Prepared in cooperation with the Lost Creek Ground Water Management District 

and the Colorado Water Conservation Board

Hydrogeology and Steady-State Numerical 

Simulation of Groundwater Flow in the Lost Creek 

Designated Ground Water Basin, Weld, Adams, 

and Arapahoe Counties, Colorado

Scientific Investigations Report 2010–5082

U.S. Department of the Interior

U.S. Geological Survey
FRONT COVER:

Base imagery for the map is from U.S. Department of AgricultureFarm Service Agency National Agriculture Imagery Program, 2009.

All photographs by L.R. Arnold, U.S. Geological Survey.
Hydrogeology and Steady-State Numerical 

Simulation of Groundwater Flow in the 

Lost Creek Designated Ground Water 

Basin, Weld, Adams, and Arapahoe 

Counties, Colorado

By L.R. Arnold

Prepared in cooperation with the Lost Creek Ground Water Management District 

and the Colorado Water Conservation Board

Scientific Investigations Report 2010–5082

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

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

reproduce any copyrighted materials contained within this report.

Suggested citation:

Arnold, L.R., 2010, Hydrogeology and steady-state numerical simulation of groundwater flow in the Lost Creek Designated 

Ground Water Basin, Weld, Adams, and Arapahoe Counties, Colorado: U.S. Geological Survey Scientific Investigations 

Report 2010–5082, 79 p.
iii

Contents

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

Introduction.....................................................................................................................................................2

Purpose and Scope ..............................................................................................................................2

Study-Area Description .......................................................................................................................2

Physiography and Climate..........................................................................................................2

Soils ...............................................................................................................................................4

Land Use and Irrigation ..............................................................................................................4

Hydrogeology..................................................................................................................................................8

Aquifer Extent and Thickness.............................................................................................................8

Water Levels and Groundwater Flow..............................................................................................13

Hydrologic Properties ........................................................................................................................13

Recharge..............................................................................................................................................18

Precipitation Infiltration............................................................................................................18

Stream-Channel Infiltration......................................................................................................25

Deep Percolation of Water Applied to Irrigated Agricultural Fields .................................26

Passive-Wick Lysimeters ................................................................................................26

Water-Balance Method...................................................................................................29

Ditch and Reservoir Seepage..................................................................................................30

Subsurface Inflow .....................................................................................................................31

Discharge.............................................................................................................................................32

Well Withdrawals ......................................................................................................................32

Evapotranspiration ....................................................................................................................32

Subsurface Outflow...................................................................................................................32

Steady-State Numerical Simulation of Groundwater Flow ..................................................................34

Previous Groundwater Flow Model.................................................................................................34

Design of Previous Model ........................................................................................................34

Inflows and Outflows Simulated by Previous Model...........................................................34

Updated Groundwater Flow Model .................................................................................................34

Design of Updated Model ........................................................................................................35

Boundary Conditions and Hydrologic Stresses....................................................................35

Model Calibration .....................................................................................................................40

Observations......................................................................................................................40

Prior Information...............................................................................................................40

Parameter Estimation.......................................................................................................42

Calibration Assessment...................................................................................................44

Sensitivity Analysis...........................................................................................................46

Model Nonlinearity...........................................................................................................46

Simulation Results .....................................................................................................................47

Model Limitations and Data Needs ........................................................................................49

Summary........................................................................................................................................................51

Acknowledgments.......................................................................................................................................52

References Cited..........................................................................................................................................53

Appendix 1. Gravimetric water content and chloride concentrations for soil samples collected 

in 2006 at six sites in the Lost Creek Designated Ground Water Basin, Colorado....................... 59

Appendix 2. Analytical quality-assurance and quality-control data for soil samples collected 

in 2006 at six sites in the Lost Creek Designated Ground Water Basin, Colorado................... 60
iv

Appendix 3. Chloride in wet and dry deposition at the National Atmospheric Deposition 

Program Pawnee site, Colorado.............................................................................................................. 62

Appendix 4. Net irrigation, precipitation, and lysimeter-drainage data for sites in the Lost 

Creek Designated Ground Water Basin, Colorado, 2007–2008 ........................................................ 63

Appendix 5. Permitted acres, commingled acres, estimated irrigated acres, and estimated

average annual withdrawals from decreed irrigation wells with final permits in the 

Lost Creek Designated Ground Water Basin, Colorado..................................................................... 74

Figures

1–9. Maps showing:

 1. Location of the Lost Creek Designated Ground Water Basin, in Weld, Adams, 

and Arapahoe Counties, Colorado .................................................................................................3

 2. Location of weather stations and the National Atmospheric Deposition Program 

site used by the study, Lost Creek Designated Ground Water Basin, Colorado.................5

 3. Distribution of major soil associations in the Lost Creek Designated Ground 

Water Basin, Colorado......................................................................................................................6

 4. Generalized land use in the Lost Creek Designated Ground Water 

Basin, Colorado......................................................................................................................7

 5. Surficial geology of the Lost Creek Designated Ground Water Basin, Colorado ............ 10

 6. Approximate thickness of regolith sediments in the Lost Creek Designated 

Ground Water Basin, Colorado.................................................................................................... 11

 7. Generalized altitude and configuration of the bedrock surface underlying 

regolith in the Lost Creek Designated Ground Water Basin, Colorado.............................. 12

 8. Ground-water levels at selected well locations in the Lost Creek Designated 

Ground Water Basin, Colorado.................................................................................................... 14

 9. Generalized configuration of the water table and extent of saturated 

sediments in the Lost Creek Designated Ground Water Basin, Colorado......................... 15

10. Plot showing relation of transmissivity determined from aquifer tests to transmissivity 

estimated from specific-capacity tests for 13 wells in the Lost Creek Designated 

Ground Water Basin............................................................................................................................... 18

11. Map showing hydraulic-conductivity distribution and location of aquifer tests 

and specific-capacity tests used to estimate hydraulic conductivity in the Lost Creek 

Designated Ground Water Basin, Colorado...................................................................................... 19

12. Map showing location of chloride-sampling sites and passive-wick lysimeters 

used for estimation of recharge beneath native grassland, nonirrigated agricultural 

fields, irrigated agricultural fields, and ephemeral stream channels in the Lost Creek 

Designated Ground Water Basin, Colorado...................................................................................... 21

13. Lithologic descriptions of soils at chloride-sampling sites used to estimate 

recharge beneath native grassland, nonirrigated agricultural fields, and ephemeral 

stream channels in the Lost Creek Designated Ground Water Basin, Colorado..................... 22

14. Graph showing vertical profiles of chloride concentrations in soil water beneath 

native grassland, nonirrigated agricultural fields, and ephemeral stream channels 

in the Lost Creek Designated Ground Water Basin, Colorado ..................................................... 23

15. Diagram of passive-wick lysimeter design and installation.......................................................... 27

16–21. Maps showing:

 16. Location of decreed irrigation wells with final permits in the Lost Creek 

Designated Ground Water Basin, Colorado.............................................................................. 33

 17. Grid and boundary conditions of the groundwater flow model, Lost Creek 

Designated Ground Water Basin, Colorado.............................................................................. 36

 18. Hydraulic conductivity zones of the groundwater flow model, Lost Creek 

Designated Ground Water Basin, Colorado.............................................................................. 37
v

 19. Recharge zones of the groundwater flow model, Lost Creek Designated 

Ground Water Basin, Colorado.................................................................................................... 38

 20. Multiplier array used to increase recharge in areas representing sandy 

soils in the groundwater flow model, Lost Creek Designated Ground Water 

Basin, Colorado................................................................................................................................ 39

 21. Location of hydraulic-head observations used to calibrate the groundwater 

flow model, Lost Creek Designated Ground Water Basin, Colorado.................................. 41

22–25. Graphs showing:

 22. Relation of weighted residuals to weighted simulated values in the groundwater 

flow model for (A) hydraulic head and prior information and (B) hydraulic head 

only, Lost Creek Designated Ground Water Basin, Colorado............................................... 45

 23. Normal probability plot of weighted residuals for the groundwater flow model, 

Lost Creek Designated Ground Water Basin, Colorado......................................................... 45

 24. Relation of weighted observations to weighted simulated values in the groundwater flow model for (A) hydraulic head and prior information and (B) hydraulic 

head only, Lost Creek Designated Ground Water Basin, Colorado..................................... 46

 25. Composite scaled sensitivities of parameters in the groundwater flow model, 

Lost Creek Designated Ground Water Basin, Colorado......................................................... 47

26. Map showing steady-state altitude and configuration of the water table simulated by 

the groundwater flow model, Lost Creek Designated Ground Water Basin, Colorado ......... 48

27. Map showing saturated thickness simulated by the groundwater flow model, Lost 

Creek Designated Ground Water Basin, Colorado.......................................................................... 50

Tables

1. Annual water deliveries to irrigated agricultural fields in the Lost Creek Designated 

Ground Water Basin by Prospect Lateral Ditch, Lowline Canal, and the 1053 ditch, 

1990–2001......................................................................................................................................................9

2. Aquifer transmissivity and hydraulic conductivity determined from aquifer tests 

and estimated from specific capacity of wells in the Lost Creek Designated Ground 

Water Basin.............................................................................................................................................. 16

3. Chloride concentration of soil water and precipitation, rate of precipitation, 

and recharge rates estimated from soil-chloride profiles beneath native grassland, 

nonirrigated agricultural fields, and ephemeral stream channels in the Lost Creek 

Designated Ground Water Basin......................................................................................................... 24

4. Net irrigation, precipitation, crop consumptive use, and recharge estimated by 

lysimeter drainage and a water-balance method for four irrigated agricultural 

fields in the Lost Creek Designated Ground Water Basin............................................................. 28

5. Annual water deliveries to Olds Reservoir for recharge to the Lost Creek 

Designated Ground Water Basin......................................................................................................... 31

6. Hydraulic-head observations used to calibrate the Lost Creek Designated 

Ground Water Basin model................................................................................................................... 42

7. Initial and final parameter values, prior-information values, and prior-information 

weights used in the Lost Creek Designated Ground Water Basin model.................................. 43

8. Statistics used to assess calibration of the Lost Creek Designated Ground 

Water Basin model.................................................................................................................................. 44

9. Simulated steady-state groundwater budget of the Lost Creek Designated 

Ground Water Basin model representing conditions for 1990–2001..................................51
vi

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

square foot (ft2) 0.09290 square meter (m2)

square mile (mi2) 2.590 square kilometer (km2)

Volume

gallon (gal) 3.785 liter (L) 

cubic foot (ft3) 0.02832 cubic meter (m3) 

acre-foot (acre-ft) 1,233 cubic meter (m3)

Flow rate

acre-foot per day (acre-ft/d) 0.01427 cubic meter per second (m3/s)

acre-foot per year (acre-ft/yr) 1,233 cubic meter per year (m3/yr)

foot per day (ft/d) 0.3048 meter per day (m/d)

cubic foot per day (ft3/d) 0.02832 cubic meter per day (m3/d)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

inch per hour (in/h) 0 .0254 meter per hour (m/h)

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

Specific capacity

gallon per minute per foot

[(gal/min)/ft)]

0.2070 liter per second per meter [(L/s)/m]

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day (m/d)

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

Transmissivity*

foot squared per day (ft2/d) 0.09290 meter squared per day (m2/d) 

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

°C=(°F–32)/1.8

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

*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.

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft) 

Volume

cubic centimeter (cm3) 0.06102 cubic inch (in3) 

liter (L) 61.02 cubic inch (in3) 

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

Pressure

kilopascal (kPa) 0.1450 pound per square inch (lb/in2) 

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L).
vii

Other abbreviations used in this report:

(MJ/m

2

)/d Megajoule per square meter per day

kPa/°C Kilopascal per degree Celsius

kg/m

3 Kilogram per cubic meter

(MJ/kg)/°C Megajoule per kilogram per degree Celsius

m/s Meter per second

s/m Second per meter

mm/d Millimeters per day

Abstract

The Lost Creek Designated Ground Water Basin (Lost 

Creek basin) is an important alluvial aquifer for irrigation, public supply, and domestic water uses in northeastern Colorado. 

Urban growth in the adjacent Front Range urban corridor has 

increased demand for groundwater in the basin, and potential 

exportation of groundwater from the basin has raised concerns about the long-term sustainability and management of 

the basin’s groundwater resources. Beginning in 2005, the 

U.S. Geological Survey, in cooperation with the Lost Creek 

Ground Water Management District and the Colorado Water 

Conservation Board, collected hydrologic data and constructed 

a numerical groundwater flow model of the Lost Creek basin. 

The steady-state model builds upon the work of previous investigators to provide an updated tool for simulating the potential 

effects of various hydrologic stresses on groundwater flow and 

evaluating possible aquifer-management strategies.

As part of model development, the thickness and extent 

of regolith sediments in the basin were mapped, and data were 

collected concerning aquifer recharge beneath native grassland, nonirrigated agricultural fields, irrigated agricultural 

fields, and ephemeral stream channels. The thickness and 

extent of regolith in the Lost Creek basin indicate the presence of a 2- to 7-mile-wide buried paleovalley that extends 

along the Lost Creek basin from south to north, where it joins 

the alluvial valley of the South Platte River valley. Regolith 

that fills the paleovalley is as much as about 190 ft thick. 

Recharge from infiltration of precipitation on native grassland 

and nonirrigated agricultural fields was estimated by using the 

chloride mass-balance method at four sites in the Lost Creek 

basin. Recharge from infiltration of ephemeral streamflow was 

estimated by using apparent downward velocities of chloride peaks in soil profiles at two sites in the basin. Recharge 

from deep percolation of water applied to irrigated agricultural fields was estimated by using passive-wick lysimeters 

installed at four sites in the basin and by using a water-balance 

approach. Average annual recharge from infiltration of 

precipitation on native grassland and nonirrigated agricultural 

fields was estimated to range from 0.1 to 0.6 inch, which 

represents about 1–4 percent of long-term average precipitation. Average annual recharge from infiltration of ephemeral 

streamflow was estimated to range from 5.7 to 8.2 inches. 

Average annual recharge beneath irrigated agricultural fields 

was estimated to range from 0 to 11.3 inches, depending on 

irrigation method, soil type, crop type, and the net quantity of irrigation water applied. Estimated average annual 

recharge beneath irrigated agricultural fields represents about 

0–43 percent of net irrigation.

The U.S. Geological Survey modular groundwater 

modeling program, MODFLOW–2000, was used to develop a 

steady-state groundwater flow model of the Lost Creek basin. 

The model primarily was calibrated to average hydrologic 

conditions representing the period 1990–2001 by using the 

inverse modeling capabilities of MODFLOW–2000. Simulated water levels generally have acceptable agreement with 

water levels measured at 43 locations in the Lost Creek basin, 

and calibration statistics indicate that residuals between simulated and measured values of hydraulic head likely are random, independent, and normally distributed. Composite scaled 

sensitivities were highest for parameters representing withdrawals from wells lacking pumping data, recharge beneath 

nonirrigated areas, and recharge beneath flood-irrigated fields, 

indicating that these parameters likely are the most important 

to accurately define for model simulations.

Groundwater in the simulated Lost Creek basin generally 

flows from basin margins toward the center of the basin and 

northward along the paleovalley of the basin. The largest source 

of inflow to the model occurs from recharge beneath floodand sprinkler-irrigated agricultural fields (14,510 acre-ft/yr), 

which represents 39.7 percent of total simulated inflow. Other 

substantial sources of inflow to the model are recharge from 

precipitation and stream-channel infiltration in nonirrigated 

areas (13,810 acre-feet per year [acre-ft/yr]), seepage from Olds 

Reservoir (4,280 acre-ft/yr), and subsurface inflow from ditches 

and irrigated fields outside the model domain (2,490 acre-ft/yr), 

Hydrogeology and Steady-State Numerical 

Simulation of Groundwater Flow in the Lost Creek 

Designated Ground Water Basin, Weld, Adams, 

and Arapahoe Counties, Colorado

By L.R. Arnold
2 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

which contribute 37.7, 11.7, and 6.8 percent, respectively, of total 

inflow. The largest outflow from the model occurs from irrigation 

well withdrawals (26,760 acre-ft/yr), which represent 73.2 percent 

of total outflow. Groundwater discharge (6,640 acre-ft/yr) at the 

downgradient end of the Lost Creek basin represents 18.2 percent 

of total outflow, and evapotranspiration (3,140 acre-ft/yr) represents about 8.6 percent of total outflow.

Introduction

The Lost Creek Designated Ground Water Basin (Lost 

Creek basin; fig. 1) consists of an alluvial aquifer that is an 

important source of water for irrigation, public supply, and 

domestic use in northeastern Colorado. Perennial streams do 

not exist within the basin, and groundwater in the basin historically has been used primarily for irrigation of agricultural 

land within the basin’s boundaries. However, urban growth 

in the adjacent Front Range urban corridor has increased 

demand for groundwater in the basin, and potential exportation of groundwater from the basin has raised concerns about 

the long-term sustainability and management of the basin’s 

groundwater resources.

The hydrogeology and groundwater resources of the Lost 

Creek basin originally were characterized in 1967 by Nelson, 

Haley, Patterson,and Quirk, Inc. (1967) in a report to the 

Colorado Ground Water Commission. The purpose of the report 

was to provide information for legally defining the basin as a 

Designated Ground Water Basin, subject to a set of water rules 

separate from the Doctrine of Prior Appropriation used for regulation of tributary waters in the State of Colorado. Designated 

groundwater in alluvial aquifers generally is defined as groundwater in areas not adjacent to a continuously flowing natural 

stream wherein groundwater withdrawals have constituted the 

principal water usage for at least 15 years (Jones and Cech, 

2009). Data from the Nelson, Haley, Patterson, and Quirk, Inc. 

report were used in the development of a steady-state numerical groundwater flow model of the Lost Creek basin in 1995 

(Thomas Hatton, J.R. Engineering, Inc., written commun., 

2004), and the model subsequently was modified between 1995 

and 2004 (Barbara Ford, HRS Water Consultants, Inc., written commun., 2005) for use in simulating the effects of several 

pumping scenarios under different recharge and hydrogeologic 

conditions. Since development of the previous groundwater 

models, new hydrogeologic information has been collected 

in the Lost Creek basin as part of the U.S. Geological Survey 

(USGS) National Water Quality Assessment (NAWQA) program and the State of Colorado’s South Platte Decision Support 

System (SPDSS) program.

In 2005 the USGS began a study in cooperation with 

the Lost Creek Ground Water Management District to review 

and summarize the 2004 version of the existing groundwater 

model and to construct an updated numerical groundwater 

flow model of the Lost Creek basin using new data and numerical simulation capabilities. In 2007, the study was expanded 

in cooperation with the Colorado Water Conservation Board to 

collect data concerning aquifer recharge occurring from deep 

percolation of water applied to agricultural fields within the 

basin in order to improve estimates of irrigation recharge and 

reduce model uncertainty as related to irrigation recharge.

Purpose and Scope

The purpose of this report is to describe the hydrogeology 

and a steady-state numerical groundwater flow model of the 

Lost Creek Designated Ground Water Basin in Weld, Adams, 

and Arapahoe Counties in Colorado. The description of hydrogeology provides new information, with particular emphasis 

on aquifer geometry and recharge, that builds upon the work 

of previous investigators. The steady-state model also builds 

upon the work of previous investigators to provide an updated 

tool for simulating the potential effects of various hydrologic 

stresses on groundwater flow and evaluating possible aquifermanagement strategies.

The extent and thickness of regolith (unconsolidated 

sediments) in the basin were mapped to better characterize 

the subsurface geometry of the basin. Water-level data were 

compiled for the period 1990–2001 for use in calibrating 

the steady-state groundwater flow model. Data concerning 

infiltration of precipitation, infiltration from stream channels, 

deep percolation of water applied to irrigated agricultural 

fields, ditch and reservoir seepage, and subsurface inflow 

were collected to improve estimates of recharge to the basin. 

Data concerning well withdrawals, evapotranspiration, and 

subsurface outflow were used to estimate discharge from 

the basin. The USGS modular groundwater modeling program MODFLOW–2000 (Harbaugh and others, 2000; Hill 

and others, 2000) was used to construct and calibrate the 

updated steady-state groundwater flow model using inversemodeling methods.

Study-Area Description

The Lost Creek basin occupies an area of about 432 square 

miles (mi2) in parts of Weld, Adams, and Arapahoe Counties in 

northeastern Colorado (fig. 1). The administrative boundary of the 

Lost Creek basin is defined approximately by the drainage basin 

of Lost Creek and its tributaries. Population centers in the basin 

include the towns of Keenesburg, Roggen, Prospect Valley, and 

Bennett. The Lost Creek basin is about 43 mi long and extends 

from about 6 mi south of Bennett northward to the South Platte 

River valley. The basin is as much as 14 mi wide.

Physiography and Climate

The Lost Creek basin lies within the Colorado Piedmont 

section of the Great Plains physiographic province (Fenneman, 

1946) and generally is characterized by relatively flat to gently 

sloping terrain with local relief of tens of feet. North of Roggen, 
Introduction 3

Figure 1. Location of the Lost Creek Designated Ground Water Basin, in Weld, Adams, and Arapahoe Counties, Colorado.

!(

!(

!(

!(

!(

Box Elder Creek

¬«

¬«

£¤

£¤

 ̈¦§

§ ̈¦

EXPLANATION

Lost Creek Designated Ground Water 

 Basin administrative boundary

Lost Creek drainage basin boundary

Ephemeral stream

Base from U.S. Geological Survey digital data, 1:100,000

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

0 5

0 5 10 KILOMETERS

10 MILES

Riverside

Reservoir

Empire

Reservoir

Lord

Reservoir

Olds

Reservoir

Prospect

Reservoir

Horse Creek

Reservoir

South Platte River

Lost Creek

Box Elder Creek

Kiowa Creek

Sand

Creek

Long

Draw

Lost Creek

Sand Creek

Box Elder Creek

Comanche Creek

Kiowa Creek

Box Elder Creek

West Sand Creek

Roggen

Keenesburg

Prospect

Valley

Masters

Bennett

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

104°30' 104°15'

40°15'

40°00'

39°45'

34

76

52

36

79

70

C O L O R A D O

Denver

Map

area

Front Rang e urban corridor
4 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

the landscape is composed largely of vegetated sand dunes, 

and topography commonly is hilly. Land-surface altitudes in 

the Lost Creek basin range from about 4,550 ft, where the Lost 

Creek channel exits the north end of the basin, to about 5,880 ft 

at the southern end of the basin. Three reservoirs (Prospect, 

Lord, and Olds) are located in the Lost Creek basin (fig. 1). 

Prospect and Lord Reservoirs are used primarily for storage 

and delivery of irrigation water to agricultural fields in the 

Lost Creek basin. Olds Reservoir is used primarily to recharge 

groundwater in the Lost Creek basin through lakebed seepage. 

No perennial streams exist in the Lost Creek basin, but drainage in ephemeral streams generally is northward toward the 

South Platte River. Primary ephemeral stream channels in the 

Lost Creek basin are Lost Creek, Sand Creek, West Sand Creek, 

and Long Draw, which usually are dry except after significant 

storm events. Based on discussions with local residents of the 

Lost Creek basin, Skinner (1963) reported that, historically, Lost 

Creek had stormflow about once every 2 years on average, and 

Sand Creek had stormflow an average of about twice per year. 

Long Draw historically has had stormflow about once every 

2 years (John Cordes, Lost Creek Ground Water Management 

District, oral commun., 2006). Since 2000, streams generally 

have had stormflow an average of about once every 3 years 

(Thomas Sauter and Kent Crisman, Lost Creek Ground Water 

Management District, oral commun., 2008). When streams 

do flow after storms, runoff seeps rapidly into the ground. 

Any runoff in upper Lost Creek is captured by Lord Reservoir 

(Code, 1945; Skinner, 1963), and runoff in Sand Creek and 

Long Draw rarely reaches the town of Roggen (John Cordes, 

Lost Creek Ground Water Management District, oral commun., 

2006). Runoff from rainstorms typically lasts less than 1 day, 

and runoff from local snowmelt typically lasts less than 1 week 

(Skinner, 1963).

The Lost Creek basin has a semiarid continental climate 

with large differences in temperature between summer and 

winter; sudden and extreme temperature changes on a daily 

basis are common. Temperatures recorded at three long-term 

weather stations (Brighton, period of record 1973–2007; 

Byers 5 ENE, period of record 1893–2007; Fort Morgan, 

period of record 1896–2008) (fig. 2) near the Lost Creek basin 

range from a mean monthly low of 9.6°F during January to a 

mean monthly high of 90.3°F during July (Western Regional 

Climate Center, 2008). Long-term average annual precipitation for the periods of record at the three weather stations 

ranged from 13.3 to 14.8 inches (Western Regional Climate 

Center, 2008) with a mean value of 14.1 inches. Average annual pan evaporation measured at the Wiggins 7 SW 

weather station (period of record 1960–1971) (fig. 2) near the 

Lost Creek basin was 54.1 inches (Western Regional Climate 

Center, 2008), which greatly exceeds average annual precipitation in the basin. About 70–80 percent of annual precipitation 

and about 88 percent of annual evapotranspiration in the Lost 

Creek basin occurs from April through September.

Soils

Soils in the Lost Creek basin consist of six general soil 

associations—Weld-Norka-Adena, Valent-Julesburg-Vona, 

Otero-Thedalund-Olney, Altvan-Dacono-Nunn, Heldt-NunnLimon, and Kutch-Bresser-Louviers (U.S. Department of 

Agriculture, 1994) (fig. 3). Most soils south of Roggen are 

composed of loam or silt loam of the Weld-Norka-Adena 

group with soil permeability generally ranging from 0.2 to 

2 in/hr (Heil and others, 1978). Sand dunes north of Roggen 

are composed almost entirely of the Valent-Julesburg-Vona 

group with soil permeability generally ranging from 2 to 

20 in/hr. Soils of the Altvan-Dacono-Nunn group are located 

along the stream channels of Lost Creek, Sand Creek, and 

West Sand Creek (fig. 3), and soils of the Otero-ThedalundOlney group cover localized areas in the central and southern 

parts of the basin. Soils of the Altvan-Dacono-Nunn group 

generally are composed of clay loam to sandy loam and have 

permeability (0.2–2 in/hr) similar to soils of the Weld-NorkaAdena group (Heil and others, 1978). Soils of the OteroThedalund-Olney group are composed of loam to loam sand 

and have permeability (0.6–20 in/hr) similar to soils of the 

Valent-Julesburg-Vona group. Soils of the Heldt-Nunn-Limon 

and Kutch-Bresser-Louviers groups cover small areas at the 

southern end of the basin.

Land Use and Irrigation

Land in the Lost Creek basin is used primarily for agriculture and rangeland (fig. 4), but small areas of urban and 

other land uses also occur in the basin. Irrigated agricultural 

land primarily is located in the central and northern parts of 

the basin, and nonirrigated agricultural land primarily is in the 

southern part of the basin and near the basin margins. Rangeland is prominent in the northern part of the basin where soils 

are highly permeable and hilly topography exists. Based on 

mapping of irrigated acres (Riverside Technology, Inc., 2007) 

(fig. 4), about 32,500 acres in the Lost Creek basin were irrigated in 2001. About 57 percent of the area was irrigated using 

flood-irrigation methods and about 43 percent was irrigated by 

sprinklers. Crops commonly grown in the irrigated parts of the 

basin include corn, wheat, barley, alfalfa, and small vegetables 

(Richard Huwa, Lost Creek Ground Water Management 

District, oral commun., 2007). Dryland crops cultivated in the 

nonirrigated parts of the basin consist mainly of wheat and 

other small grains.

Both surface water and groundwater are used for irrigation in the Lost Creek basin, and a parcel of irrigated agricultural land may be supported by surface water, groundwater, 

or both. Surface water is conveyed to the Lost Creek basin by 

the Denver-Hudson Canal (fig. 4) and is stored in Prospect 

and Lord Reservoirs. Surface water is delivered to agricultural 
Introduction 5

Figure 2. Location of weather stations and the National Atmospheric Deposition Program site used by the study, 

Lost Creek Designated Ground Water Basin, Colorado.

"

•

•

•

•

•

!

!

!

Weather station locations modified from Colorado

Division of Water Resources (2007)

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

EXPLANATION

Lost Creek Designated Ground Water Basin 

 administrative boundary

Climate station and name

National Atmospheric Deposition Program 

 site and name

0 10 20 MILES

0 10 20 KILOMETERS

Pawnee

Greeley

CoAgMet

Fort Morgan

Fort

Morgan

City of

Fort Morgan

Denver

Brighton

WELD COUNTY

MORGAN COUNTY

ADAMS COUNTY

ARAPAHOE COUNTY

BROOMFIELD

COUNTY LARIMER COUNTY

WASHINGTON COUNTY

DENVER

COUNTY

South Platte River Cac he La Poudre River

Byers 5 ENE

Wiggins 7 SW

C O L O R A D O

Map

area

105°00' 104°30' 104°00'

40°30'

40°00'
6 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Figure 3. Distribution of major soil associations in the Lost Creek Designated Ground Water Basin, Colorado.

!(

!(

!(

!(

!(

¬«

§ ̈¦ £¤

£¤

¬«

34

52

36

79

70

§ ̈¦76

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

Soil groups modified from U.S. Department of Agriculture (1994)

North American Datum of 1983

EXPLANATION

Lost Creek Designated Ground Water 

 Basin administrative boundary

Weld–Norka–Adena

Valent–Julesburg–Vona

Otero–Thedalund–Olney

Altvan–Dacono–Nunn

Heldt–Nunn–Limon

Kutch–Bresser–Louviers

Masters Soil Group

Keenesburg

Prospect

Valley

Bennett

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Roggen

Long

Draw

S outh Platte River

Lost Creek

Lord

Reservoir

Prospect

Reservoir

Olds

Reservoir

Lost Creek

We st Sand

Creek

Sand Creek

0 5 10 MILES

0 5 10 KILOMETERS

104°30'

40°15'

40°00'

39°45'

104°15'
Introduction 7

Figure 4. Generalized land use in the Lost Creek Designated Ground Water Basin, Colorado.

!(

!(

!(

!(

!(

£¤

¬«

§ ̈¦

§ ̈¦

£¤

«

52

70 36

76

79

Streams, ditches, and reservoirs modified from Schupbach and Lewis (1996a, b)

Nonirrigated land use modified from U.S. Geological Survey (2000)

Areas of irrigated agriculture modified from Riverside Technology, Inc. (2007)

Henrylyn Irrigation District extent modified from Riverside Technology, Inc. (2006)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

Prospect

Valley

Masters

Keenesburg

Roggen

Prospect

Valley

Bennett

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Lord Reservoir

Prosp e ct Lateral Ditch

Olds

Reservoir

Prospect

Reservoir

Lost Creek

Horse Creek

Reservoir

Olds

Reservoir

Lord Reservoir

West Sand

Creek

Sand

Creek

Long Draw

Lost Creek

Sout h Platte River

Prosp e ct Lateral Ditch

Keen

Lateral

Lowline CanalLowline Canal

1053 ditch1053 ditch

Canal

Denver H- udson

Lost Creek Designated Ground Water

 Basin administrative boundary

Henrylyn Irrigation District

Canal or ditch

Land use

 Flood-irrigated agriculture

 Sprinkler-irrigated agriculture

 Nonirrigated agriculture

 Rangeland/grassland

 Urban/residential

 Open water

 Other

EXPLANATION

0 5 10 MILES

0 5 10 KILOMETERS

34

104°30'

40°15'

40°00'

39°45'

104°15'
8 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

fields in the basin by the Henrylyn Irrigation District (fig. 4) 

primarily by using Prospect Lateral Ditch, Lowline Canal, 

and the 1053 ditch (Rodney Baumgartner, Henrylyn Irrigation 

District, oral commun., 2008). Prospect Lateral Ditch is used 

to deliver releases from Prospect Reservoir to irrigated fields 

in the Lost Creek basin. Lowline Canal and the 1053 ditch 

divert water directly from the Denver-Hudson Canal before 

it reaches Prospect Reservoir. Lowline Canal also is used 

to deliver releases from Lord Reservoir to irrigated fields. 

Surface water also is delivered to agricultural fields in the 

Lost Creek basin by using Keen Lateral, but the number of 

acres (about 200–300) estimated by this study to be irrigated 

by Keen Lateral within the boundaries of the basin represents only a small portion of the total irrigated land area in 

the basin.

An average of about 4,300 acre-ft of water was delivered annually by Prospect Lateral Ditch during the period 

1990–2001 (Rodney Baumgartner, Henrylyn Irrigation District, 

written commun., 2008) (table 1) to irrigate about 9,600 acres, 

which amounts to about 0.45 acre-ft of water per acre of land, 

not considering seepage or other conveyance losses. During the 

same time period, average annual deliveries by Lowline Canal 

were about 2,800 acre-ft of water to irrigate about 6,500 acres, 

amounting to about 0.43 acre-ft of water per acre of land, 

and average annual deliveries by the 1053 ditch were about 

4,700 acre-ft for irrigation of about 6,000 acres, amounting to 

about 0.78 acre-ft of water per acre of land. In all, an average 

of about 11,900 acre-ft of surface water was used to irrigate 

about 22,100 acres in the Lost Creek basin, amounting to about 

0.54 acre-ft of water per acre of land.

About 266 decreed irrigation wells with final permits are located in the Lost Creek basin (Suzanne Sellers, 

Colorado Division of Water Resources, written commun., 

2007). Assuming each of these wells was actively used during 

1990–2001, it is estimated by this study that an average of 

about 44,300 acre-ft of groundwater was withdrawn annually 

to irrigate about 27,800 acres in the Lost Creek basin, providing about 1.6 acre-ft of water per acre of land. Groundwater 

withdrawals for irrigation are discussed in more detail in the 

“Well Withdrawals” section of this report.

The discrepancy between the sum of acres irrigated by 

surface water and groundwater (49,900) and the total number 

of irrigated acres (32,500) mapped by Riverside Technology, 

Inc. (2007) may reflect that some parcels are irrigated by both 

surface water and groundwater. Alternatively, the discrepancy 

may indicate inaccuracies in the estimates of irrigated acres, 

particularly the estimate of acres irrigated by groundwater, 

which is based on the number of acres permitted for each well. 

If not all wells actively withdrew water during 1990–2001, 

the number of acres irrigated by groundwater and total annual 

groundwater withdrawals might be overestimated. Based on 

a total irrigated land area of 32,500 acres, total irrigation by 

both surface water and groundwater (56,200 acre-ft) represents 

an average application of about 1.73 acre-ft of water per acre 

of land.

Hydrogeology

Aquifer Extent and Thickness

The Lost Creek basin alluvial aquifer occupies a paleovalley (ancient buried stream valley) adjoining the South Platte 

River valley. The sides and southern end of the alluvial aquifer 

are defined by uplands composed of bedrock that crops out or 

forms shallow subcrops near the land surface. The northern end 

of the Lost Creek basin connects to the alluvial aquifer of the 

South Platte River valley. Alluvial sediments in the Lost Creek 

basin locally are covered by eolian (windblown) sand deposits, 

particularly in the northern part of the basin (Braddock and 

Cole, 1978; Bryant and others, 1981) (fig. 5). Bedrock underlying the Lost Creek basin consists of sedimentary strata that 

constitute the Denver Basin aquifer system (Robson, 1987). The 

southern part of the alluvial aquifer is directly underlain by the 

Denver aquifer, the central part of the aquifer is directly underlain by the Arapahoe aquifer, and the northern part of the aquifer 

is directly underlain by the Laramie–Fox Hills aquifer.

To determine the subsurface configuration of the Lost 

Creek basin for input to the updated groundwater model, the 

thickness of regolith sediments (primarily alluvium and eolian 

deposits) in the basin was mapped using data compiled from 

Bjorklund and Brown (1957), Nelson, Haley, Patterson, and 

Quirk, Inc. (1967), Skinner (1963), Hurr and others (1972), 

HRS Water Consultants, Inc. (written commun., 2006), and 

about 550 lithologic logs from wells and test holes on file with 

the USGS Colorado Water Science Center in Lakewood, Colorado and the Colorado Division of Water Resources (CDWR) 

in Denver, Colorado. In some places, weathered bedrock may 

have been mapped as regolith because of inaccurate lithologic 

logs or an indistinct contact between regolith and the underlying 

bedrock. In particular, lithologic logs of deep wells completed 

in bedrock were used to map regolith thickness in the southern 

part of the basin where few other data were available, and regolith thickness determined from these logs might not be accurate 

because they commonly lacked detailed regolith information.

Regolith-thickness contours were prepared by hand 

contouring regolith-thickness data. Hand contouring, rather 

than automated methods, was used to better interpret the 

varied and inconsistent data values that sometimes resulted 

from local irregularities in the bedrock surface, the imprecise 

bedrock contact, mislocated data points, or conflicting data. 

Regolith-thickness contours generally were drawn using the 

preponderance of data in a local area and do not necessarily 

agree with each individual data value. Regolith-thickness data 

were contoured using a 20-ft contour interval with consideration of apparent data quality, topography, lithology, surface 

geology, and understanding of likely depositional and erosional processes leading to the formation of the Lost Creek 

alluvial valley. In areas where regolith-thickness data were 

unavailable, the base of the Lost Creek basin determined by 

Nelson, Haley, Patterson, and Quirk (1967, pl. 2) was used 

to estimate regolith thickness. Mapping results (figs. 6 and 7) 

indicate a well-defined paleovalley that extends along the Lost 
Introduction 

9

Table 1. Annual water deliveries to irrigated agricultural fields in the Lost Creek Designated Ground Water Basin by Prospect Lateral Ditch, Lowline Canal, and the 1053 ditch, 1990–2001.[--, no data]

Year

Prospect Lateral Ditch Lowline Canal 1053 ditch Total

Total water

delivered1

(acre-feet)

Irrigated

area2

(acres)

Effective water

application3

(acre-foot/acre)

Total water

delivered1

(acre-feet)

Irrigated

area2

(acres)

Effective water

application3

(acre-foot/acre)

Total water

delivered1

(acre-feet)

Irrigated

area2

(acres)

Effective water

application3

(acre-foot/acre)

Total water

delivered1

(acre-feet)

Irrigated

area2

(acres)

Effective water

application3

(acre-foot/acre)

1990 1,947 9,632 0.20 2,480 6,453 0.38 4,005 6,004 0.67 8,432 22,089 0.381991 3,897 9,632 0.40 2,834 6,453 0.44 4,936 6,004 0.82 11,667 22,089 0.531992 3,605 9,632 0.37 2,471 6,453 0.38 3,906 6,004 0.65 9,982 22,089 0.451993 3,785 9,632 0.39 2,517 6,453 0.39 4,015 6,004 0.67 10,317 22,089 0.471994 3,695 9,632 0.38 2,457 6,453 0.38 4,516 6,004 0.75 10,668 22,089 0.481995 4,734 9,632 0.49 2,819 6,453 0.44 5,200 6,004 0.87 12,753 22,089 0.581996 3,918 9,632 0.41 2,903 6,453 0.45 4,775 6,004 0.80 11,596 22,089 0.521997 5,515 9,632 0.57 3,278 6,453 0.51 5,902 6,004 0.98 14,695 22,089 0.671998 6,979 9,632 0.72 3,630 6,453 0.56 6,187 6,004 1.03 16,796 22,089 0.761999 6,611 9,632 0.69 3,238 6,453 0.50 4,826 6,004 0.80 14,675 22,089 0.662000 3,511 9,632 0.36 2,193 6,453 0.34 3,335 6,004 0.56 9,039 22,089 0.412001 3,573 9,632 0.37 -- -- -- -- -- -- -- -- --

Average 4,314 9,632 0.45 2,802 6,453 0.43 4,691 6,004 0.78 11,875 22,089 0.54

1Total water delivered provided by Rodney Baumgartner, Henrylyn Irrigation District, written commun., 2008.2Irrigated area based on 1990 acreage provided by Rodney Baumgartner, Henrylyn Irrigation District, written commun., 2008.3Effective water applications assumes no conveyance loss.
10 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Figure 5. Surficial geology of the Lost Creek Designated Ground Water Basin, Colorado.

!(

!(

!(

!(

!(

¬«

¬«

£¤

£¤

§¦ ̈

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Surficial geology modified from Braddock and Cole (1978) and Bryant and others (1981)

Bedrock geology modified from Schupbach and Lewis (1995)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American datum of 1983

Bennett

Masters

Roggen

Keenesburg

Prospect

Valley

West Sand

Creek

Olds

Reservoir

Lord

Reservoir

Prospect

Reservoir

Lost Cree k

South Platte River

Long Draw

Sand Creek

LostCreek

EXPLANATION

Lost Creek Designated Ground Water

 Basin administrative boundary

Lost Creek drainage basin boundary

Hydrogeologic unit

 Eolian deposits (Quaternary)

 Alluvium (Quaternary)

 Upper Dawson aquifer (Tertiary)

 Denver aquifer (Tertiary/Cretaceous)

 Arapahoe aquifer (Cretaceous)

 Laramie Formation (Cretaceous)

 Laramie–Fox Hills aquifer (Cretaceous)

0 5 10 MILES

0 5 10 KILOMETERS

34

52

79

36 70

§¦ ̈76

104°30'

40°15'

40°00'

39°45'

104°15'
Introduction 11

Figure 6. Approximate thickness of regolith sediments in the Lost Creek Designated Ground Water Basin, Colorado.

!(

!(

!(

!(

!(

¬«

§ ̈¦

§ ̈¦ £¤

£¤

¬«

36 70

40°15'

40°00'

39°45'

104°30' 104°15'

34

76

52

79

20

100

60

60

80

140

40

40

40

80

120

40

180

80

100 40

20

120 80

60

100

160

40

60

20

60

140

120

40

100

80

20

60

20

60

20

100

60

60

80

140

40

40

40

80

120

40

180

80

100 40

20

120 80

60

100

160

40

60

20

60

140

120

40

100

80

20

60

20

60

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

0 5 10 MILES

0 5 10 KILOMETERS

EXPLANATION

Lost Creek Designated Ground Water

 Basin administrative boundary

Lost Creek drainage basin boundary

Line of equal regolith thickness—

 Contour interval 20 feet

Location of well or test hole with 

 lithologic data

Regolith thickness, in feet

 0–40

 40–80

 80–120

 120–160

 160–200

Roggen

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Masters

Roggen

Keenesburg

Prospect Valley

Bennett

Hay Gulch

Lost Creek

Sand

Creek

West Sand Creek

Lost Creek

West Sand Creek

Lost Creek

Sand

Creek

Long Draw

Lost Creek

Prospect

Reservoir

Olds

Reservoir

Lord

Reservoir

Sou th Platte River
12 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Figure 7. Generalized altitude and configuration of the bedrock surface underlying regolith in the Lost Creek Designated Ground Water 

Basin, Colorado.

!(

!(

!(

!(

!(

¬«

§ ̈¦

§ ̈¦ £¤

£¤

¬«

4500

5000

5500

34

76

52

79

36 70

40°15'

40°00'

39°45'

104°30' 104°15'

0 5 10 MILES

0 5 10 KILOMETERS

5000

EXPLANATION

Lost Creek Designated Ground Water Basin 

 administrative boundary

Lost Creek drainage basin boundary

Bedrock-surface contour—Shows approximate 

 altitude of bedrock surface underlying regolith. 

 Contour interval 100 feet. National Geodetic

 Vertical Datum of 1929

Roggen

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Masters

Roggen

Keenesburg

Prospect Valley Prospect Valley

Bennett

Hay Gulch

West Sand CreekWest Sand Creek

Lost CreekLost Creek

Sand

Creek SandCreek Long Draw

Lost CreekLost Creek

Prospect

Reservoir

Olds

Reservoir

Lord

Reservoir

Sou th Platte River

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983
Hydrogeology 13

Creek basin from south to north, where it joins the alluvial 

valley of the South Platte River. Regolith along the main part 

of the paleovalley is as much as about 190 ft thick, and several 

smaller paleovalleys (such as along Long Draw and west of 

West Sand Creek in the southern part of the basin) appear 

tributary to the main paleovalley and have regolith as much as 

120 ft thick. In the area of Hay Gulch, a substantial paleovalley appears to be separated from the main paleovalley of the 

Lost Creek basin by a ridge of relatively shallow bedrock. 

However, few data were available to map regolith thickness 

in the area between Hay Gulch and the main paleovalley. The 

extent of the main paleovalley and Hay Gulch generally coincides with the extent of alluvial and eolian sediments mapped 

by Braddock and Cole (1978) and Bryant and others (1981). 

However, some areas mapped as bedrock at the land surface 

by the two investigations were found to have regolith sediments generally 20–40 ft thick based on borehole information, 

particularly in the area of upper Long Draw. Discrepancies 

between the maps of surficial geology and regolith thickness 

might be the result of poorly exposed outcrops, relatively 

soft weathered bedrock at the land surface being mapped 

as regolith, or the different scales at which the maps were 

prepared. Geographic Information System datasets (Arnold, 

2010) showing regolith-thickness and bedrock-altitude data, 

regolith-thickness contours, and raster-based regolith thickness 

are available at http://water.usgs.gov/lookup/getgislist.

Examination of lithologic logs along and in cross section 

to the main paleovalley and its tributaries indicates sediments 

along the deepest part of the paleovalleys are composed primarily of sand and gravel with interbedded clay layers. Sediments 

adjacent to the deepest part of paleovalleys generally appear to 

have approximately equal amounts of sand, gravel, and clay, 

and clay content generally increases toward paleovalley margins 

except where thick eolian (windblown) sands are present at 

the land surface. In topographically high areas at the edges of 

paleovalleys, bedrock commonly is at or near land surface and 

sediments generally are composed primarily of clay.

Water Levels and Groundwater Flow

Groundwater levels in the study area (fig. 8) generally are 

highest in winter and early spring before the irrigation season and 

generally decline during the summer season as a result of pumping for irrigation. The magnitude of groundwater-level fluctuations between seasons and from year to year varies by location. 

Long-term historical water levels measured in the Lost Creek 

basin (Colorado Division of Water Resources, 2000; Schaubs, 

2007) indicate seasonal and yearly groundwater-level fluctuations generally range from about 0 to 3 ft throughout most of 

the basin. Groundwater-level fluctuations are greater (generally 

1–5 ft) in and immediately downgradient from irrigated areas 

in the Henrylyn Irrigation District (well GS–2), and they are 

greatest (generally 2–10 ft) downgradient from Olds Reservoir 

(well GS–3). Groundwater levels in and immediately downgradient from irrigated areas in the Henrylyn Irrigation District 

commonly rose about 10–25 ft during the early to mid-1980s, 

remained relatively stable from 1990 through the spring of 2002, 

and began declining in 2003. Groundwater levels in the Lost 

Creek basin north of Roggen (well N–8) generally have declined 

a total of 3 to 10 ft in a relatively steady manner since the early 

1980s. Well GS–6 is the only site for which long-term water-level 

measurements were available upgradient from the area irrigated 

by the Henrylyn Irrigation District. Groundwater levels at well 

GS–6 rose about 8 ft gradually during the 1980s and declined 

about 5 ft gradually from the mid-1990s through 2006. Groundwater-level fluctuations in the Lost Creek basin likely are caused 

by differences in recharge from infiltration of precipitation and 

ephemeral stream water, deep percolation of water applied to irrigated agricultural fields, seepage beneath reservoirs and irrigation 

ditches, and groundwater withdrawals from wells.

Groundwater in the Lost Creek basin flows generally 

northward under unconfined conditions toward the South Platte 

River valley with hydraulic gradients ranging from about 10 to 

80 ft/mi (Nelson, Haley, Patterson, and Quirk, Inc., 1967, pl. 3) 

(fig. 9). The steeper gradients generally occur in the southern 

part of the basin and along basin margins. Saturated thickness 

in the Lost Creek basin ranges from zero near the basin margins 

to about 120 ft in the north-central part of the basin (Nelson, 

Haley, Patterson, and Quirk, Inc., 1967, pl. 3). The water table in 

the northern part of the Lost Creek basin generally is 10 to 50 ft 

below land surface but can be less than 10 ft below land surface 

in some topographically low areas. The water table in the southern part of the Lost Creek basin generally is about 50 to 130 ft 

below land surface.

Hydrologic Properties

Aquifer transmissivity of the Lost Creek basin was 

estimated for this study from the results of 14 aquifer tests 

presented in published reports (Bjorklund and Brown, 1957; 

Skinner, 1963; Nelson, Haley, Patterson, and Quirk, Inc., 1967; 

Wilson, 1965) and consultant reports (JR Engineering, written commun., 2005; HRS Water Consultants, Inc., written 

commun., 2006) and from specific-capacity data from wellconstruction records on file with USGS and CDWR (table 2). 

The method of Theis and others (1963, p. 331–341) was used 

to estimate aquifer transmissivity from specific-capacity data 

by using a modified form of Theis’s equation 1 as presented by 

Prudic (1991). The modified form of the equation is given as:

T = 15.32(Q/s)(–0.577 – ln[r2S/4Tt]) (1)

where

	 T is aquifer transmissivity, in feet squared 

per day;

	 Q/s is specific capacity of the pumped well, 

in gallons per minute per foot;

	 r is effective radius of the pumped well, 

in feet;

	 S is storage coefficient of the aquifer 

(dimensionless); 

and

	 t is elapsed pumping time, in days.
14 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Because aquifer transmissivity (T) is on both sides of 

equation 1, an iterative process was used to solve the equation. Given input values of Q/s, r, S, and t, the value of T

on the left side of the equation was calculated by providing an initial estimate of T on the right side of the equation. 

The calculated value of T was then substituted into the right 

side of the equation, and the process was repeated until the 

values of T on both sides of the equation were essentially the 

same. Because the alluvial aquifer that constitutes the Lost 

Creek basin generally is unconfined, the storage coefficient is 

approximately equal to the specific yield of the aquifer, and 

specific yield was substituted for S in equation 1. Specific 

yield of sediments in the Lost Creek basin was estimated by 

Code (1945) to have an average value of about 0.17. Therefore, a specific yield of 0.17 was assumed in calculations of 

transmissivity using equation 1. Because storage coefficient 

(S) and well radius (r) are within the natural-log term of 

equation 1, calculated transmissivity is relatively insensitive 

to errors in estimates of S and r. Transmissivities estimated 

from the specific capacity of small-diameter wells with small 

pumping rates typically were found to be an order of magnitude smaller than those estimated from larger-diameter 

wells with large pumping rates. Therefore, only wells with 

diameters larger than 16 inches and pumping rates greater 

than 100 gal/min were used to estimate transmissivity from 

specific capacity.

Figure 8. Groundwater levels at selected well locations in the 

Lost Creek Designated Ground Water Basin, Colorado.

!(

!(

!(

!(

!(

§ ̈¦ £¤

 ̈¦§

£¤

¬«

¬«

34

76

52

79

70 36

0 5 10 MILES

0 5 10 KILOMETERS

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Henrylyn Irrigation District extent modified from Riverside Technology, Inc. (2006)

Roads modified from Colorado Department of Transportation

Designated basin extent from Lewis (1996)

North American Datum of 1983

EXPLANATION

Lost Creek Designated Ground Water 

 Basin administrative boundary

Henrylyn Irrigation District

Alluvial well and identifier

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Masters

Roggen

Keenesburg

Prospect

Valley

Bennett

GS–6

GS–3 C

GS–2

N–8

40°15'

40°00'

39°45'

104°30' 104°15'

West Sand

Creek

Lost Creek

Sand

Creek

Lon g Draw

Lost Creek

Prospect

Reservoir

Olds

Reservoir

Lord

Reservoir

Sout h Platte Riv er

N–8

GS–2

GS–3

GS–6

1950 1960 1970 1980 1990 2000 2010

1950 1960 1970 1980 1990 2000 2010

1950 1960 1970 1980 1990 2000 2010

1950 1960 1970 1980 1990 2000 2010

YEAR

DEPTH TO WATER,

IN FEET BELOW LAND SURFACE

0

10

20

30

40

50

20

30

40

50

60

70

30

40

50

60

70

80

100

110

120

130

140

150
Hydrogeology 15

Figure 9. Generalized configuration of the water table and extent of saturated sediments in the Lost Creek Designated Ground Water 

Basin, Colorado.

!(

!(

!(

!(

!(

r

¬«

¦ ̈§

§ ̈¦ £¤

£¤

¬«

m

m

m

m

m

m

5000

m

4600

76

34

52

79

36 70

4700

4800

4900

5000

5100

5200

5300

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Water-table contours and extent of saturated sediments modified from unpublished 

digital datasets derived from Nelson, Haley, Patterson, and Quirk, Inc. (1967) by the 

Colorado Water Conservation Board and Colorado Division of Water Resources

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

EXPLANATION

Lost Creek Designated Ground Water Basin

 administrative boundary

Extent of saturated sediments

Line of equal hydraulic head—Shows approximate

 altitude of water table, spring 1967. Contour

 interval 50 feet. National Geodetic Vertical Datum

 of 1929

Generalized direction of groundwater flow

0 5 10 MILES

0 5 10 KILOMETERS

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Masters

Keenesburg

Bennett

Prospect

Valley

Roggen

104°30' 104°15'

40°15'

40°00'

39°45'

Lost Creek

West Sand

Creek

Lost Creek

Lost Creek

Olds

Reservoir

Sou th Platte River

Sand

Cr eek

Long

Draw

Lord

Reservoir

West Sand

Creek

Prospect

Reservoir
16 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado Table 2. Aquifer transmissivity and hydraulic conductivity determined from aquifer tests and estimated from specific capacity of wells in the Lost Creek Designated Ground Water Basin.—Continued [CDWR, Colorado Division of Water Resources; USGS, U.S. Geological Survey; (gal/min)/ft, gallons per minute per foot; ft, feet; ft/d, feet per day; ft2/d, feet squared per day] Well number1 Well identifier2 Specific capacity [(gal/min)/ft)] Transmissivity value estimated from specific capacity3 (ft2/d) Transmissivity value from aquifer test (ft2/d) Adjusted transmissivity value from power regression4 (ft2/d) Saturated thickness5 (ft) Estimated hydraulic conductivity (ft/d) Source

1 NW SW, Sec. 30, T1N, R63W 16 2,900 5,300 60 90 Nelson, Haley, Patterson, and 

Quirk, Inc. (1967)

2 SW SW, Sec. 35, T2N, R63W 43 8,300 9,000 44 200 Nelson, Haley, Patterson, and 

Quirk, Inc. (1967)

3 B2-63-26bcc 35 6,500 12,000 59 200 Wilson (1965)4 Well 5 38 7,100 9,900 48 210 HRS Water Consultants, Inc., 

written commun. (2006)

5 B2-62-19cd 41 8,600 12,300 48 260 Bjorklund and Brown (1957)6 Well 6 33 6,100 13,000 51 260 HRS Water Consultants, Inc., 

written commun. (2006)

7 B2-62-18bca 51 9,800 14,700 55 270 Wilson (1965)8 Well 2 48 9,200 19,700 71 280 HRS Water Consultants, Inc., 

written commun. (2006)

9 Well 4 48 9,200 18,300 63 290 HRS Water Consultants, Inc., 

written commun. (2006)

10 SE SE, Sec. 7, T2N, R62W 44 8,400 13,400 43 310 Nelson, Haley, Patterson, and 

Quirk, Inc. (1967)

11 B1-63-22acc 71 14,100 30,700 91 340 Wilson (1965)

12 NE SW, Sec. 27, T1N, R63W 61 12,600 26,700 79 340 JR Engineering, written 

commun. (2005)

13 Well 1 59 11,500 18,300 50 370 HRS Water Consultants, Inc., 

written commun. (2006)

14 B1-63-9ddc 51 8,650 58,200 65 900 Skinner (1963)15 31608FP 15 2,200 3,600 40 90 CDWR16 12474F 20 2,900 4,900 50 100 CDWR17 12179F 15 2,200 3,600 30 120 CDWR
Hydrogeology 17

Table 2. Aquifer transmissivity and hydraulic conductivity determined from aquifer tests and estimated from specific capacity of wells in the Lost Creek Designated Ground Water Basin.—Continued[CDWR, Colorado Division of Water Resources; USGS, U.S. Geological Survey; (gal/min)/ft, gallons per minute per foot; ft, feet; ft/d, feet per day; ft2/d, feet squared per day]

Well 

number1 Well identifier2

Specific

capacity

[(gal/min)/ft)]

Transmissivity value

estimated from

specific capacity3

(ft2/d)

Transmissivity

value from

aquifer test

(ft2/d)

Adjusted

transmissivity

value from power

regression4

(ft2/d)

Saturated

thickness5

(ft)

Estimated

hydraulic

conductivity

(ft/d)

Source

18 175945 19 2,800 4,700 40 120 CDWR19 31641FP 19 3,000 5,000 40 130 CDWR20 31605RFP 18 2,500 4,200 30 140 CDWR21 31607F 24 3,800 6,400 40 160 CDWR22 9595FPR 31 4,700 8,000 44 180 CDWR23 18338F 26 4,200 7,000 40 180 CDWR24 31634F 28 4,200 7,100 40 180 CDWR25 9598FP 30 4,600 7,700 40 190 CDWR26 9596FPR 35 5,500 9,400 44 210 CDWR27 SB00106316AD 64 9,700 16,800 80 210 USGS28 12172FPR 38 5,900 10,100 44 230 CDWR29 31604FP 41 5,800 9,900 40 250 CDWR30 16644FP 41 6,500 11,100 40 280 CDWR31 17502FP 32 5,200 8,800 30 290 CDWR32 9594FP 50 7,900 13,500 40 340 CDWR33 49907F 54 7,900 13,600 40 340 CDWR34 31635FP 59 9,100 15,700 40 390 CDWR35 31576F 91 15,300 26,900 65 410 CDWR36 31555FPR 85 14,500 25,400 36 710 CDWR37 15719F 100 17,200 30,200 37 820 CDWR

1Well number shown in figure 11.2Well identifier for Nelson, Haley, Patterson, and Quirk Inc. (1967) and JR Engineering (written commun., 2005) is well location identifier. Identifier for Wilson (1965) is location number. Identifier for Bjorklund 

and Brown (1957) and Skinner (1963) is well number. Identifier for CDWR wells is well permit number. Identifier for USGS well is local well number.

3The method of Theis and others (1963, p. 331–341) was used to estimate aquifer transmissivity from specific-capacity data by using a modified form of Theis’s equation 1 as presented by Prudic (1991).4Adjusted transmissivity value from power regression determined by relating transmissivity from aquifer tests to transmissivity estimated from specific-capacity at wells for which aquifer-test data were available.5Saturated thickness at wells for which transmissivity was estimated from specific capacity is approximated as the length of the perforated well interval.
18 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Comparison of transmissivities calculated using equation 1 

to transmissivities determined from aquifer tests at the same wells 

indicated that transmissivities estimated from specific capacity 

were less than those from aquifer tests. Because transmissivity values from aquifer tests are considered more representative 

than those from specific-capacity tests, transmissivity values 

estimated from specific-capacity were adjusted on the basis of an 

equation developed by regressing transmissivity values from 13 

of the 14 aquifer tests relative to transmissivity values estimated 

from specific capacity (fig. 10). Data for one well (B1-63-9ddc) 

(table 2) was omitted from the regression because the duration of 

the aquifer test was only 6 hours, and results of the test skewed 

regression results. The equation used to adjust transmissivities 

calculated from specific capacity data is:

Tadj = 1.30Tsc

1.03 (2)

where

	 Tadj is the final, adjusted transmissivity value, 

in feet squared per day; 

and

	 Tsc is transmissivity estimated from specific 

capacity, in feet squared per day.

The correlation coefficient of the regression is 0.89, and the 

coefficient of determination (R2) is 0.79.

Hydraulic conductivity was estimated by dividing estimated transmissivity by the saturated thickness at each well. 

Saturated thickness at wells for which transmissivity was estimated from specific capacity was approximated as the length 

of the perforated well interval. The hydraulic-conductivity 

distribution and location of wells used to estimate hydraulic 

conductivity are shown in figure 11. The locations and values 

of aquifer-test and specific-capacity data also are available as 

a Geographic Information System dataset (Arnold, 2010) at 

http://water.usgs.gov/lookup/getgislist. Data from aquifer tests 

and specific-capacity estimates indicate hydraulic conductivity ranges from 90 to 900 ft/d with most values ranging 

from about 100 to 400 ft/d (table 2). Hydraulic conductivity 

generally is largest near the middle of the Lost Creek basin, 

where the deepest part of the paleovalley is located, and 

hydraulic conductivity generally decreases toward the basin 

margins. Although hydraulic-conductivity estimates were 

not available for sediments near the basin margins, hydraulic 

conductivity in these areas likely is less than 100 ft/d based on 

the generally higher clay content of sediments in these areas. 

Although eolian sands cover much of the study area (fig. 5), 

these deposits generally do not extend below the water table. 

For this reason, surface geology was not used to guide the 

hydraulic-conductivity distribution of the aquifer. Average 

hydraulic-conductivity values of bedrock aquifers (Denver, 

Arapahoe, and Laramie–Fox Hills) underlying the Lost Creek 

basin ranges from 0.5 to 2 ft/d (Robson, 1983, sheet 1), which 

is about 2 orders of magnitude less than the hydraulic conductivity of most alluvium in the Lost Creek basin.

Recharge

Recharge to the Lost Creek basin primarily occurs as 

(1) infiltration of precipitation, (2) infiltration of ephemeral 

stream water, (3) deep percolation of water applied to irrigated 

agricultural fields, and (4) seepage beneath irrigation ditches 

and reservoirs. Septic-system return flow of water withdrawn 

by low-capacity domestic wells completed in the Denver 

Basin bedrock aquifers underlying the Lost Creek basin also 

likely contributes a small amount of recharge to the basin, 

but recharge from domestic septic systems is not explicitly 

considered by this study. Depending on the hydraulic gradient 

between the alluvial aquifer of the Lost Creek basin and the 

underlying bedrock aquifers, the Lost Creek basin also may 

receive groundwater inflow directly from the bedrock aquifers. 

However, because the hydraulic conductivity of the bedrock 

aquifers is much smaller than that of the alluvial aquifer, 

inflow from the bedrock aquifers likely is small compared to 

recharge from other sources. Estimation of groundwater inflow 

to the Lost Creek basin from bedrock aquifers is beyond the 

scope of this report.

Precipitation Infiltration

Recharge from infiltration of precipitation on native grassland and nonirrigated agricultural fields in the Lost Creek basin 

was estimated for this study by using the chloride mass-balance 

method (CMB). The CMB method uses the concentration of 

chloride in soil profiles to estimate the flux of water from land 

surface to the water table. The CMB method has been used in 

several previous studies (Allison and Hughes, 1978; Allison and 

others, 1994; Roark and Healy, 1998; Maurer and Thodal, 2000; 

McMahon and others, 2003; Stonestrom and others, 2003) to 

estimate aquifer recharge. Chloride profiles develop in soil as 

water containing small quantities of chloride infiltrates into the 

Figure 10. Relation of transmissivity determined from aquifer 

tests to transmissivity estimated from specific-capacity tests for 

13 wells in the Lost Creek Designated Ground Water Basin.

0

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000

TRANSMISSIVITY FROM AQUIFER TESTS,

IN FEET SQUARED PER DAY

TRANSMISSIVITY FROM SPECIFIC-CAPACITY TESTS,

IN FEET SQUARED PER DAY

Tadj is adjusted transmissivity

Tsc is transmissivity estimated

 from specific capacity

Tadj = 1.30Tsc

1.03

R2 = 0.79
Hydrogeology 19

Figure 11. Hydraulic-conductivity distribution and location of aquifer tests and specific-capacity tests used to estimate 

hydraulic conductivity in the Lost Creek Designated Ground Water Basin, Colorado.

!(

!(

!(

!(

§ ̈¦ £¤

¬«

¬«

 ̈¦§

£¤

4

3300

3311

233

34

76

52

79

70 36

16

2

288

21

100

9

2277

1155

22 18

266

225

322

17 34

2

20 2299

19

3377

36

33

355

1 12

3

5

7

4

2

11

1133

6

88

14

34

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

Lost Creek Designated Ground Water Basin

 administrative boundary

Site of aquifer test. Number is well number

 shown in table 2

Site of specific-capacity test. Number is well

 number shown in table 2

Hydraulic conductivity, in feet per day

 Less than 100

 100 to 200

 200 to 300

 300 to 900

EXPLANATION

0 5 10 MILES

0 5 10 KILOMETERS

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Masters

Keenesburg

Bennett

Roggen

Hay Gulch

Prospect

Valley

Lost Creek

Sou th Platte River

Sand

Creek

Long

Draw

West Sand Creek

Prospect

Reservoir

Olds

Reservoir

Lord

Reservoir

Lost CreekLost Creek

104°30' 104°15'

40°15'

40°00'

39°45'
20 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

ground. For nonirrigated areas, the chloride concentration in the 

infiltrating water represents the sum of chloride in precipitation 

(wetfall) and aerosols (dryfall). For irrigated areas, chloride 

in the applied irrigation water also contributes to the chloride 

concentration of the infiltrating water. As water is removed from 

the soil profile by evapotranspiration, chloride accumulates in 

the root zone. Under true steady-state conditions, the chloride 

concentration in the soil profile is expected to increase gradually 

from land surface to a maximum concentration near a depth not 

affected by evapotranspiration (Wood, 1999). The exact depth at 

which maximum chloride concentration (chloride peak) occurs 

is a function of climate, soil texture, vegetation root depth, 

and other factors. Between the point of maximum chloride 

concentration and the water table, the chloride concentration 

is expected to be relatively constant because water infiltrating 

below this depth is not affected by evapotranspiration. If water 

infiltrating below the depth of effective evapotranspiration is 

assumed to flow to the aquifer, the chloride concentration in soil 

water below this depth can be related to the recharge rate (qw) 

using the equation (Allison and others, 1994):

qw= (CpP)/Cs (3)

where

	 qw is the recharge rate, in inches per year;

	 Cp is the effective chloride concentration 

in precipitation (wetfall plus dryfall), 

in milligrams per liter;

	 P is the rate of precipitation, in inches 

per year;

and

	 Cs is the average chloride concentration in 

soil water below the depth of effective 

evapotranspiration, in milligrams 

per liter.

Assumptions made in application of equation 3 are that 

(1) land surface is neither aggrading nor degrading, (2) atmospheric deposition (wetfall plus dryfall) is the only chloride 

source and is constant through time, (3) the chloride moves 

steadily and uniformly downward with the infiltrating water, 

and (4) soil-water chloride concentrations are in equilibrium 

with chloride flux at the land surface. Important sources of 

uncertainty in estimating recharge rates by using equation 3 

are the chloride concentration in precipitation and the selection of appropriate depths to represent steady-state water flux 

in the unsaturated zone, which is subject to interpretation and 

therefore has inherent uncertainty that cannot be quantified.

Long-term average recharge rates from precipitation were 

estimated for four sites (fig. 12) in the Lost Creek basin by using 

the CMB method. Sites C1 and C4 are located in native grassland 

areas, and sites C3 and C5 are located in nonirrigated agricultural 

fields. Sites in nonirrigated agricultural fields were selected where 

fertilizers containing chloride were not known to have been 

applied. Soil samples were collected at each site in 2-ft intervals 

to a depth of 20 ft below land surface by using a hand-driven 

bucket auger, and samples immediately were placed in soil tins 

and sealed with plastic tape to preserve soil moisture. Laboratory 

measurements of gravimetric water content and chloride concentration were completed for each sample at the USGS National 

Research Program laboratory in Lakewood, Colorado. Gravimetric water content was determined by measuring the weight of soil 

samples before and after oven drying using methods described by 

Dane and Topp (2002). Chloride concentrations were determined 

using methods described by McMahon and others (2003). As 

a brief description of the process used, air-dried sediment was 

mixed with deionized water in a 1:10 (sediment:water) mass ratio. 

After mixing, samples were placed on an orbital shaker for 1 hour 

at 170 revolutions per minute. The samples were then spun in a 

centrifuge for 10 minutes, after which water was extracted and 

passed through a 0.45-μm filter. Chloride concentrations in the 

filtered solution were quantified using ion chromatography. Gravimetric water content and chloride concentrations determined for 

each site are presented in Appendix 1. Chloride data were quality 

assured by analyzing deionized water or a method blank generally 

after about every third field sample to assess contamination and 

by analyzing 2–4 duplicate samples per site to assess analytical 

precision (Appendix 2). Lithologic logs of soils at each site are 

presented in figure 13. Profiles of chloride concentrations at each 

site are presented in figure 14.

Chloride concentrations in wet plus dry deposition were 

estimated from data (Appendix 3) collected at the Pawnee 

National Atmospheric Deposition Program (NADP) site 

(fig. 2) located about 40 mi north of the Lost Creek basin, 

where climatic and physiographic conditions are similar 

to those in the Lost Creek basin. Estimates of wet deposition in the Lost Creek basin are based on data collected at 

the Pawnee site from 1979 to 2004 (National Atmospheric 

Deposition Program, 2005). Estimates of dry deposition in the 

Lost Creek basin are based on unpublished data collected at 

the Pawnee site from 1979 to 1990 (Robert Larson, National 

Atmospheric Deposition Program, written commun., 2006). 

The average effective chloride concentration in precipitation 

(0.13 mg/L) at the Pawnee site represents the sum of average 

wet and dry deposition rates, divided by the average precipitation rate. Average recharge rates (table 3) at sites in the Lost 

Creek basin were estimated using equation 3 with the average 

effective chloride concentration in precipitation at the Pawnee 

site, the average long-term precipitation rate (14.1 in/yr) in the 

Lost Creek basin, and chloride concentrations of soil water 

collected at each site. The sample depths used to calculate the 

average chloride concentration in soil water were selected to 

represent steady-state flux of water through the unsaturated 

zone. In cases where a single chloride peak occurred near the 

top of the soil profile (sites C1 and C5), the average chloride 

concentration of soil water in the interval of relatively uniform 

values below the peak was used to calculate recharge using 

equation 3. In cases where a chloride peak appears to have 

been flushed downward (sites C3 and C4), the average chloride concentration of soil water above, between, and below the 

peak(s) was used to calculate recharge by using equation 3.
Hydrogeology 21

Figure 12. Location of chloride-sampling sites and passive-wick lysimeters used for estimation of recharge beneath native 

grassland, nonirrigated agricultural fields, irrigated agricultural fields, and ephemeral stream channels in the Lost Creek Designated 

Ground Water Basin, Colorado.

!(

!(

!(

!(

!(

!(

!(

!(

!(

")")

")

")

¬«

 ̈¦§

§ ̈¦ £¤

£¤

¬«

34

76

52

79

36 70

L4

L3

L1 L2

C5

C6

C4

C3

C1

C2

Streams and reservoirs modified from U.S. Geological Survey National Hydrography Dataset, 1:100,000

Soil groups modified from U.S. Department of Agriculture 1994 State Soil Geographic (STATSGO) database

Areas of irrigated agriculture modified from Riverside Technology, Inc. (2007)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

!(

"

EXPLANATION

Lost Creek Designated Ground Water 

 Basin administrative boundary

Chloride-sampling site and number

Lysimeter site and number

Land use

 Flood-irrigated agriculture

 Sprinkler-irrigated agriculture

 Reservoir

Soil group

 Weld-Norka-Adena

 Valent-Julesburg-Vona

 Otero-Thedalund-Olney

 Altvan-Dacono-Nunn

 Heldt-Nunn-Limon

 Kutch-Bresser-Louviers

C5

L1

0 5 10 MILES

0 5 10 KILOMETERS

Masters

Keenesburg

Bennett

Roggen

Prospect

Valley

Lost Creek

Sou th Platte River

Sand

Creek

Long

Draw

West Sand Creek

Lost Cre ek

104°30' 104°15'

40°15'

40°00'

39°45'
22 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Figure 13. Lithologic descriptions of soils at chloride-sampling 

sites used to estimate recharge beneath native grassland, 

nonirrigated agricultural fields, and ephemeral stream channels in 

the Lost Creek Designated Ground Water Basin, Colorado.

Site C1 - Native grassland

Latitude: 39°52'01.8"

Longitude: 104°27'41.0"

Land-surface altitude: 5,223 feet

Depth

(feet) Description

0–0.7 Clayey fine sand, dark brown, frozen

0.7–2.5 Clayey fine sand, light brown, moist

2.5–5 Clayey fine sand, grayish tan, dry

5–16 Well-graded sand, fine to coarse with minor gravel, 

subangular to subrounded, slightly clayey in lenses, 

light brown, dry 5–10 ft, damp 10–11 ft, moist 

11–16 ft

16–20 Clay, slightly sandy to sandy, clayey sand lens from 

19–19.5 ft, light brown, moist

Site C2 - West Sand Creek channel

Latitude: 39°52'01.7"

Longitude: 104°27'42.4"

Land-surface altitude: 5,218 feet

Depth

(feet) Description

0–5 Sand, fine to coarse, subangular to subrounded, light 

brown, dry 0–0.5 ft, damp 0.5–1ft, moist 1–4.5 ft, 

wet 4.5–5 ft

5–6.8 Sand, fine to coarse, subangular to subrounded, slightly 

gravelly, slightly clayey to clayey, light brown, wet

6.8–7 Clay, slightly sandy, light brown, moist

7–9 Sand, fine with minor medium, subangular to 

subrounded, silty, tan, moist

9–15 Silty clay, sandy in lenses, light brown, moist

15–17.5 Sand, fine, subangular to subrounded, silty to clayey, 

tan, moist

17.5–19 Clay, light brown, moist

19–20 Sand, fine, subangular to subrounded, silty to clayey, 

tan, moist

Site C3 - Nonirrigated agricultural field

Latitude: 39°55'35.0"

Longitude: 104°23'59.5"

Land-surface altitude: 5,115 feet

Depth

(feet) Description

0–7 Clayey silt with very fine sand, light brown, moist 

0–2 ft, damp 2–7 ft

7–14 Silty clayey sand, very fine to fine, contains caliche 

and minor coarse material, reddish brown 7–9 ft, 

light brown 9–14 ft, damp to moist

14–15.5 Silty fine sand, slightly clayey with caliche, tan, damp

15.5–17 Silty clayey sand, very fine to fine, contains caliche 

and minor coarse material, reddish brown to light 

brown, damp to moist

17–20 Sand, fine to coarse, subangular to subrounded, 

slightly gravelly, tan, damp

Site C4 - Native grassland (previously nonirrigated 

agricultural field)

Latitude: 40°00'03.0"

Longitude: 104°27'06.9"

Land-surface altitude: 4,971 feet

Depth

(feet) Description

0–7 Silty sand, fine with minor coarse, slightly clayey 

to clayey, light brown 0–2.5 ft, tan with caliche 

2.5–7 ft

7–9.5 Silty sand, fine with minor coarse and gravel, tan, dry 

to damp

9.5–20 Clayey silty sand, fine with minor medium to coarse 

and gravel, contains caliche, light brown to tan, 

damp 9.5–19 ft, moist 19–20 ft

Site C5 - Nonirrigated agricultural field

Latitude: 40°06'06.2"

Longitude: 104°21'24.4"

Land-surface altitude: 4,770 feet

Depth

(feet) Description

0–2 Silty, clayey fine sand, dark brown, damp to moist

2–19 Silty, clayey fine sand, light brown 2–9 ft, dark brown 

9–10 ft and 15.5 to 19 ft, dry to damp

19–20 Sandy, silty clay, contains caliche, grayish-brown, damp

Site C6 - Long Draw channel

Latitude: 40°06'06.3"

Longitude: 104°21'23.5"

Land-surface altitude: 4,766 feet

Depth

(feet) Description

0–5 Silty clay, slightly sandy, dark brown and damp 0–2 ft, 

brown and dry to damp 2–5 ft

5–13.5 Clayey fine sand, silty, light brown and damp to moist 

5–13.5 ft, brown to dark brown and moist 13.5–15 ft

13.5–15 Silty clay with fine sand and caliche, light grayish-brown

15–19.8 Clayey silt with fine sand to clayey, silty sand, light 

grayish-brown with abundant rust staining, damp 

to moist

19.8–20 Silty sand, fine with minor medium and coarse, tan 

with rust staining, damp

Latitude and longitude referenced to the North American Datum of 1983

Land-surface altitude referenced to the National Geodetic Vertical Datum of 1929
Hydrogeology 23

Figure 14. Vertical profiles of chloride concentrations in soil water beneath native grassland, 

nonirrigated agricultural fields, and ephemeral stream channels in the Lost Creek Designated 

Ground Water Basin, Colorado.

0

5

10

15

20

25

0

5

10

15

20

25

0 20 40 60 0 50 100

CHLORIDE CONCENTRATION IN SOIL WATER,

IN MILLIGRAMS PER LITER

(Axis scale varies by site)

150 0 20 40 60 80

0

5

10

15

20

25

0

5

10

15

20

25

0

5

10

15

20

25

0

5

10

15

20

25

0 200 400 600 800 0 10 20 30 40 0 1,000 2,000 3,000

SAMPLE DEPTH, IN FEET BELOW LAND SURFACE

SITE C1–

NATIVE GRASSLAND

SITE C3–

NONIRRIGATED

AGRICULTURAL FIELD

SITE C2–

WEST SAND

CREEK CHANNEL

SITE C6–

LONG DRAW CHANNEL

SITE C5–

NONIRRIGATED

AGRICULTURAL FIELD

SITE C4–

NATIVE GRASSLAND

(PREVIOUSLY NONIRRIGATED

AGRICULTURAL FIELD)
24 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado Table 3. Chloride concentration of soil water and precipitation, rate of precipitation, and recharge rates estimated from soil-chloride profiles beneath native grassland, nonirrigated agricultural fields, and ephemeral stream channels in the Lost Creek Designated Ground Water Basin. [ft, feet; mg/L, milligrams per liter; g/g, gram water per gram soil; cm3/cm3, cubic centimeter water per cubic centimeter soil; in/yr, inches per year; –, no data] Site Site description Depth interval(s)1 (ft) Average chloride concentration of soil water2 (mg/L) Average effective chloride concentration of precipitation3 (mg/L) Average annual precipitation (inches) Average gravimetric water content2 (g/g) Average volumetric water content4 (cm3/cm3

)

Apparent

displacement

velocity of

chloride peak5

(in/yr)

Estimated

average annual

recharge6

(inches)

C1 Native grassland 14–20 3.24 0.13 14.1 0.17 0.29

– 0.6

C2 West Sand Creek channel 4–12

–

–

– 0.15 0.26 32 8.2

C2 West Sand Creek channel 12–16

–

–

– 0.24 0.41 16 6.5

C3 Nonirrigated agricultural field 2–8 22.2 0.13 14.1 0.17 0.29

– 0.1

C4 Native grassland/nonirrigated 

agricultural field

10, 20 10.3 0.13 14.1 0.20 0.34

– 0.2

C5 Nonirrigated agricultural field 16–20 8.75 0.13 14.1 0.22 0.37

– 0.2

C6 Long Draw channel 4–10

–

–

– 0.15 0.26 24 6.1

C6 Long Draw channel 10–14

–

–

– 0.21 0.36 16 5.7

C6 Long Draw channel 14–20

–

–

– 0.20 0.34 24 8.2 1Depth intervals referenced to land surface.

2Average chloride concentration of soil water and average gravimetric moisture content are the arithmetic averages of all samples in depth interval(s) indicated.3Average effective chloride concentration of precipitation represents the sum of average wet and dry deposition rates, divided by the average precipitation rate, during 1979–2004 at the Pawnee National 

Atmospheric Deposition Program site.

4Average volumetric water content is calculated as average gravimetric water content multiplied by an assumed soil bulk density of 1.70 grams per cubic centimeter and divided by a water density of 1 gram 

per cubic centimeter. 

5Average displacement velocity of chloride peak calculated as depth interval in inches divided by an assumed traveltime (streamflow frequency) of 3 years.6Average annual recharge at sites C1, C3, C4, and C5 estimated by using the chloride mass-balance method. Average annual recharge at sites C2 and C6 estimated by using the apparent displacement 

velocity of chloride peaks as presented by Stonestrom and others (2003).
Hydrogeology 25

The chloride profile (fig. 14) at site C1 (native grassland) 

has a peak chloride concentration of 592 mg/L at a depth 6 ft 

below land surface (Appendix 1), and chloride concentrations 

decrease below the peak to relatively uniform values in the 

interval from 14 to 20 ft with an average value of 3.24 mg/L 

(table 3). The single chloride peak near land surface likely 

represents the accumulation of chloride by evapotranspiration 

just below the root zone, and the relatively uniform chloride 

concentrations below the peak indicates the recharge rate at 

site C1 likely has been relatively stable over time. Average 

annual recharge at site C1 is estimated by using equation 3 to 

be about 0.6 inch based on the average chloride concentration 

in soil water from 14 to 20 ft below land surface.

At the time of sampling (2006), site C4 was located in 

native grassland; however, a local landowner reported that 

site C4 previously was used for nonirrigated agriculture 

several (unspecified) years prior to sampling. The chloride 

profile (fig. 14) at site C4 has two distinct chloride concentration peaks. The first peak has a chloride concentration of 

56.1 mg/L at a depth of 8 ft (Appendix 1), and the second peak 

has a chloride concentration of 47.6 mg/L at a depth of 16 ft. 

The average chloride concentration of soil water in the intervals between (10-ft depth) and below (20-ft depth) the chloride 

peaks is 10.3 mg/L (table 3). The presence of two peaks in the 

chloride profile at site C4 may be the result of changing land 

use and vegetation at the site. The chloride peak at a depth of 

8 ft, which has a depth similar to that beneath native grassland 

at site C1, may have developed under current native grassland 

conditions at the site, whereas the chloride peak at a depth of 

16 ft may represent chloride that accumulated under native 

conditions prior to using the site for nonirrigated agriculture 

and was subsequently flushed downward when the site was 

converted to nonirrigated agriculture. Average annual recharge 

at site C4 is estimated by using equation 3 to be about 0.2 inch 

based on the average chloride concentration of soil water at 

depths of 10 and 20 ft below land surface.

Chloride concentrations in soil water at site C3 (nonirrigated agricultural field) are relatively uniform in the interval 

from 2 to 8 ft below land surface (fig. 14) with an average value 

of 22.2 mg/L (table 3) and increase to a peak value of 2,480 mg/L 

at a depth of 20 ft below land surface (Appendix 1). The peak 

chloride concentration at a depth of 20 ft may represent flushing 

of root-zone accumulated chloride to greater depth. Because the 

relatively uniform chloride concentrations from 2 to 8 ft appear 

to represent steady-state conditions, the average chloride concentration of soil water in the interval from 2 to 8 ft was used to 

estimate recharge at site C3. Average annual recharge at site C3 

is estimated by using equation 3 to be about 0.1 inch based on the 

average chloride concentration of soil water from 2 to 8 ft below 

land surface.

The chloride profile (fig. 14) at site C5 (nonirrigated agricultural field) has a peak chloride concentration of 120 mg/L 

at a depth 8 ft below land surface (Appendix 1), and chloride 

concentrations decrease below the peak to relatively uniform 

values in the interval from 16 to 20 ft with an average value 

of 8.75 mg/L (table 3). The depth of the peak chloride concentration at site C5 is similar to the depth of the peak at site C1 

and the upper peak at site C4, indicating that the chloride peak 

at site C5 represents the accumulation of chloride by evapotranspiration just below the root zone. Similar to site C1, the 

relatively uniform chloride concentrations below the peak also 

indicates the recharge rate at site C5 has been relatively stable 

over time. Average annual recharge at site C5 is estimated by 

using equation 3 to be about 0.2 inch based on the average 

chloride concentrations in the interval from 16 to 20 ft.

Additional chloride profiles distributed throughout the 

Lost Creek basin would be useful for verifying recharge 

estimates and providing estimates of basin-scale recharge. 

However, estimates of recharge beneath native grassland 

and nonirrigated agricultural fields are reasonably consistent 

(0.1–0.6 in/yr) among the sites analyzed and are within the 

range (0.008–1.4 inches) reported for recharge in semiarid and 

arid regions worldwide (Scanlon and others, 2006). Estimated 

recharge beneath native grassland and nonirrigated agricultural 

fields in the Lost Creek basin represents about 1–4 percent of 

long-term average precipitation (14.1 inch).

Stream-Channel Infiltration

Recharge from stream-channel infiltration is dependent on the thickness and hydraulic properties of sediments 

underlying the stream channel, streambed geomorphology, 

runoff characteristics of the contributing drainage basin, and 

the availability of streamflow (Coes and Pool, 2005). Recharge 

from infiltration of ephemeral streamflow in the Lost Creek 

basin was estimated for this study by using the concentration 

of chloride in soil profiles beneath West Sand Creek (site C2; 

fig. 12) and Long Draw (site C6). Because the volume and 

chloride concentration of streamflow in West Sand Creek and 

Long Draw are unknown, recharge beneath ephemeral stream 

channels was estimated by using apparent downward velocities of chloride peaks in the profiles rather than using the 

CMB method. Recharge can be estimated from apparent travel 

velocities of chloride peaks by using the equation (Stonestrom 

and others, 2003):

qw = θ(z2 – z1)/(t

2

 – t

1

) (4)

where

	 qw is the recharge rate, in inches per year;

	 θ is the average volumetric water content 

in the interval traveled by the chloride 

peak (dimensionless);

(z2 – z1) is the vertical distance traveled by the 

chloride peak, in inches;

and

(t

2

 – t

1

) is the elapsed time of chloride peak 

movement, in years.
26 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Application of equation 4 assumes that chloride moves 

conservatively downward with infiltrating water and that the 

volumetric water content between chloride peaks is constant 

through time. Assumptions about the timing and frequency 

of flow in stream channels is an important source of uncertainty in the application of equation 4 to estimation of streamchannel infiltration in the Lost Creek basin.

Chloride profiles at sites C2 and C6 have multiple chloride peaks (fig. 14) to the depths sampled, which may indicate 

periodic flushing of chloride that accumulated in the root zone 

between stormflow events. The peak chloride concentrations 

generally are less than at other sites, indicating that chloride 

had less time to accumulate in the root zone before being 

flushed downward by the next stormflow event. Peak chloride 

concentrations at site C2 occur at depths of 4 ft (35.3 mg/L), 

12 ft (14.4 mg/L), and 16 ft (15.8 mg/L) (Appendix 1), and 

peak chloride concentrations occur at site C6 at depths of 4 ft 

(13.4 mg/L), 10 ft (53.0 mg/L), 14 ft (64.5 mg/L), and 20 ft 

(50.7 mg/L). The uppermost chloride peak at a depth of 4 ft 

at site C2 and the slightly elevated chloride concentration 

at a depth of 4 ft at site C6 may represent the accumulation 

of chloride in the root zone since the most recent stormflow 

event. Assuming deeper chloride peaks also initially developed in the root zone at a depth of 4 ft, the vertical distance 

between successive peaks provides an indication of the 

distance traveled by the peaks. Using the vertical distance 

between successive peaks (z2 – z1), the average volumetric 

water content in the interval between successive peaks (θ ), 

and an assumed streamflow frequency (t

2

 – t

1

) of once every 

3 years (see “Physiography and Climate”), average annual 

recharge at site C2 (West Sand Creek) is estimated by using 

equation 4 to range from about 6.5 to 8.2 inches (table 3) 

with an average value of 7.4 inches. Similarly, average annual 

recharge at site C6 (Long Draw) is estimated by using equation 4 to range from about 5.7 to 8.2 inches with an average 

value of 6.7 inches. Although infiltration below ephemeral 

stream channels occurs only infrequently and is confined to 

narrow areas, available streamflow generally infiltrates rapidly 

below the depth of effective evapotranspiration, and water that 

infiltrates below ephemeral stream channels likely contributes 

recharge to the Lost Creek basin.

Deep Percolation of Water Applied

to Irrigated Agricultural Fields

Recharge from deep percolation of water applied to 

irrigated agricultural fields was estimated for this study by 

using passive-wick lysimeters to measure subsurface drainage beneath irrigated fields during the 2007 and 2008 irrigation seasons and by a water-balance method. Although the 

CMB method has been used to estimate recharge beneath 

irrigated agricultural fields by other studies (Roark and 

Healy, 1998; Maurer and Thodal, 2000; Stonestrom and 

others, 2003), passive-wick lysimeters, rather than the CMB 

method, was the primary method used to estimate recharge 

beneath irrigated agricultural fields in this study because of 

uncertainties associated with the concentration of chloride in 

irrigation water and fertilizer applied to irrigated agricultural 

fields in the Lost Creek basin. Recharge also was estimated 

by using a water-balance method to provide for comparison 

of the two methods. Although recharge estimated by lysimeter 

drainage might not represent long-term steady-state conditions, lysimeter-drainage data were used to estimate recharge 

because other data concerning recharge beneath irrigated fields 

were lacking. Additional data concerning recharge beneath 

irrigated fields would be important to improving estimates of 

long-term average recharge rates beneath irrigated fields in the 

Lost Creek basin.

Passive-Wick Lysimeters

Passive-wick lysimeters were installed at four sites 

(fig. 12) in the Lost Creek basin. Sites were selected to represent different irrigation methods and major soil types within 

the basin to provide for comparison of recharge under different 

conditions. Sites L1 and L4 are located in agricultural fields 

irrigated by center-pivot sprinkler systems. Sites L2 and L3 

are located in fields irrigated by using flood furrows. All four 

sites were irrigated with groundwater. Sites L1, L2, and L3 are 

located in loam soils of the Weld-Norka-Adena group. Site L4 

is located in sandy soils of the Valent-Julesburg-Vona group. 

Deep percolation beneath a flood-irrigated field overlying 

sandy soils of the Valent-Julesburg-Vona group was not measured because flood-irrigated fields generally are not present 

on this soil group in the Lost Creek basin.

Each passive-wick lysimeter consists of a 26-inch-long, 

7.9-inch-diameter, soil-filled metal cylinder (divergencecontrol tube; DCT) mounted above a collector plate that 

funnels percolating water into a small measurement chamber 

monitored by a water-depth sensor (fig. 15). When the water 

level in the measurement chamber reaches the top of a siphon 

tube, the water drains from the measurement chamber, and the 

volume of water drained is recorded by a data logger. Capillary suction is maintained in the lysimeter by a fiberglass wick 

that extends between the collector plate and the measurement 

chamber to passively drain the lysimeter (Gee and others, 

2002). The DCT is designed to minimize divergence of water 

around the lysimeter so that measured drainage is representative of percolation outside the lysimeter.

Lysimeters were installed by excavating a small 2-ft-deep 

pit within the irrigated area of each field and driving the DCT 

into soils at the bottom of the pit in order to fill the tube with 

relatively undisturbed soil representative of in-situ soil layers 

at the site (fig. 15). The soil-filled DCT was then extracted 

and installed along with other components of the lysimeter 

adjacent to and at the same depth as the core-sample location. 

The pit was backfilled in compacted layers with soil excavated 
Hydrogeology 27

from the pit to restore soil as nearly as possible to in-situ 

conditions, and any vegetation was replaced at land surface. 

The top of the DCT was installed about 2 ft below land surface 

to enable farming practices, such as plowing or tilling, to be 

conducted normally without interference by the lysimeter and 

to maintain representative field conditions. The collector plate 

at the base of the DCT was located about 4 ft below land surface at a depth generally below substantial root development. 

Each lysimeter was connected to an automated data logger 

installed at the outside edge of the irrigated field by means of a 

buried cable, and the volume of drainage through the lysimeter 

was recorded. Small tipping-bucket rain gages were installed 

within the irrigated area of each sprinkler site (sites L1 and 

L4) to record the volume of applied water for comparison to 

farmer’s irrigation records.

Daily net irrigation, precipitation, crop evapotranspiration, and lysimeter-drainage data for each site are presented 

in Appendix 4, and total values for each period of analysis are 

shown in table 4. Data were collected for parts of the 2007 

and 2008 irrigation seasons. The period of analysis generally is 

from the first irrigation event to 15 days after the last irrigation 

event in each season. However, the period of analysis in 2008 

for site L1 ends only 6 days after an irrigation event because 

irrigation continued at the site beyond the end of the study 

period. A period of 15 days after the last irrigation event is used 

to allow time for any water stored in the unsaturated zone above 

the lysimeter to percolate downward to the lysimeter.

Net irrigation of sprinkler-irrigated fields (sites L1 and 

L4) was estimated based on farmer application records and 

verified by data from rain gages installed within the irrigated 

area. Net irrigation of flood-irrigated fields (sites L2 and L3) 

was estimated as the total volume of water pumped to the field 

minus assumed runoff, divided by the number of irrigated 

acres. The total volume of water applied to fields was determined by multiplying the estimated well-pumping rate by the 

estimated pumping duration based on farmers’ records. Based 

on observations during irrigation events and discussions with 

farmers, runoff was assumed to be 10 percent of total applied 

Figure 15. Passive-wick lysimeter design and installation.

Land surface 2 ft

Data logger

Edge of

irrigated field

Location of in-situ soil 

profile collected by driving

divergence-control tube

Divergencecontrol tube

Collector plate

Fiberglass wick

Tubing shield

Measurement chamber

with water-depth sensor

Polyvinyl chloride

(PVC) sheath

Siphon tube

Overflow port

Backfilled pit

Sensor cable

NOT TO SCALE
28 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado Table 4. Net irrigation, precipitation, crop consumptive use, and recharge estimated by lysimeter drainage and a water-balance method for four irrigated agricultural fields in the Lost Creek Designated Ground Water Basin. [–, no data] Site Period1 Irrigation method Soil type2 Crop type Net irrigation3 (inches) Precipi- tation4 (inches) Crop evapo- transpi- ration5 (inches) Recharge estimated by lysimeter drainage6 (inches) Recharge estimated by water balance7 (inches) Ratio of recharge estimated by lysimeter drainage to net irrigation (percent) Ratio of recharge estimated by lysimeter drainage to net irrigation plus precipitation (percent) Ratio of recharge estimated by water balance to net irrigation (percent) Ratio of recharge estimated by water balance to net irrigation plus precipitation (percent) L1 6/3–10/20/07 Center-pivot sprinkler Loam Alfalfa 19.4 5.7 30.5 1.0 0.0 5 4 0 0 L1 4/8–9/17/08 Alfalfa 26.6 5.1 26.7 1.8 5.0 7 6 19 16 L2 5/19–6/15/07 Flood furrow Loam Wheat 0.5 1.5 8.2 0.1 0.0 20 5 0 0 L2 5/20–9/17/08 Corn – – – – – – – – – L3 6/22–9/14/07 Flood furrow Loam Corn 26.0 4.6 19.3 3.5 11.3 13 11 43 37 L3 6/28–9/1/08 Sunflowers – – – – – – – – – L4 6/30–10/5/07 Center-pivot sprinkler Sand Corn 13.1 4.5 19.9 3.0 0.0 23 17 0 0 L4 5/8–9/30/08 Alfalfa 13.2 2.2 17.1 4.0 0.0 30 26 0 0 Average sprinkler Loam 1.4 2.5 6 5 10 8 Average sprinkler Sand 3.5 0.0 27 22 0 0 Average flood furrow Loam 1.8 5.7 17 8 22 19

1Period is from first irrigation event over lysimeter to 15 days after last irrigation event over lysimeter or the end of the study on September 30, 2008.2Soil type from Heil and others (1978).3Net irrigation of flood fields is calculated as the difference between the total volume of water pumped onto the field minus estimated runoff, divided by the number of irrigated acres. Pumping data were 

provided by farmers. Net irrigation of sprinkler fields is estimated based on farmer’s application records and verified by data from rain gages installed in fields.

4Precipitation measured at the Colorado Agricultural Meteorological Network Fort Morgan station.5Crop evapotranspiration estimated by using the evapotranspiration calculator provided by the Colorado Agricultural Meteorological Network at http://ccc.atmos.colostate.edu/cgi-bin/extended_etr_form.pl. 

Crop evapotranspiration was calculated using the Penman-Monteith combination equation (Jensen and others, 1990) with data from the Colorado Agricultural Meteorological Network Fort Morgan station.

6Estimated recharge at sites L2 and L3 in 2008 is not reported because furrows overlying lysimeters were not used in 2008.7Recharge estimated by water balance calculated as net irrigation plus precipitation minus consumptive use.
Hydrogeology 29

water at site L2 and 30 percent of applied water at site L3. 

Net irrigation of flood-irrigated fields (table 4) represents 

average uniform application across the field. Because floodfurrow irrigation may be nonuniform due to differences in soil 

permeability, irrigation exposure time, and location relative to 

the distribution system, net irrigation over lysimeters at floodirrigated sites might not be representative of net irrigation at 

other locations within the field.

Precipitation measured at the Colorado Agricultural 

Meteorological Network (CoAgMet) Fort Morgan weather 

station (fig. 2) located about 8 mi west of Fort Morgan was 

used to represent precipitation at each site. Drainage measured by lysimeters was used as a direct estimate of recharge 

beneath irrigated fields. Recharge estimated by lysimeter 

drainage assumes evapotranspiration at the depth (4 ft) of 

lysimeter collector plates is negligible and that water percolating deeper than 4 ft ultimately reaches the water table. As indicated by the depth of chloride peaks in soil profiles beneath 

native and nonirrigated areas (see “Precipitation Infiltration”), 

some evapotranspiration may occur at depths greater than 4 ft, 

and lysimeter drainage may overestimate recharge.

Recharge estimated by lysimeter drainage (table 4) 

measured beneath irrigated fields varies by irrigation method, 

soil type, crop type, and the net quantity of irrigation water 

applied. Crop types at each site were selected by farmers each 

year as part of their normal operations. Recharge estimated 

by lysimeter drainage beneath the sprinkler-irrigated field 

on loam soil (site L1; alfalfa) ranged from 1.0 to 1.8 inches, 

which equals 5–7 percent of net irrigation (table 4) and 

4–6 percent of net irrigation plus precipitation. The ratio 

of lysimeter drainage to net irrigation varies only slightly 

between 2007 and 2008, likely because the same crop was 

grown and irrigation conditions were similar in each year.

Recharge estimated by lysimeter drainage beneath the 

sprinkler-irrigated field on sandy soil (site L4; corn 2007, 

alfalfa 2008) ranged from 3.0 to 4.0 inches (table 4), which 

equals 23–30 percent of net irrigation and 17–26 percent of 

net irrigation plus precipitation. Lysimeter drainage in 2008 

is more than in 2007, likely because the newly planted alfalfa 

crop in 2008 had less vegetative cover and consumptive use 

(table 4) than the corn crop in 2007, allowing more irrigation 

water to percolate below the root zone. The ratio of lysimeter 

drainage to net irrigation in both years at site L4 is more than 

at site L1, likely because the sandy soils at site L4 are more 

permeable than the loam soils at site L1, allowing more deep 

percolation to occur.

Recharge estimated by lysimeter drainage beneath 

flood-irrigated fields on loam soil at sites L2 (wheat 2007) 

and L3 (corn 2007) ranged from 0.1 to 3.5 inches (table 4), 

which equals 13–20 percent of net irrigation and 5–11 percent of net irrigation plus precipitation. Recharge at site L3 

is larger than at site L2 because substantially more irrigation water was applied to the field at site L3 than at site L2. 

Variation in the ratio of lysimeter drainage to net irrigation at 

sites 2 and 3 likely is caused primarily by differences in soil 

permeability and the extent to which assumed uniform net 

irrigation represents actual net irrigation over the lysimeter 

at each site. Lysimeter drainage measured at sites 2 and 3 in 

2008 was not used to estimate recharge beneath flood-irrigated 

fields because furrows overlying the lysimeters were not used 

to irrigate crops in 2008. Because of the potential variability 

of actual net irrigation over the area of flood-irrigated fields, 

recharge estimates for flood-irrigated fields have larger uncertainty than recharge estimates for sprinkler-irrigated fields.

Water-Balance Method

Recharge beneath irrigated agricultural fields also was 

estimated for this study by using a water-balance method for 

comparison to recharge estimates based on lysimeter drainage. 

The control volume for recharge estimated by the waterbalance method at each site is a soil column of unit surface 

area extending from land surface to the depth of effective 

evapotranspiration. Recharge estimated by the water-balance 

method for each period of measurement (table 4) was calculated as:

R = Inet + P – Et + ΔS (5)

where

	 R is recharge, in inches;

Inet is net irrigation water applied (total 

application minus estimated runoff), 

in inches;

	 P is precipitation, in inches; 

	 Et is crop evapotranspiration (consumptive 

use), in inches;

and

	 ΔS is net change in soil water stored in the 

unsaturated zone, in inches.

Each component of equation 5 was calculated as the sum 

of all daily values in each measurement period. Net irrigation and precipitation values used to estimate recharge by the 

water-balance method (table 4) were the same as those used 

to estimate the ratio of lysimeter drainage to net irrigation and 

net irrigation plus precipitation. Net change in soil moisture stored in the unsaturated zone is assumed equal to zero 

because each measurement period generally extends 15 days 

beyond the last irrigation event and allows sufficient time for 

transient increases in soil moisture resulting from irrigation 

to subside. The assumption that soil-moisture changes in the 

unsaturated zone are negligible over sufficiently long periods 

is supported by Susong (1995), who measured soil moisture 

throughout the irrigation season at flood- and sprinklerirrigated sites having similar climatic and soil conditions 

to those in this study. Susong (1995) concluded that soilmoisture changes caused by irrigation were transient (lasting 

a few days), and soil moisture did not change substantially 

in the unsaturated zone between the beginning and end of 

the irrigation season. Crop evapotranspiration (consumptive 
30 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

use) was estimated for the period of lysimeter measurements 

at each site by using the evapotranspiration calculator provided by CoAgMet at http://ccc.atmos.colostate.edu/cgi-bin/

extended_etr_form.pl, which can compute daily evapotranspiration using the Penman-Monteith combination equation as 

presented by Jensen and others (1990) (Troy Bauder, Colorado 

State University, written commun., 2008). A general form 

of the Penman-Monteith combination equation (Jensen and 

others, 1990) can be written as:

 



E

R G c e e r n p z

o

z a = − + −

+

Δ

Δ

( ) ( )/

* (6)

where

	 λE is latent heat flux density, in megajoules per square 

meter per day;

Δ is slope of saturation vapor-pressure temperature 

curve, in kilopascals per degree Celsius;

Rn	 is net radiation, in megajoules per square meter 

per day;

G is heat-flux density to the ground, megajoules per 

square meter per day;

ρ is air density, in kilograms per cubic meter;

cp	 is specific heat of air at constant pressure, in 

megajoules per kilogram per degree Celsius;

ez

o is saturation vapor pressure of air at height z above 

evapotranspiration surface, in kilopascals;

ez is actual vapor pressure of air at height z above 

evapotranspiration surface, in kilopascals;

ra is aerodynamic resistance to sensible heat 

and vapor transfer, calculated as

ln z d z ln z d z

u

w om p ov

z

[( )/ ] [( )/ ]

( . )

− −

0 41 2

,

γ* is calculated γ(1 + rc/ra),

zw is height of windspeed measurement, in meters;

	 d is displacement height of crop, in meters;

zom is roughness length for momentum transfer, 

in meters;

zp is height of humidity and temperature measurements, in meters;

zov is roughness length for vapor transfer, in meters;

uz is windspeed at height zw, in meters per second;

γ is psychometric constant, in kilopascals per 

degree Celsius;

and

rc is crop canopy resistance, in seconds per meter.

Meteorological data required for computing daily evapotranspiration were obtained from the CoAgMet Fort Morgan 

station located about 8 mi west of the city of Fort Morgan. 

Total crop evapotranspiration was estimated by summing daily 

evapotranspiration during the period of analysis. Planting and 

harvest dates were provided by the farmer at each site. Alfalfa 

crops at site L1 and L4 were cut multiple times during the 

period of analysis, and alfalfa crops were assumed to become 

reestablished (green up) 5 days after each cut for the purpose 

of estimating evapotranspiration. The accuracy of recharge 

estimates calculated by using the water-balance method can 

vary, depending on a number of factors. Because recharge 

estimated by the water-balance method is calculated as the 

residual of all other components of equation 5, the accuracy 

of the estimates depends on the accuracy with which the other 

components are estimated. Because the magnitude of recharge 

is smaller than that of the other variables, small changes in 

values of those variables can result in relatively large changes 

in recharge estimates. Recharge estimated by the waterbalance method also can be sensitive to the period of time over 

which estimates are made. Over the period of measurement, 

cumulative crop evapotranspiration can exceed the sum of net 

irrigation and precipitation, and estimated recharge will be 

zero. Recharge may be occurring during short-term events, 

such as when irrigation water is applied, but the longer-term 

water balance does not consider these events.

Recharge estimated for this study by the water-balance 

method (table 4) has a wider range of values than recharge 

estimated by lysimeter drainage, likely because recharge estimated by the water-balance method is sensitive to inaccuracies 

in the estimates of other water-balance components. Recharge 

estimated by the water-balance method at site L1 (sprinklerirrigated field on loam soil) ranges from 0.0 to 5.0 inches, 

which equals 0–19 percent of net irrigation and 0–16 percent 

of net irrigation plus precipitation.

Recharge estimated by the water-balance method at 

site L4 (sprinkler-irrigated field on sandy soil) is zero in both 

2007 and 2008 (table 4) because cumulative evapotranspiration exceeded cumulative net irrigation plus precipitation over 

the period of measurement in each year. The water-balance 

method likely underestimates recharge at site L4 because the 

highly permeable soils at the site may allow water to percolate 

rapidly below the root zone before full potential evapotranspiration can occur at the time scale measured.

Recharge estimated by the water-balance method at 

sites L2 and L3 (flood-irrigated fields on loam soil) ranges 

from 0.0 to 11.3 inches (table 4), which equals 0–43 percent of 

net irrigation and 0–37 percent of net irrigation plus precipitation. Although the average ratio of recharge to net irrigation 

based on the water-balance method (22 percent) for the two 

sites is similar to that based on lysimeter drainage (17 percent), 

the range of values estimated by the water-balance method is 

much larger, and the ratio of recharge to net irrigation determined for each site individually is substantially different using 

the two methods.

Ditch and Reservoir Seepage

Seepage beneath irrigation ditches in the Lost Creek 

basin varies depending on such factors as ditch construction, 

ditch water stage, and soil permeability. Lowline Canal (fig. 4) 

and the portion of Prospect Lateral Ditch between Prospect 

Reservoir and Highway 79 are unlined; all other laterals and 

sublaterals in the Henrylyn Irrigation District that deliver water 
Hydrogeology 31

to the Lost Creek basin have been lined with cement since 

the 1980s (Rodney Baumgartner, Henrylyn Irrigation District, 

oral commun., 2008). Total water loss (including evaporation) 

along the unlined ditches varies over the irrigation season and 

is estimated to range from about 10 to 50 percent, depending on 

the water stage in the ditches (Rodney Baumgartner, Henrylyn 

Irrigation District, oral commun., 2008). Code (1945) estimated seepage loss from ditches delivering water to the Lost 

Creek basin to be about 33 percent. Assuming a seepage loss of 

30 percent, about 1,290 of the average 4,300 acre-ft released by 

Prospect Reservoir during 1990–2001 would be lost to seepage 

along the Prospect Lateral Ditch and about 840 of the average 2,800 acre-ft diverted into Lowline Canal would be lost to 

seepage. Seepage losses from ditches lined with cement likely 

are substantially less than losses from unlined ditches, but the 

percentage of water lost is not known.

Water delivered to Olds Reservoir is used primarily to 

recharge the alluvial aquifer of the Lost Creek basin. Seepage beneath Olds Reservoir has been estimated by several 

studies (Code, 1945; Glover, 1959; Skinner, 1963) to range 

from about 17 to 70 acre-ft/d with most variation caused by 

differences in reservoir stage. Based on a reservoir surface 

area of about 58 acres (Skinner, 1963), the average seepage rate estimated by these studies ranged from about 0.3 

to 1.2 ft/d over the area of the reservoir when the reservoir 

contained water.

Delivery records provided for this study by the Henrylyn 

Irrigation District (Rodney Baumgartner, written commun., 

2008) indicate an average of 2,955 acre-ft (table 5) of water 

was delivered annually to Olds Reservoir over an average of 

70 days during each year from 1990 to 2001. Because most 

water delivered to Olds Reservoir is during the cool nonirrigation season and seepage from the reservoir is rapid, evaporative 

losses are small and nearly all water delivered to Olds Reservoir 

likely recharges the Lost Creek basin. Assuming all water delivered to Olds Reservoir becomes recharge, the average seepage 

rate from the reservoir on an annual basis (including days that 

water was not in the reservoir) during 1990–2001 was about 

8 acre-ft/d (0.14 ft/d over the reservoir’s surface area).

Seepage beneath Lord Reservoir was estimated by Code 

(1945) to be about 8 acre-ft/d at very low stage and by Skinner 

(1963) to be about 25 acre-ft/d at full stage. Based on a reservoir surface area of about 170 acres (Schupbach and Lewis, 

1996a), the average seepage rate over the area of the reservoir 

at very low stage was then 0.05 ft/d, and the average seepage 

rate over the reservoir’s area at full stage was 0.15 ft/d.

During 1990–92 (no data were available for 1993–2001), 

water was stored in Lord Reservoir an average of 54 days 

(Colorado Division of Water Resources, 2008). Assuming 

the average seepage rate from Lord Reservoir is 17 acre-ft/d 

(mean seepage rate of very low stage and full stage), average annual seepage from Lord Reservoir during 1990–92 was 

about 918 acre-ft, and the average seepage rate from the reservoir on an annual basis (including days water was not stored 

in the reservoir) during 1990–92 was 2.5 acre-ft/d (0.015 ft/d 

over the reservoir’s surface area).

Seepage beneath Prospect Reservoir has not been estimated but likely is small because the reservoir is located 

near the western margin of the Lost Creek basin, where the 

alluvial aquifer is thin or absent. Based on geologic mapping by Bryant and others (1981) (fig. 5) and aquifer mapping 

presented by Schupbach and Lewis (1995), much of Prospect 

Reservoir appears to be directly underlain by bedrock strata of 

the Arapahoe aquifer rather than alluvial sediments. Therefore 

seepage into the Lost Creek basin from Prospect Reservoir 

likely occurs only along the east side of the reservoir, where the 

reservoir contacts the alluvial aquifer of the Lost Creek basin.

Subsurface Inflow

Although the alluvial aquifer of the Lost Creek basin is 

bounded by bedrock along most of its eastern, western, and 

southern edges, the main part of the aquifer (primarily in 

the main paleovalley) may receive subsurface inflow from 

upgradient tributary valleys that are within the basin’s administrative extent. The main part of the aquifer also may receive 

irrigation return flow from ditch seepage and deep percolation 

of water beneath irrigated fields that are located upgradient 

and west of the main aquifer but are within the basin’s administrative extent. Because data concerning inflow from tributary 

valleys and irrigation return flow are lacking, flows from these 

sources are unknown but likely are relatively small in comparison to other sources of recharge to the basin.

Table 5. Annual water deliveries to Olds Reservoir for recharge 

to the Lost Creek Designated Ground Water Basin.

[acre-ft, acre-feet; acre-ft/d, acre-ft per day; ft/d, feet per day; –, infrequent 

diversion records] 

Year

Total water

delivered

for recharge1

(acre-ft)

Number of

days water

delivered2

Annually

averaged

seepage rate3

(acre-ft/d)

Annually

averaged

seepage rate over

reservoir area4

(ft/d)

1990 2,041 39 6 0.10

1991 2,758 69 8 0.13

1992 2,362 99 6 0.11

1993 3,280 – 9 0.15

1994 2,792 84 8 0.13

1995 5,258 104 14 0.25

1996 1,726 48 5 0.08

1997 1,660 42 5 0.08

1998 2,769 64 8 0.13

1999 2,805 55 8 0.13

2000 2,528 50 7 0.12

2001 5,480 117 15 0.26

Average 2,955 70 8 0.14 1

Total water delivered for recharge provided by Rodney Baumgartner, 

Henrylyn Irrigation District, written commun., 2008.

2

Number of days water delivered from Colorado Division of Water 

Resources (2008).

3

Annually averaged seepage rate calculated as total water delivered for 

recharge divided by 365 days per year.

4

Annually averaged seepage rate over reservoir area calculated as annually 

averaged seepage rate divided by a reservoir surface area of 58 acres.
32 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Discharge

Discharge from the Lost Creek basin occurs primarily as 

well withdrawals, evapotranspiration, and outflow to the South 

Platte River valley at the north end of the basin. Depending 

on the hydraulic gradient between the alluvial aquifer of the 

Lost Creek basin and the underlying Denver Basin bedrock 

aquifers, discharge also can occur to the bedrock aquifers, but 

because the hydraulic conductivity of the bedrock aquifers is 

much smaller than that of the alluvial aquifer, discharge to the 

bedrock aquifers likely is small compared to recharge from 

other sources. Estimation of discharge to the bedrock aquifers 

from the Lost Creek basin is beyond the scope of this report.

Well Withdrawals

Groundwater withdrawals in the Lost Creek basin are 

primarily from high-capacity irrigation wells. Groundwater also is 

withdrawn from small-capacity wells, such as domestic and stock 

wells, and a small number of municipal wells, but total withdrawals from these wells are estimated to be small compared to withdrawals from irrigation wells. About 266 decreed irrigation wells 

(fig. 16) are located in the Lost Creek basin with final permits 

(finalized water rights) on file with the CDWR (Suzanne Sellers, 

Colorado Division of Water Resources, written commun., 2007). 

Most wells are located along the main paleovalley in the central 

and northern parts of the basin where the saturated thickness 

of the aquifer is greatest. Average annual historical withdrawals previously were estimated for 39 irrigation wells in the Lost 

Creek basin as part of a legal stipulation concerning a change in 

water use for the wells (William Fronczac, Gateway American 

Resources, written commun., 2005). Average annual historical 

withdrawals generally were estimated for the stipulation based 

on power-conversion coefficients and power-use records from 

1985 to 1994 if power-use records were available for those years 

and from 1982 to 1985 if power-use records were not available for 1985–94. During 1990–94 (the period included in this 

study) average annual withdrawals from the 34 wells for which 

data were available during this time period were estimated by 

the stipulation to range from about 38.8 to 353.0 acre-ft per well 

(Appendix 5) with an average value of 157.2 acre-ft per well. 

Average annual withdrawals per unit area of land irrigated by 

each well ranged from about 0.9 to 2.4 acre-ft/acre with an average value of about 1.6 acre-ft/acre.

Average annual withdrawals from irrigation wells lacking 

power-use data are assumed similar to withdrawals by wells with 

power-use data. Average annual withdrawals from wells lacking power-use data were estimated for this study by multiplying 

the average annual withdrawal per unit area (1.6 acre-ft/acre) of 

all wells with power-use data by the number of estimated acres 

irrigated by each well lacking power-use data. The number of 

acres irrigated by an individual well in a group of commingled 

wells was estimated by apportioning the total number of commingled acres by the number of acres permitted for each individual well. Average annual withdrawals from irrigation wells 

lacking power-use data are estimated to range from about 32 to 

581 acre-ft with an average value of 168 acre-ft (Appendix 5). 

Assuming all decreed irrigation wells (with and without poweruse data) with final permits in the Lost Creek basin were actively 

used during 1990–2001, total average annual withdrawals from 

the wells are estimated to be about 44,300 acre-ft to irrigate about 

27,800 acres.

Evapotranspiration

Water can be removed directly from the aquifer by the 

process of evapotranspiration in locations where the water table is 

shallower than the effective depth of evapotranspiration, and the 

rate of water removal by evapotranspiration generally increases 

as water-table depth decreases. In the Lost Creek basin, the water 

table generally is deeper than the effective depth of evapotranspiration. However, in the northern part of the basin, particularly 

in topographically low areas along drainages, the water table is 

shallow, and water likely is removed directly from the aquifer by 

evapotranspiration in at least some of these areas. Potential average annual evapotranspiration by grasses and shrubs in semiarid 

to arid areas has been estimated (Thorn, 1995; DeMeo and others, 

2008) to range from about 23 to 34 inches. Evapotranspiration 

also can occur directly from the aquifer by phreatophytes (plants 

or trees with roots deep enough to reach the water table and take 

up water directly from the aquifer). Phreatophytes in the Lost 

Creek basin consist primarily of cottonwood trees growing near 

reservoirs and along drainages. Cottonwood roots have been 

estimated to extend up to 30 ft below land surface (Robinson, 

1958), and average annual evapotranspiration by cottonwoods at 

100-percent tree density has been estimated to range from about 

62 to 97 inches where the water table is 3–4 ft below land surface. 

Evapotranspiration by grasses, shrubs, and cottonwoods in the 

Lost Creek basin is estimated to fall within the ranges estimated 

by Thorn (1995), DeMeo and others (2008), and Robinson (1958) 

based on similarity of climatic and hydrologic conditions.

Subsurface Outflow

Subsurface outflow at the north end of the Lost Creek 

basin to the South Platte River valley can be estimated using 

a form of Darcy’s law (Fetter, 1994):

Q = –KA (dh/dl) (7)

where

	 Q is subsurface outflow, in cubic feet per day,

	 K is aquifer hydraulic conductivity, in feet 

per day,

	 A is aquifer cross-sectional area, in square feet,

and

	 dh/dl is water-table hydraulic gradient (dimensionless).

The negative sign on the right side of equation 7 is used to 

denote the direction of groundwater flow, which in this instance 

is out of the aquifer. Using representative values of hydraulic conductivity (150 ft/d; table 2), cross-sectional area (1,000,000 ft2

), 

and water-table hydraulic gradient (0.005) (Nelson, Haley, 
Hydrogeology 33

Figure 16. Location of decreed irrigation wells with final permits in the Lost Creek Designated Ground Water Basin, Colorado.

!(

!(

!(

!(

!(

¬«

¦ ̈§

§ ̈¦ £¤

£¤

¬«

34

76

52

36

79

70

((

(

(

((

(

(((

(

(

( ( (

( (

(

( (

(

((

(

(

(

(

(

(

(

(

(

(

(

(( (

(

(

(

(

(

(

(

((

(( (

((

((

( (

(((

(

(

(

(

(

(

(

(

(

(

(

((

(

(

(

((

(

(

(((

(

(

((

(

(

( ((

(

(

(

(

((

( (

( (

(

(

(

(

(

(

(

(

(

((

(

(

(( (

((( (

(

(

(

( (

(

(

(

(((

(

(

(

(

(

(

((

( (

((

( (

(

(

( (

(

(

(

(

(

(

(

(

(

(

(

(

(

((

(

(

(

(

((

(

(

( (

((

(

(

( ((

(

(

(

((

((

((

(

( (

(

(

(

(

( (

(

(

(

(

(

(

(

(

((((

(

((

(

(

(( (((

(

((

(

(

( (

(

(

(

(

(((

(

(

(

(

(

(

((

(

(

(

((

(

(

(

((

(

(

(

(

(

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

(

EXPLANATION

Lost Creek Designated Ground Water

 Basin administrative boundary

Location of decreed irrigation well with

 final permit. [Data provided by

 Suzanne Sellers, Colorado Division 

 of Water Resources, written commun. 

 (2007)]

0 5 10 MILES

0 5 10 KILOMETERS

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Masters

Keenesburg

Bennett

Roggen

Prospect

Valley

Lost Creek

Sou th Platte River

Sand

Creek

Long

Draw

West Sand Creek

Prospect

Reservoir

Lord

Reservoir

Lost Creek

Olds

Reservoir

104°30' 104°15'

40°15'

40°00'

39°45'
34 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Patterson, and Quirk, Inc., 1967, plate 3) of the Lost Creek alluvial aquifer at the north end of the Lost Creek basin, subsurface 

outlow to the South Platte River valley, calculated using equation 

7, is 750,000 ft3/d (17.2 acre-ft/d).

Steady-State Numerical Simulation 

of Groundwater Flow

Previous Groundwater Flow Model

In 1995, Hatton Water Consultants, Inc., constructed a 

numerical groundwater flow model of part of the Lost Creek 

basin using the U.S. Geological Survey finite-difference computer code MODFLOW–88 (McDonald and Harbaugh, 1988) 

to quantitatively evaluate the effects of a proposed well field 

under different pumping and artificial-recharge scenarios 

(Thomas Hatton, JR Engineering, written commun., 2004). The 

model subsequently was modified between 1995 and 2004 and 

used to predict the effects of additional pumping scenarios under 

different recharge and hydrogeologic conditions (Barbara Ford, 

HRS Water Consultants, Inc., written commun., 2005). Formal documentation does not accompany the modified model 

versions (Barbara Ford, HRS Water Consultants, Inc., written 

commun., 2005). Description of the 2004 version of the groundwater flow model presented below is based on examination of 

the MODFLOW–88 input files and information provided by 

Thomas Hatton (JR Engineering, written commun., 2004) and 

Barbara Ford (HRS Water Consultants, Inc., oral commun., 2004; 

written commun., 2005).

Design of Previous Model

The 2004 version of the model simulated steady-state 

groundwater flow in the Lost Creek basin using one layer and 

unconfined conditions. The model was calibrated to 24 hydraulichead observations representing average water-table conditions 

in the Lost Creek basin. Dates of hydraulic-head observations 

were not provided. The model was not calibrated to flow observations representing groundwater discharge to streams because no 

perennial streams exist in the basin. The model grid has 89 rows 

and 53 columns with a maximum cell size of 2,640 ft × 2,640 ft 

and grid refinement to 782 ft × 782 ft near wells and reservoirs. 

The eastern, southern, and western model edges were simulated 

as no-flow boundaries near the limit of zero saturated thickness 

indicated by Nelson, Haley, Patterson, and Quirk, Inc. (1967). 

The northern model edge was simulated as a constant-head 

boundary aligned east to west across the basin. The model base 

was simulated as a no-flow boundary with a configuration based 

on the altitude of the bedrock surface mapped by Nelson, Haley, 

Patterson, and Quirk, Inc. (1967), and subsequent borehole 

exploration (Barbara Ford, HRS Water Consultants, Inc., oral 

commun., 2004). The upper model boundary is defined by the 

water table. Initial hydraulic-conductivity values were estimated 

from aquifer-test results reported by Nelson, Haley, Patterson, 

and Quirk, Inc. (1967), and HRS Water Consultants, Inc. (written 

commun., 2006), and adjusted based on model calibration. 

Hydraulic-conductivity values used in the model ranged from 45 

to 360 ft/d with values generally being greatest near the center of 

the basin and decreasing toward the basin margins.

Inflows and Outflows Simulated 

by Previous Model

Aquifer recharge was distributed on the basis of model 

calibration and limited available data. Recharge values used in 

the model ranged from 0 in/yr for an area assumed to discharge 

groundwater near the northern model boundary to 43.8 in/yr 

beneath part of Prospect Reservoir and for a small area along the 

west model boundary in the northern part of the basin. Recharge 

in the northern part of the basin was simulated as 3.7 in/yr where 

groundwater was not assumed to discharge. Recharge in the 

middle part of the basin generally ranged from about 1.5–2.6 in/yr 

with the lower values near the center of the basin, away from 

basin margins. Recharge in the southern part of the basin was 

about 1.9 in/yr. Seepage from Prospect Reservoir and Lord 

Reservoir was simulated by using zones of greater recharge with 

values ranging from about 11.0 to 43.8 in/yr at reservoir locations. 

Zones of greater recharge were added downgradient from reservoirs during model calibration. Recharge occurring from seepage 

along irrigation ditches and ephemeral stream channels was considered in total estimated recharge but was not explicitly specified 

at ditch and stream locations. Inflow from the underlying Denver 

Basin aquifers was not simulated. Olds Reservoir was simulated 

as an area of specified inflow to the aquifer by using the Well 

package of MODFLOW. The simulated rate of inflow from Olds 

Reservoir was about 2.74 acre-ft/d (1,000 acre-ft/yr).

Well pumping was simulated as net withdrawals from an 

individual well or all wells within a cell, based on the amount 

of water consumed as a result of irrigation. Therefore, net well 

withdrawals reflected total estimated pumping minus return flow 

to the aquifer from infiltration of water applied to fields. An average net withdrawal of 1.23 acre-ft/acre was used for simulated 

wells unless specific withdrawal information was available. Wells 

for which net withdrawals were known were assigned actual net 

withdrawal rates, whereas net withdrawals for other irrigation 

wells in the Lost Creek basin were estimated by multiplying the 

average net withdrawal rate by the number of acres irrigated by 

each well or all wells within a cell.

The maximum evapotranspiration rate was defined as 

uniform across the model domain at 35 in/yr, but evapotranspiration occurred at only a few model cells in the northern part of the 

basin where the water table is shallow enough to be within the 

specified extinction depth of 10 ft.

Updated Groundwater Flow Model

An updated numerical groundwater flow model of the 

Lost Creek basin was constructed using information from previous investigations and data collected and compiled by this 

study. The USGS modular groundwater modeling program, 
Steady-State Numerical Simulation of Groundwater Flow 35

MODFLOW–2000 (Harbaugh and others, 2000) was used to 

simulate steady-state groundwater flow in the updated model. 

The preconditioned conjugate-gradient 2 (PCG2) solver (Hill, 

1990) was used to solve the groundwater-flow equations 

produced by MODFLOW-2000. Pre- and postprocessing of 

MODFLOW–2000 files primarily were completed using the 

MODFLOW Graphical User Interface (Winston, 2000) for the 

Argus ONE geographic information system (Argus Interware, 

1997). The model was calibrated by using the Observation, 

Sensitivity, and Parameter-Estimation Processes (Hill and 

others, 2000) of MODFLOW–2000.

Design of Updated Model 

The alluvial aquifer of the Lost Creek basin is represented 

by using a 1-layer model grid (fig. 17) with 191 rows and 70 columns having uniform cell dimensions of 1,000 ft × 1,000 ft. The 

model simulates groundwater flow under unconfined conditions 

with the rewetting capability active. The spatial extent of active 

model cells generally is limited to areas where saturated thickness is greater than 10 ft. The area of Hay Gulch (fig. 6), in the 

northeastern part of the Lost Creek basin, is not included in the 

active model extent because relatively shallow bedrock appears to 

separate Hay Gulch from the main paleovalley of the Lost Creek 

basin, and saturated thickness in the area between Hay Gulch and 

the main paleovalley generally appears to be less than about 10 ft 

except within 1–2 mi of the northern boundary of the Lost Creek 

basin, where saturated thickness is estimated to be about 20 ft 

(Nelson, Haley, Patterson, and Quirk, Inc.,1967, pl. 3). Model 

layer thickness varies from about 10 to 190 ft as determined by 

the thickness of regolith sediments mapped as part of this study 

(see “Aquifer Extent and Thickness”). The top of the model 

is defined as the altitude of the land surface derived from the 

USGS National Elevation Data Set (NED) with 10-m resolution 

(U.S. Geological Survey, 2002). The model base is defined as the 

altitude of the land surface minus regolith thickness.

Four zones (fig. 18) are used to represent the spatial 

distribution of horizontal hydraulic conductivity in the model. 

The hydraulic-conductivity distribution estimated from aquifer 

and specific-capacity tests (fig. 11) was used to define initial 

(precalibrated) hydraulic conductivity within the model, and 

the distribution of hydraulic conductivity was adjusted during 

model calibration. Hydraulic conductivity of zones 1, 2, 3, 

and 4 are represented by parameters HK_1, HK_2, HK_3, and 

HK_4, respectively.

Boundary Conditions and Hydrologic Stresses

The base of the model is simulated as a no-flow boundary to represent relatively low permeability bedrock in contact 

with the alluvial aquifer. The eastern, western, and southern 

edges of the model also are simulated as no-flow boundaries 

(fig. 17) except in small areas where general-head boundaries 

are simulated by using the General-Head Boundary Package 

of MODFLOW–2000. General-head boundaries allow 

groundwater to flow into or out of the model in proportion 

to the difference between hydraulic head at the boundary 

and a user-specified hydraulic head external to the model 

(McDonald and Harbaugh, 1988). Simulated hydraulic head 

also can vary at the boundary. The northern (downgradient) 

edge of the model is simulated as a general-head boundary to 

allow groundwater flow and hydraulic head at the boundary to 

change in response to simulated hydrologic stresses. Hydraulic 

conductance of the general-head boundary at the downgradient 

edge of the model is represented by the parameter GHB_Out. 

General-head boundaries along parts of the eastern, western, and southern edges of the model simulate inflow from 

tributary valleys at the edge of the model domain and irrigation return flow from ditch seepage and deep percolation of 

water beneath irrigated fields located upgradient and west of 

the model domain (fig. 17). Hydraulic conductances of the 

general-head boundaries used to simulate inflow from tributary valleys and from irrigation return flow along the west 

model boundary are represented by the parameters GHB_In 

and GHB_Return, respectively. All general-head boundaries 

in the model are defined using a saturated thickness, hydraulic conductivity, and hydraulic gradient representative of the 

aquifer at each boundary location.

Areal recharge is simulated by using the Recharge 

Package of MODFLOW–2000 and is distributed by land use 

(fig. 19) and soil type. Recharge in nonirrigated areas (native 

grassland and nonirrigated agricultural fields) (parameter 

RCH_Nonirr) includes contributions from precipitation, 

stream-channel infiltration, and any other localized sources of 

recharge such as seepage from domestic septic systems, within 

the nonirrigated area. Recharge from infiltration of water in 

ephemeral stream channels is not explicitly simulated at the 

locations of stream channels in the model because stream 

channels are narrow compared to model cell size and are 

distributed relatively evenly throughout the southern part of 

the basin (fig. 1), where nonirrigated land is prevalent (fig. 4). 

Recharge from deep percolation of water beneath areas of irrigated agriculture is assigned on the basis of irrigation method 

(flood or sprinkler) and the distribution of irrigated acres in 

2001, as mapped by Riverside Technology, Inc. (2007). About 

28,000 (86.2 percent) of the 32,500 acres that are irrigated in 

the Lost Creek basin are within the domain of the simulated 

aquifer. Recharge beneath flood-irrigated fields is represented 

by the parameter RCH_Flood; recharge beneath sprinklerirrigated fields is represented by the parameter RCH_Sprink. 

Because the location of ditches (Prospect Lateral Ditch, 

Lowline Canal, and the 1053 ditch) within the model domain 

generally coincides with the location of irrigated fields, and 

because ditches are narrow compared to model cell size, 

seepage from irrigation ditches within the model domain is 

not explicitly simulated by the model. Instead, seepage from 

ditches within the model domain is implicitly included as part 

of recharge occurring from deep percolation of water beneath 

irrigated fields. Recharge rates for all land uses are multiplied 

by 1.5 where sandy soils are present at the land surface to represent larger recharge rates in areas of sandy soil (fig. 20).
36 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Figure 17. Grid and boundary conditions of the groundwater flow model, Lost Creek Designated Ground Water Basin, Colorado.

!(

!(

!(

!(

!(

¬«

¦ ̈§

§ ̈¦ £¤

£¤

¬«

Columns

Rows

34

76

52

79

36 70

EXPLANATION

Active model cell

Inactive model cell

General-head boundary cell

Specified-flow cell that simulates withdrawals 

 from irrigation wells

Specified-flow cell that simulates seepage 

 from reservoirs

Lost Creek Designated Ground Water Basin 

 administrative boundary

0 5 10 MILES

0 5 10 KILOMETERS

Streams and reservoirs modified from Schupbach ad Lewis (1996a, b)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Masters

Keenesburg

Bennett

Roggen

Prospect

Valley Valley

Lost Creek

Lost Creek

Olds

Reservoir

Sou th Platte River

Sand

Creek

Long

Draw

Lord

Reservoir

West S and

Creek

Olds

Reservoir

Prospect

Reservoir

104°30' 104°15'

40°15'

40°00'

39°45'
Steady-State Numerical Simulation of Groundwater Flow 37

Figure 18. Hydraulic conductivity zones of the groundwater flow model, Lost Creek Designated Ground Water Basin, Colorado.

!(

!(

!(

!(

!(

¬«

¦ ̈§

§ ̈¦ £¤

£¤

¬«

79

70 36

52

34

76

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

EXPLANATION

Active model cell

Inactive model cell

Lost Creek Designated Ground Water Basin

 administrative boundary

Hydraulic-conductivity zone and associated

 parameter (parameter values are shown

 in table 7)

 1—HK_1

 2—HK_2

 3—HK_3

 4—HK_4

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Masters

Keenesburg

Bennett

Roggen

Prospect

Valley

Lost Creek

Sou th Platte River

Sand

Creek

Long

Draw

West S and

Creek

Prospect

Reservoir

Olds

Reservoir

Lord

Reservoir

Lost CreekLost Creek

104°30' 104°15'

40°15'

40°00'

39°45'

0

0 5 10 KILOMETERS

5 10 MILES
38 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Figure 19. Recharge zones of the groundwater flow model, Lost Creek Designated Ground Water Basin, Colorado.

!(

!(

!(

!(

!(

¬«

§ ̈¦ £¤

§ ̈¦

£¤

¬«

34

76

52

36 70

79

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

EXPLANATION

Active model cell

Inactive model cell

Lost Creek Designated Ground Water 

 Basin administrative boundary

Recharge zone and associated parameter 

 (parameter values are shown in table 7)

 1—RCH_Nonirr

 2—RCH_Flood

 3—RCH_Sprink

0 5 10 MILES

0 5 10 KILOMETERS

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Masters

Keenesburg

Bennett

Roggen

Prospect

Valley

Lost Creek

Sou th Platte River

Sand

Creek

Long

Draw

Olds

Reservoir

Lord

Reservoir

Lost Creek

West S and Creek

Prospect

Reservoir

104°30' 104°15'

40°15'

40°00'

39°45'
Steady-State Numerical Simulation of Groundwater Flow 39

Figure 20. Multiplier array used to increase recharge in areas representing sandy soils in the groundwater flow model, Lost 

Creek Designated Ground Water Basin, Colorado.

!(

!(

!(

!(

!(

¬«

¦ ̈§

§ ̈¦ £¤

£¤

¬«

34

76

52

36

79

70

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

EXPLANATION

0 5 10 MILES

0 5 10 KILOMETERS

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Masters

Keenesburg

Bennett

Roggen

Prospect

Valley

Lost Creek

Sou th Platte River

Sand

Creek

Long

Draw

Olds

Reservoir

Lord

Reservoir

Lost Creek

West S and Creek

Prospect

Reservoir

104°30' 104°15'

40°15'

40°00'

39°45'

Active model cell where recharge

 multiplier equals 1.0

Active model cell where recharge

 multiplier equals 1.5

Inactive model cell

Lost Creek Designated Ground Water

 Basin administrative boundary
40 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Groundwater withdrawals from wells in the Lost Creek basin 

are simulated by using the Well Package of MODFLOW–2000. 

Withdrawals are simulated only for decreed irrigation wells with 

final permits on file with the CDWR. The average withdrawal 

rate per acre of irrigated land for wells with power-use (powerconversion coefficient) data is represented by the parameter 

Wells_PCC. The average withdrawal rate per acre of irrigated 

land for wells lacking power-use data is represented by the 

parameter Wells_Irr. Multipliers are used to compute the total 

volumetric withdrawal rate for each well simulated by the model. 

Multipliers for wells with power-use data are assigned values 

that convert average withdrawal rates per acre to total volumetric 

withdrawal rates estimated from power-use records for each well. 

Multipliers for wells lacking power-use data are assigned values 

equal to the estimated number of acres irrigated by each well 

(Appendix 5) to compute total volumetric withdrawal rates.

Seepage from Olds and Lord Reservoirs also is simulated 

by using the Well Package of MODFLOW–2000. Seepage is 

simulated as specified inflow of water at the locations of each 

reservoir. The seepage rate per unit area of Olds Reservoir is 

represented by the parameter Q_Olds. The seepage rate per unit 

area of Lord Reservoir is represented by the parameter Q_Lord. 

The volumetric seepage rate for each model cell simulating seepage from the reservoirs is computed by multiplying the seepage rate per unit area by the reservoir’s area within each model 

cell. Because Prospect Reservoir is located at the edge of the 

model domain and appears to mainly overlie bedrock, seepage 

from Prospect Reservoir is simulated only along the east side of 

the reservoir by using the General-Head Boundary Package of 

MODFLOW–2000. Hydraulic conductance of the general-head 

boundary used to simulate seepage from Prospect Reservoir is 

represented by the parameter GHB_Prspct.

Evapotranspiration is simulated by using the 

Evapotranspiration (EVT) Package of MODFLOW–2000. 

Evapotranspiration is simulated throughout the model domain 

with an extinction depth of 5 ft, relative to NED-derived 

land-surface altitude. The maximum evapotranspiration 

rate is represented by parameter EVT_Par.

Model Calibration 

The model was calibrated by using the Observation, 

Sensitivity, and Parameter-Estimation Processes of 

MODFLOW-2000 (Hill and others, 2000), which uses inverse 

modeling methods to minimize the difference between measured values and model-simulated values. The model primarily is calibrated to average hydrologic conditions during the 

period 1990–2001 because groundwater levels in the Lost 

Creek basin generally were relatively stable during that period.

To evaluate the viability of alternative conceptual models, 

calibration began with a simple model and complexity was added 

incrementally, based on the contribution of the added complexity to improving statistical measures of model fit and related 

measures. The hydraulic-conductivity distribution and model 

extent also were adjusted to evaluate their effect on calibration. 

Incremental additions that improved model calibration included 

(1) simulation of inflow from tributary valleys at the edge of the 

model domain, (2) simulation of irrigation return flow along part 

of the west model boundary, (3) use of separate parameters for 

flood- and sprinkler-irrigation recharge, (4) use of a multiplier to 

increase recharge where sandy soils are present in the Lost Creek 

basin, (5) use of separate parameters for wells with power-use 

data and wells lacking power-use data, (6) simulation of seepage 

from Olds, Lord, and Prospect Reservoirs, and (7) simulation of 

evapotranspiration.

Observations

An observation is a measurement of actual conditions, 

such as hydraulic head or flow, that can be compared to a 

model-calculated value. Forty-three hydraulic-head observations (fig. 21; table 6) distributed throughout Lost Creek basin 

were used to calibrate the model. Hydraulic-head observations 

consist primarily of water-level measurements made during 

the period 1990–2001. However, hydraulic-head observations made during other years were used to calibrate the 

model at locations (primarily in the southern part of the basin) 

where data were not available for 1990–2001. At locations 

where multiple water-level measurements were made during 

1990–2001, the average of all measurements made during the 

period is used to represent hydraulic head. Using statistical 

methods described by Hill (1998, p. 45–49), the standard deviation of measurement error for hydraulic-head observations is 

estimated to be about 3 ft. Because perennial streams do not 

exist in the Lost Creek basin, the model is not calibrated to 

flow observations representing streamflow gains or losses.

Prior Information

Data (such as results of aquifer tests or deep-percolation 

studies) used to estimate a parameter value by using inverse 

modeling methods is called prior information. Use of prior information allows direct measurements of model input values to be 

included in the calibration regression (Hill, 1998). Prior information is used in the Lost Creek basin model to reduce parameter 

correlation (possibly caused by a lack of flow observations) and 

obtain a well-posed regression problem for estimation of many 

parameters. Prior information was used to constrain estimates 

of parameters HK_1, HK_2, HK_3, RCH_Nonirr, RCH_Flood, 

RCH_Sprink, Wells_PCC, Wells_Irr, and Q_Olds. Priorinformation values were assigned on the basis of initial parameter 

estimates; however, prior-information values for RCH_Nonirr 

and Wells_Irr were adjusted during calibration to promote convergence of the solution to the finite-difference equations used by 

the model. Weights for prior-information values initially were 

assigned on the basis of the standard deviation of calculated or 

estimated prior-information measurement error as described by 

Hill (1998, p. 45–49). However, to constrain estimated parameters to values near those indicated by prior information, values 

for parameters HK_1, HK_2, RCH_Flood, and Wells_Irr were 

regularized by using prior-information weights that are smaller 

than indicated by the standard deviation of prior-information 

measurement error. Weights used for prior-information values 

are presented in table 7.
Steady-State Numerical Simulation of Groundwater Flow 41

Figure 21. Location of hydraulic-head observations used to calibrate the groundwater flow model, Lost Creek Designated 

Ground Water Basin, Colorado.

!(

!(

!(

!(

!(

¬«79

 ̈§76

£¤36 § ̈¦70

£¤34

¬«52

AgLUS-24

AgLUS-13

AgLUS-2

AgLUS-26

AgLUS-Ref1

AgLUS-19

AgLUS-29 AglUS-4

AgLUS-30

A-4

PVTH-11

PVTH-10

PRTH-8

GS-6

PVTH-14

GS-5

GS-4

GS-3

GS-2

PVTH-12

PVTH-8 PVTH-7

S-18

S-12 S-10

A-2

GS-1

A-1

S-3

S-2

S-23A

S-26A

S-24

N-8

N-6

A-3

A-3

N-1

N-5

N-7

N-11

AgLUS-3

AgLUS-27

AgLUS-11

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

" "

"

"

"

"

"

"

"

"

"

"

"

"

"

"

" "

"

"

"

"

¦

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

EXPLANATION

Active model cell

Inactive model cell

Lost Creek Designated Ground Water

 Basin administrative boundary

Hydraulic-head observation location

 and name

"

0 5 10 MILES

0 5 10 KILOMETERS

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Masters

Keenesburg

Bennett

Roggen

Prospect

Valley

Lost Creek

Sou th Platte River

Sand

Creek

Long

Draw

Olds

Reservoir

Lord

Reservoir

Lost Creek

West S and Creek

Prospect

Reservoir

104°30' 104°15'

40°15'

40°00'

39°45'
42 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Parameter Estimation

Sixteen parameters are used in the Lost Creek basin model, 

10 of which were estimated by using inverse modeling methods. Parameters HK_1, HK_2, HK_3, HK_4, RCH_Nonirr, 

RCH_Flood, RCH_Sprink, Wells_PCC, Wells_Irr, and Q_Olds 

were estimated by using inverse methods. Parameters GHB_Out, 

GHB_In, GHB_Return, Q_Lord, GHB_Prspct, and EVT_Par 

were not estimated by inverse modeling methods because the 

relatively low sensitivity (see “Sensitivity Analysis”) of these 

parameters prevented unique estimation of the parameters and 

convergence of the parameter-estimation process. Instead, these 

parameters were assigned reasonable values based on available 

data. The initial and final estimated parameter values used in the 

model are shown in table 7. All final estimated parameter values 

appear reasonable compared to available data and estimated error 

associated with the data. Because the model is highly nonlinear 

(see “Model Nonlinearity”), linear confidence intervals are not 

presented for parameters.

Initial estimates of parameter values were assigned on the 

basis of data presented in the “Hydrogeology,” “Recharge,” 

and “Discharge” sections of this report, and parameter values 

were adjusted during model calibration. Initial estimates of 

HK_1, HK_2, and HK_3 are based on representative hydraulicconductivity values estimated from aquifer-test and specificcapacity data presented in table 2. Because data were not 

available to estimate the value of HK_4, the initial parameter 

value was assigned a reasonable value without consideration of 

Table 6. Hydraulic-head observations used to calibrate the Lost Creek Designated Ground Water Basin model.

[Hydraulic head in feet above National Geodetic Vertical Datum of 1929; CDWR, Colorado Division of Water Resources; USGS, U.S. Geological Survey; 

HRS, HRS Water Consultants, Inc. (written commun., 2006); --, not known or not applicable]

Observation name Hydraulic head1 Observation date(s) Well permit number Source

A-1 4,730 5/25/2002 57812-A CDWR

A-2 4,747 5/10/2006 31555-FPR CDWR

A-3 4,672 9/23/1981 121539-A CDWR

A-4 4,977 3/13/1984 69045-A CDWR

AgLUS-11 5,233 3/5/2003 MH-41855 USGS

AgLUS-13 5,342 3/10/2003 MH-41893 USGS

AgLUS-19 5,210 1/23/2003 MH-41723 USGS

AgLUS-2 5,304 3/6/2003 MH-41852 USGS

AgLUS-24 5,363 2/10/2003 MH-41720 USGS

AgLUS-26 5,245 1/20/2003 MH-41688 USGS

AgLUS-27 5,158 1/14/2003 MH-41652 USGS

AgLUS-29 5,109 2/6/2003 MH-41725 USGS

AgLUS-3 5,117 3/2/2003 MH-41856 USGS

AgLUS-30 5,074 1/13/2003 MH-41648 USGS

AgLUS-4 5,108 3/5/2003 MH-41853 USGS

AgLUS-REF1 5,172 2/7/2003 MH-41787 USGS

GS-1 4,742 1990–2001 -- CDWR

GS-2 4,758 1991–1999 -- CDWR

GS-3 4,825 1990–2001 -- CDWR

GS-4 4,838 1990–2001 6693-R CDWR

GS-5 4,875 1990–2001 -- CDWR

GS-6 4,897 1990–2001 14856-R CDWR

N-1 4,539 1990–93, 1995–2001 -- CDWR

N-11 4,682 1990–2001 -- CDWR

N-5 4,589 1991–93, 1995–2001 -- CDWR

N-6 4,609 1990–2001 12174-F CDWR

N-7 4,632 1990–99 12225-F CDWR

N-8 4,626 1991–2001 -- CDWR

PRTH-8 4,972 5/19/1999 -- HRS

PVTH-10 4,918 3/18/1997 -- HRS

PVTH-11 4,895 3/18/1997 -- HRS

PVTH-12 4,890 3/18/1997 -- HRS

PVTH-14 4,866 3/18/1997 -- HRS

PVTH-7 4,945 3/7/1997 -- HRS

PVTH-8 4,943 3/12/1997 -- HRS

S-10 4,721 1991–2001 -- CDWR

S-12 4,725 1990–1996, 1998–2001 10477-F CDWR

S-18 4,706 1991–2001 -- CDWR

S-2 4,682 1990–96, 1998–2001 -- CDWR

S-23A 4,746 1994–1999, 2001 -- CDWR

S-24 4,681 1991–1994, 1996–2001 -- CDWR

S-26A 4,708 1993, 1995–96, 1998–2001 -- CDWR

S-3 4,698 1990–91, 1993–2001 31563-FP CDWR 1

Hydraulic head is average of observations on dates indicated.
Steady-State Numerical Simulation of Groundwater Flow 43

hydraulic-conductivity data. Final calibrated values of hydraulicconductivity parameters (HK_1, HK_2, HK_3, and HK_4) range 

from 15 to 330 ft/d.

The initial estimate of RCH_Nonirr is based on average 

recharge values presented in table 3, assuming infiltration of 

water in ephemeral stream channels contributes about 5 percent 

of total recharge in nonirrigated areas. The final calibrated value 

of RCH_Nonirr is 1.5 in/yr. Initial estimates of RCH_Flood and 

RCH_Sprink are based on average recharge values for loam 

soils estimated by this study (table 4). Final calibrated values 

of RCH_Flood and RCH_Sprink are 8.2 in/yr and 3.4 in/yr, 

respectively. Although the final calibrated values of RCH_Nonirr, 

RCH_Flood, and RCH_Sprink are higher than initial estimates 

based on data collected during the study, the final values appear 

reasonable considering the potentially large variability and 

uncertainty associated with the parameters. The increased value 

of RCH_Nonirr is considered reasonable because it includes 

recharge from ephemeral streamflow and septic-system return 

flow of water withdrawn from bedrock aquifers underlying 

the Lost Creek basin, and both sources of recharge have substantial uncertainty. The increased values of RCH_Flood and 

RCH_Sprink are considered reasonable because the final values 

are within the range of values expected for deep-percolation 

return flow beneath irrigated fields, the initial estimates do not 

consider recharge from precipitation during the nonirrigation 

season, and recharge at the lysimeter locations may not be representative of recharge at other locations in the Lost Creek basin. 

Assuming average combined irrigation with surface water and 

groundwater is 1.73 acre-ft/acre (20.8 inches) (see “Land Use 

and Irrigation”) and long-term average annual precipitation is 

14.1 inches, the final calibrated parameter value for RCH_Flood 

represents about 23 percent of applied water plus precipitation, and the final calibrated parameter value for RCH_Sprink 

represents about 10 percent of applied water plus precipitation. 

These ratios are within the range of values presented by other 

investigators, who estimated that about 49 percent (Susong, 1995) 

and 14–43 percent (Roark and Healy, 1998) of applied irrigation 

water plus precipitation became recharge beneath flood-irrigated 

fields and about 10 percent (Roark and Healy, 1998) to 12 percent 

(Gaggiani, 1995) of applied water plus precipitation became 

recharge beneath sprinkler-irrigated fields.

Initial estimates of Wells_PCC and Wells_Irr represent 

average withdrawal rates per acre of irrigated land based on 

data provided in Appendix 5. The final calibrated value of 

Wells_PCC is –l.5 acre-ft/acre/yr, and the final calibrated 

value of Wells_Irr is –0.94 acre-ft/acre/yr. The negative sign 

of the parameter values indicates water is withdrawn from 

the simulated aquifer rather than added. The downward 

adjustment of Wells_Irr from an initial estimated value of 

–1.6 acre-ft/acre/yr to –0.94 acre-ft/acre/yr is considered reasonable because the parameter represents average withdrawal 

rates for all irrigation wells lacking power-use data, whether or 

not the wells actually withdraw water in a given year. Because 

not all wells represented by parameter Wells_Irr might withdraw water in a given year, the average withdrawal rate can 

reasonably be expected to be less than if all wells were active.

Table 7. Initial and final parameter values, prior-information values, and prior-information weights used in the Lost Creek Designated 

Ground Water Basin model.

[ft/d, feet per day; ft2/d, square feet per day; acre-ft/acre/yr, acre-feet per acre per year; --, no value]

Parameter1 Model feature

represented by parameter

Initial

value

Final

calibrated

value

Priorinformation

value

Priorinformation

weight2

Units

HK_1 Horizontal hydraulic conductivity of zone 1 350 330 350 15 ft/d

HK_2 Horizontal hydraulic conductivity of zone 2 250 270 250 15 ft/d

HK_3 Horizontal hydraulic conductivity of zone 3 150 123 150 30 ft/d

HK_4 Horizontal hydraulic conductivity of zone 4 50 15 -- -- ft/d

RCH_Nonirr Recharge rate beneath nonirrigated areas 0.7 1.5 0.9 0.2 in/yr

RCH_Flood Recharge rate beneath flood-irrigated fields 4 8.2 4.9 1.2 in/yr

RCH_Sprink Recharge rate beneath sprinkler-irrigated fields 2 3.4 2.4 1.2 in/yr

Wells_PCC Withdrawal rate of irrigation wells with power-use data –1.6 –1.5 –1.6 0.1 acre-ft/acre/yr

Wells_Irr Withdrawal rate of irrigation wells lacking power-use data –1.6 –0.94 –1.2 0.2 acre-ft/acre/yr

Q_Olds Seepage rate of Olds Reservoir 0.14 0.19 0.14 0.02 ft/d

GHB_Out Hydraulic conductance of the general-head boundary 

at the downgradient edge of the model

275,000 275,000 -- -- ft2/d

GHB_In Hydraulic conductance of general-head boundaries 

at tributary valleys along the edge of the model

5,000 5,000 -- -- ft2/d

GHB_Return Hydraulic conductance of the general-head boundary 

representing subsurface return flow along the west 

model boundary 

5,000 5,000 -- -- ft2/d

Q_Lord Seepage rate of Lord Reservoir 0.015 0.015 -- -- ft/d

GHB_Prspct Hydraulic conductance of the general-head boundary 

at Prospect Reservoir 

1,000 1,000 -- -- ft2/d

EVT_Par Evapotranspiration rate 31 31 -- -- in/yr 1

Parameters in bold were estimated by inverse methods.

2

Prior-information weights represent assigned standard deviations of measurement error.
44 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

The initial estimate of Q_Olds (0.14 ft/d) is based on the 

annually averaged seepage rate during 1990–2001 (table 5), and 

the initial estimate of Q_Lord (0.015 ft/d) is based on the annually 

averaged seepage rate during 1990–92. Final calibrated values 

of Q_Olds and Q_Lord are 0.19 ft/d and 0.015 ft/d, respectively. 

Parameter EVT_Par was assigned a value of about 31 in/yr. 

Hydraulic conductance of the general-head boundary representing groundwater outflow at the northern end of the Lost Creek 

basin (GHB_Out) was assigned a value of 275,000 ft2/d, and 

multipliers were used to adjust the hydraulic conductance of each 

cell represented by parameter GHB_Out to reflect variations in 

saturated thickness and hydraulic conductivity along the length of 

the boundary. Hydraulic conductances of general-head boundaries representing inflow from Prospect Reservoir (GHB_Prspct), 

tributary valleys at the edge of the model domain (GHB_In), 

and irrigation return flow along a part of the west model boundary (GHB_Return) were assigned values ranging from 1,000 

to 5,000 ft2

/d on the basis of estimated saturated thickness and 

hydraulic conductivity along the length of each boundary.

Calibration Assessment

The difference between an observation and a simulated 

value or between a prior-information value and a parameter 

estimate is called a residual. Overall model fit was evaluated 

with respect to residuals by using the standard error of the 

model regression and the fitted standard deviation of hydraulic 

head. The standard error of the regression is an indicator of 

the overall magnitude of weighted residuals and is provided 

as output from MODFLOW–2000. The standard error of the 

regression is expressed as (Hill, 1998):

s

S b

ND NPR NP = + −

( )

( )

(8)

where

	 s	 is the standard error of the regression,

	 S(b) is the value of the weighted least-squares 

objective function, calculated as

i i i  p p p

p

NPR

i

ND

[y − y (b)] + [P − P (b)] = =

∑ ∑ 2 2

1 1

' '

	 ND	 is the number of observations,

	 NPR is the number of prior-information values,

	 NP	 is the number of estimated parameters,

	 yi is the ith observation being matched by 

the regression,

y′

i

(b )	 is the simulated value that corresponds 

to the ith observation (a function of b),

	 Pp is the pth prior estimate included in 

the regression,

	 P′

p

(b )	 is the pth simulated value,

ωi is the weight for the ith observation, 

and

ωp is the weight for the pth prior estimate.

Smaller values of standard error indicate better fit of simulated values to observations. The value of standard error should 

be close to 1.0 if weighting used on observations and prior 

information represents true data accuracy. In practice, standard 

error commonly is greater than 1.0 because of model error or 

greater-than-expected measurement error. The standard error of 

regression (table 8) for the calibrated model is 1.9.

The fitted standard deviation of hydraulic head is calculated by multiplying the standard error of the regression by 

the standard deviation of measurement error for hydraulichead observations (Hill, 1998). Using a standard deviation of 

measurement error for hydraulic-head observations of 3 ft, the 

fitted standard deviation (overall fit) of hydraulic head in the 

model is 5.7 ft, which is about 0.7 percent of the total simulated head range in the model. Although the standard error of 

the model regression and fitted standard deviation of hydraulic head provide a general measure of model fit, they do not 

indicate the spatial distribution of error or the validity of the 

model regression (calibration).

A valid regression requires observation and priorinformation errors used in the regression to be random and 

weighted errors to be uncorrelated (Draper and Smith, 1981). 

In addition, observation errors need to be normally distributed 

for use in calculating inferential statistics (Helsel and Hirsch, 

1992) such as confidence intervals on parameters and predictions. If the model accurately represents the groundwater 

system and the foregoing conditions are met, weighted residuals should either be random, independent, and normal or have 

predictable correlations (Hill, 1998). To evaluate the randomness and independence of weighted residuals, weighted residuals are plotted relative to weighted simulated values (figs. 22A, 

B). For a valid regression, weighted residuals are randomly 

distributed above and below the zero line for all weighted simulated values (Draper and Smith, 1981). A nonrandom distribution or systematic trend in weighted residuals may indicate 

weighted residuals are not random or independent (Hill, 1994). 

The relation of weighted residuals to weighted simulated values for both hydraulic head and prior information are shown 

in figure 22A. Residuals in figure 22A plot in two general 

bands because the range of simulated hydraulic head values 

is different than the range of prior-information values. The 

Table 8. Statistics used to assess calibration of the Lost Creek 

Designated Ground Water Basin model.

[Fitted standard deviation of hydraulic head in feet; all other values dimensionless]

Statistic Value

Standard error of regression, s 1.9

Fitted standard deviation of hydraulic head 5.7

Minimum weighted hydraulic-head residual –3.6

Maximum weighted hydraulic-head residual 4.3

Average weighted hydraulic-head residual –0.03

Correlation coefficient, R2

N 0.979

Critical value of R2

N at the 5-percent 

significance level

0.956

Modified Beale’s measure 2.7
Steady-State Numerical Simulation of Groundwater Flow 45

measure of residual independence and normality by determining 

the correlation between ordered weighted residuals and order 

statistics from a probability distribution function (Hill, 1998). If 

the value of R2

N is significantly less than 1.0, weighted residuals 

are not likely to be independent and normally distributed. The 

value of R2

N is calculated by MODFLOW–2000 and presented 

along with critical values for R2

N representing significance 

levels of 0.05 and 0.10. The value of R2

N for the final calibrated 

model is 0.979 (table 8) for observations and prior information, 

which is greater than the 5-percent significance level of 0.956 

and indicates that the probability is greater than 95 percent that 

weighted residuals are independent and normally distributed.

Other statistical measures used to assess calibration of 

the final model are the runs statistic (Draper and Smith, 1981, 

p. 157–162) and the correlation between weighted observations 

and weighted simulated values. The runs statistic evaluates 

the spatial and temporal randomness of weighted residuals. A 

run consists of an unbroken sequence of positive or negative 

residuals. Too few or too many runs may indicate significant model error that could affect predictions (Hill, 1998). 

MODFLOW–2000 uses the order of observations listed in 

the observation input file to determine the runs statistic. The 

number of runs in the final calibrated model is 31 in 52 observations (including prior information), which equals the number of 

runs expected and indicates that weighted residuals likely are 

randomly distributed in the model domain. Because the model 

is calibrated to steady-state conditions, temporal randomness is 

not considered. Correlation between weighted observations and 

weighted simulated values is evaluated by plotting weighted 

observations relative to weighted simulated values (figs. 24A, 

B). If weighted simulated values are similar to weighted observations, points should fall on a straight line with an intercept 

of zero (Hill, 1998). Because the plots shown in figure 24 are 

approximately linear, weighted simulated values (and consequently, unweighted simulated values) can be considered to reasonably approximate weighted (and unweighted) observations.

Figure 23.  Normal probability plot of weighted residuals for the 

groundwater flow model, Lost Creek Designated Ground Water 

Basin, Colorado.

Figure 22.  Relation of weighted residuals to weighted simulated 

values in the groundwater flow model for (A) hydraulic head 

and prior information and (B) hydraulic head only, Lost Creek 

Designated Ground Water Basin, Colorado.

relation of weighted residuals to weighted simulated values for 

hydraulic head only is shown in figure 22B to better illustrate 

the distribution of weighted hydraulic-head residuals. Because 

weighted residuals generally appear randomly distributed 

above and below the zero line for weighted simulated values 

in figures 22A and 22B, weighted residuals likely are nearly 

random and independent in the model. Slight divergence of 

weighted residuals relative to increasing weighted simulated 

values in figure 22B may indicate that simulated heads in the 

upgradient (southern) part of the basin do not match observed 

heads quite as well as in the downgradient (northern) part of 

the basin. A summary of the minimum, maximum, and average 

weighted hydraulic-head residual for the final calibrated model 

is presented in table 8.

To evaluate normality of weighted residuals and further 

test for their independence, a normal-probability graph of 

weighted residuals (fig. 23) was used. Because weighted residuals fall approximately on a straight line in the graph, weighted 

residuals may be considered independent and normally distributed. The correlation coefficient R2

N provides another statistical 

6

0

WEIGHTED RESIDUAL,

DIMENSIONLESS

WEIGHTED RESIDUAL,

DIMENSIONLESS

–6

6

0

–6

–500 0 500 1,000 1,500 2,000

WEIGHTED SIMULATED VALUE,

DIMENSIONLESS

1,500 1,600 1,700 1,800

WEIGHTED SIMULATED VALUE,

DIMENSIONLESS

Hydraulic head

Prior information

A

B

–3 –2 –1 0 1 2 3

STANDARD NORMALLY DISTRIBUTED NUMBER

–4

–3

–2

–1

0

1

2

3

4

5

WEIGHTED RESIDUAL,

DIMENSIONLESS

Hydraulic head

Prior information
46 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Parameter correlation coefficients indicate whether estimated parameter values are likely to be unique (Hill, 1998). 

Models calibrated to only hydraulic-head observations commonly 

have high parameter correlation, indicating problems with parameter uniqueness. Although the Lost Creek basin model is calibrated to only hydraulic head, parameter correlation coefficients 

for most estimated parameters in the final model are less than 

0.85, indicating that most parameters likely could be uniquely 

estimated. One parameter pair (RCH_Flood and Wells_Irr) has a 

parameter correlation coefficient of –0.89, indicating that the two 

parameters were less likely independently estimated. The negative sign indicates that an increase in the estimate of RCH_Flood 

was correlated with a decrease (more negative, but greater magnitude) in the estimate of Wells_Irr.

Overall, calibration statistics indicate that simulated water 

levels generally have acceptable agreement with water levels 

measured at 43 locations in the Lost Creek basin. Hydraulic-head 

residuals likely are random, independent, and normal, indicating 

that the model regression likely is valid.

Sensitivity Analysis

Composite scaled sensitivities were calculated for each 

parameter using the Sensitivity Process (Hill and others, 2000) of 

MODFLOW–2000. Composite scaled sensitivities are dimensionless quantities that indicate the total amount of information provided by all observations for estimation of a parameter 

(Hill, 1998). When parameter correlation is not a problem, 

parameters with high sensitivity generally can be more precisely 

estimated from available observations than parameters with low 

sensitivity. Parameters with high sensitivity also have greater 

influence on hydraulic head simulated by the model and may 

be more important to accurately define for model simulations 

than parameters with low sensitivity. Parameters with very low 

sensitivity have little effect on simulated values, and accurate 

definition of these parameters is less important to model calibration. However, parameters with low sensitivity may be important 

to predictions if predictions are distant from observation locations 

or they differ in type (for example, flow rather than head) from 

the observations used to calibrate the model. Because composite 

scaled sensitivities depend on model structure and the number 

and location of observations, the absolute magnitude of composite scaled sensitivity for a parameter is less meaningful than its 

magnitude relative to that of other parameters. The composite 

scaled sensitivity of each parameter in the final calibrated model 

is presented in figure 25. The parameter representing withdrawals 

from irrigation wells lacking pumping data (Wells_Irr) has the 

highest composite scaled sensitivity in the model. Other parameters with relatively high composite scaled sensitivities represent 

recharge beneath nonirrigated areas (RCH_Nonirr) and recharge 

beneath flood-irrigated fields (RCH_Flood). Parameters with 

relatively low composite scaled sensitivities represent seepage 

from Lord Reservoir (Q_Lord), evapotranspiration (EVT_Par), 

and the hydraulic conductance of general-head boundaries 

simulating (1) seepage from Prospect Reservoir (GHB_Prspct), 

(2) subsurface return flow from ditches and irrigated fields 

located outside the model domain (GHB_Return), (3) subsurface 

inflow from tributary valleys (GHB_In), and (4) subsurface outflow at the north end of the Lost Creek basin (GHB_Out). Other 

model parameters have moderate sensitivity. Because parameter Wells_Irr, RCH_Nonirr, and RCH_Flood have the greatest 

composite scaled sensitivity, these parameters likely are the most 

important to accurately define for model simulations.

Model Nonlinearity

The postprocessing program BEALE–2000 (Hill and 

others, 2000) provided with MODFLOW–2000 is used to evaluate model nonlinearity. BEALE–2000 uses the modified Beale’s 

measure (Cooley and Naff, 1990) to test model nonlinearity near 

the optimized parameter values. The model needs to be approximately linear for parameter values close to optimum parameter 

values for linear confidence intervals on predictions to be valid 

(Hill, 1994). Interpretation of the modified Beale’s measure is different for each model and is provided as output by BEALE–2000. 

Results of BEALE–2000 indicate that the model can be considered effectively linear near optimized parameter values if the 

Figure 24. Relation of weighted observations to weighted 

simulated values in the groundwater flow model for (A) hydraulic 

head and prior information and (B) hydraulic head only, Lost Creek 

Designated Ground Water Basin, Colorado. WEIGHTED OBSERVATION, DIMENSIONLESS WEIGHTED OBSERVATION, DIMENSIONLESS

Hydraulic head

Prior information

WEIGHTED SIMULATED VALUE,

DIMENSIONLESS

WEIGHTED SIMULATED VALUE,

DIMENSIONLESS

1,400 1,500 1,600 1,700 1,800 1,900

–500

0

500

1,000

1,500

2,000

–500 0 500 1,000 1,500 2,000

1,400

1,500

1,600

1,700

1,800

1,900

A

B
Steady-State Numerical Simulation of Groundwater Flow 47

Beale’s measure is less than 0.043. The model can be considered 

intermediate if the Beale’s measure is between 0.043 and 0.48 and 

nonlinear if it is greater than 0.48. Because the Beale’s measure 

for the calibrated model is 2.7 (table 8), the model is considered 

nonlinear, and linear confidence intervals on parameters likely do 

not accurately represent parameter uncertainty. Similarly, linear 

confidence intervals on predictions made using the model likely 

would not accurately represent prediction uncertainty. The model 

is most nonlinear with respect to (1) sprinkler-irrigation recharge 

(RCH_Sprink), (2) flood-irrigated recharge (RCH_Flood), 

(3) seepage from Olds Reservoir (Q_Olds), and (4) withdrawals 

from irrigation wells lacking power-use data (Wells_Irr).

Simulation Results

The calibrated steady-state distribution of hydraulic head 

representing average water-table conditions in the Lost Creek 

basin during 1990–2001 is shown in figure 26. The simulated 

water table ranges in altitude from about 4,530 ft at the northern 

end of the Lost Creek basin to about 5,390 ft at the southern end 

of the basin. Groundwater in the simulated Lost Creek basin generally flows from the basin margins toward the center of the basin 

and northward along the main paleovalley of the basin. Watertable gradients range from about 10 ft/mi near Roggen to about 

80 ft/mi in the southern part of the basin. Water-table gradients are 

flattest near Roggen because the main paleovalley in this area is 

Figure 25. Composite scaled sensitivities of parameters in the groundwater flow model, Lost Creek Designated 

Ground Water Basin, Colorado.

13.43

9.41

3.36

5.74

18.39

4.88

0.92

0.24 0.03 0.11 0.04 0.43

3.80

4.75

3.37 3.82

Q_Olds

Q_Lord

EVT_Par

GHB_Out

GHB_Prspct

GHB_In

RCH_Nonirr

GHB_Return

RCH_Flood

RCH_Sprink

Wells_PCC

Wells_Irr

PARAMETER

HK_1

HK_2

HK_3

HK_4

14

16

18

20

0

2

4

6

8

10

12

COMPOSITE SCALED SENSITIVITY,

DIMENSIONLESS

EXPLANATION

Hydraulic conductivity of zone 1

Hydraulic conductivity of zone 2

Hydraulic conductivity of zone 3

Hydraulic conductivity of zone 4

Recharge rate beneath nonirrigated areas

Recharge rate beneath flood-irrigated fields

Recharge rate beneath sprinkler-irrigated fields

Withdrawal rate of irrigations wells with power-use data

Withdrawal rate of irrigations wells lacking power-use data

Seepage rate of Olds Reservoir

Seepage rate of Lord Reservoir

Evapotranspiration rate

Hydraulic conductance of the general-head boundary at the downgradient edge of the model

Hydraulic conductance of the general-head boundary at Prospect Reservoir

Hydraulic conductance of general-head boundaries at tributary valleys along the edge of the model

Hydraulic conductance of the general-head boundary representing subsurface return flow along the 

 west model boundary

HK_1 

HK_2

HK_3

HK_4

RCH_Nonirr

RCH_Flood

RCH_Sprink

Wells_PCC

Wells_Irr

Q_Olds

Q_Lord

EVT_Par

GHB_Out

GHB_Prspct

GHB_In

GHB_Return
48 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Figure 26. Steady-state altitude and configuration of the water table simulated by the groundwater flow model, Lost Creek Designated 

Ground Water Basin, Colorado.

!(

!(

!(

!

!(

(

¬«

¦ ̈§

§ ̈¦ £¤

£¤

¬«

m

m

m m

m

m

m

m

m

34

76

52

79

36 70

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

EXPLANATION

Active model cell

Inactive model cell

Lost Creek Designated Ground Water Basin

 administrative boundary

Water-table contour—Shows altitude of simulated

 water table. Contour interval 20 feet. National

 Geodetic Vertical Datum of 1929

Generalized direction of simulated groundwater flow

5000

0

0

5

5 10 KILOMETERS

10 MILES

5200

5300

5100

5000

4900

4900

4800

4700

4600

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Masters

Keenesburg

Bennett

Roggen

Prospect

Valley

Lost Creek

Sou th Platte River

Sand

Creek

Long

Draw

Olds

Reservoir

Lord

Reservoir

Lost Creek

Lost Creek

Prospect

Reservoir

West S and

Creek West S andCreek

104°30' 104°15'

40°15'

40°00'

39°45'
Steady-State Numerical Simulation of Groundwater Flow 49

wide, the bedrock surface is relatively flat, and aquifer transmissivity is high. Similarly, water-table gradients in the southern part 

of the basin are steepest because the main paleovalley in this area 

is comparatively narrow, the bedrock surface is relatively steep, 

and transmissivity is relatively low. Irregularities in the configuration of water-table contours are caused primarily by local variations in aquifer transmissivity, primarily as it relates to saturated 

thickness. Where transmissivity is relatively low, groundwater 

flow is impeded, and simulated hydraulic head is higher than in 

areas with greater transmissivity. Localized mounds in the water 

table near Olds and Lord Reservoirs are caused by simulated 

seepage from these reservoirs. Saturated thickness (fig. 27) in the 

model domain generally ranges from about 10 to 120 ft. Saturated 

thickness is greatest along the main paleovalley, especially in the 

northern part of the basin, where saturated thickness is as much as 

about 140 ft. Saturated thickness is least near basin margins and 

in areas of shallow bedrock, where saturated thickness can be less 

than 10 ft.

The computer program ZONEBUDGET (Harbaugh, 1990) 

was used to calculate the contribution of individual simulated 

components (such as recharge from nonirrigated areas, floodirrigated fields, and sprinkler-irrigated fields) to the overall water 

budget (table 9). Combined recharge from deep percolation of 

water beneath flood- and sprinkler-irrigated agricultural fields 

(14,510 acre-ft/yr) is the largest source of inflow to the model, 

contributing 39.7 percent of the total inflow. Recharge from 

precipitation and stream-channel infiltration in nonirrigated 

areas (13,810 acre-ft/yr) is the second largest source of inflow 

to the model, contributing 37.7 percent of the total inflow. Other 

relatively substantial sources of inflow to the model are seepage 

from Olds Reservoir (4,280 acre-ft/yr) and subsurface inflow 

from ditches and irrigated fields outside the model domain 

(2,490 acre-ft/yr), which contribute 11.7 and 6.8 percent, respectively, of the total inflow. Inflow from small tributary valleys 

connected to the main Lost Creek basin paleovalley and seepage from Prospect and Lord Reservoirs collectively contribute 

4.1 percent of the total inflow to the model. Irrigation well withdrawals (26,760 acre-ft/yr) are the largest source of outflow from 

the model, representing 73.2 percent of the total outflow. Groundwater discharge at the downgradient end of the Lost Creek basin 

(6,640 acre-ft/yr) represents 18.2 percent of the total outflow, and 

evapotranspiration (3,140 acre-ft/yr) represents 8.6 percent of the 

total outflow.

All values of the simulated water budget appear reasonable 

compared to available data. Although combined recharge from 

deep percolation of water beneath flood- and sprinkler-irrigated 

agricultural fields represents about 54 percent of irrigation-well 

withdrawals, this percentage does not consider other sources of 

water, such as surface-water irrigation and precipitation, that contribute to recharge beneath irrigated agricultural fields. Assuming 

surface-water irrigation is uniform, the amount of surface water 

applied to irrigated agricultural fields within the model domain 

(86.2 percent of the 32,500 acres irrigated acres in the Lost Creek 

basin, or 28,000 acres) is about 10,300 acre-ft (86.2 percent of 

the 11,900 acre-ft diverted to the Lost Creek basin), and water 

supplied to irrigated agricultural fields in the model domain by 

precipitation (14.1 in/yr, or about 1.18 acre-ft per acre) is about 

32,900 acre-ft. When total water supplied to irrigated agricultural 

fields from groundwater, surface water, and precipitation are 

considered (69,960 acre-ft), total simulated recharge from deep 

percolation of water beneath irrigated fields represents about 

21 percent of the total supplied water.

Model Limitations and Data Needs

Although the updated groundwater model presented in 

this report provides a reasonable representation of groundwater 

flow in the Lost Creek basin and statistics indicate the model is 

relatively well calibrated, the model is a simplified mathematical 

representation of a complex hydrologic system that is subject to 

limitations. The model cell size (1,000 ft × 1,000 ft) and level of 

detail are designed for simulating wide-scale aquifer responses 

to hydrologic stresses such as well withdrawals and changes in 

recharge. The model cannot accurately simulate aquifer responses 

to hydrologic stresses at a scale smaller than the model cell size. 

Because steady-state simulations represent average hydrologic 

conditions in the Lost Creek basin, short-term (seasonal) variations in hydrologic stresses are not considered, and use of the 

model for transient simulations might not accurately predict shortterm hydrologic effects. Although calibration results indicate that 

most parameters likely were uniquely estimated, the addition of 

other types of observations, such as advective transport, could be 

useful to improving model calibration and reducing parameter 

correlation between the parameter representing recharge beneath 

flood-irrigated fields and the parameter representing withdrawals 

from wells lacking power-use data.

Several data needs were identified during this study that, 

if fulfilled, would improve hydrogeologic characterization of 

the Lost Creek basin and reduce model uncertainty as it relates 

to model input. Additional drilling or geophysical investigations 

could be undertaken to better define the saturated thickness and 

subsurface configuration of the Lost Creek basin in areas of 

little data or questionable data quality. In particular, additional 

hydrogeologic information would be useful to better define the 

hydrologic connection between the main Lost Creek paleovalley 

and the South Platte River valley and between the main paleovalley and Hay Gulch. Additional hydrogeologic information also 

would be useful to better define the configuration and thickness 

of the tributary paleovalley in the northwestern part of the study 

area and the main paleovalley in the southern part of the basin 

near the town of Bennett, particularly where saturated thickness is 

simulated as greater than 80 ft. Additional aquifer tests would be 

useful to better define the hydraulic properties of sediments in the 

southern part of the Lost Creek basin. Study of groundwater interaction between the Lost Creek basin and the underlying Denver 

Basin bedrock aquifers would be important to understanding the 

possible effects of groundwater withdrawals on flow between the 

aquifers. Monitoring of groundwater levels during the irrigation season as well as the nonirrigation season could provide for 

evaluation of the transient response of the aquifer to pumping 

and seasonal variations in recharge. Because simulated hydraulic 

head in the model is most sensitive to groundwater withdrawals 

from irrigation wells lacking power-use data, and withdrawals 

from these wells are not well quantified, additional evaluation of 
50 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Figure 27. Saturated thickness simulated by the groundwater flow model, Lost Creek Designated Ground Water Basin, Colorado.

!(

!(

!(

!(

!(

¬«

¦ ̈§

§ ̈¦ £¤

£¤

76

34

79

70 36

¬«52

Streams and reservoirs modified from Schupbach and Lewis (1996a, b)

Roads modified from Colorado Department of Transportation

Designated basin extent modified from Lewis (1996)

North American Datum of 1983

EXPLANATION

Active model cell

Inactive model cell

Lost Creek Designated Ground Water 

 Basin administrative boundary

Saturated thickness, in feet

 0 to 20

 20 to 40

 40 to 60

 60 to 80

 80 to 100

 100 to 120

 120 to 140

0 5 10 MILES

0 5 10 KILOMETERS

ARAPAHOE COUNTY

WELD COUNTY

ADAMS COUNTY

MORGAN COUNTY

Masters

Keenesburg

Bennett

Roggen

Prospect

Valley

Lost Creek

Sou th Platte River

Sand

Creek

Long

Draw

West S and

Creek West S andCreek

Prospect

Reservoir

Olds

Reservoir

Lord

Reservoir

Lost CreekLost Creek

104°30' 104°15'

40°15'

40°00'

39°45'
Summary 51

well withdrawals would be important to improving simulations 

of groundwater flow in the Lost Creek basin and reducing model 

uncertainty. Estimates of recharge to the Lost Creek basin could 

be improved by additional study of deep-percolation return flow 

beneath flood- and sprinkler-irrigated fields and by detailed investigation of seepage loss along ditches in the Henrylyn irrigation 

system in the Lost Creek basin.

Summary

The Lost Creek Designated Ground Water Basin (Lost 

Creek basin) is an important alluvial aquifer for irrigation, 

public supply, and domestic water uses in northeastern Colorado. 

Urban growth in the adjacent Front Range urban corridor has 

increased demand for groundwater in the basin, and potential 

exportation of groundwater from the basin has raised concerns 

about the long-term sustainability and management of the basin’s 

groundwater resources. Beginning in 2005 the U.S. Geological 

Survey, in cooperation with the Lost Creek Ground Water 

Management District and the Colorado Water Conservation 

Board, collected hydrologic data and constructed a numerical 

groundwater flow model of the Lost Creek basin. The steady-state 

model builds upon the work of previous investigators to provide 

an updated tool for simulating the potential effects of various 

hydrologic stresses on groundwater flow and evaluating possible 

aquifer-management strategies.

Development of the Lost Creek basin model included 

(1) mapping the thickness and extent of regolith sediments to 

define the subsurface configuration of the Lost Creek basin and 

(2) collecting data related to infiltration of precipitation and 

stream channels, deep percolation of water applied to irrigated 

agricultural fields, ditch and reservoir seepage, and subsurface 

inflow to improve estimates of recharge to the basin. Data concerning well withdrawals, evapotranspiration, and subsurface 

outflow were used to estimate discharge from the basin.

The thickness and extent of regolith sediments indicate 

a well-defined paleovalley that extends along the Lost Creek 

basin from south to north, where it joins the alluvial valley 

of the South Platte River. Regolith along the main part of 

the paleovalley is as much as about 190 ft thick, and several 

smaller paleovalleys appear tributary to the main paleovalley 

that have regolith as much as 120 ft thick.

Recharge from infiltration of precipitation on native 

grassland and nonirrigated agricultural fields was estimated 

by using the chloride mass-balance method at four sites in 

the Lost Creek basin. Recharge from infiltration of ephemeral streamflow was estimated by using apparent downward 

velocities of chloride peaks in soil profiles at two sites located 

in the stream channels of West Sand Creek and Long Draw. 

Recharge from deep percolation of water applied to irrigated 

agricultural fields was estimated by using passive-wick 

lysimeters installed at four sites in the Lost Creek basin and by 

using a water-balance approach.

Average annual recharge from infiltration of precipitation on native grassland and nonirrigated agricultural fields 

was estimated to range from 0.1 to 0.6 inch, which represents 

about 1–4 percent of long-term average precipitation. Average annual recharge from infiltration of ephemeral streamflow 

in the channels of West Sand Creek and Long Draw was 

estimated to range from 5.7 to 8.2 inches over the area of the 

stream channels.

Table 9. Simulated steady-state groundwater budget of the Lost Creek Designated Ground Water Basin model representing conditions 

for 1990–2001.

[ft3/d, cubic feet per day; acre-ft, acre-feet]

Budget component

Flow

rate

(ft3/d)

Annual

flow volume

(acre-ft)

Percentage

of total inflow

or outflow

Inflows1

Recharge from precipitation and stream-channel infiltration in nonirrigated areas 1,648,000 13,810 37.7

Recharge from deep percolation of water beneath flood-irrigated agricultural fields 1,162,000 9,740 26.6

Recharge from deep percolation of water beneath sprinkler-irrigated agricultural fields 569,600 4,770 13.1

Groundwater inflow from small tributary valleys 35,100 290 0.8

Groundwater inflow from ditches and irrigated fields outside the model domain 297,100 2,490 6.8

Seepage from Prospect Reservoir 37,800 320 0.9

Seepage from Olds Reservoir 510,800 4,280 11.7

Seepage from Lord Reservoir 105,600 890 2.4

Total 4,366,000 36,590 100.0

Outflows1

Irrigation well withdrawals 3,193,000 26,760 73.2

Groundwater outflow at downgradient end of the Lost Creek Designated Ground Water Basin 792,800 6,640 18.2

Evapotranspiration 375,100 3,140 8.6

Total 4,360,900 36,540 100.0

Percent discrepancy2 (Inflows–Outflows) 0.1 0.1 1

Inflows and outflows are net values (flow into minus flow out of cells representing each budget component).

2

Percent discrepancy represents error due to the limited precision of the solution to the finite-difference equations used by the model.
52 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Recharge from deep percolation of water applied to irrigated 

agricultural fields varied by irrigation method, soil type, crop 

type, and the net quantity of irrigation water applied. Recharge 

estimated by lysimeter drainage at a sprinkler-irrigated alfalfa 

field on loam soil ranged from 1.0 to 1.8 inches during the 

irrigation season and represented 5–7 percent of net irrigation 

and 4–6 percent of net irrigation plus precipitation. Recharge 

estimated by lysimeter drainage at a sprinkler-irrigated field on 

sandy soil ranged from 3.0 to 4.0 inches during the irrigation 

season for corn and alfalfa crops and represented 23–30 percent 

of net irrigation and 17–26 percent of net irrigation plus precipitation. Recharge estimated by lysimeter drainage beneath floodirrigated fields on loam soil ranged from 0.1 to 3.5 inches during 

the irrigation season for wheat and corn crops and represented 

13–20 percent of net irrigation and 5–11 percent of net irrigation plus precipitation. Because of the potential variability of net 

irrigation over the area of flood-irrigated fields, recharge estimates 

for flood-irrigated fields have larger uncertainty than recharge 

estimates for sprinkler-irrigated fields.

Recharge estimated by using a water-balance method had 

a wider range of values than recharge estimated by lysimeter 

drainage, likely because recharge estimated by the waterbalance method was sensitive to inaccuracies in the estimates 

of other water-balance components. Recharge estimated using 

the water-balance method at a sprinkler-irrigated field on loam 

soil ranged from 0 to 5.0 inches, which represented 0–19 percent of net irrigation and 0–16 percent of net irrigation plus 

precipitation. Recharge estimated by using the water-balance 

method at a sprinkler-irrigated field on sandy soil indicated no 

recharge occurred during the period of study because cumulative evapotranspiration exceeded cumulative net irrigation 

plus precipitation. Recharge estimated by the water-balance 

method at flood-irrigated fields on loam soil ranged from 0 to 

11.3 inches, which represented 0–43 percent of net irrigation 

and 0–37 percent of net irrigation plus precipitation.

The USGS modular groundwater modeling program, 

MODFLOW–2000, was used to develop a steady-state groundwater flow model of the Lost Creek basin. The model primarily 

was calibrated to average hydrologic conditions representing 

the period 1990–2001 by using the Observation, Sensitivity, 

and Parameter-Estimation Processes of MODFLOW–2000. 

Forty-three hydraulic-head observations were used to calibrate 

the model. Because perennial streams do not exist in the Lost 

Creek basin, the model was not calibrated to flow observations 

representing streamflow gains or losses. Sixteen parameters 

were used in the model, 10 of which were estimated by using 

inverse modeling methods. Simulated water levels generally 

have acceptable agreement with measured water levels, and 

calibration statistics indicate that residuals between simulated 

and measured values of hydraulic head likely are random, independent, and normally distributed. 

The parameter representing withdrawals from irrigation wells lacking pumping data had the highest composite 

scaled sensitivity in the model. Other parameters with relatively high composite scaled sensitivities represent recharge 

beneath nonirrigated areas and recharge beneath flood-irrigated 

fields. Because composite scaled sensitivities were highest 

for parameters representing withdrawals from wells lacking 

pumping data, recharge beneath nonirrigated areas, and recharge 

beneath flood-irrigated fields, these parameters likely are the 

most important to accurately define for model simulations.

Groundwater in the simulated Lost Creek basin generally 

flows from the basin margins toward the center of the basin 

and northward along the main paleovalley of the basin. Watertable gradients range from about 10 ft/mi near Roggen to about 

80 ft/mi in the southern part of the basin. Water-table gradients 

are flattest near Roggen because the main paleovalley in this 

area is wide, the bedrock surface is relatively flat, and aquifer 

transmissivity is high. Water-table gradients in the southern part 

of the basin are steepest because the main paleovalley in this 

area is comparatively narrow, the bedrock surface is relatively 

steep, and transmissivity is low. Saturated thickness in the 

model domain ranges from less than 10 to about 140 ft. Saturated thickness is greatest along the main paleovalley, especially 

in the northern part of the basin. Saturated thickness is least near 

basin margins and in areas of shallow bedrock.

The largest source of inflow to the model domain occurs 

from recharge beneath flood- and sprinkler-irrigated agricultural 

fields (14,510 acre-ft/yr), which represents 39.7 percent of total 

simulated inflow. Other substantial sources of inflow to the 

model domain are recharge by precipitation and stream-channel 

infiltration in nonirrigated areas (13,810 acre-ft/yr), seepage 

from Olds Reservoir (4,280 acre-ft/yr), and subsurface inflow 

from ditches and irrigated fields outside the model domain 

(2,490 acre-ft/yr), which contribute 37.7, 11.7, and 6.8 percent, 

respectively, of total inflow. The largest outflow from the model 

occurs from irrigation well withdrawals (26,760 acre-ft/yr), 

which represent 73.2 percent of total outflow. Groundwater 

discharge (6,640 acre-ft/yr) at the downgradient end of the 

Lost Creek basin represents 18.2 percent of total outflow, and 

evapotranspiration (3,140 acre-ft/yr) represents 8.6 percent of 

total outflow.

Acknowledgments

Many individuals contributed to this study. Thanks are 

extended to all landowners who granted access to their properties for the collection of data. Special thanks go to Rich Huwa, 

Dave and Paul Rupple, and Steve Bruntz for allowing installation of lysimeters to measure deep percolation beneath 

their irrigated agricultural fields. Thanks also are extended 

to Tom Sauter, John Cordes, Rich Huwa, Steven Deutch, 

Steven Jansen, and Woody Eppelsheimer for providing 

valuable information about farming practices, hydrologic 

conditions, and water development in the Lost Creek basin. 

Rod Baumgartner of the Henrylyn Irrigation District provided 

important irrigation data, and his contribution is gratefully 

acknowledged. Technical support provided by Rick Healy 

(USGS National Research Program) concerning the collection 

and analysis of data used to estimate recharge also is gratefully 

acknowledged.
References Cited 53

References Cited

Allison, G.B., Gee, G.W., and Tyler, S.W., 1994, A review 

of vadose-zone techniques for estimating groundwater 

recharge in arid and semiarid regions: Soil Science Society 

of America Journal, v. 58, p. 63–72.

Allison, G.B., and Hughes, M.W., 1978, The use of environmental chloride and tritium to estimate total recharge to an 

unconfined aquifer: Australian Journal of Soil Research, 

v. 16, p. 181–195.

Argus Interware, 1997, Argus ONE user’s guide, Argus Open 

Numerical Environments—A GIS Modeling System, version 4.0: Jericho, N.Y., Argus Holdings, Limited, 320 p.

Arnold, L.R., 2010, Geographic information system datasets 

of regolith-thickness data, regolith-thickness contours, 

raster-based regolith thickness, and aquifer-test and specificcapacity data for the Lost Creek Designated Ground Water 

Basin, Weld, Adams, and Arapahoe Counties, Colorado: 

U.S. Geological Survey Data Series 507.

Bjorklund, L.J., and Brown, R.F., 1957, Geology and groundwater resources of the lower South Platte River valley 

between Hardin, Colorado, and Paxton, Nebraska: U.S. Geological Survey Water-Supply Paper 1378, 431 p., 4 pls.

Braddock, W.A., and Cole, J.C., 1978, Preliminary geologic 

map of the Greeley 1°×2° quadrangle, Colorado and Wyoming: U.S. Geological Survey Open-File Report 78–532, 

scale 1:250,000.

Bryant, B., McGrew, L.W., and Wobus, R.A., 1981, Geologic 

map of the Denver 1°×2° quadrangle, north-central Colorado: U.S. Geological Survey Miscellaneous Investigations 

Series Map I–1163, 2 sheets, scale 1:250,000.

Code, W.E., 1945, Ground water supply of Prospect Valley, 

Colorado: Colorado Agricultural Experiment Station Technical Bulletin 34, 40 p.

Coes, A.L., and Pool, D.R., 2005, Ephemeral stream-channel and 

basin-floor infiltration and recharge in the Sierra Vista subwatershed of the Upper San Pedro Basin, southeastern Arizona: 

U.S. Geological Survey Open-File Report 2005–1023, 67 p.

Colorado Division of Water Resources, 2000, Ground water 

levels in the Lost Creek Designated Ground Water Basin 

2000: Colorado Division of Water Resources, Denver, Colo.

Colorado Division of Water Resources, 2007, CDSS climate 

stations, Division 1, database version 20070901: Colorado’s 

Decision Support Systems spatial dataset available on the 

Web, accessed May 30, 2008, at http://cdss.state.co.us/

DNN/GIS/tabid/67/Default.aspx.

Colorado Division of Water Resources, 2008, Colorado’s 

Decision Support Systems: Colorado Division of Water 

Resources diversion data available on the Web, accessed 

February 20, 2008, at http://cdss.state.co.us/DNN/

Structures/tabid/75/Default.aspx.

Cooley, R.L., and Naff, R.L., 1990, Regression modeling of 

ground-water flow: U.S. Geological Survey Techniques of 

Water-Resources Investigations, book 3, chap. B4, 232 p.

Dane, J.H., and Topp, G.C., eds., 2002, Methods of soil analysis, part 4, Physical methods: Madison, Wis., Soil Science 

Society of America Book Series, v. 5, 866 p.

DeMeo, G.A., Smith, J.L., Damar, N.A., and Darnell, J., 2008, 

Quantifying ground-water and surface-water discharge from 

evapotranspiration processes in 12 hydrographic areas of 

the Colorado Regional Groundwater Flow System, Nevada, 

Utah, and Arizona: U.S. Geological Survey Scientific Investigations Report 2008–5116, 22 p.

Draper, N.R., and Smith, H., 1981, Applied regression analysis 

(2d ed.): New York, John Wiley, 709 p.

Fenneman, N.M., 1946, Physical divisions of the United 

States: U.S. Geological Survey map, scale 1:7,000,000.

Fetter, C.W., 1994, Applied hydrogeology (3d ed.): New York, 

Prentice-Hall, 691 p.

Gaggiani, N.G., 1995, Ground-water flow and effects of agricultural applications of sewage sludge and other fertilizers 

on the chemical quality of sediments in the unsaturated 

zone and ground water near Platteville, Colorado, 1985–89: 

U.S. Geological Survey Water-Resources Investigations 

Report 94–4037, 41 p.

Gee, G.W., Ward, A.L., Caldwell, T.G., and Ritter, J.C., 2002, 

A vadose zone water fluxmeter with divergence control: 

Water Resources Research, v. 38, no. 8, p. 16–1—16–7.

Glover, R.E., 1959, Ground water recharge in Prospect Valley, 

Colorado—Part I, Analytical studies: Colorado Agricultural 

Experiment Station Research Project 112, Preliminary Progress Report, 25 p.

Harbaugh, A.W., 1990, A computer program for calculating 

subregional water budgets using results from the U.S. Geological Survey modular three-dimensional finite-difference 

ground-water flow model: U.S. Geological Survey OpenFile Report 90–392, 46 p.

Harbaugh, A.W., Banta, E.R., Hill, M.C., and McDonald, 

M.C., 2000, MODFLOW–2000, the U.S. Geological Survey 

modular ground-water model—User guide to modularization concepts and the ground-water flow process: U.S. Geological Survey Open-File Report 2000–92, 121 p.
54 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Heil, R.D., Moreland, D.C., Cipra, J.E., Phillips, J.R., and 

Williams, R.D., 1978, Soil resources of Colorado Region 2—

Larimer and Weld Counties: Colorado State University Experiment Station Special Series no. 1, 141 p., 3 pls.

Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in 

water resources: Elsevier, 522 p.

Hill, M.C., 1990, Preconditioned conjugate-gradient 2 

(PCG2), a computer program for solving ground-water flow 

equations: U.S. Geological Survey Water-Resources Investigations Report 90–4048, 43 p.

Hill, M.C., 1994, Five computer programs for testing weighted 

residuals and calculating linear confidence and prediction 

intervals on results from the ground-water parameter estimation computer program MODFLOWP: U.S. Geological 

Survey Open-File Report 93–481, 81 p.

Hill, M.C., 1998, Methods and guidelines for effective model 

calibration: U.S. Geological Survey Water-Resources Investigations Report 98–4005, 90 p.

Hill, M.C., Banta, E.R., Harbaugh, A.W., and Anderman, 

E.R., 2000, MODFLOW-2000, the U.S. Geological Survey 

modular ground-water model—User guide to the Observation, Sensitivity, and Parameter-Estimation Processes and 

three post-processing programs: U.S. Geological Survey 

Open-File Report 2000–184, 209 p.

Hurr, R.T., Schneider, P.A., Jr., and others, 1972, Hydrogeologic characteristics of the valley-fill aquifer in the Weldona 

reach of the South Platte River valley, Colorado: U.S. Geological Survey Open-File Report 73–127, 2 p. 6 pl.

Jensen, M.E., Burman, R.D., and Allen, R.G., eds., 1990, 

Evapotranspiration and irrigation water requirements: 

American Society of Civil Engineers Manuals and Reports 

on Engineering Practice no. 70, 332 p.

Jones, P.A, and Cech, T.C., 2009, Colorado Water Law: 

Boulder, University Press of Colorado, 276 p.

Lewis, L.E., 1996, Designated basin: Colorado Division of 

Water Resources spatial dataset available on the Web, accessed 

May 30, 2008, at http://water.state.co.us/pubs/gis.asp.

Maurer, D.K., and Thodal, C.E., 2000, Quantity and chemical quality of recharge, and updated water budgets, for 

the basin-fill aquifer in Eagle Valley, western Nevada: 

U.S. Geological Survey Water-Resources Investigations 

Report 99–4289, 46 p.

McDonald, M.G., and Harbaugh, A.W., 1988, A modular 

three-dimensional finite-difference ground-water flow 

model: U.S. Geological Survey Techniques of WaterResources Investigations, book 6, chap. A1, 586 p.

McMahon, P.B., Dennehy, K.F., Michel, R.L., Sophocleous, 

M.A., Ellett, K.M., and Hurlbut, D.B., 2003, Water movement through thick unsaturated zones overlying the central 

High Plains aquifer, southwestern Kansas, 2000–2001: 

U.S. Geological Survey Water-Resources Investigations 

Report 2003–4171, 32 p.

National Atmospheric Deposition Program, 2005, Atmospheric deposition data on the Web, accessed November 21, 

2005 at http://nadp.sws.uiuc.edu/sites/ntnmap.asp.

Nelson, Haley, Patterson, and Quirk, Inc., 1967, Ground water 

resources of the Lost Creek drainage basin, Weld, Adams, 

and Arapahoe Counties, Colorado: Report prepared for the 

Colorado Ground Water Commission, 32 p., 3 pls.

Prudic, D.E., 1991, Estimates of hydraulic conductivity from 

aquifer-test analyses and specific-capacity data, Gulf Coast 

regional aquifer systems, south-central United States: 

U.S. Geological Survey Water-Resources Investigations 

Report 90–4121, 38 p.

Riverside Technology, Inc., 2006, SPDSS, 2001 Division 1 

ditch service areas: Colorado’s Decision Support Systems spatial dataset available on the Web, accessed 

May 30, 2008, at http://cdss.state.co.us/DNN/GIS/tabid/67/

Default.aspx.

Riverside Technology, Inc., 2007, South Platte Decision Support System, Division 1 irrigated lands, 2001: Colorado’s 

Decision Support Systems spatial dataset available on the 

Web, accessed May 30, 2008, at http://cdss.state.co.us/

DNN/GIS/tabid/67/Default.aspx.

Roark, D.M., and Healy, D.F., 1998, Quantification of deep 

percolation from two flood-irrigated alfalfa fields, Roswell 

Basin, New Mexico: U.S. Geological Survey WaterResources Investigations Report 98–4096, 32 p.

Robinson, T.W., 1958, Phreatophytes: U.S. Geological Survey 

Water-Supply Paper 1423, 84 p. 

Robson, S.G., 1983, Hydraulic characteristics of the principal 

bedrock aquifers in the Denver Basin, Colorado: U.S. Geological Survey Hydrologic Investigations Atlas HA–659, 

3 sheets, scale 1:500,000.

Robson, S.G., 1987, Bedrock aquifers in the Denver Basin, 

Colorado—A quantitative water-resources appraisal: 

U.S. Geological Survey Professional Paper 1257, 73 p.

Scanlon, B.R., Keese, K.E., Flint, A.L., Flint, L.E., Gaye, 

C.B., Edmunds, W.M., and Simmers, I., 2006, Global synthesis of groundwater recharge in semiarid and arid regions: 

Hydrological Processes, v. 20, p. 3335–3370.

Schaubs, M.P., 2007, Ground water levels in the Lost Creek 

Designated Ground Water Basin 2007: Colorado Division 

of Water Resources, Denver, Colorado, 10 p.
References Cited 55

Schupbach, S.A., and Lewis, L.E., 1995, Denver Basin aquifer 

boundaries: Colorado Division of Water Resources spatial 

dataset available on the Web, accessed May 30, 2008, at 

http://water.state.co.us/pubs/gis.asp.

Schupbach, S.A., and Lewis, L.E., 1996a, CDSS lakes 

Division 1: Colorado’s Decision Support Systems spatial 

dataset available on the Web, accessed May 30, 2008 at 

http://cdss.state.co.us/DNN/GIS/tabid/67/Default.aspx.

Schupbach, S.A., and Lewis, L.E., 1996b, CDSS rivers 

Division 1: Colorado’s Decision Support Systems spatial 

dataset available on the Web, accessed May 30, 2008 at 

http://cdss.state.co.us/DNN/GIS/tabid/67/Default.aspx.

Skinner, M.M., 1963, Artificial ground-water recharge in 

the Prospect Valley area, Colorado: Colorado Agricultural 

Experiment Station General Series 792, 89 p.

Stonestrom, D.A., Prudic, D.E., Laczniak, R.J., Akstin, 

K.C., Boyd, R.A., and Henkelman, K.K., 2003, Estimates 

of deep percolation beneath native vegetation, irrigated 

fields, and the Amargosa River channel, Amargosa Desert, 

Nye County, Nevada: U.S. Geological Survey Open-File 

Report 2003–104, 88 p.

Susong, D.D., 1995, Water budget and simulation of onedimensional unsaturated flow for a flood- and a sprinklerirrigated field near Milford, Utah: U.S. Geological Survey 

Water-Resources Investigations Report 95–4072, 32 p. 

Theis, C.V., Brown, R.H., and Meyer, R.R., 1963, Estimating 

the transmissibility of aquifers from the specific capacities 

of wells, in Bentall, Ray, 1963, Methods of determining 

permeability, transmissibility and drawdown: U.S. Geological Survey Water-Supply Paper 1536–I, p. 331–341.

Thorn, C.R., 1995, Surface-water discharge and evapotranspiration rates for grass and bare soil along a reach 

of the Rio Grande, Albuquerque, New Mexico, 1989–95: 

U.S. Geological Survey Open-File Report 95–419, 23 p.

U.S. Department of Agriculture, Natural Resources Conservation Service, 1994, CDSS soils, Division 1: Colorado’s 

Decision Support Systems spatial dataset available on the 

Web, accessed May 30, 2008, at http://cdss.state.co.us/

DNN/GIS/tabid/67/Default.aspx.

U.S. Geological Survey, 2000, CDSS National Land Cover 

Dataset, Division 1: Colorado’s Decision Support Systems 

spatial dataset available on the Web, accessed May 30, 2008, 

at http://cdss.state.co.us/DNN/GIS/tabid/67/Default.aspx.

U.S. Geological Survey, 2002, 1/3-Arc Second National 

Elevation Dataset: U.S Geological Survey raster digital 

data available on the Web, accessed February 15, 2008, 

at http://seamless.usgs.gov.

Western Regional Climate Center, 2008, Historical climate information: Western Regional Climate Center data available on 

the Web, accessed May 23, 2008, at http://www.wrcc.dri.edu/

CLIMATEDATA.html.

Wilson, W.W., 1965, Pumping tests in Colorado: Denver, Colorado Water Conservation Board Ground Water Circular 11, 

361 p.

Winston, R.B., 2000, Graphical user interface for MODFLOW, version 4: U.S. Geological Survey Open-File 

Report 2000–0315, 27 p.

Wood, W.W., 1999, Use and misuse of the chloride-mass balance method in estimating ground water recharge: Ground 

Water, v. 37, no. 1, p. 2–3.

Appendixes

Appendix 1 59

Appendix 1. Gravimetric water content and chloride concentrations for soil samples collected in 2006 at six sites in the Lost Creek 

Designated Ground Water Basin.

[ft, feet; g/g, grams of water per gram of dry sediment; μg/g, micrograms of chloride per gram of dry sediment; mg/L, milligrams of chloride per liter of water]

Site Latitude Longitude

Sample 

depth

(ft)

Gravimetric

water content

(g/g)

Chloride 

concentration1

(μg/g)

Chloride 

concentration1

(mg/L)

C1 39°52'01.8" 104°27'41.0" 2 0.100 2.96 29.6

4 0.062 8.66 140

6 0.013 7.70 592

8 0.026 6.47 249

10 0.022 1.42 64.5

12 0.045 0.55 12.2

14 0.034 0.20 5.88

16 0.074 0.32 4.32

17 0.241 0.42 1.74

18 0.225 0.39 1.73

20 0.268 0.67 2.50

C2 39°52'01.7" 104°27'42.4" 2 0.030 0.86 28.7

4 0.043 1.52 35.3

6 0.091 2.50 27.5

8 0.093 0.77 8.28

10 0.244 0.72 2.95

12 0.258 3.71 14.4

14 0.247 1.02 4.13

16 0.213 3.37 15.8

18 0.302 2.33 7.72

20 0.146 1.44 9.86

C3 39°55'35.0" 104°23'59.5" 2 0.183 5.49 30.0

4 0.179 3.45 19.3

6 0.178 1.85 10.4

8 0.144 4.20 29.2

10 0.176 63.5 361

12 0.160 66.5 416

14 0.182 213 1,170

16 0.134 312 2,330

18 0.045 77.5 1,722

20 0.028 70.6 2,480

C4 40°00'03.0" 104°27'06.9" 2 0.132 2.38 18.0

4 0.110 1.47 13.4

6 0.123 2.00 16.3

8 0.130 7.29 56.1

10 0.167 1.50 8.98

12 0.085 2.08 24.5

14 0.158 3.93 24.9

16 0.196 9.32 47.6

18 0.195 4.38 22.5

20 0.223 2.58 11.6

C5 40°06'06.2" 104°21'24.4" 2 0.063 2.06 32.7

4 0.079 1.28 16.2

6 0.111 6.16 55.5

8 0.158 19.0 120

10 0.209 3.82 18.3

12 0.230 6.84 29.7

14 0.180 3.63 20.2

16 0.212 2.14 10.1

18 0.243 2.26 9.30

20 0.206 1.41 6.84

C6 40°06'06.3" 104°21'23.5" 2 0.133 0.85 6.39

4 0.121 1.62 13.4

6 0.124 1.21 9.76

8 0.173 1.71 9.88

10 0.176 9.32 53.0

12 0.206 2.21 10.7

14 0.244 15.7 64.5

16 0.213 2.67 12.5

18 0.231 4.83 20.9

20 0.118 5.98 50.7

1

Chloride concentrations are the average value of any duplicate samples from the same depth. The chloride concentration of each duplicate sample is 

presented in Appendix 2.
60 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Appendix 2. Analytical quality-assurance and quality-control data for soil samples collected in 2006 at six sites in the Lost Creek 

Designated Ground Water Basin, Colorado.—Continued

[μg/g, micrograms of chloride per gram of sediment; mg/L, milligrams of chloride per liter of water; Relative % Diff., the difference between duplicate or replicate 

analyses divided by the average of the analyses and expressed as percent; Grand Avg. Precision, the average of Relative % Diff. for all duplicate samples]

Site1 Depth

(ft)

Quality-control

sample

Chloride

concentration

(μg/g)

Chloride

concentration

(mg/L)

Bias

Minimum reporting limit 0.06

Maximum reporting limit 3,526

C1 Deionized water 1 < 0.06

Deionized water 2 < 0.06

Deionized water 3 < 0.06

Blank 1 < 0.06

Blank 2 < 0.06

C2 Deionized water 1 < 0.06

Deionized water 2 < 0.06

Blank 1 < 0.06

Blank 2 < 0.06

C3 Deionized water 1 < 0.06

Deionized water 2 < 0.06

Deionized water 3 < 0.06

Blank < 0.06

C4 Deionized water 1 < 0.06

Deionized water 2 0.41

Deionized water 3 0.60

Blank < 0.06

C5 Deionized water 1 0.84

Deionized water 2 0.90

Blank 0.10

C6 Deionized water 1 0.19

Deionized water 2 0.26

Deionized water 3 0.33

Blank 0.16

Precision, laboratory duplicates

C1 6 A 7.87 605

6 B 7.52 578

Average 7.70 592

Relative % Diff. 5

C1 12 A 0.58 12.9

12 B 0.52 11.6

Average 0.55 12.2

Relative % Diff. 11

C1 17 A 0.38 1.58

17 B 0.45 1.87

Average 0.42 1.74

Relative % Diff. 17

C1 20 A 0.66 2.46

20 B 0.67 2.50

Average 0.67 2.50

Relative % Diff. 1

C2 6 A 2.06 22.6

6 B 2.93 32.2

Average 2.50 27.5

Relative % Diff. 35

C2 16 A 2.95 13.8

16 B 3.80 17.8

Average 3.37 15.8

Relative % Diff. 25
Appendix 2 61

Appendix 2. Analytical quality-assurance and quality-control data for soil samples collected in 2006 at six sites in the Lost Creek 

Designated Ground Water Basin, Colorado.—Continued

[μg/g, micrograms of chloride per gram of sediment; mg/L, milligrams of chloride per liter of water; Relative % Diff., the difference between duplicate or replicate 

analyses divided by the average of the analyses and expressed as percent; Grand Avg. Precision, the average of Relative % Diff. for all duplicate samples]

Site1 Depth

(ft)

Quality-control

sample

Chloride

concentration

(μg/g)

Chloride

concentration

(mg/L)

Precision, laboratory duplicates—Continued

C3 6 A 1.66 9.33

6 B 2.04 11.5

Average 1.85 10.4

Relative % Diff. 20

C3 14 A 211 1,160

14 B 215 1,180

Average 213 1,170

Relative % Diff. 2

C4 6 A 1.36 11.1

6 B 2.64 21.5

Average 2.00 16.3

Relative % Diff. 64

C4 18 A 5.76 29.5

18 B 3.01 15.4

Average 4.38 22.5

Relative % Diff. 63

C5 8 A 27.1 172

8 B 10.9 69.0

Average 19.0 120

Relative % Diff. 85

C5 18 A 2.64 10.9

18 B 1.87 7.70

Average 2.26 9.30

Relative % Diff. 34

C6 8 A 2.13 12.3

8 B 1.28 7.40

Average 1.71 9.88

Relative % Diff. 50

C6 16 A 2.37 11.1

16 B 2.97 13.9

Average 2.67 12.5

Relative % Diff. 23

Grand Avg. Precision 31

Precision, field replicates

C1 20 A 0.66 2.46

20 B 0.61 2.28

Average 0.63 2.35

Relative % Diff. 9 1

Site for deionized water and blank samples indicates site of field samples for which deionized water and blank samples are associated. All deionized water 

and blank samples are laboratory procedural quality-control samples. Deionized water or a blank sample generally was analyzed after about every third field 

sample.
62 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Appendix 3. Chloride in wet and dry deposition at the National Atmospheric Deposition Program Pawnee site (Site ID CO22), Colorado.

[Date in month/day/year; kg/ha/yr, kilogram per hectare per year; cm/yr, centimeters per year; mg/L, milligrams per liter] 

Wet deposition1 Dry deposition2

Period of measurement Chloride

deposition rate

(kg/ha/yr)

Precipitation

rate 

(cm/yr)

Period of measurement Chloride

deposition rate

Start date End date Start date End date (kg/ha/yr)

5/22/1979 1/1/1980 0.49 33.09 10/2/1979 11/6/1979 0.05

1/1/1980 12/30/1980 0.63 32.99 11/6/1979 1/1/1980 0.07

12/30/1980 12/29/1981 0.51 34.38 3/4/1980 4/1/1980 0.31

12/29/1981 1/4/1983 0.32 41.41 4/1/1980 6/3/1980 0.17

1/4/1983 1/3/1984 0.47 37.28 10/7/1980 12/2/1980 0.12

1/3/1984 1/2/1985 0.64 41.48 12/2/1980 1/27/1981 0.06

1/2/1985 12/31/1985 0.35 29.35 1/27/1981 3/24/1981 0.03

12/31/1985 12/30/1986 0.23 24.52 7/21/1981 9/8/1981 0.13

12/30/1986 12/29/1987 0.36 31.19 9/8/1981 11/3/1981 0.06

12/29/1987 1/3/1989 0.28 31.42 11/3/1981 12/30/1981 0.05

1/3/1989 1/2/1990 0.29 28.91 12/30/1981 2/23/1982 0.03

1/2/1990 1/2/1991 0.35 27.97 2/23/1982 4/20/1982 0.04

1/2/1991 12/31/1991 0.31 31.23 4/20/1982 6/15/1982 0.23

12/31/1991 12/29/1992 0.25 34.36 10/5/1982 12/1/1982 0.04

12/29/1992 1/4/1994 0.37 36.88 12/1/1982 1/25/1983 0.04

1/4/1994 1/3/1995 0.17 24.14 1/25/1983 3/23/1983 0.05

1/3/1995 1/2/1996 0.3 40.66 9/6/1983 11/1/1983 0.09

1/2/1996 12/30/1996 0.41 37.37 11/1/1983 12/27/1983 0.04

12/30/1996 12/30/1997 0.34 51.88 12/27/1983 2/14/1984 0.06

12/30/1997 12/29/1998 0.21 28.62 10/2/1984 11/27/1984 0.04

12/29/1998 12/28/1999 0.27 47.88 2/12/1985 3/19/1985 0.03

12/28/1999 1/2/2001 0.16 21.92 3/19/1985 5/14/1985 0.12

1/2/2001 1/1/2002 0.22 29.47 7/9/1985 9/3/1985 0.04

1/1/2002 12/31/2002 0.12 17.67 9/3/1985 10/29/1985 0.04

12/31/2002 12/30/2003 0.2 30.57 10/29/1985 12/24/1985 0.03

12/30/2003 12/28/2004 0.19 26.18 12/24/1985 2/18/1986 0.03

Average 0.32 32.80 2/18/1986 4/15/1986 0.05

4/15/1986 6/10/1986 0.15

11/25/1986 1/20/1987 0.06

1/20/1987 3/17/1987 0.05

3/17/1987 5/12/1987 0.06

7/7/1987 9/1/1987 0.13

9/3/1987 10/27/1987 0.08

10/27/1987 12/22/1987 0.07

12/22/1987 2/16/1988 0.04

2/16/1988 4/12/1988 0.45

4/12/1988 6/7/1988 0.42

6/7/1988 8/23/1988 0.32

8/23/1988 9/27/1988 0.12

9/27/1988 11/22/1988 0.05

11/22/1988 1/3/1989 0.04

1/3/1989 1/17/1989 0.03

1/17/1989 3/14/1989 0.03

5/9/1989 8/8/1989 0.16

8/8/1989 8/29/1989 0.06

8/29/1989 10/24/1989 0.04

10/24/1989 12/19/1989 0.04

12/19/1989 2/13/1990 0.03

2/13/1990 4/9/1990 0.04

4/9/1990 6/5/1990 0.09

6/5/1990 7/31/1990 0.10

Average 0.09 3

Average effective chloride concentration of precipitation, in milligrams per liter 0.13 1

Wet-deposition data from National Atmospheric Deposition Program (2005).

2

Dry-depostion data from Robert Larson, National Atmospheric Deposition Program (written commun., 2006).

3

Average effective chloride concentration of precipitation calculated as the sum of average wet and dry deposition rates, divided by the average precipitation 

rate, converted to units of milligrams per liter.
Appendix 4 63

Appendix 4. Net irrigation, precipitation, crop evapotranspiration, and lysimeter-drainage data for four sites in the Lost Creek 

Designated Ground Water Basin, Colorado, 2007–2008.—Continued

Site L1

Latitude/longitude: 40°03'18.8"/104°24'50.4", North American Datum of 1983

Irrigation method: center-pivot sprinkler

Soil type: loam

Crop type: alfalfa

[--, no data or not reported]

2007 2008

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage

(inches)

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage 

(inches)

06/03/2007 0.75 0.00 0.24 0.00 04/08/2008 0.50 0.00 0.05 0.00

06/04/2007 0.00 0.00 0.24 0.00 04/09/2008 0.00 0.00 0.04 0.00

06/05/2007 0.60 0.00 0.33 0.00 04/10/2008 0.00 0.02 0.01 0.00

06/06/2007 0.00 0.00 0.52 0.00 04/11/2008 0.00 0.16 0.06 0.00

06/07/2007 0.00 0.00 0.35 0.00 04/12/2008 0.00 0.10 0.07 0.00

06/08/2007 0.00 0.00 0.34 0.00 04/13/2008 0.00 0.12 0.08 0.00

06/09/2007 0.00 0.00 0.35 0.00 04/14/2008 0.00 0.52 0.14 0.00

06/10/2007 0.65 0.00 0.39 0.00 04/15/2008 0.00 1.00 0.24 0.00

06/11/2007 0.65 0.11 0.44 0.00 04/16/2008 0.00 0.00 0.11 0.00

06/12/2007 0.00 0.05 0.11 0.00 04/17/2008 0.00 0.06 0.11 0.00

06/13/2007 0.65 0.00 0.25 0.00 04/18/2008 0.00 0.03 0.17 0.00

06/14/2007 0.75 0.00 0.31 0.00 04/19/2008 0.65 0.19 0.31 0.00

06/15/2007 0.00 0.00 0.37 0.13 04/20/2008 0.00 0.24 0.38 0.00

06/16/2007 0.75 0.00 0.45 0.00 04/21/2008 0.65 0.21 0.23 0.00

06/17/2007 0.00 0.01 0.52 0.00 04/22/2008 0.00 0.18 0.31 0.00

06/18/2007 0.00 0.00 0.39 0.00 04/23/2008 0.00 0.00 0.33 0.00

06/19/2007 0.00 0.00 0.37 0.00 04/24/2008 0.00 0.00 0.37 0.00

06/20/2007 0.75 0.00 0.46 0.00 04/25/2008 0.00 0.00 0.21 0.00

06/21/2007 0.00 0.00 0.51 0.00 04/26/2008 0.00 0.00 0.19 0.00

06/22/2007 0.75 0.57 0.3 0.00 04/27/2008 0.00 0.00 0.29 0.00

06/23/2007 0.00 0.00 0.36 0.00 04/28/2008 0.75 0.00 0.24 0.00

06/24/2007 0.75 0.00 0.49 0.00 04/29/2008 0.00 0.00 0.32 0.00

06/25/2007 0.00 0.00 0.52 0.00 04/30/2008 0.75 0.01 0.48 0.00

06/26/2007 0.00 0.00 0.25 0.00 05/01/2008 0.00 0.00 0.09 0.00

06/27/2007 0.00 0.00 First cut4 0.00 05/02/2008 0.00 0.00 0.12 0.00

06/28/2007 0.00 0.00 -- 0.00 05/03/2008 0.00 0.00 0.19 0.00

06/29/2007 0.00 0.00 -- 0.00 05/04/2008 0.00 0.00 0.28 0.00

06/30/2007 0.00 0.00 -- 0.00 05/05/2008 0.00 0.00 0.27 0.00

07/01/2007 0.00 0.06 -- 0.00 05/06/2008 0.75 0.01 0.34 0.00

07/02/2007 0.00 0.00 0.16 0.00 05/07/2008 0.00 0.02 0.15 0.00

07/03/2007 0.00 0.00 0.16 0.00 05/08/2008 0.00 0.00 0.24 0.00

07/04/2007 0.00 0.00 0.12 0.00 05/09/2008 0.00 0.26 0.21 0.00

07/05/2007 0.00 0.00 0.15 0.00 05/10/2008 0.00 0.00 0.13 0.00

07/06/2007 0.00 0.00 0.21 0.00 05/11/2008 0.00 0.01 0.2 0.00

07/07/2007 0.00 0.00 0.26 0.00 05/12/2008 0.75 0.05 0.38 0.00

07/08/2007 0.75 0.28 0.16 0.00 05/13/2008 0.00 0.00 0.11 0.00

07/09/2007 0.00 0.00 0.22 0.00 05/14/2008 0.00 0.01 0.21 0.00

07/10/2007 0.00 0.00 0.21 0.00 05/15/2008 0.00 0.00 0.15 0.00

07/11/2007 0.75 0.07 0.29 0.00 05/16/2008 0.75 0.00 0.24 0.00

07/12/2007 0.00 0.37 0.18 0.09 05/17/2008 0.00 0.2 0.32 0.00

07/13/2007 0.00 0.00 0.24 0.00 05/18/2008 0.00 0.3 0.36 0.00

07/14/2007 0.75 0.00 0.29 0.12 05/19/2008 0.40 0.1 0.27 0.00

07/15/2007 0.00 0.00 0.34 0.12 05/20/2008 0.50 0.1 0.21 0.00

07/16/2007 0.75 0.00 0.36 0.00 05/21/2008 0.40 0.0 0.55 0.00

07/17/2007 0.00 0.00 0.43 0.00 05/22/2008 0.40 0.0 0.45 0.00

07/18/2007 0.75 0.00 0.33 0.00 05/23/2008 0.50 0.0 0.32 0.00
64 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Appendix 4. Net irrigation, precipitation, crop evapotranspiration, and lysimeter-drainage data for four sites in the Lost Creek 

Designated Ground Water Basin, Colorado, 2007–2008.—Continued

Site L1

Latitude/longitude: 40°03'18.8"/104°24'50.4", North American Datum of 1983

Irrigation method: center-pivot sprinkler

Soil type: loam

Crop type: alfalfa

[--, no data or not reported]

2007 2008

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage

(inches)

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage 

(inches)

07/19/2007 0.00 0.00 0.25 0.00 05/24/2008 0.00 0.0 0.14 0.00

07/20/2007 0.75 0.00 0.39 0.00 05/25/2008 0.00 0.0 0.26 0.00

07/21/2007 0.00 0.11 0.43 0.00 05/26/2008 0.00 0.0 0.12 0.00

07/22/2007 0.75 0.00 0.4 0.00 05/27/2008 0.00 0.0 0.14 0.00

07/23/2007 0.00 0.00 0.34 0.00 05/28/2008 0.40 0.0 0.3 0.00

07/24/2007 0.75 0.00 0.38 0.12 05/29/2008 0.40 0.0 0.29 0.00

07/25/2007 0.00 0.00 0.46 0.00 05/30/2008 0.00 0.0 0.19 0.00

07/26/2007 0.75 0.00 0.28 0.08 05/31/2008 0.00 0.0 0.27 0.00

07/27/2007 0.00 1.37 0.23 0.00 06/01/2008 0.00 0.0 0.3 0.00

07/28/2007 0.00 0.10 0.17 0.00 06/02/2008 0.00 0.0 0.3 0.00

07/29/2007 0.00 0.00 Second cut4 0.00 06/03/2008 0.00 0.0 0.21 0.00

07/30/2007 0.00 0.00 -- 0.00 06/04/2008 0.00 0.0 0.23 0.00

07/31/2007 0.00 0.00 -- 0.00 06/05/2008 0.00 0.0 0.11 0.00

08/01/2007 0.00 0.04 -- 0.00 06/06/2008 0.00 0.0 0.23 0.00

08/02/2007 0.00 0.21 -- 0.00 06/07/2008 0.00 0.0 0.21 0.00

08/03/2007 0.00 0.47 0.09 0.00 06/08/2008 0.00 0.0 0.22 0.00

08/04/2007 0.00 0.00 0.1 0.00 06/09/2008 0.00 0.0 0.21 0.00

08/05/2007 0.00 0.09 0.1 0.00 06/10/2008 0.00 0.0 0.42 0.00

08/06/2007 0.00 0.19 0.06 0.00 06/11/2008 0.00 0.0 0.3 0.00

08/07/2007 0.00 0.03 0.08 0.09 06/12/2008 0.00 0.0 0.29 0.00

08/08/2007 0.00 0.01 0.11 0.01 06/13/2008 0.50 0.0 0.15 0.00

08/09/2007 0.00 0.1 0.15 0.03 06/14/2008 0.55 0.0 First cut4 0.00

08/10/2007 0.00 0.0 0.14 0.00 06/15/2008 0.55 0.0 -- 0.00

08/11/2007 0.00 0.0 0.17 0.00 06/16/2008 0.40 0.0 -- 0.00

08/12/2007 0.00 0.0 0.18 0.00 06/17/2008 0.55 0.0 -- 0.00

08/13/2007 0.00 0.0 0.21 0.00 06/18/2008 0.00 0.0 -- 0.00

08/14/2007 0.00 0.0 0.22 0.00 06/19/2008 0.30 0.0 0.07 0.00

08/15/2007 0.00 0.0 0.16 0.00 06/20/2008 0.50 0.0 0.06 0.00

08/16/2007 0.00 0.0 0.2 0.00 06/21/2008 0.00 0.0 0.06 0.00

08/17/2007 0.00 0.0 0.28 0.00 06/22/2008 0.55 0.0 0.09 0.00

08/18/2007 0.00 0.0 0.24 0.00 06/23/2008 0.55 0.0 0.09 0.00

08/19/2007 0.00 0.0 0.24 0.00 06/24/2008 0.50 0.0 0.09 0.00

08/20/2007 0.00 0.0 0.3 0.00 06/25/2008 0.00 0.0 0.1 0.00

08/21/2007 0.00 0.0 0.31 0.00 06/26/2008 0.50 0.0 0.1 0.00

08/22/2007 0.00 0.0 0.2 0.00 06/27/2008 0.50 0.0 0.11 0.00

08/23/2007 0.00 0.0 0.14 0.00 06/28/2008 0.50 0.0 0.12 0.00

08/24/2007 0.00 0.3 0.25 0.00 06/29/2008 0.00 0.0 0.09 0.00

08/25/2007 0.00 0.0 0.23 0.00 06/30/2008 0.00 0.0 0.13 0.00

08/26/2007 0.00 0.0 0.31 0.00 07/01/2008 0.50 0.0 0.15 0.00

08/27/2007 0.75 0.1 0.28 0.00 07/02/2008 0.45 0.0 0.14 0.00

08/28/2007 0.00 0.0 0.23 0.00 07/03/2008 0.65 0.0 0.05 0.00

08/29/2007 0.75 0.0 0.18 0.00 07/04/2008 0.00 0.0 0.12 0.00

08/30/2007 0.00 0.0 0.32 0.00 07/05/2008 0.40 0.0 0.2 0.00

08/31/2007 0.00 0.0 0.34 0.00 07/06/2008 0.40 0.0 0.12 0.00

09/01/2007 0.75 0.0 0.26 0.08 07/07/2008 0.60 0.0 0.1 0.00

09/02/2007 0.00 0.0 0.3 0.01 07/08/2008 0.00 0.0 0.12 0.00
Appendix 4 65

Appendix 4. Net irrigation, precipitation, crop evapotranspiration, and lysimeter-drainage data for four sites in the Lost Creek 

Designated Ground Water Basin, Colorado, 2007–2008.—Continued

Site L1

Latitude/longitude: 40°03'18.8"/104°24'50.4", North American Datum of 1983

Irrigation method: center-pivot sprinkler

Soil type: loam

Crop type: alfalfa

[--, no data or not reported]

2007 2008

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage

(inches)

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage 

(inches)

09/03/2007 0.75 0.0 0.29 0.08 07/09/2008 0.00 0.0 0.26 0.00

09/04/2007 0.00 0.0 0.3 0.00 07/10/2008 0.00 0.0 0.22 0.00

09/05/2007 0.00 0.1 0.35 0.00 07/11/2008 0.00 0.0 0.43 0.00

09/06/2007 0.70 0.0 0.24 0.00 07/12/2008 0.00 0.0 0.18 0.00

09/07/2007 0.00 0.0 0.26 0.00 07/13/2008 0.00 0.0 0.31 0.00

09/08/2007 0.00 0.0 0.36 0.00 07/14/2008 0.00 0.0 0.28 0.00

09/09/2007 0.00 0.0 0.18 0.00 07/15/2008 0.00 0.0 0.31 0.00

09/10/2007 0.00 0.0 0.18 0.00 07/16/2008 0.00 0.0 0.34 0.00

09/11/2007 0.00 0.0 0.25 0.00 07/17/2008 0.00 0.0 0.15 0.00

09/12/2007 0.65 0.0 0.3 0.00 07/18/2008 0.00 0.0 0.15 0.00

09/13/2007 0.00 0.0 0.22 0.00 07/19/2008 0.00 0.0 0.17 0.00

09/14/2007 0.00 0.0 0.25 0.00 07/20/2008 0.00 0.0 0.31 0.00

09/15/2007 0.00 0.0 Third cut4 0.00 07/21/2008 0.70 0.0 0.17 0.00

09/16/2007 0.00 0.0 -- 0.00 07/22/2008 0.00 0.0 0.18 0.00

09/17/2007 0.00 0.1 -- 0.00 07/23/2008 0.75 0.0 0.23 0.00

09/18/2007 0.00 0.0 -- 0.00 07/24/2008 0.00 0.0 0.15 0.00

09/19/2007 0.00 0.0 -- 0.00 07/25/2008 0.80 0.0 0.16 0.00

09/20/2007 0.00 0.0 0.11 0.00 07/26/2008 0.00 0.0 0.11 0.00

09/21/2007 0.00 0.0 0.12 0.00 07/27/2008 0.80 0.0 0.16 0.00

09/22/2007 0.00 0.0 0.16 0.00 07/28/2008 0.00 0.0 0.13 0.00

09/23/2007 0.00 0.0 0.16 0.00 07/29/2008 0.80 0.0 0.12 0.00

09/24/2007 0.00 0.1 0.06 0.00 07/30/2008 0.80 0.0 0.28 0.00

09/25/2007 0.00 0.0 0.08 0.00 07/31/2008 0.00 0.0 0.21 0.00

09/26/2007 0.00 0.0 0.09 0.00 08/01/2008 0.00 0.0 0.16 0.00

09/27/2007 0.00 0.0 0.13 0.00 08/02/2008 0.80 0.0 0.22 0.00

09/28/2007 0.00 0.00 0.23 0.00 08/03/2008 0.80 0.0 0.22 0.12

09/29/2007 0.50 0.00 0.3 0.00 08/04/2008 0.00 0.0 0.17 0.15

09/30/2007 0.00 0.25 0.18 0.00 08/05/2008 0.80 0.0 0.11 0.03

10/01/2007 0.00 0.00 0.17 0.00 08/06/2008 0.00 0.0 0.14 0.21

10/02/2007 0.00 0.00 0.28 0.00 08/07/2008 0.00 0.0 0.06 0.28

10/03/2007 0.00 0.00 0.21 0.00 08/08/2008 0.00 0.0 0.11 0.08

10/04/2007 0.00 0.00 0.28 0.00 08/09/2008 0.00 0.2 0.06 0.12

10/05/2007 0.75 0.00 0.27 0.00 08/10/2008 0.00 0.2 0.06 0.43

10/06/2007 0.00 0.00 0.59 0.00 08/11/2008 0.00 0.2 0.09 0.03

10/07/2007 0.00 0.00 0.16 0.00 08/12/2008 0.00 0.0 0.1 0.00

10/08/2007 0.00 0.00 Fourth cut4 0.00 08/13/2008 0.00 0.0 0.16 0.11

10/09/2007 0.00 0.00 -- 0.00 08/14/2008 0.00 0.0 0.1 0.17

10/10/2007 0.00 0.00 -- 0.00 08/15/2008 0.00 0.0 0.07 0.00

10/11/2007 0.00 0.00 -- 0.00 08/16/2008 0.00 0.0 0.08 0.00

10/12/2007 0.00 0.00 -- 0.00 08/17/2008 0.00 0.0 0.25 0.00

10/13/2007 0.00 0.05 0.01 0.00 08/18/2008 0.00 0.0 0.05 0.00

10/14/2007 0.00 0.4 0.01 0.00 08/19/2008 0.00 0.0 0.13 0.04

10/15/2007 0.00 0.01 0.09 0.00 08/20/2008 0.00 0.0 0.15 0.04

10/16/2007 0.00 0.00 0.1 0.00 08/21/2008 0.00 0.0 0.14 0.00

10/17/2007 0.00 0.00 0.14 0.00 08/22/2008 0.00 0.0 0.13 0.00

10/18/2007 0.00 0.00 0.23 0.00 08/23/2008 0.00 0.0 0.11 0.00
66 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Appendix 4. Net irrigation, precipitation, crop evapotranspiration, and lysimeter-drainage data for four sites in the Lost Creek 

Designated Ground Water Basin, Colorado, 2007–2008.—Continued

Site L1

Latitude/longitude: 40°03'18.8"/104°24'50.4", North American Datum of 1983

Irrigation method: center-pivot sprinkler

Soil type: loam

Crop type: alfalfa

[--, no data or not reported]

2007 2008

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage

(inches)

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage 

(inches)

10/19/2007 0.00 0.00 0.2 0.00 08/24/2008 0.00 0.0 0.12 0.00

10/20/2007 0.00 0.05 0.29 0.00 08/25/2008 0.00 0.0 Second cut4 0.00

Total 19.4 5.7 30.5 1.0 08/26/2008 0.00 0.0 -- 0.00

08/27/2008 0.00 0.0 -- 0.00

08/28/2008 0.00 0.0 -- 0.00

08/29/2008 0.00 0.0 -- 0.00

08/30/2008 0.00 0.0 0.08 0.00

08/31/2008 0.00 0.0 0.07 0.00

09/01/2008 0.00 0.0 0.06 0.00

09/02/2008 0.00 0.0 0.09 0.00

09/03/2008 0.00 0.0 0.06 0.00

09/04/2008 0.00 0.0 0.04 0.00

09/05/2008 0.00 0.0 0.07 0.00

09/06/2008 0.00 0.0 0.03 0.00

09/07/2008 0.00 0.0 0.07 0.00

09/08/2008 0.00 0.0 0.06 0.00

09/09/2008 0.75 0.0 0.05 0.00

09/10/2008 0.00 0.0 0.05 0.00

09/11/2008 0.75 0.0 0.05 0.00

09/12/2008 0.00 0.0 0.05 0.00

09/13/2008 0.00 0.1 0.09 0.00

09/14/2008 0.00 0.0 0.03 0.00

09/15/2008 0.00 0.5 0.05 0.00

09/16/2008 0.00 0.0 0.06 0.00

09/17/2008 0.00 0.0 0.06 0.00

Total 26.6 5.0 26.7 1.8

1

Net irrigation based on farmer’s records.

2

Precipitation measured at CoAgMet Fort Morgan station (fig. 2).

3

Crop evapotranspiration estimated by using the evapotranspiration calculator provided by the Colorado Agricultural Meteorological Network at 

http://ccc.atmos.colostate.edu/cgi-bin/extended_etr_form.pl. Crop evapotranspiration was calculated using the Penman-Monteith combination equation (Jensen 

and others, 1990) with data from the Colorado Agricultural Meteorological Network Fort Morgan station.

4

Alfalfa crops were cut multiple times during the period of analysis. Alfalfa crops were assumed to become reestablished 5 days after each cut for the purpose of 

estimating evapotranspiration.
Appendix 4 67

Appendix 4. Net irrigation, precipitation, crop evapotranspiration, and lysimeter-drainage data for four sites in the Lost Creek 

Designated Ground Water Basin, Colorado, 2007–2008.—Continued

Site L2

Latitude/longitude: 40°03'37.6"/104°25'25.0", North American Datum of 1983

Irrigation method: flood furrow

Soil type: loam

Crop type: wheat

2007 2008

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage

(inches)

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage

(inches)

05/19/2007 0.22 0.00 0.28 0.00

05/20/2007 0.00 0.00 0.33 0.00 No data4

05/21/2007 0.00 0.00 0.28 0.00

05/22/2007 0.00 0.34 0.23 0.00

05/23/2007 0.00 0.00 0.18 0.00

05/24/2007 0.00 0.00 0.25 0.00

05/25/2007 0.00 0.00 0.33 0.00

05/26/2007 0.00 0.00 0.28 0.00

05/27/2007 0.00 0.00 0.34 0.00

05/28/2007 0.00 0.47 0.37 0.00

05/29/2007 0.00 0.48 0.23 0.00

05/30/2007 0.22 0.00 0.21 0.00

05/31/2007 0.00 0.00 0.29 0.04

06/01/2007 0.00 0.00 0.18 0.00

06/02/2007 0.00 0.00 0.25 0.00

06/03/2007 0.00 0.00 0.24 0.00

06/04/2007 0.00 0.00 0.24 0.00

06/05/2007 0.00 0.00 0.33 0.00

06/06/2007 0.00 0.00 0.52 0.00

06/07/2007 0.00 0.00 0.35 0.00

06/08/2007 0.00 0.00 0.34 0.00

06/09/2007 0.00 0.00 0.35 0.00

06/10/2007 0.00 0.00 0.39 0.00

06/11/2007 0.00 0.00 0.44 0.00

06/12/2007 0.00 0.16 0.11 0.00

06/13/2007 0.00 0.00 0.24 0.03

06/14/2007 0.00 0.00 0.3 0.00

06/15/2007 0.00 0.00 0.35 0.04

Total 0.5 1.5 8.2 0.1

1

Net irrigation calculated as the total volume of water pumped to field minus estimated runoff (10 percent of pumped water), divided by the number of 

irrigated acres (32). Pumping data were provided by the farmer.

2

Precipitation measured at CoAgMet Fort Morgan station (fig. 2).

3

Crop evapotranspiration estimated by using the evapotranspiration calculator provided by the Colorado Agricultural Meteorological Network at 

http://ccc.atmos.colostate.edu/cgi-bin/extended_etr_form.pl. Crop evapotranspiration was calculated using the Penman-Monteith combination equation (Jensen 

and others, 1990) with data from the Colorado Agricultural Meteorological Network Fort Morgan station.

4

No data are reported for 2008 because furrows overlying lysimeter were not used in 2008.
68 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Appendix 4. Net irrigation, precipitation, crop evapotranspiration, and lysimeter-drainage data for four sites in the Lost Creek 

Designated Ground Water Basin, Colorado, 2007–2008.—Continued

Site L3

Latitude/longitude: 40°07'06.9"/104°24'51.7", North American Datum of 1983

Irrigation method: flood furrow

Soil type: loam

Crop type: corn

2007 2008

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage

(inches)

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage

(inches)

06/22/2007 0.93 0.57 0.23 0.00

06/23/2007 0.93 0.00 0.28 0.00 No data4

06/24/2007 0.93 0.00 0.39 0.04

06/25/2007 0.93 0.00 0.42 0.00

06/26/2007 0.00 0.00 0.21 0.07

06/27/2007 0.00 0.00 0.23 0.00

06/28/2007 0.00 0.00 0.29 0.00

06/29/2007 0.00 0.00 0.36 0.00

06/30/2007 0.00 0.06 0.38 0.00

07/01/2007 0.00 0.00 0.44 0.00

07/02/2007 0.00 0.00 0.43 0.00

07/03/2007 0.00 0.00 0.41 0.00

07/04/2007 0.00 0.00 0.3 0.00

07/05/2007 0.00 0.00 0.33 0.00

07/06/2007 0.00 0.00 0.42 0.00

07/07/2007 0.93 0.00 0.44 0.00

07/08/2007 0.93 0.28 0.26 0.00

07/09/2007 0.93 0.00 0.31 0.00

07/10/2007 0.93 0.00 0.28 0.00

07/11/2007 0.00 0.07 0.35 0.12

07/12/2007 0.00 0.37 0.21 0.00

07/13/2007 0.00 0.00 0.27 0.00

07/14/2007 0.00 0.00 0.3 0.00

07/15/2007 0.00 0.00 0.34 0.00

07/16/2007 0.93 0.00 0.35 0.22

07/17/2007 0.93 0.00 0.41 0.20

07/18/2007 0.93 0.00 0.31 0.00

07/19/2007 0.93 0.00 0.24 0.00

07/20/2007 0.00 0.00 0.37 0.00

07/21/2007 0.00 0.11 0.41 0.00

07/22/2007 0.00 0.00 0.38 0.00

07/23/2007 0.93 0.00 0.33 0.00

07/24/2007 0.93 0.00 0.37 0.39

07/25/2007 0.93 0.00 0.44 0.00

07/26/2007 0.93 0.00 0.27 0.00

07/27/2007 0.00 1.37 0.22 0.00

07/28/2007 0.00 0.10 0.16 0.00

07/29/2007 0.00 0.00 0.22 0.00

07/30/2007 0.00 0.00 0.25 0.00

07/31/2007 0.00 0.00 0.29 0.00

08/01/2007 0.00 0.04 0.26 0.00

08/02/2007 0.00 0.21 0.21 0.00

08/03/2007 0.00 0.47 0.22 0.00

08/04/2007 0.93 0.00 0.24 0.00

08/05/2007 0.93 0.09 0.24 1.01

08/06/2007 0.93 0.19 0.15 1.02

08/07/2007 0.93 0.03 0.18 0.00
Appendix 4 69

Appendix 4. Net irrigation, precipitation, crop evapotranspiration, and lysimeter-drainage data for four sites in the Lost Creek 

Designated Ground Water Basin, Colorado, 2007–2008.—Continued

Site L3

Latitude/longitude: 40°07'06.9"/104°24'51.7", North American Datum of 1983

Irrigation method: flood furrow

Soil type: loam

Crop type: corn

2007 2008

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage

(inches)

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage

(inches)

08/08/2007 0.00 0.01 0.22 0.00

08/09/2007 0.00 0.08 0.26 0.00

08/10/2007 0.00 0.00 0.22 0.00

08/11/2007 0.00 0.00 0.24 0.00

08/12/2007 0.00 0.00 0.22 0.00

08/13/2007 0.00 0.00 0.23 0.00

08/14/2007 0.00 0.00 0.22 0.00

08/15/2007 0.00 0.00 0.15 0.00

08/16/2007 0.00 0.00 0.17 0.00

08/17/2007 0.00 0.00 0.21 0.00

08/18/2007 0.00 0.00 0.17 0.00

08/19/2007 0.93 0.00 0.16 0.00

08/20/2007 0.93 0.00 0.19 0.05

08/21/2007 0.93 0.00 0.18 0.16

08/22/2007 0.93 0.02 0.11 0.00

08/23/2007 0.00 0.00 0.07 0.00

08/24/2007 0.00 0.28 0.13 0.00

08/25/2007 0.00 0.00 0.11 0.00

08/26/2007 0.00 0.00 0.14 0.00

08/27/2007 0.93 0.11 0.13 0.00

08/28/2007 0.93 0.04 0.1 0.20

08/29/2007 0.93 0.03 0.07 0.00

08/30/2007 0.93 0.00 0.12 0.00

08/31/2007 0.00 0.00 0.12 0.00

09/01/2007 0.00 0.00 0.08 0.00

09/02/2007 0.00 0.00 0.09 0.00

09/03/2007 0.00 0.00 0.08 0.00

09/04/2007 0.00 0.00 0.07 0.00

09/05/2007 0.00 0.06 0.08 0.00

09/06/2007 0.00 0.01 0.05 0.00

09/07/2007 0.00 0.00 0.06 0.00

09/08/2007 0.00 0.00 0.08 0.00

09/09/2007 0.00 0.04 0.04 0.00

09/10/2007 0.00 0.00 0.04 0.00

09/11/2007 0.00 0.00 0.06 0.00

09/12/2007 0.00 0.00 0.07 0.00

09/13/2007 0.00 0.00 0.05 0.00

09/14/2007 0.00 0.00 0.06 0.00

Total 26.0 4.6 19.3 3.5

1

Net irrigation calculated as the total volume of water pumped to field minus estimated runoff (30 percent of pumped water), divided by the number of 

irrigated acres (64). Pumping data were provided by the farmer.

2

Precipitation measured at CoAgMet Fort Morgan station (fig. 2).

3

Crop evapotranspiration estimated by using the evapotranspiration calculator provided by the Colorado Agricultural Meteorological Network at 

http://ccc.atmos.colostate.edu/cgi-bin/extended_etr_form.pl. Crop evapotranspiration was calculated using the Penman-Monteith combination equation (Jensen 

and others, 1990) with data from the Colorado Agricultural Meteorological Network Fort Morgan station.

4

No data are reported for 2008 because furrows overlying lysimeter were not used in 2008.
70 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Appendix 4. Net irrigation, precipitation, crop evapotranspiration, and lysimeter-drainage data for four sites in the Lost Creek 

Designated Ground Water Basin, Colorado, 2007–2008.—Continued

Site L4

Latitude/longitude: 40°09’43.6”/104°24’46.9”, North American Datum of 1983

Irrigation method: center-pivot sprinkler

Soil type: sand

Crop type: 2007—corn; 2008—alfalfa

[--, no data or not reported]

2007 2008

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage

(inches)

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage4

(inches)

06/30/2007 0.4 0 0.33 0.00 05/08/2008 0.50 0.00 -- --

07/01/2007 0.4 0.06 0.39 0.00 05/09/2008 0.00 0.26 -- --

07/02/2007 0.4 0 0.39 0.00 05/10/2008 0.00 0.00 -- 0.04

07/03/2007 0 0 0.37 0.00 05/11/2008 0.00 0.01 -- --

07/04/2007 0 0 0.27 0.00 05/12/2008 0.00 0.05 -- 0.08

07/05/2007 0.26 0 0.3 0.00 05/13/2008 0.25 0.00 -- --

07/06/2007 0.4 0 0.38 0.00 05/14/2008 0.00 0.01 -- 0.04

07/07/2007 0 0 0.41 0.00 05/15/2008 0.00 0.00 -- 0.04

07/08/2007 0.4 0.28 0.24 0.00 05/16/2008 0.00 0.00 -- 0.00

07/09/2007 0 0 0.29 0.00 05/17/2008 0.00 0.16 -- --

07/10/2007 0 0 0.27 0.00 05/18/2008 0.30 0.31 -- 0.04

07/11/2007 0 0.07 0.34 0.00 05/19/2008 0.00 0.07 -- 0.08

07/12/2007 0.4 0.37 0.2 0.04 05/20/2008 0.00 0.14 -- 0.00

07/13/2007 0.26 0 0.26 0.00 05/21/2008 0.00 0.01 -- 0.04

07/14/2007 0 0 0.3 0.00 05/22/2008 0.30 0.00 -- 0.00

07/15/2007 0.4 0 0.34 0.00 05/23/2008 0.00 0.00 0.11 0.00

07/16/2007 0.4 0 0.35 0.00 05/24/2008 0.00 0.00 0.05 0.04

07/17/2007 0 0 0.41 0.00 05/25/2008 0.00 0.00 0.09 0.00

07/18/2007 0.4 0 0.31 0.00 05/26/2008 0.00 0.00 0.04 0.00

07/19/2007 0 0 0.24 0.00 05/27/2008 0.35 0.00 0.05 0.00

07/20/2007 0 0 0.37 0.00 05/28/2008 0.00 0.00 0.12 0.00

07/21/2007 0.4 0.11 0.41 0.00 05/29/2008 0.00 0.00 0.12 0.04

07/22/2007 0.26 0 0.38 0.00 05/30/2008 0.00 0.00 0.09 0.00

07/23/2007 0 0 0.33 0.04 05/31/2008 0.00 0.00 0.13 0.00

07/24/2007 0.4 0 0.37 0.04 06/01/2008 0.00 0.00 0.16 0.00

07/25/2007 0 0 0.44 0.00 06/02/2008 0.40 0.00 0.18 0.00

07/26/2007 0.26 0 0.27 0.00 06/03/2008 0.00 0.00 0.13 0.00

07/27/2007 0 1.37 0.22 0.00 06/04/2008 0.00 0.00 0.15 0.00

07/28/2007 0.4 0.1 0.16 0.00 06/05/2008 0.00 0.00 0.08 0.00

07/29/2007 0.26 0 0.23 0.00 06/06/2008 0.00 0.00 0.17 0.00

07/30/2007 0 0 0.26 0.00 06/07/2008 0.00 0.00 0.16 0.00

07/31/2007 0.4 0 0.31 0.00 06/08/2008 0.00 0.00 0.18 0.04

08/01/2007 0 0.04 0.28 0.00 06/09/2008 0.00 0.00 0.18 0.00

08/02/2007 0 0.21 0.23 0.04 06/10/2008 0.00 0.00 0.38 0.00

08/03/2007 0 0.47 0.24 0.12 06/11/2008 0.30 0.00 0.28 0.00

08/04/2007 0.26 0 0.26 0.00 06/12/2008 0.00 0.00 0.28 0.00

08/05/2007 0 0.09 0.26 0.00 06/13/2008 0.00 0.00 0.15 0.04

08/06/2007 0.4 0.19 0.17 0.00 06/14/2008 0.00 0.00 0.14 0.04

08/07/2007 0 0.03 0.2 0.00 06/15/2008 0.40 0.00 0.33 0.43

08/08/2007 0.26 0.01 0.26 0.00 06/16/2008 0.00 0.00 0.19 0.24

08/09/2007 0 0.08 0.3 0.70 06/17/2008 0.00 0.00 0.25 0.00

08/10/2007 0.4 0 0.26 0.00 06/18/2008 0.40 0.00 0.22 0.00

08/11/2007 0.24 0 0.29 0.00 06/19/2008 0.00 0.00 0.2 0.00

08/12/2007 0.4 0 0.27 0.00 06/20/2008 0.00 0.00 0.17 0.00

08/13/2007 0 0 0.28 0.00 06/21/2008 0.00 0.00 0.16 0.00
Appendix 4 71

Appendix 4. Net irrigation, precipitation, crop evapotranspiration, and lysimeter-drainage data for four sites in the Lost Creek 

Designated Ground Water Basin, Colorado, 2007–2008.—Continued

Site L4

Latitude/longitude: 40°09’43.6”/104°24’46.9”, North American Datum of 1983

Irrigation method: center-pivot sprinkler

Soil type: sand

Crop type: 2007—corn; 2008—alfalfa

[--, no data or not reported]

2007 2008

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage

(inches)

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage4

(inches)

08/14/2007 0.26 0 0.28 0.52 06/22/2008 0.00 0.00 First cut5 0.00

08/15/2007 0 0 0.18 0.47 06/23/2008 0.00 0.00 -- 0.04

08/16/2007 0.4 0 0.21 0.00 06/24/2008 0.00 0.00 -- 0.00

08/17/2007 0 0 0.27 0.00 06/25/2008 0.00 0.00 -- 0.00

08/18/2007 0 0 0.22 0.00 06/26/2008 0.00 0.00 -- 0.00

08/19/2007 0.26 0 0.21 0.00 06/27/2008 0.00 0.00 0.08 0.00

08/20/2007 0 0 0.25 0.12 06/28/2008 0.30 0.00 0.08 0.00

08/21/2007 0.40 0 0.24 0.00 06/29/2008 0.00 0.00 0.06 0.00

08/22/2007 0 0 0.15 0.00 06/30/2008 0.00 0.00 0.08 0.00

08/23/2007 0 0 0.1 0.00 07/01/2008 0.40 0.00 0.09 0.00

08/24/2007 0.4 0.28 0.18 0.00 07/02/2008 0.00 0.00 0.08 0.00

08/25/2007 0 0 0.16 0.00 07/03/2008 0.30 0.00 0.03 0.00

08/26/2007 0.26 0 0.21 0.00 07/04/2008 0.00 0.00 0.07 0.00

08/27/2007 0 0.11 0.19 0.00 07/05/2008 0.00 0.00 0.12 0.00

08/28/2007 0 0.04 0.15 0.00 07/06/2008 0.00 0.00 0.08 0.00

08/29/2007 0 0.03 0.11 0.00 07/07/2008 0.40 0.00 0.06 0.00

08/30/2007 0.4 0 0.2 0.00 07/08/2008 0.00 0.00 0.08 0.00

08/31/2007 0 0 0.2 0.00 07/09/2008 0.00 0.00 0.17 0.00

09/01/2007 0 0 0.15 0.01 07/10/2008 0.40 0.00 0.15 0.04

09/02/2007 0.4 0 0.16 0.01 07/11/2008 0.00 0.00 0.31 0.00

09/03/2007 0 0 0.16 0.00 07/12/2008 0.30 0.00 0.13 0.00

09/04/2007 0 0 0.15 0.03 07/13/2008 0.00 0.00 0.24 0.00

09/05/2007 0 0.06 0.17 0.03 07/14/2008 0.00 0.00 0.23 0.00

09/06/2007 0.4 0.01 0.11 0.04 07/15/2008 0.30 0.00 0.28 0.04

09/07/2007 0 0 0.11 0.04 07/16/2008 0.00 0.00 0.32 0.00

09/08/2007 0 0 0.14 0.04 07/17/2008 0.40 0.00 0.14 0.00

09/09/2007 0 0.04 0.07 0.04 07/18/2008 0.00 0.00 0.14 0.04

09/10/2007 0.4 0 0.06 0.04 07/19/2008 0.25 0.00 0.16 0.04

09/11/2007 0 0 0.09 0.04 07/20/2008 0.00 0.00 0.31 0.04

09/12/2007 0.4 0 0.09 0.03 07/21/2008 0.00 0.00 0.17 0.00

09/13/2007 0 0 0.06 0.02 07/22/2008 0.40 0.00 0.18 0.00

09/14/2007 0 0 0.07 0.04 07/23/2008 0.00 0.00 0.23 0.04

09/15/2007 0 0 0.08 0.03 07/24/2008 0.00 0.00 0.15 0.08

09/16/2007 0.4 0 0.06 0.01 07/25/2008 0.40 0.00 0.16 0.00

09/17/2007 0 0.06 0.03 0.04 07/26/2008 0.00 0.00 0.11 0.00

09/18/2007 0 0 0.06 0.03 07/27/2008 0.30 0.00 0.16 0.04

09/19/2007 0 0 0.08 0.01 07/28/2008 0.00 0.00 0.13 0.00

09/20/2007 0.25 0 0.07 0.04 07/29/2008 0.40 0.00 0.12 0.12

09/21/2007 0 0 0.07 0.04 07/30/2008 0.00 0.00 0.28 0.35

09/22/2007 0 0 0.1 0.02 07/31/2008 0.00 0.00 0.21 0.00

09/23/2007 0 0.04 0.08 0.02 08/01/2008 0.00 0.00 0.16 0.00

09/24/2007 0 0.07 0.03 0.04 08/02/2008 0.50 0.00 0.22 0.08

09/25/2007 0 0 0.04 0.00 08/03/2008 0.00 0.00 0.22 0.04

09/26/2007 0 0 0.04 0.04 08/04/2008 0.30 0.00 0.17 0.12

09/27/2007 0 0 0.05 0.02 08/05/2008 0.00 0.00 0.11 0.08
72 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Appendix 4. Net irrigation, precipitation, crop evapotranspiration, and lysimeter-drainage data for four sites in the Lost Creek 

Designated Ground Water Basin, Colorado, 2007–2008.—Continued

Site L4

Latitude/longitude: 40°09’43.6”/104°24’46.9”, North American Datum of 1983

Irrigation method: center-pivot sprinkler

Soil type: sand

Crop type: 2007—corn; 2008—alfalfa

[--, no data or not reported]

2007 2008

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage

(inches)

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage4

(inches)

09/28/2007 0 0 0.09 0.00 08/06/2008 0.00 0.04 0.14 0.00

09/29/2007 0 0 0.1 0.01 08/07/2008 0.40 0.01 0.06 0.00

09/30/2007 0 0.25 0.05 0.04 08/08/2008 0.00 0.01 0.11 0.00

10/01/2007 0 0 0.05 0.00 08/09/2008 0.00 0.15 0.06 0.00

10/02/2007 0 0 0.07 0.04 08/10/2008 0.00 0.17 0.06 0.00

10/03/2007 0 0 0.05 0.02 08/11/2008 0.00 0.17 0.09 0.00

10/04/2007 0 0 0.07 0.02 08/12/2008 0.00 0.00 0.10 0.00

10/05/2007 0 0 0.06 0.02 08/13/2008 0.00 0.00 0.16 0.04

Total 13.1 4.5 19.9 3.0 08/14/2008 0.30 0.00 0.10 0.00

08/15/2008 0.00 0.01 0.07 0.04

08/16/2008 0.00 0.01 0.08 0.00

08/17/2008 0.00 0.00 0.25 0.00

08/18/2008 0.00 0.00 0.05 0.00

08/19/2008 0.00 0.00 0.13 0.04

08/20/2008 0.30 0.00 0.15 0.00

08/21/2008 0.00 0.00 0.14 0.00

08/22/2008 0.40 0.00 0.13 0.00

08/23/2008 0.00 0.00 0.11 0.00

08/24/2008 0.30 0.00 0.12 0.00

08/25/2008 0.00 0.00 0.15 0.08

08/26/2008 0.00 0.00 0.12 0.00

08/27/2008 0.30 0.00 0.08 0.00

08/28/2008 0.00 0.00 0.10 0.00

08/29/2008 0.25 0.00 0.15 0.00

08/30/2008 0.00 0.00 0.22 0.08

08/31/2008 0.00 0.00 0.20 0.00

09/01/2008 0.00 0.00 0.17 --

09/02/2008 0.40 0.00 0.25 0.16

09/03/2008 0.00 0.00 0.16 0.24

09/04/2008 0.25 0.00 0.11 0.39

09/05/2008 0.00 0.00 0.17 0.04

09/06/2008 0.00 0.00 0.07 0.35

09/07/2008 0.25 0.00 0.17 0.20

09/08/2008 0.00 0.01 0.12 0.00
Appendix 4 73

Appendix 4. Net irrigation, precipitation, crop evapotranspiration, and lysimeter-drainage data for four sites in the Lost Creek 

Designated Ground Water Basin, Colorado, 2007–2008.—Continued

Site L4

Latitude/longitude: 40°09’43.6”/104°24’46.9”, North American Datum of 1983

Irrigation method: center-pivot sprinkler

Soil type: sand

Crop type: 2007—corn; 2008—alfalfa

[--, no data or not reported]

2007 2008

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage

(inches)

Date

Net

irrigation1

(inches)

Precipitation2

(inches)

Crop

evapotranspiration3

(inches)

Lysimeter

drainage4

(inches)

09/09/2008 0.25 0.00 0.12 0.04

09/10/2008 0.00 0.00 0.10 0.00

09/11/2008 0.00 0.00 0.09 0.00

09/12/2008 0.40 0.02 0.09 0.00

09/13/2008 0.00 0.05 0.16 0.00

09/14/2008 0.00 0.00 Second cut5 0.00

09/15/2008 0.00 0.49 -- 0.00

09/16/2008 0.00 0.02 -- 0.08

09/17/2008 0.00 0.00 -- 0.00

09/18/2008 0.00 0.00 -- 0.04

09/19/2008 0.00 0.00 0.04 0.00

09/20/2008 0.00 0.02 0.04 0.00

09/21/2008 0.30 0.00 0.09 0.04

09/22/2008 0.00 0.00 0.08 0.00

09/23/2008 0.25 0.00 0.03 0.00

09/24/2008 0.00 0.00 0.04 0.00

09/25/2008 0.00 0.00 0.04 0.04

09/26/2008 0.00 0.00 0.08 0.00

09/27/2008 0.00 0.00 0.12 0.08

09/28/2008 0.30 0.00 0.16 0.00

09/29/2008 0.00 0.00 0.13 0.00

09/30/2008 0.00 0.00 0.15 0.00

Total 13.2 2.2 17.1 4.0

1

Net irrigation based on farmer’s records.

2

Precipitation measured at CoAgMet Fort Morgan station (fig. 2).

3

Crop evapotranspiration estimated by using the evapotranspiration calculator provided by the Colorado Agricultural Meteorological Network at 

http://ccc.atmos.colostate.edu/cgi-bin/extended_etr_form.pl. Crop evapotranspiration was calculated using the Penman-Monteith combination equation 

(Jensen and others, 1990) with data from the Colorado Agricultural Meteorological Network Fort Morgan station. Crop evapotranspiration not reported before 

05/17/2008 to account for lack of evapotranspiration by newly planted crop prior to becoming established. Crop was planted 05/03/2008.

4

Lysimeter drainage reported as “--” represents unreasonably high values likely resulting from lysimeter malfunction or flushing of center-pivot sprinkler 

system over lysimeter location.

5

Alfalfa crops were cut multiple times during the period of analysis. Alfalfa crops were assumed to become reestablished 5 days after each cut for the 

purpose of estimating evapotranspiration.
74 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Appendix 5. Permitted acres, commingled acres, estimated irrigated acres, and estimated average annual withdrawals from decreed 

irrigation wells with final permits in the Lost Creek Designated Ground Water Basin.—Continued

[acre-ft, acre-feet]

Permit

number1

Number

of permitted

acres1

Permit 

numbers of 

commingled 

wells1

Number of 

commingled

acres1

Estimated

number of

irrigated

acres2

Estimated

average

annual

withdrawal3

(acre-ft)

Estimated

average

annual

application4

(acre-ft/acre)

10249FP 80 0 80 128 1.6

10477FP 40 4061FP, 12811FP, 12812FP, 12813FP 423 40 64 1.6

10717FP 128 31580FP, 31581FP 128 43 68 1.6

10869FP 293 10870FP, 31565FP 293 98 156 1.6

10870FP 293 10869FP, 31565FP 293 98 156 1.6

11041FP 160 0 160 256 1.6

11417FP 160 0 160 256 1.6

11708FP 160 31575FP, 5035FP 160 53 85 1.6

11981FP 80 4497FP 80 40 64 1.6

12123FP 320 12124FP 320 119 203.4 1.7

12124FP 320 12123FP 320 106 181.2 1.7

12172FP 160 0 160 256 1.6

12174FP 160 0 160 256 1.6

12177FP 160 0 160 256 1.6

12470FP 80 5036FP 80 40 64 1.6

12505FP 160 0 160 256 1.6

12688FP 160 12689FP 160 80 128 1.6

12689FP 160 12688FP 160 80 128 1.6

12809FP 280 31626FP 280 140 224 1.6

12811FP 144 4061FP, 10477FP, 12812FP, 12813FP 423 144 230 1.6

12812FP 78 4061FP, 10477FP, 12811FP, 12813FP 423 78 125 1.6

12813FP 103 4061FP, 10477FP, 12811FP, 12812FP 423 103 165 1.6

12871FP 160 12872FP 160 80 128 1.6

12872FP 160 12871FP 160 80 128 1.6

13046FP 320 13047FP, 31629FP, 31630FP,

31631FP, 31632FP, 31633FP

320 46 73 1.6

13047FP 320 13046FP, 31629FP, 31630FP,

31631FP, 31632FP, 31633FP

320 46 73 1.6

13808FP 80 0 80 128 1.6

13961FP 80 31638FP 80 40 64 1.6

14153FP 40 31603FP 200 40 64 1.6

14488FP 40 0 40 64 1.6

14856FP 100 6419FP, 6420FP, 9175FP,

14857FP, 14861FP, 14862FP, 

14863FP

1,254 33 52 1.6

14857FP 260 6419FP, 6420FP, 9175FP,

14856FP, 14861FP, 14862FP, 

14863FP

1,254 85 136 1.6

14860FP 160 31643FP 160 65 152.6 2.4

14861FP 260 6419FP, 6420FP, 9175FP,

14856FP, 14857FP, 14862FP, 

14863FP

1,254 53 83.8 1.6

14862FP 390 6419FP, 6420FP, 9175FP,

14856FP, 14857FP, 14861FP, 

14863FP

1,254 152 239.2 1.6

14863FP 130 6419FP, 6420FP, 9175FP,

14856FP, 14857FP, 14861FP, 

14862FP

1,254 133 209.8 1.6

15295FP 60 0 60 96 1.6

15550FP 320 0 320 512 1.6
Appendix 5 75

Appendix 5. Permitted acres, commingled acres, estimated irrigated acres, and estimated average annual withdrawals from decreed 

irrigation wells with final permits in the Lost Creek Designated Ground Water Basin.—Continued

[acre-ft, acre-feet]

Permit

number1

Number

of permitted

acres1

Permit 

numbers of 

commingled 

wells1

Number of 

commingled

acres1

Estimated

number of

irrigated

acres2

Estimated

average

annual

withdrawal3

(acre-ft)

Estimated

average

annual

application4

(acre-ft/acre)

15756FP 120 31567FP 40 100 160 1.6

16558FP 40 25278FP 80 27 43 1.6

1730FP 160 1731FP 160 80 188.2 2.3

1731FP 160 1730FP 160 77 181.2 2.3

1771FP 320 1772FP, 1773FP, 1774FP 320 87 129.0 1.5

1772FP 320 1771FP, 1773FP, 1774FP 320 112 166.2 1.5

1773FP 320 1771FP, 1772FP, 1774FP 320 76 112.4 1.5

1774FP 320 1771FP, 1772FP, 1773FP 320 26 38.8 1.5

1775FP 80 0 80 128 1.6

1827FP 80 0 80 128 1.6

19881FP 80 0 80 128 1.6

20140FP 160 6561FP, 31658FP 480 96 154 1.6

2245FP 260 31644FP, 31523FP 260 87 139 1.6

25278FP 80 16558FP 80 53 85 1.6

25FP 80 0 80 128 1.6

26510FP 40 0 40 64 1.6

2665FP 160 0 160 256 1.6

31509FP 80 0 80 128 1.6

31510FP 120 31511FP 120 60 96 1.6

31511FP 120 31511FP 120 60 96 1.6

31512FP 160 72FP 160 80 128 1.6

31513FP 85 31514FP, 78FP 85 28 45 1.6

31514FP 85 31513FP, 78FP 85 28 45 1.6

31515FP 80 31516FP, 31517FP 80 27 43 1.6

31516FP 80 31515FP, 31517FP 80 27 43 1.6

31517FP 80 31515FP, 31516FP 80 27 43 1.6

31518FP 640 31519FP, 31520FP 640 168 160.8 1.0

31519FP 640 31518FP, 31520FP 640 144 137.4 1.0

31520FP 640 31518FP, 31519FP 640 254 243 1.0

31521FP 80 0 80 128 1.6

31522FP 160 31588FP, 31589FP 160 53 85 1.6

31523FP 260 31644FP, 2245FP 260 87 139 1.6

31524FP 160 31525FP 160 80 128 1.6

31525FP 160 31524FP 160 80 128 1.6

31526FP 280 31527FP 280 145 243.6 1.7

31527FP 280 31526FP 280 120 202.2 1.7

31528FP 320 7244FP 320 160 256 1.6

31529FP 135 0 135 216 1.6

31530FP 80 31540FP, 5866FP, 5867FP 342 29 46 1.6

31531FP 170 31532FP 170 85 136 1.6

31532FP 170 31531FP 170 85 136 1.6

31533FP 372 31534FP, 31535FP 372 124 198 1.6

31534FP 372 31533FP, 31535FP 372 124 198 1.6

31535FP 372 31533FP, 31534FP 372 124 198 1.6

31536FP 80 0 68 136.0 2.0

31537FP 240 31538FP 240 120 192 1.6

31538FP 240 31537FP 240 120 192 1.6

31539FP 296 31541FP 296 148 237 1.6

31540FP 182 31530FP, 5866FP, 5867FP 342 65 104 1.6

31541FP 296 31539FP 296 148 237 1.6

31542FP 223 0 205 307.6 1.5

31543FP 480 31649FP 480 240 384 1.6

31544FP 80 0 80 128 1.6

31545FP 160 0 160 256 1.6

31546FP 160 0 160 256 1.6
76 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Appendix 5. Permitted acres, commingled acres, estimated irrigated acres, and estimated average annual withdrawals from decreed 

irrigation wells with final permits in the Lost Creek Designated Ground Water Basin.—Continued

[acre-ft, acre-feet]

Permit

number1

Number

of permitted

acres1

Permit 

numbers of 

commingled 

wells1

Number of 

commingled

acres1

Estimated

number of

irrigated

acres2

Estimated

average

annual

withdrawal3

(acre-ft)

Estimated

average

annual

application4

(acre-ft/acre)

31547FP 160 31548FP 160 80 128 1.6

31548FP 160 31547FP 160 80 128 1.6

31549FP 160 31550FP 160 80 128 1.6

31550FP 160 31549FP 160 80 128 1.6

31551FP 90 31552FP, 31553FP 90 30 48 1.6

31552FP 90 31551FP, 31553FP 90 30 48 1.6

31553FP 90 31551FP, 31552FP 90 30 48 1.6

31554FP 480 31555FP, 31614FP 480 160 256 1.6

31555FP 480 31554FP, 31614FP 480 160 256 1.6

31556FP 360 31557FP 360 180 288 1.6

31557FP 360 31556FP 360 180 288 1.6

31558FP 80 0 80 128 1.6

31559FP 80 0 80 128 1.6

31560FP 204 7602FP 204 102 163 1.6

31561FP 160 31562FP 240 120 192 1.6

31562FP 160 31561FP 240 120 192 1.6

31563FP 134 0 134 214 1.6

31564FP 134 0 134 214 1.6

31565FP 293 10870FP, 10869FP 293 98 156 1.6

31566FP 260 31567FP 180 170 272 1.6

31567FP 220 31566FP, 15756FP 220 110 176 1.6

31568FP 640 9430FP 640 320 512 1.6

31569FP 180 31571FP, 31570FP 180 77 123 1.6

31570FP 60 31569FP, 31571FP 180 26 42 1.6

31571FP 180 31569FP, 31570FP 180 77 123 1.6

31572FP 240 31573FP 240 120 192 1.6

31573FP 240 31572FP 240 120 192 1.6

31574FP 60 0 60 96 1.6

31575FP 160 11708FP, 5035FP 160 53 85 1.6

31576FP 80 0 80 128 1.6

31577FP 160 0 160 256 1.6

31578FP 160 0 160 256 1.6

31580FP 128 10717FP, 31581FP 128 43 68 1.6

31581FP 128 31580FP, 10717FP 128 43 68 1.6

31582FP 200 31583FP 200 100 160 1.6

31583FP 200 31582FP 200 100 160 1.6

31584FP 244 31585FP, 31586FP 244 81 130 1.6

31585FP 244 31584FP, 31586FP 244 81 130 1.6

31586FP 240 31584FP, 31585FP 244 81 130 1.6

31588FP 160 31522FP, 31589FP 160 53 85 1.6

31589FP 160 31522FP, 31588FP 160 53 85 1.6

31590FP 160 31591FP 160 80 128 1.6

31591FP 160 31590FP 160 80 128 1.6

31592FP 160 31593FP 160 80 128 1.6

31593FP 160 31592FP 160 80 128 1.6

31594FP 130 0 130 208 1.6

31595FP 160 0 138 152.0 1.1

31596FP 75 0 75 120 1.6

31598FP 65 8821FP 65 33 52 1.6

31599FP 240 31600FP, 31601FP, 31602FP 240 60 96 1.6

31600FP 240 31599FP, 31601FP, 31602FP 240 60 96 1.6

31601FP 240 31599FP, 31600FP, 31602FP 240 60 96 1.6

31602FP 240 31599FP, 31600FP, 31601FP 240 60 96 1.6

31603FP 160 14153FP 200 160 256 1.6

31604FP 160 0 160 256 1.6
Appendix 5 77

Appendix 5. Permitted acres, commingled acres, estimated irrigated acres, and estimated average annual withdrawals from decreed 

irrigation wells with final permits in the Lost Creek Designated Ground Water Basin.—Continued

[acre-ft, acre-feet]

Permit

number1

Number

of permitted

acres1

Permit 

numbers of 

commingled 

wells1

Number of 

commingled

acres1

Estimated

number of

irrigated

acres2

Estimated

average

annual

withdrawal3

(acre-ft)

Estimated

average

annual

application4

(acre-ft/acre)

31605FP 160 0 160 256 1.6

31606FP 160 0 160 256 1.6

31607FP 160 31608FP, 31609FP 480 160 256 1.6

31608FP 160 31607FP, 31609FP 480 160 256 1.6

31609FP 160 31607FP, 31608FP 480 160 256 1.6

31610FP 173 31611FP 304 172 275 1.6

31611FP 132 31610FP 304 132 211 1.6

31612FP 117 0 112 102.8 0.9

31613FP 160 0 160 256 1.6

31614FP 480 31554FP, 31555FP 480 160 256 1.6

31615FP 160 0 160 256 1.6

31617FP 280 0 280 448 1.6

31618FP 280 0 280 448 1.6

31619FP 480 4263FP, 31620FP, 31621FP, 31622FP 480 96 154 1.6

31620FP 480 4263FP, 31619FP, 31621FP, 31622FP 480 96 154 1.6

31621FP 480 4263FP, 31619FP, 31620FP, 31622FP 480 96 154 1.6

31622FP 480 4263FP, 31619FP, 31620FP, 31621FP 480 96 154 1.6

31623FP 160 0 160 256 1.6

31624FP 160 7788FP 160 80 128 1.6

31625FP 160 31627FP 160 80 128 1.6

31626FP 280 12809FP 280 140 224 1.6

31627FP 160 31625FP 160 80 128 1.6

31629FP 320 13046FP, 13047FP, 31630FP,

31631FP, 31632FP, 31633FP

320 46 73 1.6

31630FP 320 13046FP, 13047FP, 31629FP,

31631FP, 31632FP, 31633FP

320 46 73 1.6

31631FP 320 13046FP, 13047FP, 31629FP,

31630FP, 31632FP, 31633FP

320 46 73 1.6

31632FP 320 13046FP, 13047FP, 31629FP,

31630FP, 31631FP, 31633FP

320 46 73 1.6

31633FP 320 13046FP, 13047FP, 31629FP,

31630FP, 31631FP, 31632FP

320 46 73 1.6

31634FP 173 0 173 277 1.6

31635FP 363 0 363 581 1.6

31636FP 191 31637FP 191 96 153 1.6

31637FP 191 31636FP 191 96 153 1.6

31638FP 80 13961FP 80 40 64 1.6

31639FP 147 0 147 235 1.6

31640FP 157 0 157 353.0 2.2

31641FP 160 0 160 256 1.6

31642FP 85 31667FP 85 35 56 1.6

31643FP 160 14860FP 160 82 194.4 2.4

31644FP 260 31523FP, 2245FP 260 87 139 1.6

31645FP 160 0 160 256 1.6

31646FP 160 31647FP 160 80 128 1.6

31647FP 160 31646FP 160 80 128 1.6

31648FP 80 0 80 128 1.6

31649FP 480 31543FP 480 240 384 1.6

31650FP 228 31651FP, 9018FP 228 76 122 1.6

31651FP 228 31650FP, 9018FP 228 76 122 1.6
78 Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado

Appendix 5. Permitted acres, commingled acres, estimated irrigated acres, and estimated average annual withdrawals from decreed 

irrigation wells with final permits in the Lost Creek Designated Ground Water Basin.—Continued

[acre-ft, acre-feet]

Permit

number1

Number

of permitted

acres1

Permit 

numbers of 

commingled 

wells1

Number of 

commingled

acres1

Estimated

number of

irrigated

acres2

Estimated

average

annual

withdrawal3

(acre-ft)

Estimated

average

annual

application4

(acre-ft/acre)

31652FP 92 172.8 1.9

31653FP 320 31652FP, 31654FP 320 67 126.8 1.9

31654FP 320 31652FP, 31653FP 320 87 162.8 1.9

31656FP 120 31657FP 120 60 96 1.6

31657FP 120 31656FP 120 60 96 1.6

31658FP 320 20140FP, 6561FP 480 192 307 1.6

31659FP 80 0 80 128 1.6

31667FP 120 31642FP 85 50 80 1.6

368FP 158 369FP, 370FP 158 53 84 1.6

369FP 158 368FP, 370FP 158 53 84 1.6

370FP 158 368FP, 369FP 158 53 84 1.6

4061FP 58 10477FP, 12811FP, 12812FP 423 58 93 1.6

4263FP 480 31619FP, 31620FP, 31621FP, 

31622FP

480 96 154 1.6

4497FP 80 11981FP 80 40 64 1.6

464FP 160 467FP 160 36 68.6 1.9

465FP 160 466FP 160 80 128 1.6

466FP 160 465FP 160 80 128 1.6

467FP 160 464FP 160 42 79.2 1.9

5035FP 160 31575FP, 11708FP 160 53 85 1.6

5036FP 80 12470FP 80 40 64 1.6

510FP 320 7245FP 320 160 256 1.6

5369FP 134 0 134 214 1.6

5370FP 134 0 134 214 1.6

5371FP 134 0 134 214 1.6

5866FP 342 31530FP, 31540FP, 5867FP 342 124 198 1.6

5867FP 342 31530FP, 31540FP, 5866FP 342 124 198 1.6

6419FP 900 6420FP, 9175FP, 14856FP,

14857FP, 14861FP, 14862FP, 

14863FP

1,254 294 470 1.6

6420FP 900 6419FP, 9175FP, 14856FP,

14857FP, 14861FP, 14862FP, 

14863FP

1,254 294 470 1.6

6561FP 320 20140FP, 31658FP 480 192 307 1.6

7105FP 240 9630FP 240 120 192 1.6

7107FP 80 0 80 128 1.6

7108FP 160 0 160 256 1.6

7200FP 80 0 80 128 1.6

7201FP 80 7203FP 80 40 64 1.6

7202FP 160 0 160 256 1.6

7203FP 80 7201FP 80 40 64 1.6

7244FP 320 31528FP 320 160 256 1.6

7245FP 320 510FP 320 160 256 1.6

7277FP 80 0 80 128 1.6

72FP 160 31512FP 160 80 128 1.6

7602FP 204 31560FP 204 102 163 1.6

7788FP 160 31624FP 160 80 128 1.6

78FP 85 31513FP, 31514FP 85 28 45 1.6

8298FP 80 0 80 128 1.6

8499FP 80 0 80 128 1.6

8500FP 62 0 62 99 1.6

8505FP 160 8506FP 160 80 128 1.6

8506FP 160 8505FP 160 80 128 1.6
Appendix 5 79

Publishing support provided by:

Denver Publishing Service Center, Denver, Colorado

Manuscript approved for publication, April 14, 2010

For more information concerning this publication, contact:

Director, USGS Colorado Water Science Center

Box 25046, Mail Stop 415

Denver, CO 80225

(303) 236-4882

Or visit the Colorado Water Science Center Web site at:

http://co.water.usgs.gov/

This publication is available online at:

http://pubs.usgs.gov/sir/2010/5082/

Appendix 5. Permitted acres, commingled acres, estimated irrigated acres, and estimated average annual withdrawals from decreed 

irrigation wells with final permits in the Lost Creek Designated Ground Water Basin.—Continued

[acre-ft, acre-feet]

Permit

number1

Number

of permitted

acres1

Permit 

numbers of 

commingled 

wells1

Number of 

commingled

acres1

Estimated

number of

irrigated

acres2

Estimated

average

annual

withdrawal3

(acre-ft)

Estimated

average

annual

application4

(acre-ft/acre)

8508FP 160 0 160 256 1.6

8533FP 320 8534FP, 8535FP 320 85 111.4 1.3

8534FP 320 8533FP, 8535FP 320 88 115.4 1.3

8535FP 320 8533FP, 8534FP 320 101 132.4 1.3

8619FP 81 8620FP 162 81 130 1.6

8620FP 81 8619FP 162 81 130 1.6

8780FP 20 0 20 32 1.6

8821FP 65 31598FP 65 33 52 1.6

8873FP 320 8874FP, 9321FP 320 100 109.2 1.1

8874FP 320 8873FP, 9321FP 320 62 68.4 1.1

9018FP 228 31651FP, 31650FP 228 76 122 1.6

9174FP 160 0 160 256 1.6

9175FP 900 6419FP, 6420FP, 14856FP,

14857FP, 14861FP, 14862FP, 14863FP

1,254 294 470 1.6

9321FP 80 8873FP, 8874FP 320 71 78.2 1.1

9430FP 640 31568FP 640 320 512 1.6

9521FP 115 9522FP 280 115 184 1.6

9522FP 165 9521FP 280 165 264 1.6

9523FP 132 0 132 211 1.6

9594FP 140 0 140 224 1.6

9595FP 140 0 140 224 1.6

9596FP 140 0 140 224 1.6

9597FP 140 0 140 224 1.6

9598FP 140 0 140 224 1.6

9601FP 140 0 140 224 1.6

9630FP 240 7105FP 240 120 192 1.6

Total 27,835 44,266

Average of irrigation wells with power-use data 103 157.2 1.6

Average of irrigation wells lacking power-use data 105 168 1.6

Average of all wells 105 166 1.6 1

Data provided by Suzanne Sellers, Colorado Division of Water Resources (written commun., 2006).

2

 Number of acres irrigated by wells with power-use data was estimated by apportioning the average number of planted acres during 1990–94 with respect to 

the average annual withdrawal from each well during 1990–94. Number of acres irrigated by wells lacking power-use data was estimated by apportioning the 

total number of commingled acres with respect to the number of acres permitted for each well.

3

 Average annual withdrawals in bold are estimated from power-use records during 1990–94. Data for wells with power-use records provided by William Fronczac, 

Gateway American Resources (written commun., 2005). Average annual withdrawals from wells lacking power-use data are estimated as the average annual withdrawal 

per unit area (1.6 acre-ft/acre) of all wells with power-use data, multiplied by the estimated number of irrigated acres.

4

Average annual application for wells with power-use data are calculated as the average annual withdrawal divided by the estimated number of irrigated acres. 

Average annual application for wells lacking power-use data is assumed equal to the average application (1.6 acre-ft/acre) by wells with power-use records.

Arnold, L.R.—Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in Colorado—USGS/SIR 2010–5082