to associate an initial hydraulic 

conductivity value with a specific lithology for this report. Typical ranges of the hydraulic conductivities of clays, silts, sands, 

and gravels (Freeze and Cherry, 1979; Driscoll, 1986; table 3) 

were used for initial values where hydraulic conductivity data 

were unavailable for a specific lithology. 

Streambed hydraulic conductivity was calculated in 

MODFLOW (McDonald and Harbaugh, 1988) by multiplying 

the hydraulic conductivity of the model cell within each river 

reach by the area of the river within the cell. This value was 

adjusted during model calibration for each river. 

 Drain conductances were calculated in the same manner 

as the streambed conductances. All drain bottoms are within 

layer 1 of the model. The altitude of the drain bottom within 

layer 1 was assigned using a constant altitude of 1 m less than 

the land surface altitude for agricultural ditches or 2 m less than 

the land surface altitude for streams. 

The simulated flow of water between model cells in adjacent model layers is controlled by the vertical conductance 

term. Vertical conductance, or leakance, is calculated within 

MODFLOW from the thickness of each model layer between its 

node and common layer contact and the vertical hydraulic conductivity of each layer (McDonald and Harbaugh, 1988). The 

vertical conductance terms between cells of adjacent layers 

simulate the presence of vertical anisotropy in clay, silt, and fine 

sand deposits. The vertical anisotropy was assumed to decrease 

with depth because of the increase in particle grain size with 

depth. There also is a high probability that fine grained layered 

depositional features such as overbank and channel fill deposits 

have been reworked or removed by erosional and depositional 

processes of the Missouri River. Therefore, the ratio of horizontal hydraulic conductivity to vertical hydraulic conductivity 

between adjacent cells of layers 1 and 2 was 5 to 1. The ratio of 

horizontal hydraulic conductivity to vertical hydraulic conductivity between layers 2, 3, and 4 was 1 to 1. 

A specific yield of 0.01 was used for layer 1. A storage 

coefficient of 0.0014 was used for layer 1, 0.0013 was used for 

layer 2, 0.0012 was used for layer 3, and 0.0013 was used for 

layer 4 and represents conditions where water is released from 

storage because of expansion of the water or compaction of the 

aquifer material and not actual drainage of the aquifer. 

Calibration 

The ground-water flow model was calibrated by adjusting 

model input data and model geometry until model results 

matched field observations within an acceptable level of accuracy (Konikow, 1978). Parameters adjusted during the calibration process include horizontal hydraulic conductivity, vertical 

hydraulic conductivity between model layers, specific storage, 
Simulation of Ground-Water Flow 25
26 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas
Simulation of Ground-Water Flow 27
28 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas
Simulation of Ground-Water Flow 29
-- --

-- --

-- --

-- --

-- --

-- --

30 

Table 2. 

2

Well 

number 

(fig. 1) 

Well 

name 

Aquifer

hydraulic Trans­

(m2

/d) 

63 Environment, Inc., 2000. 

64 Environment, Inc., 2000. 

67 Environment, Inc., 2000. 

70 Environment, Inc., 2000. 

61 Environment, Inc., 2000. 

62 Environment, Inc., 2000. 

71 7 Environment, Inc., 2000. 

56 109 Environment, Inc., 2000. 

57 4 Environment, Inc., 2000. 

65 Slug 37 Environment, Inc., 2000. 

66 Slug 15 Environment, Inc., 2000. 

59 Slug 82 Environment, Inc., 2000. 

60 Slug 9 Environment, Inc., 2000. 

Lewis and Clark 

na State Park Drawdown 126 3,105 Jeffery, 1969. 

Burns and 

na water supply well PW-9 Drawdown 196 5,341 McDonnell, 1998. 

Denne and 

na Sec. 13BAA Drawdown 298 7,452 others, 1998. 

-- --

-- --

-- --

-- --

-- --

-- --

-- --

Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

Horizontal hydraulic conductivity, transmissivity, and storage data. 

[na, not applicable; m/d, meter per day; m /d, meter squared per day; --, no data] 

test 

Horizontal 

conductivity 

(m/d)

missivity Storage 

coefficient Source 

Ecology and 

USGS WELL 1 Slug 92 

Ecology and 

USGS WELL 2 Slug 13 

Ecology and 

USGS WELL 3 Slug 78 

Ecology and 

USGS WELL 4 Slug 95 

Ecology and 

USGS WELL 5 Slug 48 

Ecology and 

USGS WELL 6 Slug 16 

Ecology and 

USGS WELL 7 Slug 

Ecology and 

USGS WELL 8 Slug 

Ecology and 

USGS WELL 9 Slug 

Ecology and 

USGS WELL 10 

Ecology and 

USGS WELL 11 

Ecology and 

USGS WELL 12 

Ecology and 

USGS WELL 13 

Emmett and 

0.17 

Ft. Leavenworth 

T-8 R-22E 

.001 - .004 
Table 3. Horizontal hydraulic conductivities for clay, silt, sand, 

and gravel. 

[Freeze and Cherry, 1979; Driscoll, 1986; m/d, meter per day] 

Lithology Horizontal hydraulic conductivity range, in m/d 

Clay 10-7to 10-4 

Silt 10-4 to 1 

Sand 10-2 to 103 

Gravel 102 to 105 

specific yield, river conductance, drain conductance, and 

recharge rates. 

After each change in one of these parameters, the simulation was run and simulated ground-water levels were compared 

to observed ground-water levels. The model accuracy was calculated using the root mean square (RMS) error between actual 

hydraulic head measurements and model-generated hydraulic 

head at the end of each model run. Model accuracy is increased 

by minimizing the RMS error. The RMS error measures the 

absolute value of the variation between measured and simulated 

hydraulic heads at control points. The equation to calculate the 

RMS error is: 

2 2 2 2 

e + e + e + ... + e 1 2 n RMSerror = -----------------------------3 

--------------------------- n 

where 

e is the difference between measured 

hydraulic heads and the simulated 

hydraulic heads; and 

n is the number of control points. 

The accuracy of water-level measurements was the basis 

for choosing the RMS error used to determine if the model simulation was acceptable. Most ground-water levels were measured with a steel tape or an electric water-level measuring tape 

to the nearest 0.003 m. Hourly ground-water level measurements were measured with vented pressure transducers to the 

nearest 0.003 m. Therefore, the largest error from measurement 

of hourly ground-water levels was 0.003 m. Water levels of 

public-water-supply wells were measured by personnel on site 

using air-line methods. Historical water levels for wells were 

measured or estimated using unknown techniques. For these 

water-level measurements, the accuracy is assumed to be within 

0.3 m.

Another component of the accuracy of the water-level 

measurement is the accuracy of the measuring point altitude. 

The measuring point altitudes for most wells used in this study 

were obtained using standard surveying or global positioning 

system methods. The accuracy of these altitudes are between 

Simulation of Ground-Water Flow 31 

0.01 and 0.15 m. The measuring point altitude of a few wells in 

the study area were estimated from 7.5-minute topographic 

maps. The vertical accuracy of land-surface altitudes from these 

maps is one-half of the contour interval. The contour interval on 

topographic maps of the alluvial valley is 5 or 10 feet (1.5 or 3 

m) and the accuracy of measuring point altitudes from these 

wells is 0.75 or 1.5 m, respectively. Therefore, the largest possible error in water level altitudes is 1.5 m. 

Missouri River stage was measured at USGS gaging stations at St. Joseph and Kansas City, and Platte River stage was 

measured at the USGS gaging station at Sharps Station. These 

gages measure river stage to the nearest 0.003 m. River stage 

was distributed among model cells using linear interpolation 

between gages along the midline of each river. Manual measurements of Missouri River stage were made from the Missouri State Highway 45 bridge in 2001 on June 11, August 1, 

September 19, and November 16, and in 2002 on January 9 and 

March 12. These measurements were compared to interpolated 

river stage for the same location to obtain an estimate of the 

accuracy of estimating Missouri River stage using linear interpolation between the St. Joseph and Kansas City gages. The 

largest absolute difference between measured and interpolated 

stage was 0.87 m, and the smallest was 0.11 m; the differences 

ranged from -0.87 to 0.68 m. 

The maximum possible error for water-level measurements is the sum of the maximum errors caused by water-level 

measurement errors, measuring point altitude errors, and errors 

introduced by interpolation of river stage. The chance that the 

maximum error would occur at any well is small. More likely to 

occur is a combination of errors of varying value and sign. 

However, knowledge of these errors and their magnitude is necessary to determine the appropriate RMS error to assess model 

accuracy. The accepted RMS errors for all the model calibrations discussed in the following sections is below the largest 

maximum measurement errors listed in table 4. 

Quasi-Steady-State and Transient Calibration 

The strategy for calibration of the ground-water flow 

model was to use both quasi-steady-state hydraulic head data 

and transient hydraulic head data. Steady-state conditions occur 

when inflow to the system equals outflow from the system. The 

quasi-steady-state calibration was used to test the conceptual 

model of ground-water flow, test the appropriateness of simulated boundary conditions, and obtain approximate transmissivity and recharge arrays in preparation for more rigorous transient calibration. The transient calibration was used to fine tune 

the model hydraulic properties determined for the quasi-steadystate simulation. 

The quasi-steady-state hydraulic head data were obtained 

from the November 16, 2001, ground-water level data measured in the 13 wells installed for this study and from historic 

ground-water level data from 51 wells in the study area. Well 

locations are shown in figure 9 and the well number and model 

simulated and average observed water level of each well used in 

the quasi-steady-state calibration is listed in table 5. The data 
32 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

Table 4. 

error 

Measurement type (m) (m) (m) 

0.003 0.153 

.3 

.3 1.5 

.87 1.02 

Water-level measurement error sources and maximum error values. 

[m, meter] 

Measurement Measuring point 

altitude error Total maximum error 

Hourly ground-water data 0.15 

Manual ground-water data .15 .45 

Historical ground-water data 1.8 

Interpolated river-stage data .15 

represent an approximation of steady-state conditions where 

water levels, river stage, antecedent precipitation (used to calculate recharge rates), and well pumping data were readily available. The rationale for using a quasi-steady-state calibration 

was based on the complexity and size of the model and the 

availability of water-level data for the study area for November 

2001, when hydrologic conditions were relatively stable and 

river stage was close to the annual average. The historical waterlevel data from 51 wells in the study area were used to calibrate 

Transient calibration of the ground-water flow model was 

accomplished by varying model parameters and matching 

ground-water levels measured between March 26, 2001, and 

July 25, 2002, with the simulated hydraulic-head distribution. 

This was done by measuring the changes in various hydrologic 

stresses that affected the distribution of hydraulic head and simulating those stresses in the model. A stress on the ground-water 

flow system was any change in river stage, recharge, or well 

pumping that caused the distribution of hydraulic head to 

the model for parts of the study area where current ground- change. These changes occurred as gradual increases or 

water level data were unavailable. 

The areal distribution of hydraulic conductivity was based 

on the lithologic distribution within each layer. Recharge rates 

were correlated to precipitation and spatially distributed according to the lithologic distribution of layer 1. Pumping rates for 

wells in the study area were determined using pumping records 

from water suppliers and industries or from the Missouri 

Department of Natural Resources (2001) when otherwise 

unavailable. 

The assignment of hydraulic conductivity based on lithologic distribution, recharge rate based on the lithologic distribution of the top layer, inclusion of well pumping, and headdependent flow boundaries to simulate the effects of small 

streams and ditches on ground-water flow reduced the RMS 

error to a value of 0.82 m. The level of accuracy of the simulation in representing the November 16, 2001, hydraulic head distribution was accepted because the hydraulic head distribution 

for that time was not completely at steady state. Further calibration of the quasi-steady-state model would have resulted in 

erroneously changing model input parameters to match a 

hydraulic head distribution that resulted partially from transient 

ground-water flow. The difference between flow into the model 

and flow out of the model across all model boundaries was 0 

percent of total flow for the quasi-steady-state calibration. The 

flow budget for the quasi-steady-state calibration simulation is 

shown in table 6. Cumulative volumes for the quasi-steady-state 

calibration simulation were calculated based on a model 

assigned single stress period of 11.774 days. Slight discrepancies between the cumulative volumes and the rates reported in 

the simulation output are caused by rounding errors. 

decreases of river stage, intermittent and varying rates of 

recharge from precipitation, and intermittent or constant pumping of wells at varying rates. The ground-water flow model 

applied areal and temporal changes in stress to the ground-water 

flow system during a series of stress periods. Within each stress 

period, river stage, recharge, and pumping rates of wells were 

held constant. Each stress period in the transient calibration was 

1 day and was divided into three time steps. In each stress 

period the first time step was 3.43 hours, the second time step 

was 6.86 hours, and the third time step was 13.71 hours. 

River stage for each stress period was assigned to each 

river model cell using interpolation methods previously discussed in the “Boundary and Initial Conditions” section. Average daily river-stage altitudes for each gaging station in the 

study area are shown in figure 10. Recharge for each stress 

period was assigned to the top most active cell in each vertical 

column using daily precipitation. Precipitation amounts from 

March 26, 2001, to July 25, 2002, are shown in figure 11. The 

percentage of precipitation that was supplied to the model as 

recharge is shown in table 1 for each zone in layer 1. Average 

well pumping rates for each stress period were assigned to each 

model cell that contained a pumping well or wells in the transient calibration simulation. 

The transient calibration of the ground-water flow model 

used hydraulic head data obtained from 13 wells located near 

Ft. Leavenworth. Hourly measurements were collected between 

April 5, 2001, and July 25, 2002, for wells 61, 62, 70, and 71; 

between April 6, 2001, and July 25, 2002, for wells 56, 57, 59, 

60, 63, 64, 65, and 66; and between April 14, 2001, and July 25, 

2002, for well 67. The model was allowed to run 548 simulated 
Simulation of Ground-Water Flow 33
34 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

Table 5. Well numbers and simulated and observed ground-water altitudes. 

[--, not applicable] 

Ground-water altitude, 


in meters 


Well number 


(fig. 9) Simulated Observed Additional well description 


1 234.41 
 233.78 --

8 

9 

12 

13 

5 

6 

1 

2 

10 

11 

3 

4 

7 

3 234.26 
 234.70 --

4 233.94 
 235.15 --

5 233.30 
 233.68 --

7 232.92 
 233.48 --

8 232.34 
 233.32 --

9 231.24 
 231.34 --

11 231.64 
 230.73 --

14 229.88 
 230.73 --

28 227.43 
 229.21 --

46 233.96 
 234.16 --

47 233.29 
 232.38 --

48 232.81 
 232.86 --

49 231.92 
 233.00 --

50 231.50 
 231.66 --

56 231.32 
 231.61 USGS WELL

57 231.32 
 231.59 USGS WELL 

59 230.78 
 230.43 USGS WELL 

60 230.78 
 230.43 USGS WELL 

61 231.00 
 230.97 USGS WELL 

62 231.00 
 230.97 USGS WELL 

63 230.74 
 230.53 USGS WELL 

64 230.74 
 230.53 USGS WELL 

65 230.48 
 230.18 USGS WELL 

66 230.48 
 230.20 USGS WELL 

67 230.48 
 230.23 USGS WELL 

70 229.77 
 230.32 USGS WELL 

71 229.77 
 230.32 USGS WELL 

80 227.29 
 228.83 --

90 226.30 
 226.59 --

91 230.64 
 230.09 FTL10W-2 

93 230.61 
 230.19 FTL10W-3 
--

--

--

--

35 

Table 5. 

Ground-water altitude, 

in meters 

Well number 

(fig. 9) 

94 230.61 FTL10W-4 

95 230.56 PZ-1 

96 230.51 PZ-2 

98 230.49 PZ-4 

101 230.07 PZ-6 

103 230.07 PZ-7 

104 229.81 PZ-9 

105 229.43 PZ-10 

106 229.68 PZ-8 

107 230.41 PZ-5 

116 230.61 FTL10W-1 

121 230.60 FTL10W-6 

122 230.60 FTL10W-7 

123 230.58 FTL10W-8 

124 230.58 FTL10W-9 

125 230.57 FTL10W-10 

126 230.57 FTL10W-11 

127 230.58 FTL10W-12 

128 230.58 FTL10W-13 

131 229.22 WELL 7 

133 229.32 WELL 9 

148 229.93

149 229.49

154 229.35 FTL03W-2 

157 227.21 WELL 5 

159 230.82 FTL57W-1 

160 230.66 FTL57W-2 

161 230.57 FTL57W-3 

162 230.57 FTL57W-4 

163 230.56 FTL57W-5 

165 227.17 

166 227.01 

Simulation of Ground-Water Flow 

Well numbers and simulated and observed ground-water altitudes.—Continued

[--, not applicable] 

Simulated Observed Additional well description 

230.14 

228.97 

229.18 

229.23 

229.76 

228.63 

229.08 

229.81 

228.88 

228.75 

230.94 

229.84 

229.91 

229.85

229.80 

230.21 

230.25 

230.03

230.08

227.69 

227.08

229.21

228.30

228.91

227.63 

230.74

230.34 

230.57 

230.68 

230.58 

228.74 

226.15 
36 

Table 6. 

[m3 3/

Rates 

3 m3

/d 

In 

0 0 0 0 

0 0 0 0 

Wells 0 175,040.0000 0 

Drains 0 806.20 0 

River leakage 9,276.5000

Head dependent boundaries 1,653.5000

Recharge 0 14,095.0000

Total 294,660.0000 25,025.0000 

.00 

Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

Volumetric budget for quasi-steady-state calibration simulation.

, cubic meter; m d, cubic meter per day] 

Cumulative volumes 

(11.774 days) m

Out In Out 

Storage

Constant head

14,867.0000 

68.4720 

109,220.0000 81,237.0000 6,899.6000 

19,469.0000 37,574.0000 3,191.2000 

165,960.0000 0.0000 

294,650.0000 25,026.0000 

Total in - out -10.0 -1.0 

Percent discrepancy .00 

days divided into daily stress periods. Simulated and observed 

ground-water levels are shown for the 13 wells in figure 12. 

The RMS error calculated using 548 daily water-level 

observations for 13 wells (6,172 observations) and the corresponding simulated water levels was 0.33 m for the accepted 

calibration simulation. This value is less than the maximum 

measurement errors (table 4) and indicates the acceptability of 

the calibrated model. Calibrated parameter values for the 

ground-water simulations are listed in table 1. 

Sensitivity Analysis 

A sensitivity analysis was performed to assess the 

response of the model simulation to changes in various input 

parameter values. The model is considered sensitive to a parameter when a change of the parameter value changes the distribution of simulated hydraulic head. When the model is sensitive 

to an input parameter, the value of that parameter within the 

model is more accurately determined during model calibration 

because small changes to the parameter value cause large 

changes in hydraulic head. If a change of parameter value does 

not change the simulated hydraulic head distribution, the model 

is considered insensitive to that parameter. When the model is 

insensitive to an input parameter, the value of that parameter 

within the model is more difficult to accurately determine from 

model calibration because large changes to the parameter do not 

cause large changes in hydraulic head. 

Composite scaled sensitivities are calculated by MODFLOW-2000 using scaled sensitivities for all observations and 

indicate the total amount of information provided by the observations for the estimation of a parameter (Hill, 1998). Composite scaled sensitivities are shown for both the quasi-steady-state 

and transient calibration simulations for parameters with composite scaled sensitivities greater than 0.01 (fig. 13). The model 

is more sensitive to a parameter with a large composite sensitivity value than to a parameter with a small value. The quasisteady-state simulation is most sensitive to the WELLS (well 

pumping), RECH4 (recharge in layer 1, zone 4), L3-Z2 (horizontal hydraulic conductivity in layer 3, zone 2), and RECH3 

(recharge in layer 1, zone 3) parameters. The transient simulation is most sensitive to the RECH3, MRV21 (Missouri River 

conductance layer 2, zone 1), MRV22 (Missouri River conductance layer 2, zone 2), and L3-Z2 parameters. Composite scaled 

sensitivities for parameters differ between the quasi-steadystate and transient calibration simulations for several reasons. 

Ground-water level data used for the quasi-steady-state calibration are from locations throughout the study area, but groundwater level data used for the transient calibration were measured hourly from the 13 wells near Ft. Leavenworth. Observations may be highly sensitive to a parameter change if the observation is located where a parameter change has great effect. For 

example, the WELLS parameter has the largest composite sensitivity for the quasi-steady-state simulation because more 

observations are located close to or are based on observations 

within pumping wells. Observations used in the transient calibration were located farther from pumping wells, and the composite sensitivity for the WELLS parameter is smaller for the 

transient calibration. The RECH3 parameter has the largest 

composite sensitivity for the transient calibration because most 

of the observations used were located in the RECH3 zone. The 

transient calibration is more sensitive to the conductance of the 
Simulation of Ground-Water Flow 37 

Missouri River (MRV21, MRV22) than the quasi-steady-state 

calibration because river stage changed with each stress period 

in the transient calibration, and ground-water levels in all wells 

used for the transient calibration changed in response to 

changes in Missouri River stage. 

One percent scaled sensitivities indicate how much a simulated value of head would change for an observation location 

based on a one-percent increase in the value of the parameter 

and show the relative importance of a parameter value between 

observation locations. One percent scaled sensitivities for 

ground-water level observations used for the quasi-steady-state 

calibration simulation are shown for selected parameters in figure 14. Positive sensitivities indicate an increase in head with an 

increase in parameter value; negative sensitivities indicate a 

decrease in head with an increase in parameter value. Different 

one-percent sensitivities for different water-level observations 

are caused by the location of the observed head value (location 

of the measured well) with respect to the value of the model 

parameter. A water-level observation from a well located close 

to the Missouri River will be more sensitive to the MRV21 

(Missouri River conductance layer 2, zone 1) parameter than a 

well located far from the river. Wells 28, 105, and 131 are 

located close to the Missouri River (fig. 9) and water levels have 

larger one-percent sensitivities to MRV21 (fig. 14) than water 

levels in other wells. Similarly, water-level observations from a 

well screened at a depth and represented by the L3-Z2 (hydraulic conductivity layer 3, zone 2) parameter will have a larger 

one-percent sensitivity to that parameter than to a parameter 

representing hydraulic conductivity in layer 1. For example, 

wells 105 and 133 (a pumping well) have large positive onepercent sensitivities to the L3-Z2 parameter, but well 14 has a 

large negative one-percent sensitivity to the L3-Z2 parameter. 

Increasing the value of L3-Z2 causes an increase in simulated 

water level for well 105 because it is close to the Missouri River 

and the Ft. Leavenworth well field (fig. 9). More water can supply the nearby pumping well from the river when L3-Z2 is 

larger, drawdown is reduced near the well field, and simulated 

ground-water levels increase. Well 133 is a pumping well in the 

Ft. Leavenworth well field. Increasing the L3-Z2 parameter 

value increases the simulated ground-water level for well 133 
38 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

because drawdown is less in a pumping well when hydraulic 

conductivity is larger and more water can supply the well from 

the Missouri River. Well 14 is located farther from the Missouri 

River and is not located near well pumping (fig. 9). Increasing 

the L3-Z2 parameter value allows ground water to move more 

quickly to the Missouri River and simulated ground-water levels decrease. 

Ground-water level data from June 13, 2001, to July 31, 

2001, were used to calculate the one-percent scaled sensitivities 

for the transient ground-water flow simulation because of 

excessive execution times required to calculate sensitivities for 

the entire 548 days of data. The one-percent scaled sensitivities 

for selected parameters for each observed head value in the transient calibration simulation are shown for well 63 (USGS Well 

1) in figure 15 to illustrate how one-percent sensitivities for 

ground-water level observations change with time as different 

stresses are applied to the model. The change in sensitivity to 

the RECH3 parameter is caused by changes in recharge with 

time. Rainfall events increase the sensitivity of the simulated 

ground-water level to the RECH3 parameter by a large amount 

on the day the event occurred, but the sensitivity decreases during subsequent stress periods where no rainfall occurs. Similarly, changes in the MRV21 parameter are caused by changes 

in stage of the Missouri River with time. The one-percent sensitivity to the SS2 (specific storage for layer 2) parameter 

changes as water enters and is released from storage. This 

occurs when recharge occurs and water enters storage (negative 

one-percent sensitivity), and when the Missouri River stage 

decreases and water is released from storage (positive one-percent sensitivity). 

Model Limitations 

A ground-water model is a simplified approximation of 

actual conditions. The accuracy of the ground-water model 

results depends on the accuracy of the input data. The groundwater flow model for this study was constructed with available 

historical and site specific hydrologic data to determine groundwater flow direction, contributing recharge areas to publicwater-supply wells, and ground-water travel time in the 
Simulation of Ground-Water Flow 39 
40 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 
Simulation of Ground-Water Flow 41 
42 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

Missouri River alluvial aquifer in the study area. To correctly 

interpret model results the following limitations of the model 

should be considered. 

1.	 Model parameters such as hydraulic conductivity and 

recharge are applied uniformly to a model cell. The 

assumption of homogeneity can cause inaccuracies 

because geologic materials and climatic conditions are 

typically heterogeneous. 

2.	 The ground-water flow model was discretized using a grid 

with cells measuring 100 m by 100 m. Model results were 

evaluated on a relatively large scale and cannot be used for 

detailed analyses such as simulating water-level drawdown 

near a single well. A grid with smaller cells would be 

needed for such detailed analysis. 

3.	 Although the model was calibrated to both steady-state 

and transient conditions, analyses of ground-water flow, 

contributing recharge areas, and travel time were based on 

simulated steady-state conditions. In alluvial aquifers like 

the Missouri River alluvial aquifer, steady-state conditions 

rarely, if ever, occur because of constantly changing river 

stage, rainfall, and well pumping. Analyses based on 

steady-state conditions should be considered approximations of actual or historical conditions. 

4.	 Well pumping rates used in the ground-water flow model 

were average annual rates for public-water-supply wells or 

well fields. Average pumping rates may introduce some 

error in contributing recharge areas if most pumping is 

from a small subset of wells in a well field but pumping is 

distributed evenly between all wells of the well field. 
Simulation of Ground-Water Flow 43 
44 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

Contributing Recharge Areas and GroundWater Travel Time 

Particle tracking analysis, using the USGS particle-tracking program MODPATH (Pollock, 1994), was used to determine the CRA and ground-water travel times for each known 

pumping well or well field in the study area. MODPATH uses 

the hydraulic heads and flow distribution output from MODFLOW to calculate the paths and travel times of imaginary particles of water moving through the simulated ground-water flow 

system. The accuracy of particle-tracking analysis must be 

known for correct interpretation of MODPATH results. Limitations of particle-tracking analysis are discussed at length by 

Pollock (1994), but several important factors that affect particle 

tracking results follow. Ground-water particle movement and 

ground-water travel times computed by MODPATH are based 

solely on ground-water flow. Because hydraulic conductivities 

are large in the Missouri River alluvial aquifer, ground-water 

flow probably is the largest component of contaminant movement. While the rate of movement of a particular contaminant 

is not fully described by MODPATH results alone, a conservative estimate is computed that can be used for planning purposes. The spatial discretization of the ground-water flow 

model also may limit the accuracy of particle tracking results 

because cells containing sinks that do not discharge at a rate 

large enough to consume all the water entering the cell introduce uncertainty into the computed path of the imaginary water 

particle. However, the most significant factor affecting the 

accuracy of particle-tracking analysis is the accuracy of the 

hydraulic head and flow distribution computed by the groundwater flow model. Therefore, all of the limitations associated 

with the ground-water flow model also apply to the particletracking analysis. 

The porosity of the alluvial aquifer has a large affect on 

ground-water velocities computed by MODPATH. The same 

ground-water discharge through a unit cross-sectional area of 

porous material with a high porosity will have a lower average 

ground-water flow velocity than a material with a low porosity. 

This occurs because the higher porosity material has more 

openings per unit area of porous material than does a lower 

porosity material, thereby allowing the same amount of discharge at a lower average ground-water velocity than in a lower 

porosity material. Typical values of porosity (Freeze and 

Cherry, 1979; Driscoll, 1986) were based on lithology and were 

distributed among model cells by assigning porosity values to 

hydraulic conductivity zones listed in table 1. 
Contributing Recharge Areas and Ground-Water Travel Time 45 

Pumping- and River-Stage Scenarios 

Steady-state ground-water flow was simulated for five different combinations of well pumping and river stage to determine the hydraulic head distribution in the study area during 

low, average, and high well pumping rates and low, average, 

and high river stage. Particle tracking analysis was used to 

determine the CRA for pumping wells in each of the five scenarios. The well pumping, river stage scenarios are: low pumping rate, average river stage (LPAR); high pumping rate, average river stage (HPAR); average pumping rate, average river 

stage (APAR); average pumping rate, low river stage (APLR); 

and average pumping rate, high river stage (APHR). 

Well pumping rates used in the quasi-steady-state calibration and average well-pumping simulations are average annual 

pumping rates. Average annual pumping rates for each well 

field are listed in table 7. High well pumping rates were set at 

1.25 times average annual pumping rates; low pumping rates 

were set at 0.75 times average annual pumping rates. 

The river-surface altitude was defined for each cell in the 

model that contained a river for the quasi-steady-state calibration and for each stress period of the transient calibration. Low, 

average, and high river stage data sets were chosen from the 

transient stress period data based on a comparison of the river 

stage at the USGS gaging station located in St. Joseph, Missouri, with the average annual high, average, and low stages. For 

the USGS gaging station in St. Joseph, Missouri, between 1958 

and 2001 a discharge of 2,084 m3/s (cubic meters per second) 

[73,600 ft3

/s (cubic feet per second)] was exceeded 10 percent 

of the time, the annual mean discharge was 1,333 m3/s (47,070 

ft3

/s) and a discharge of 626 m3/s (22,100 ft3/s) was exceeded 

90 percent of the time (Hauck and Nagel, 2001). High river 

stage conditions were represented by the May 8, 2001, river 
46 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

Table 7. Well field, well number, well name, well layer, row, column, and pumping rates used for the steady state and transient simulation ground-water flow. 

[na, not applicable; gal/min, gallon per minute; m3/d, cubic meter per day] 

Well field Well number Pump rate Pump rate 


(fig. 1) (fig. 9) Well name Layer Row Column (gal/min) (m3

/d) 


Iatan 	 172 Well E 


171 Well D 


Weston 	 51 Well 4 


52 Well 3 


53 Well 2 


54 Well 1 


Ft. Leavenworth 	 133 Well 9 


131 Well 7 


132 Well 8 


130 Well 6 


Leavenworth 	 29 Well 3 


30 Well 3A 


31 Well 4 


33 Well 5A 


34 Well 6 


35 Well 7 


36 Well 8 


37 Well 9 


40 Well 12 


4 67 105 175 954 

4 69 102 100 545 

4 113 157 106 578 

4 114 157 106 578 

4 115 157 59 322 

4 116 157 59 322 

4 168 162 100 545 

4 170 163 100 545 

4 171 162 100 545 

4 171 163 100 545 

3 264 191 200 1,090 

3 265 192 200 1,090 

3 265 193 200 1,090 

3 266 196 200 1,090 

3 266 196 200 1,090 

3 267 198 200 1,090 

3 268 199 200 1,090 

4 269 201 200 1,090 

4 273 206 200 1,090 

stage data when the stage at the St. Joseph, Missouri, gage was puted by MODPATH include the source area of water to each 

245.92 m (2,917 m3

/s discharge). Average river stage condi- well or well field and advective ground-water travel times from 

tions were represented by the July 11, 2001, river stage data the land surface and the major rivers to each well or well field. 

when the stage at the St. Joseph, Missouri, gage was 243.21 m The starting locations and travel times of the particles that even-

(1,133 m3

/s discharge). Low river stage conditions were repre- tually discharged to a well or well field were identified for each 

sented by the December 27, 2001, river stage data when the scenario, which estimated the entire CRAs for each well field. 

stage at the St. Joseph, Missouri, gage was 241.59 m (637 m3

/s Next particles with travel times from 0 to 6 months, 6 months to 

discharge). 1 year, 1 to 2 years, 2 to 3 years, 3 to 4 years, 4 to 5 years, 5 to 

For each scenario, one imaginary particle of water was 10 years, 10 to 25 years, 25 to 50 years, 50 to 100 years, 100 to 

placed on the water table in each quadrant of the top-most active 200 years, 200 to 300 years, 300 to 400 years, and 400 to 500 

model cell and tracked to its eventual discharge point. Particles years were grouped to create CRAs for each scenario. 

were placed in this manner for two reasons: most water entering The shape, size, and ground-water travel time within the 

the alluvial aquifer comes from direct infiltration by precipita- CRA for each well or well field is affected by changes in river 

tion or from the major rivers, and the primary source of poten- stage and pumping rates and by the location of the well or well 

tial contamination to the alluvial aquifer is from leaks or spills field with respect to the major rivers, alluvial valley walls, and 

that occur on the land surface. Consequently, the CRAs com- other pumping wells. Similarities in the shapes of CRAs 
between different wells and well fields can be attributed to similarities in the pumping rate, and the position of the wells or well 

fields in relation to the major rivers, the alluvial valley walls, or 

other well fields. A typical CRA shape for a well located within 

an aquifer with uniform hydraulic conductivity such that effects 

from any hydrologic boundary are negligible will be circular. 

The simulated potentiometric surface and entire CRA for each 

well-pumping/river-stage scenario are shown for the Iatan, 

Weston, Ft. Leavenworth (wells 6, 7, 8, and 9; table 7), and 

Leavenworth well fields in figure 16. The size of the CRA for 

each well-pumping/river-stage scenario for each well field is 

listed in table 8. 

Ground-water velocity is affected by the ground-water 

gradient, hydraulic conductivity of the aquifer, and porosity. 

Ground-water velocity is greater with increased ground-water 

gradient, larger hydraulic conductivity, or smaller porosity. The 

greatest ground-water gradients within the Missouri River alluvial aquifer in the study area are located near pumping wells and 

rivers. Pumping wells create a cone of depression on the potentiometric surface such that the ground-water gradient and 

ground-water velocity are greatest near a pumping well. Rivers 

can produce large changes in ground-water gradient and direction as stage rises and falls. Hydraulic conductivity is smallest 

in clays and silts, larger in sands, and largest in gravels. Within 

the Missouri River alluvial aquifer in the study area, clay and 

silt overlie sand and gravel (fig. 3). Assuming a constant 

ground-water gradient, ground-water velocity increases with 

depth. Ground-water velocity is smaller in clay and silt, larger 

in sand, and largest in gravel and because of the lithologic distribution within the alluvial aquifer; this relation causes groundwater velocity to increase with depth. A typical map of groundwater travel time for a well located within an aquifer such that 

effects from any hydrologic boundary are negligible would 

have a bull’s-eye pattern with shorter travel times in the center 

and longer travel times at the edges. The simulated groundwater travel time within the 500-year CRA for each well-pumping/river-stage scenario is shown for the Iatan, Weston, Ft. 

Leavenworth (wells 6, 7, 8, and 9; table 7), and Leavenworth 

well fields in figure 17. The 500-year CRAs for the well-pumping/river-stage scenarios are substantially smaller than the 

CRAs shown in figure 16, because 500-year CRAs depict simulated ground-water travel time to the well fields of 500 years 

or less. 

Iatan Power Plant Well Field 

The shape of the simulated CRA for the Iatan Power Plant 

well field is elongated in the upstream direction for all wellpumping/river-stage scenarios (fig. 16). The capture of ground 

water by the pumping wells as it moved downgradient toward 

the Missouri River caused the long up-valley extent of the CRA. 

The CRAs listed from smallest to largest are LPAR (5.59 km2), 

APLR (7.47 km2

), APAR (7.55 km2), APHR (8.18 km2), and 

HPAR (9.34 km2

). The alluvial valley walls form the northeast 

boundary of the CRA, which is 5.5 km long for the LPAR sceContributing Recharge Areas and Ground-Water Travel Time 47 

nario and 7.6 km long for the HPAR scenario (fig. 16). The 

width of the CRAs range from approximately 1.8 km for the 

LPAR scenario to approximately 2.3 km for the HPAR scenario. The southwest boundary of the CRA is the computed 

ground-water divide between flow to the Missouri River, flow 

to the small lakes on the Iatan Power Plant property, and flow 

to the well field. Recharge to the well field primarily is from 

precipitation and surface runoff from the surrounding uplands. 

Little, if any, recharge to the well field comes from the Missouri 

River because the CRA does not intersect the Missouri River for 

any well-pumping/river-stage scenarios. Ground-water discharges to the two small lakes on the Iatan Power Plant property 

when the potentiometric surface is higher than lake stages. This 

is most obvious for the HPAR scenario, where the CRA for the 

Iatan well field encloses the CRA for the two small lakes. Lake 

stage and potentiometric surface altitude are nearly the same for 

the APHR and APLR scenarios, and the Iatan CRAs are not 

substantially affected by ground-water discharge to these lakes. 

Minimum ground-water travel time to the Iatan well field 

ranges from 5.15 years for the HPAR scenario to 7.55 years for 

the LPAR scenario. Maximum ground-water travel time ranges 

from 288 years for the APLR scenario to about 5,000 years for 

the APHR scenario. Simulated ground-water travel times from 

the top of the potentiometric surface to the well field are shown 

for the Iatan Power Plant well field in figure 17. 

Weston Well Field 

The shape of the simulated CRA for the Weston well field 

is elongated in the upstream direction for all pumping/riverstage scenarios (fig. 16). The capture of ground water by the 

pumping wells as it moved downgradient toward the Missouri 

River caused the long up-valley extent of the CRA. The CRAs 

listed from smallest to largest are LPAR (6.66 km2

), APAR 

(8.77 km2), APLR (8.79 km2), APHR (9.14 km2

), and HPAR 

(11.11 km2

). The alluvial valley walls form the northeast 

boundary of the CRA, which is 4.6 km long for the LPAR scenario and 6.0 km long for the HPAR scenario (fig. 16). The 

width of the CRA ranges from approximately 1.7 km for the 

LPAR scenario to approximately 2.3 km for the HPAR scenario. The southwest boundary of the CRA is the computed 

ground-water divide between flow to the Missouri River and 

flow to the well field. This divide changes position with changes 

in pumping and river stage. High pumping rates (HPAR) move 

the divide away from the Weston well field as the CRA 

increases in size; the opposite occurs for low pumping rates 

(LPAR). High river stage moves the computed divide away 

from the Weston well field; the opposite again occurs for low 

river stage, but to a much lesser degree than with changes in 

pumping rate. Recharge to the well field primarily is from precipitation and surface runoff from the surrounding uplands. Little, if any, recharge to the well field comes from the Missouri 

River because the CRA does not intersect the Missouri River for 

any well-pumping/river-stage scenarios. 
48 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas
Contributing Recharge Areas and Ground-Water Travel Time 49
50 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas
Contributing Recharge Areas and Ground-Water Travel Time 51
52 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas
Contributing Recharge Areas and Ground-Water Travel Time 53 

Table 8. 

2

Weston Leavenworth 

2

) 2) 2) 2) 

28.20 25.06 

64.27 33.47 

36.73 32.88 

APLR 51.11 32.89 

29.67 34.61 

Contributing recharge areas for all well fields and all well-pumping/river-stage scenarios. 

[km , square kilometer] 

Well field

 Well-pumping/river-stage Iatan Ft. Leavenworth 

scenario (km (km (km (km

LPAR 5.59 6.66 

(Low pumping, average river stage) 

HPAR 9.34 11.11 

(High pumping, average river stage) 

APAR 7.55 8.77 

(Average pumping, average river stage) 

7.47 8.79 

(Average pumping, low river stage) 

APHR 8.18 9.14 

(Average pumping, high river stage) 

Minimum ground-water travel time to the Weston well 

field ranges from 6.7 years for the HPAR scenario to 9.5 years 

for the LPAR scenario. Maximum ground-water travel time 

ranges from about 13,000 years for the APHR scenario to about 

17,600 years for the APAR scenario. Simulated ground-water 

travel times from the top of the potentiometric surface to the 

well field are shown for the Weston well field in figure 17. 

Leavenworth Well Field 

The shape of the simulated CRA for the Leavenworth well 

field is elongated in the upstream direction for all well-pumping/river-stage scenarios (fig. 16). The capture of ground water 

by the pumping wells as it moved downgradient toward the 

Missouri River and downgradient along the Platte River flood 

plain towards the Missouri River caused the long up-valley 

extent of the CRA. The CRAs listed from smallest to largest are 

LPAR (28.20 km2

), APHR (29.67 km2), APAR (36.73 km2), 

APLR (51.11 km2

), and HPAR (64.27 km2). The alluvial valley 

walls form the southwest boundary of the CRA, which is 4.4 km 

long for the LPAR scenario and 9.6 km long for the HPAR scenario (fig. 16). The eastern and western boundaries of the CRA 

define the computed ground-water divides between flow to the 

Missouri River and flow to the well field for the LPAR, APAR, 

and APHR scenarios. The northwestern boundaries of the CRA 

define the computed ground-water divides between flow to the 

Missouri River and flow to the well field for the HPAR and 

APLR scenarios. The eastern boundaries of the HPAR and 

APLR CRAs are formed by the valley walls within the Missouri 

River flood plain, and the valley walls and the computed 

ground-water flow divide between flow to the Missouri and 

Platte rivers and flow to the well field within the Platte River 

flood plain. The length of the CRA ranges from 11.7 km for the 

LPAR scenario to 13.8 km within the Missouri River flood 

plain, and 18.5 km within the Platte River flood plain for the 

HPAR scenario. The width of the CRA within the Missouri 

River flood plain ranges from approximately 3.5 km for the 

LPAR scenario to approximately 4.5 km (the width of the flood 

plain) for the HPAR scenario. Ground-water discharge to Mud 

Lake for the LPAR and APHR scenarios is indicated by the area 

near the lake that does not contribute to the Leavenworth well 

field. Recharge to the well field is from precipitation, surface 

runoff from the surrounding uplands, and the Missouri River 

because the CRA intersects these boundaries for all well-pumping/river-stage scenarios. 

The CRAs of the LPAR, APAR, and APHR scenarios are 

small relative to the HPAR and APLR scenarios. Low pumping 

and high river stage result in a smaller CRA because less water 

is required from the alluvial aquifer for low pumping, and more 

water is available to the well field from the Missouri River at 

high river stage. The CRAs of the APLR and HPAR scenarios 

extend for some distance up the Platte River flood plain because 

at low river stage, less water is available to the well field from 

the Missouri River and more water must come from the alluvial 

aquifer. Similarly, at a high well-pumping rate, more water must 

come from the alluvial aquifer to supply enough water to the 

well field. For both situations the result is an increase in the size 

of the CRA. 

Minimum ground-water travel time to the Leavenworth 

well field ranges from 4.29 years for the HPAR scenario to 7.07 

years for the LPAR scenario. Maximum ground-water travel 

time ranges from about 35,200 years for the APAR scenario to 

about 51,000 years for the APHR scenario. Simulated groundwater travel times from the top of the potentiometric surface to 
54 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas
Contributing Recharge Areas and Ground-Water Travel Time 55
56 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas
Contributing Recharge Areas and Ground-Water Travel Time 57
58 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas
Contributing Recharge Areas and Ground-Water Travel Time 59 

the well field are shown for the Leavenworth well field in figure 

17. 

Ft. Leavenworth Well Field 

The shape of the simulated CRA for the Ft. Leavenworth 

well field is elongated in the upstream direction for all wellpumping/river-stage scenarios and is split into two arms up-valley from the well field (fig. 16). The capture of ground water by 

the pumping wells as it moved downgradient toward the Missouri River caused the long up-valley extent of the CRA. The 

CRAs listed from smallest to largest are LPAR (25.06 km2

), 

APAR (32.88 km2

), APLR (32.89 km2), HPAR (33.47 km2), 

and APHR (34.61 km2

). The alluvial valley walls form the 

southwest boundary of the CRA for the LPAR scenario, which 

is 9.4 km long and 15.6 km long for the APHR scenario (fig. 

16). The boundaries of the two arms of the CRA are the computed ground-water divides between flow to the Missouri River 

and flow to the well field. The length of the CRA for the LPAR 

scenario ranges from 11.2 km to 20.3 km within the Missouri 

River flood plain along the longest arm for the HPAR scenario. 

The width of the CRA within the Missouri River flood plain 

ranges from approximately 3.0 km for the LPAR scenario, to 

approximately 3.9 km for the HPAR scenario. Recharge to the 

well field is from precipitation, surface runoff from the surrounding uplands, and the Missouri River because the CRA 

intersects these boundaries for all well-pumping/river-stage 

scenarios. 

The CRA of the LPAR scenario is substantially smaller 

than the other CRAs for the Ft. Leavenworth well field. Low 

pumping results in a smaller CRA because less water is required 

from the alluvial aquifer by the well field. The HPAR scenario 

is larger than the LPAR scenario because more water must 

come from the alluvial aquifer to supply enough water to the 

well field. Low river stage decreases the amount of water available to the well field, and increases the size of the CRA for the 

APLR scenario in the down-valley direction compared to the 

high river stage of the APHR scenario. High river stage 

increases the amount of water available to the well field from 

the Missouri River and reduces the slope of the potentiometric 

surface. The CRA for the APHR scenario is smaller than for the 

APLR scenario in the down-valley direction (close to the Missouri River) but extends substantially farther in the up-valley 

direction because the slope of the potentiometric surface is less, 

and more water is captured by the well field from this direction 

as it moves down-valley. 

Minimum ground-water travel time to the Ft. Leavenworth 

well field ranges from 4.46 years for the HPAR scenario to 6.31 

years for the LPAR scenario. Maximum ground-water travel 

time ranges from about 50,100 years for the APLR scenario to 

about 63,700 years for the HPAR scenario. Simulated groundwater travel times from the top of the potentiometric surface to 

the well field are shown for the Ft. Leavenworth well field in 

figure 17. 

Individual Wells of the Ft. Leavenworth Well Field 

Four wells of the Ft. Leavenworth well field (wells, 6, 7, 8, 

and 9) are actively pumped. These wells are numbered 130, 

131, 132, and 133 in table 7 and on figure 9. The CRAs for each 

well-pumping/river-stage scenario are shown for each well of 

the Ft. Leavenworth well field in figure 16. The size of the CRA 

for each well and each well-pumping/river-stage scenario are 

listed in table 9. The CRAs, listed from smallest to largest, for 

all well-pumping scenarios are well 7, well 6, well 9, and well 8. 

Table 9. 

2

2

) 2) 

Well 8

(km2) 

Well 9

2

) 

LPAR 2.90 13.97 5.51 

HPAR 3.90 20.28 5.51 

APAR 3.47 19.85 6.32 

3.48 19.44 6.70 

APHR 3.56 23.30 4.43 

Contributing recharge areas for individual Ft. Leavenworth wells for each well-pumping/river-stage scenario. 

[km , square kilometer] 

Well 

Well-pumping/river-stage scenario

Well 6

(km

Well 7

(km (km

2.68 

(Low pumping, average river stage) 

3.79 

(High pumping, average river stage) 

3.24 

(Average pumping, average river stage) 

APLR 3.28 

(Average pumping, low river stage) 

3.31 

(Average pumping, high river stage) 
60 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

The well 8 CRA forms the outer most boundary of the Ft. 

Leavenworth well field CRA for the LPAR and APHR scenarios, and forms the southwest and south boundaries for the 

HPAR, APAR, and APLR scenarios. The well 6 CRA forms the 

eastern boundary for the HPAR, APAR, and APLR scenarios. 

The well 7 CRA is long and narrow, and is bounded by the well 

8 CRA on the west and the well 6 CRA on the east for all wellpumping/river-stage scenarios. The well 9 CRA is long and narrow, and is bounded by the well 7 CRA for all well-pumping/ 

river-stage scenarios. 

Minimum ground-water travel time to the Ft. Leavenworth 

wells ranges from 4.46 years for well 9 (HPAR scenario) to 

12.00 years for well 8 (LPAR scenario). Maximum groundwater travel time ranges from 490 years for well 6 (APLR scenario) to about 63,700 years for well 8 (HPAR scenario). Simulated ground-water travel times from the top of the potentiometric surface to the Ft. Leavenworth well field are shown in 

figure 17. 

Three sites with known ground-water contamination 

(FTL-10, FTL-11, and FTL-69) are upgradient from the Ft. 

Leavenworth well field (fig. 2). These sites are within the Ft. 

Leavenworth well field CRA, and ground water flows only to 

the Ft. Leavenworth well field for all simulated well-pumping/ 

river-stage scenarios. The FTL-10 site is within the well 9 CRA 

for all simulated well-pumping/river-stage scenarios. FTL-11 

and FTL-69 are within the well 7 CRA for the LPAR, APAR, 

APLR, and APHR scenarios, and are within the well 9 and well 

7 CRAs for the HPAR scenario (fig. 16). 

Simulated ground-water travel times between FTL-10, 

FTL-11, and FTL-69 and the Ft. Leavenworth well field in are 

shown in figure 18. Minimum ground-water travel time to the 

Ft. Leavenworth well field from FTL-10 is 43.8 years for the 

HPAR scenario, from FTL-11 is 28.8 years for the APLR scenario, and from FTL-69 is 43.8 years for the HPAR scenario. 

Maximum ground-water travel time to the Ft. Leavenworth well 

field is 75.4 years from FTL-10 for the LPAR scenario, is 42.1 

years from FTL-11 for the LPAR scenario, and is 59.6 years 

from FTL-69 for the LPAR scenario. Ground-water travel times 

from the three contaminated sites to the Ft. Leavenworth well 

field for the APAR scenario are most representative of longterm ground-water flow conditions that occurred in the study 

area. For the APAR scenario, minimum ground-water travel 

time from FTL-10 to the Ft. Leavenworth well field is 44.2 

years, maximum is 70.8 years and mean is 55 years. Minimum 

ground-water travel time from FTL-11 to the Ft. Leavenworth 

well field is 33.5 years, maximum is 38.9 years, and mean is 

36.1 years. Minimum ground-water travel time from FTL-69 to 

the Ft. Leavenworth well field is 48 years, maximum is 53.3 

years, and mean is 49.8 years. 

FTL-10 operated from the 1950s to 1980. If ground-water 

contamination began in 1950, the results from the APAR scenario indicate ground water from FTL-10 will arrive at the Ft. 

Leavenworth well field sometime between 1994 and 2020. 

FTL-11 operated from 1980 to 1989. If ground-water contamination began in 1980, the results from the APAR scenario indicate ground water from FTL-11 will arrive at the Ft. Leavenworth well field sometime between 2014 and 2019. The 

buildings at FTL-69 were built in the 1950s; the site was abandoned in the early 1970s, and a 30,000-gallon diesel underground fuel tank was removed in July 1991. If ground-water 

contamination began in 1950, the results from the APAR scenario indicate ground water from FTL-69 will arrive at the Ft. 

Leavenworth well field sometime between 1998 and 2003. 

Although these model results estimate the arrival of ground 

water from the contaminated sites at the Ft. Leavenworth well 

field, the movement of the contaminants within ground water 

are subject to dispersion that may increase or decrease the rate 

of contaminant movement relative to the rate of ground-water 

movement and chemical or biological processes that may 

decrease the rate of contaminant movement relative to the rate 

of ground-water movement. Therefore, the arrival of contaminants at the Ft. Leavenworth well field from these sites will 

likely take longer than the arrival of ground water. 

Hydrologic Controls On Contributing 

Recharge Areas 

The effect of well pumping and river stage on the size of 

the total CRA of well fields in the study area is complex because 

each well field has a unique orientation with respect to the 

geometry of the aquifer, the alluvial valley walls, the rivers, and 

the other pumping wells in the study area; the hydraulic properties of the aquifer in the vicinity of each well field are different 

in both magnitude and spatial orientation; and although each 

well field pumps at a different rate, an increase of well pumping 

always increased the CRA. The largest effect of a change in 

river stage is the change in the potentiometric surface. Typically, an increase of river stage lowers the regional groundwater gradient between the alluvial valley and the rivers in the 

study area. The effect on the CRA of each well field from a 

change in the ground-water gradient is different for each well 

field. The CRAs for the Iatan, Weston, and Ft. Leavenworth 

well fields increased with increased river stage. The CRA for 

the Leavenworth well field decreased with an increase in river 

stage. 

Well fields without close hydrologic boundaries upgradient from the regional flow direction, such as the Missouri River 

or the alluvial valley walls, have long elliptically shaped CRAs 

because ground water in the simulation travelled a long distance 

along the flow gradient before it was affected by and discharged 

by the pumping wells. Wells located closer to the alluvial walls, 

like the Iatan and Weston well fields, have wide CRAs that 

extend away from the alluvial valley walls because little water 

is available from this boundary. 

Proximity to a major river reduces the size of the CRA 

when compared to the CRAs of other wells or well fields with 

similar pumping rates but located farther from a major river, 
Hydrologic Controls On Contributing Recharge Areas 61 
62 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 
Hydrologic Controls On Contributing Recharge Areas 63 
64 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 
Hydrologic Controls On Contributing Recharge Areas 65 
66 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

because the well or well field obtains a large part of its water 

from recharge induced from the river. A comparison of the 

pumping rates and CRAs for Weston well field, which is not 

supplied water by the Missouri River, and the Leavenworth well 

field, which induces recharge from the Missouri River, illustrates the effect of river induced recharge. The simulated average pumping rate for the Weston well field is 1,800 m3/d, which 

corresponds to a total CRA of 8.77 km2

 for the APAR scenario. 

The simulated average pumping rate for the Leavenworth well 

field is 9,810 m3

/d, which corresponds to a total CRA of 36.73 

km2

 for the APAR scenario. The ratio of pumping rate to CRA 

is a rough estimate of water supplied to the well field per unit 

CRA. The ratio for the Weston well field is 205.25 m3

/d/km2 

(cubic meters per day per square kilometer); the ratio for the 

Leavenworth well field is 267.08 m3

/d/km2. The higher number 

for the Leavenworth well field indicates more water is supplied 

to the well field per unit CRA, although the aquifer properties 

are similar. The extra water supplied to the Leavenworth well 

field is from induced recharge from the Missouri River. Dividing the pumping rate of the Leavenworth well field by the ratio 

for the Weston well field yields a CRA of 47.79 km2, a rough 

estimate of how large the CRA for the Leavenworth well field 

would be without induced recharge from the Missouri River. 

The vertical conductance term limits water flow between 

layers of the model to simulate the vertical anisotropy of 

hydraulic conductivity within the alluvial aquifer. This anisotropy is greatest in the heterogeneously distributed clay, silty 

clay, and silt present at shallow depths and represented in the 

model by layer 1. The distribution of vertical conductance 

between layers 1 and 2 affect the distribution of ground-water 

travel times within the total CRA of each well or well field. The 

most obvious example of this is within the Ft. Leavenworth 

CRA. The typical distribution of ground-water travel time has 

shorter travel times near pumping wells and longer travel times 

farther away. The typical distribution of ground-water travel 

times does not occur near the FTL-10 site for all well-pumping/ 

river-stage scenarios. For example, in the APAR scenario a 

small area of 100- to 200-year ground-water travel time and 

another area of 25- to 50-year ground-water travel time exists 

within the larger 50- to 100-year travel time area that is more 

common near FTL-10. This occurred because in layer 1 aquifer 

material with lower hydraulic conductivity is located near the 

area of longer ground-water travel time. A low rate of vertical 

water movement caused by the presence of clay or silt near the 

land surface increased the travel time of water from the water 

table to deeper parts of the aquifer. In layer 2, aquifer material 

with higher hydraulic conductivity is located near the area of 

shorter ground-water travel time. A higher rate of vertical water 

movement caused by sand or coarse sand in layer 2 decreased 

the travel time of water from the water table to deeper parts of 

the aquifer. Because the hydraulic conductivity values in the 

deeper parts of the aquifer are higher and more uniformly distributed, the rate of water movement there is faster and more 

uniform than in shallower parts of the aquifer. Therefore, the 

rate of water flow vertically from the shallower to the deeper 

parts of the aquifer has a large effect on the travel time of water 

from the water table to the screened interval of a pumping well 

and on the distribution of the CRA of a well or well field. 

Interference between pumping well fields also affects the 

size and shape of CRAs of well fields. Well interference 

between the Iatan, Weston, and Ft. Leavenworth well fields is 

evident for all well-pumping/river-stage scenarios, but is most 

evident for the HPAR and APHR scenarios where CRAs of the 

Ft. Leavenworth well field separates the CRAs of the Iatan and 

Weston well fields and the boundaries of the CRAs are close to 

one another. Reduction or elimination of pumping from the 

Weston well field would cause the CRA of the Ft. Leavenworth 

well field to shift toward the Weston well field and may cause 

the Iatan well field CRA to slightly shift down valley. The most 

notable effect of interference between pumping wells is within 

the Ft. Leavenworth well field. The individual CRAs of wells 6, 

7, 8, and 9 are adjacent to each other and any change or elimination of pumping in one well will dramatically change the 

shape of the other CRAs. Wells or well fields located in the 

upgradient direction from the regional flow field will intercept 

ground water before it reaches wells or well fields located in the 

downgradient direction. This effectively cuts off the groundwater supply to the well fields located downgradient and causes 

the CRA of the downgradient well fields to expand to either side 

of the CRA of the upgradient well. This is shown for wells 6, 7, 

and 8 with respect to the CRA for well 9 in the Ft. Leavenworth 

well field for all well-pumping/river-stage scenarios (fig. 16 

and fig. 17). 

FTL-10, FTL-11, and FTL-69 are within the Ft. Leavenworth well field CRA for all well-pumping/river-stage scenarios. Both the Iatan and Weston well fields are located upgradient from the contaminated sites with respect to the regional flow 

field and it is unlikely that ground water will flow from the contaminated sites to these well fields. The Leavenworth well field 

is located downgradient from the three contaminated sites and 

the Ft. Leavenworth well field. Ground-water flow from the 

three contaminated sites to the Leavenworth well field likely 

will not occur as long as pumping continues from the Ft. Leavenworth well field. If pumping is discontinued from the Ft. 

Leavenworth well field, and pumping is not substantially 

increased from the Leavenworth well field, it is unlikely that 

ground-water flow from the three contaminated sites to the 

Leavenworth well field will occur because ground water from 

the sites will likely discharge to the Missouri River and the 

CRA for the Leavenworth well field does not extend north to 

the CRA of the Ft. Leavenworth well field. 

Summary 

The Missouri River alluvial aquifer in the Ft. Leavenworth, Kansas, area supplies all or part of the drinking water for 

Ft. Leavenworth, Kansas; Leavenworth, Kansas; and Weston, 

Missouri. Ft. Leavenworth has four operating water-supply 

wells on the west bank of the Missouri River that pump 1.5 million gallons per day and are a reliable source of drinking water. 
The presence of ground-water contamination and inundation of 

the existing supply wells by the Missouri River during the flood 

of 1993 have raised concerns about the future reliability of the 

existing drinking water supply at Ft. Leavenworth. The Missouri River alluvial aquifer, and to a lesser extent, the adjoining 

alluvial aquifer of the Platte River, are the only aquifers in the 

study area that can supply large quantities of ground water for 

public and industrial use. Ground-water contamination poses a 

potential threat to the existing public-water-supply well field 

and other nearby public-water-supply well fields. 

In 2003, three public-water-supply well fields (Weston, Ft. 

Leavenworth, and Leavenworth) and one industrial well field 

(Kansas City Power and Light, Iatan Power Plant) were in operation in the study area. Most water recharging the Missouri 

River alluvial aquifer comes from surface recharge from precipitation or recharge from the Missouri River. The source area for 

water that discharges from a pumping well is the contributing 

recharge area for that well. In the absence of pumping, groundwater flow within the alluvial aquifer typically is away from the 

valley walls, toward the Missouri River, and down the river valley. A sudden increase in river stage temporarily can reverse the 

direction of ground-water flow. 

Ground-water flow was simulated for the Missouri River 

alluvial aquifer using the three-dimensional finite-difference 

ground-water flow model MODFLOW-2000. MODFLOW2000 is a modified version of MODFLOW that incorporates the 

use of parameters to define model input, the calculation of 

parameter sensitivities, and the modification of parameter values to match observed heads, flows, or advective transport 

using the observation, sensitivity and parameter-estimation processes.

 The modeled area is 28.6 kilometers by 32.6 kilometers 

and contains the entire study area. The model uses a uniform 

grid size of 100 meters by 100 meters, and contains 372,944 

cells in 4 layers, 286 columns, and 326 rows. The model represents the alluvial aquifer using layers numbered 1 to 4 of variable thickness with no intervening confining layers. 

The ground-water flow model was calibrated by adjusting 

model input data and model geometry to modify model output 

so that model results matched field observations within an 

acceptable level of accuracy. Parameters changed during the 

calibration process include horizontal hydraulic conductivity, 

vertical hydraulic conductivity between model layers, specific 

storage, specific yield, river conductance, drain conductance, 

and recharge rates. The strategy for calibration of the groundwater flow model was to use both quasi-steady-state hydraulic 

head data and transient hydraulic head data. The quasi-steadystate calibration was used to assess model geometry, confirm 

the conceptual model of ground-water flow, test the appropriateness of simulated boundary conditions, and obtain approximate transmissivity and recharge arrays in preparation for more 

rigorous transient calibration. The transient calibration was 

used to fine-tune the model hydraulic properties. 

 The model accuracy was calculated using the root mean 

square (RMS) error between actual measurements of hydraulic 

head and model generated hydraulic head at the end of each 

Summary 67 

model run. The accepted RMS errors for the model calibrations 

were below the maximum measurement errors. The RMS error 

for the quasi-steady-state calibration was 0.82 meter and 0.33 

meter for the transient calibration. 

A sensitivity analysis was performed to assess the 

response of the model simulation to changes in various input 

parameter values. Composite scaled sensitivities indicate the 

quasi-steady-state simulation is most sensitive to the parameters 

for well pumping rate, recharge in zone 4, hydraulic conductivity in layer 3, zone 2, and recharge in zone 3, and the transient 

simulation is most sensitive to the parameters for recharge in 

zone 3, river conductance in layer 2, zone 1, river conductance 

in layer 2, zone 2, and hydraulic conductivity in layer 3, zone 2. 

One percent scaled sensitivities indicate how much a simulated 

value of head would change based on a one-percent increase in 

the value of the parameter. Different one-percent sensitivities 

for different water-level observations are caused by the location 

of the observed head value with respect to the value of the 

parameter in the model. The one-percent scaled sensitivities for 

parameters for each observed head value in the transient calibration simulation change with time as different stresses are 

applied to the model. 

Particle tracking analysis using the U.S. Geological Survey (USGS) particle-tracking program MODPATH determined 

the contributing recharge area and ground-water travel times for 

each known pumping well or well field in the study area. 

Steady-state ground-water flow was simulated for five different 

combinations of well pumping and river stage to determine the 

hydraulic head distribution in the study area. Particle tracking 

analysis then determined the contributing recharge area (CRA) 

for pumping wells in each of the five scenarios. The well-pumping/river-stage scenarios are low pumping rate, average river 

stage (LPAR); high pumping rate, average river stage (HPAR); 

average pumping rate, average river stage (APAR); average 

pumping rate, low river stage (APLR); and average pumping 

rate, high river stage (APHR). Well pumping rates used in the 

quasi-steady-state calibration and average well pumping simulations are average annual pumping rates. 

For each scenario, one imaginary particle of water was 

placed on the water table in each quadrant of the top-most active 

model cell and tracked to its eventual discharge point. Particles 

were placed in this manner for two reasons: most water entering 

the alluvial aquifer comes from direct infiltration by precipitation or from the major rivers, and the primary source of potential contamination to the alluvial aquifer is from leaks or spills 

that occur on the land surface. Consequently, the CRAs computed by MODPATH include the source area of water to each 

well or well field and advective ground-water travel times from 

the land surface and the major rivers to each well or well field. 

The shape, size, and ground-water travel time within the 

CRA for each well or well field is affected by changes in river 

stage and pumping rates and by the location of the well or well 

field with respect to the major rivers, alluvial valley walls, and 

other pumping wells. Similarities in the shapes of CRAs 

between different wells and well fields can be attributed to similarities in the pumping rate and the position of the wells or well 
68 Simulation of Ground-Water Flow and Travel Time in the Missouri River Alluvial Aquifer near Ft. Leavenworth, Kansas 

fields in relation to the major rivers, the alluvial valley walls, or 

other well fields. 

The shapes of the simulated CRAs for the well fields in the 

study area are elongated in the upstream direction for all wellpumping/river-stage scenarios because of the capture of ground 

water by the pumping wells as it moved downgradient toward 

the Missouri River. 

The CRAs for the Iatan well field listed from smallest to 

largest are LPAR [5.59 km2 (square kilometers)], APLR (7.47 

km2), APAR (7.55 km2), APHR (8.18 km2), and HPAR (9.34 

km2). Recharge to the well field primarily is from precipitation 

and surface runoff from the surrounding uplands. Little if any 

recharge to the well field comes from the Missouri River 

because the CRA does not intersect the Missouri River for any 

well-pumping/river-stage scenarios. The CRAs for the Weston 

well field listed from smallest to largest are LPAR (6.66 km2), 

APAR (8.77 km2), APLR (8.79 km2), APHR (9.14 km2), and 

HPAR (11.11 km2). Recharge to the well field primarily is from 

precipitation and surface runoff from the surrounding uplands. 

Little, if any, recharge to the well field comes from the Missouri 

River because the CRA does not intersect the Missouri River for 

any well-pumping/river-stage scenarios. The CRAs for the 

Leavenworth well field listed from smallest to largest are LPAR 

(28.2 km2), APHR (29.67 km2), APAR (36.73 km2), APLR 

(51.11 km2

), and HPAR (64.27 km2). Recharge to the well field 

is from precipitation, surface runoff from the surrounding 

uplands, and the Missouri River because the CRA intersects 

these boundaries for all well-pumping/river-stage scenarios. 

The CRAs for the Ft. Leavenworth well field listed from 

smallest to largest are LPAR (25.06 km2

), APAR (32.88 km2), 

APLR (32.89 km2

), HPAR (33.47 km2), and APHR (34.61 

km2

). Recharge to the well field is from precipitation, surface 

runoff from the surrounding uplands, and the Missouri River 

because the CRA intersects these boundaries for all well-pumping/river-stage scenarios. Four wells of the Ft. Leavenworth 

well field (wells, 6, 7, 8, and 9) are actively pumped. The CRAs 

listed from smallest to largest for all well-pumping/river-stage 

scenarios are well 7, well 6, well 9, and well 8. Well 7 has the 

smallest CRA (2.68 km2) for the LPAR scenario. Well 8 has the 

largest CRA (23.3 km2) for the APHR scenario. 

Three sites with known ground-water contamination 

(FTL-10, FTL-11, and FTL-69) exist upgradient from the Ft. 

Leavenworth well field. These sites are within the Ft. Leavenworth well field CRA for all simulated well-pumping/riverstage scenarios. The FTL-10 site is within the well 9 CRA for 

all simulated well-pumping/river-stage scenarios. FTL-11 and 

FTL-69 are within the well 7 CRA for the LPAR, APAR, 

APLR, and APHR scenarios, and are within the well 9 and well 

7 CRAs for the HPAR scenario. 

Minimum ground-water travel time to the Ft. Leavenworth 

well field from FTL-10 is 43.8 years for the HPAR scenario, 

from FTL-11 is 28.8 years for the APLR scenario, and from 

FTL-69 is 43.8 years for the HPAR scenario. Maximum 

ground-water travel time to the Ft. Leavenworth well field from 

FTL-10 is 75.4 years for the LPAR scenario, from FTL-11 is 

42.1 years for the LPAR scenario, and from FTL-69 is 59.6 

years for the LPAR scenario. Ground-water travel times from 

the three contaminated sites to the Ft. Leavenworth well field 

for the APAR scenario are most representative of long-term 

ground-water flow conditions that occurred in the study area. 

For the APAR scenario, minimum ground-water travel time 

from FTL-10 to the Ft. Leavenworth well field is 44.2 years, 

maximum is 70.8 years, and the mean is 55 years. Minimum 

ground-water travel time from FTL-11 to the Ft. Leavenworth 

well field is 33.5 years, maximum is 38.9 years, and the mean is 

36.1 years. Minimum ground-water travel time from FTL-69 to 

the Ft. Leavenworth well field is 48 years, maximum is 53.3 

years, and the mean is 49.8 years. 

The effect of well pumping and river stage on the total 

CRA of well fields in the study area is complex because each 

well field has a unique orientation with respect to the geometry 

of the aquifer, the alluvial valley walls, the rivers, and the other 

pumping wells in the study area; the hydraulic properties of the 

aquifer in the vicinity of each well field are different in both 

magnitude and spatial orientation; and although each well field 

pumps at a different rate, an increase in well pumping always 

increased the CRA. The CRAs for the Weston, Iatan, and Ft. 

Leavenworth well fields increased with increased river stage. 

The CRA for the Leavenworth well field decreased with an 

increase in river stage. 

Proximity to a major river reduces the size of the CRA, 

when compared to the CRAs of other wells or well fields with 

similar pumping rates, but located farther from a major river, 

because the well or well field obtains a large part of its water 

from recharge induced from the river. The ratio of pumping rate 

to CRA is a rough estimate of water supplied to the well field 

per unit CRA. The ratio for the Weston well field is 205.25; the 

ratio for the Leavenworth well field is 267.08. The higher number for the Leavenworth well field indicates more water is supplied to the well field per unit CRA although the properties of 

the alluvial aquifer are similar. The extra water supplied to the 

City of Leavenworth well field is from induced recharge from 

the Missouri River. 

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