U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2008–5020

Prepared in cooperation with Delta County, Colorado

Availability, Sustainability, and Suitability of Ground Water, 

Rogers Mesa, Delta County, Colorado—Types of Analyses 

and Data for Use in Subdivision Water-Supply Reports
Front cover photographs: A, East side of Rogers Mesa showing contact between Mancos Shale and alluvium; B, Riverside 

Cemetary entrance with flowing springs on either side of gate; C, wetlands; D, irrigated field; E, mule deer; and F, pond. 

Photographs by Judith C. Thomas, U.S. Geological Survey.

Back cover photograph: Aerial photograph of Rogers Mesa, Colorado. Photograph courtesy of Dave Rice, Delta County 

Planning and Community Development.

A

B

C

D

E

F
Availability, Sustainability, and Suitability 

of Ground Water, Rogers Mesa, Delta 

County, Colorado—Types of Analyses and 

Data for Use in Subdivision Water-Supply 

Reports

By Kenneth R. Watts

Prepared in cooperation with Delta County, Colorado

Scientific Investigations Report 2008–5020

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

For product and ordering information:

World Wide Web: http://www.usgs.gov/pubprod

Telephone: 1–888–ASK–USGS

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

natural hazards, and the environment:

World Wide Web: http://www.usgs.gov

Telephone: 1–888–ASK–USGS

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:

Watts, K.R., 2008, Availability, sustainability, and suitability of ground water, Rogers Mesa, Delta County, 

Colorado—types of analyses and data for use in subdivision water-supply reports: U.S. Geological Survey 

Scientific Investigations Report 2008–5020, 53 p.
iii

Contents

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

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

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

Acknowledgments................................................................................................................................4

Background and Review of Subdivision Water-Supply Plans and Reports................................4

Definition of a Subdivision..........................................................................................................5

Requirements of Subdivision Water-Supply Plans ................................................................5

Administrative Rules for Subdivisions and Well Permits ......................................................5

Referral and Review of Subdivision Water-Supply Plans.....................................................6

Subdivision Water-Supply Reports...........................................................................................7

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa....................................7

Types of Analyses and Data for Use in Subdivision Water-Supply Reports ...............................7

Example of Preliminary Analyses and Data for a Subdivision Water-Supply Report................8

Availability...................................................................................................................................10

Hydrogeologic Setting of Rogers Mesa........................................................................10

Climate........................................................................................................................10

Soils. .......................................................................................................................13

Irrigation....................................................................................................................14

Residential Water Supplies....................................................................................17

Aquifer Boundary Conditions..........................................................................................17

Lower Boundary—Base of the Aquifer ...............................................................17

Upper Boundary—Water Table.............................................................................18

Lateral Boundaries—Aquifer Extent ....................................................................18

Hydraulic and Storage Properties .................................................................................18

Saturated Thickness and Aquifer Storage ...................................................................21

Well Yields..........................................................................................................................22

Sustainability ..............................................................................................................................22

Water Budget ....................................................................................................................22

Surface Inflow..........................................................................................................24

Surface Outflow .......................................................................................................24

Ground-Water Inflow ..............................................................................................25

Ground-Water Outflow............................................................................................28

Ground-Water Storage ...........................................................................................28

Water-Budget Errors...............................................................................................29

Suitability.....................................................................................................................................29

Potential Hydrologic Effects of Ground-Water Use for Hypothetical Subdivisions.................39

Effects of Pumping on Nearby Wells......................................................................................40

Depletion of Ground-Water Storage.......................................................................................41

Capture of Ground-Water Discharge .....................................................................................42

Suggestions for Collection and Analyses of Additional Data......................................................43

Summary........................................................................................................................................................45

References Cited..........................................................................................................................................46

Glossary.........................................................................................................................................................49

.....
iv

Figures

1–3. Maps showing:

1. Location of Rogers Mesa, Delta County, Colorado ........................................................3

2. Generalized topography, subdivisions, water company service areas, 

springs, and wells, Rogers Mesa, Delta County, Colorado.........................................11

3. Generalized surface geology and configuration of the base of the 

aquifer on Rogers Mesa, Delta County, Colorado........................................................12

4. Photograph showing contact of alluvial deposits with weathered 

Mancos Shale near Riverside Cemetery, Rogers Mesa, Delta County, 

Colorado .......................................................................................................................................13

5. Graph showing mean monthly precipitation and estimated reference 

evapotranspiration at meteorological station HOT01, Rogers Mesa, 

Delta County, Colorado, May 21, 1998, through December 31, 2006...................................14

6–8. Maps showing:

6. Estimated vertical hydraulic conductivity and specific retention of 

soils derived from alluvial-fan deposits, Rogers Mesa, Delta County, 

Colorado ..............................................................................................................................15

7. Irrigated cropland, pasture, and orchards, and locations of canals, 

ditches, diversion structures, irrigation wells, and selected springs 

on Rogers Mesa, Delta County, Colorado, 2000............................................................16

8. Generalized configuration and altitude of the water table, and 

locations of springs, Rogers Mesa, Delta County, Colorado......................................19

9. Graph showing estimated specific capacity for small- and large-capacity 

wells, Rogers Mesa, Delta County, Colorado.........................................................................21

10. Map showing generalized saturated thickness of the Rogers Mesa aquifer, 

Delta County, Colorado ..............................................................................................................23

11–13. Graphs showing:

11. Reported yields of wells, Rogers Mesa, Delta County, Colorado ..............................25

12. Relation between theoretical drawdown and radial distance in an 

idealized unconfined aquifer for a constant pumping rate and elapsed 

times of 1, 10, and 100 years ............................................................................................41

13. Relation between depletion of boundary flow to ground-water 

withdrawal, distance of pumped well from flow boundary, and 

elapsed time since pumping began in an idealized aquifer .......................................44

Tables

1. Selected sources of hydrologic data for water-supply reports............................................4

2. Types of analyses and data that may be needed for subdivision water-supply 

reports. ...........................................................................................................................................9

3. Estimated average annual water budget for Rogers Mesa, Delta County, 

Colorado, November 1998 through October 2006..................................................................26

4. Values of physical properties and concentrations of selected chemical 

constituents in ground and surface water from Rogers Mesa and vicinity, 

Delta County, Colorado ..............................................................................................................30
v

Conversion Factors and Datums

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

section (640 acres or 1 square mile) 259.0 square hectometer (hm2) 

square foot (ft2) 0.09290 square meter (m2)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3) 

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

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 year (ft/yr) 0.3048 meter per year (m/yr)

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

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)

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

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

Specific capacity

cubic foot per day per foot [(ft3/d)/ft] 0.09290 cubic meter per day per meter [(m3/d)/m]

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)

foot per day (ft/d) 3.528 micrometer per second (μm/s)

Transmissivity*

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

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

°F=(1.8×°C)+32

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

°C=(°F-32)/1.8
vi

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

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.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25°C).

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

or micrograms per liter (μg/L).
Availability, Sustainability, and Suitability of Ground 

Water, Rogers Mesa, Delta County, Colorado—Types of 

Analyses and Data for Use in Subdivision Water-Supply 

Reports

By Kenneth R. Watts

Abstract

The population of Delta County, Colorado, like that in 

much of the Western United States, is forecast to increase 

substantially in the next few decades. A substantial portion 

of the increased population likely will reside in rural subdivisions and use residential wells for domestic water supplies. 

In Colorado, a subdivision developer is required to submit 

a water-supply plan through the county for approval by the 

Colorado Division of Water Resources. If the water supply is 

to be provided by wells, the water-supply plan must include a 

water-supply report. The water-supply report demonstrates the 

availability, sustainability, and suitability of the water supply 

for the proposed subdivision. During 2006, the U.S. Geological Survey, in cooperation with Delta County, Colorado, 

began a study to develop criteria that the Delta County Land 

Use Department can use to evaluate water-supply reports for 

proposed subdivisions.

A table was prepared that lists the types of analyses and 

data that may be needed in a water-supply report for a watersupply plan that proposes the use of ground water. A preliminary analysis of the availability, sustainability, and suitability 

of the ground-water resources of Rogers Mesa, Delta County, 

Colorado, was prepared for a hypothetical subdivision to 

demonstrate hydrologic analyses and data that may be needed 

for water-supply reports for proposed subdivisions.

Rogers Mesa is a 12-square-mile upland mesa located 

along the north side of the North Fork Gunnison River about 

15 miles east of Delta, Colorado. The principal land use on 

Rogers Mesa is irrigated agriculture, with about 5,651 acres of 

irrigated cropland, grass pasture, and orchards. The principal 

source of irrigation water is surface water diverted from the 

North Fork Gunnison River and Leroux Creek. The estimated 

area of platted subdivisions on or partially on Rogers Mesa in 

2007 was about 4,792 acres of which about 2,756 acres was 

irrigated land in 2000.

The principal aquifer on Rogers Mesa consists of 

alluvial-fan deposits that overlie shale and, locally, sandstone. 

Maps of the base of the aquifer, the water table, and the 

saturated thickness of the aquifer were prepared from 

data from the well files of the Colorado Division of Water 

Resources. The base of the aquifer generally is topographically higher than the valleys of the North Fork Gunnison 

River and Leroux Creek, and direct hydraulic connection of 

the aquifer to North Fork Gunnison River and Leroux Creek 

is limited. The aquifer is recharged primarily by infiltration of 

surface water diverted for irrigation. Ground water discharges 

to seeps and springs and through slope deposits at the boundaries of the aquifer. Data from the well files also were used 

to estimate the specific capacity of wells and to estimate the 

transmissivity and hydraulic conductivity of the aquifer.

A water budget was used to estimate recharge to and 

discharge from the aquifer. Although storage within the 

aquifer likely varies seasonally and from year to year, it was 

assumed that there were no long-term changes in ground-water 

storage. Estimated average annual recharge to and discharge 

from the aquifer during November 1998 through October 2006 

were about 30,767 acre-feet per year.

Although sufficient ground water is available on Rogers 

Mesa for additional domestic water supplies, conversion of 

irrigated land to residential land use likely would reduce 

recharge to the aquifer, affecting the sustainability of groundwater supplies on Rogers Mesa. Stream-depletion analyses 

indicate that the ground water in the aquifer likely would 

be considered tributary ground water and additional uses of 

ground water to supply new subdivisions likely would require 

implementation of augmentation plans.

Although the dissolved solids and dissolved sulfate 

concentrations in ground water from Rogers Mesa aquifer 

commonly exceeded the U.S. Environmental Protection 

Agency Secondary Maximum Contaminant Levels for 

drinking-water supplies, the quality of ground water from the 

aquifer generally is suitable for residential use. Concentrations 

of total nitrogen (nitrite plus nitrate, as nitrogen) in ground 

water ranged from 0.38 to 3.2 milligrams per liter and were 

less than the State of Colorado maximum contaminant level 

of 10 milligrams per liter. Concentrations of selenium from 

seeps and springs at the boundaries of the aquifer commonly 
2 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

exceeded 50 micrograms per liter, the State of Colorado 

maximum contaminant level for drinking-water supplies.

This preliminary evaluation of ground-water supplies 

on Rogers Mesa could be improved with the collection of 

additional data including: additional mapping of hydrogeologic features; more accurate locations and altitudes of wells; 

accurate estimates of water-budget components; measurements 

of ground-water levels; and collection and analyses of groundwater samples. The use of numerical models of ground-water 

flow could improve evaluations of the potential effects of 

changes in land and water use on the water budget, aquifer 

storage, stream depletion, and well interference.

Introduction

The population of the Western United States is forecast 

to increase substantially during the next few decades. The 

population of Delta County, Colo. (fig. 1), is projected to 

increase by 79 to 105 percent, from about 28,000 in 2000 to 

between 50,200 and 57,500 in 2030 (Colorado Water Conservation Board, 2004; Colorado Department of Local Affairs, 

2006). Much of the population increase in Delta County likely 

will be in rural subdivisions. Because new subdivisions may 

not have access to public water supplies and municipal sewage 

treatment systems, ground water from individual on-lot wells 

likely will be the source of domestic water, and individual 

sewage disposal systems (ISDS) likely will be used to treat 

and dispose of sanitary waste. The withdrawal of ground water 

and the discharge of sanitary waste from ISDS to the subsurface can have unanticipated and (or) undesirable effects on 

the availability, sustainability, and suitability of local groundwater supplies.

In Colorado, subdivision developers are required to 

submit subdivision plans, including a water-supply plan, for 

review and approval by the county and the Colorado Division 

of Water Resources (DWR). Generally, subdivision watersupply plans are prepared by consulting engineers, who 

specialize in water resources, and by attorneys, who specialize in water law. Water-supply plans for subdivisions that 

will use wells are required to include a water-supply report to 

provide adequate evidence that the proposed water supply is 

sufficient in terms of availability, sustainability, and suitability 

(Colorado Division of Water Resources, 2006).

In Colorado, the county reviews the water-supply plan 

and report for a proposed subdivision and submits them to 

the DWR for review and approval or modification. Because 

ground-water conditions in Colorado are highly variable and 

often are not defined by previous water-resources investigations, county land-use planners and subdivision developers 

need criteria to define the types of analyses and data that are 

needed in water-supply reports. The subdivision water-supply 

report also may provide information for future residents of a 

subdivision about the reliability and safety of the ground-water 

supply.

During 2006, the U.S. Geological Survey (USGS), in 

cooperation with Delta County, Colo., began a study to define 

the types of hydrologic analyses and data that may be needed 

in water-supply reports for proposed subdivisions. The Delta 

County Land Use Department can evaluate adequacy of watersupply reports on the basis of the inclusion or omission of the 

defined types of hydrologic analyses and data in the watersupply reports. As part of this study, a preliminary analysis 

of ground-water resources was prepared for a hypothetical 

subdivision as an example of the types of analyses and data 

that subdivision developers may use to prepare water-supply 

reports for proposed subdivisions.

Purpose and Scope

This report describes availability, sustainability, and 

suitability of ground water using preliminary analyses of 

example data for use in a water-supply report for a hypothetical subdivision on Rogers Mesa in Delta County, Colo. 

(fig. 1). Types of hydrogeologic data and analyses of those 

data that may be needed in subdivision water-supply reports 

to demonstrate the availability, sustainability, and suitability 

of the proposed water supply for residential use are described. 

Subdivision developers can use the information in this report 

and the types of hydrogeologic data and analyses as a guide to 

compile, collect, and analyze data for preparation of watersupply plans for proposed subdivisions. County officials can 

use this report as criteria to evaluate adequacy of water-supply 

plans for proposed subdivisions that plan the use of individual 

on-lot wells.

Data used in this report were compiled from publicly 

available sources, including the Colorado Decision Support 

System (CDSS), the DWR, the Colorado Water Conservation Board (CWCB), Delta County, the Natural Resources 

Conservation Service (NRCS), and the USGS. Data are 

available from the sources listed in table 1 for most of Delta 

County. Similar data generally are available for other areas 

in Colorado. The principal source of ground-water data used 

in this study was DWR well files. A field reconnaissance of 

Rogers Mesa was done in December 2006, primarily to better 

define the lateral extent of the surficial aquifer and to locate 

seeps and springs.

Data from DWR well files, from the field reconnaissance, and from other sources listed in table 1 were used to 

prepare hydrogeologic maps of Rogers Mesa. These maps 

show the approximate extent of the aquifer, the generalized 

configurations and altitudes of the base of the aquifer and the 

water table, the estimated saturated thickness of the aquifer, 

locations of water-supply wells, ground-water discharge 

areas, and other hydrologic features. Well yields and aquifer 

properties were estimated from drilling and pump-installation 

reports from the DWR well files. A preliminary water budget 

was prepared from available data to estimate ground-water 

recharge and discharge. A brief evaluation of the quality of 

ground water and its suitability for a domestic water supply 
0 2 4 6 8 10 MILES

0 2 4 6 8 10 KILOMETERS

EXPLANATION

Urban areaRogers Mesa

C O L O R A D O

Denver Grand 

Junction

Rogers Mesa

Delta

Highline Ditch Diversion

Fire Mountain Ditch Diversion

Leroux Creek Diversion

Highline Ditch 

Head of alluvial fan

Toe of alluvial fan

Delta

Gunnison River

River

North Fork Gunnison

348

50

92

50

133

92

65

MESA COUNTY DELTA COUNTY Grand Mesa

GUNNISON COUNTY

Leroux

Creek

38°45’

39°

108°

Universal Transverse Mercator projection, Zone 13North American Datum of 1983

107°45’ 107°30’

Fire

Mountain

Canal

Irrigation canal or ditch

ROGERS

MESA

Figure 1. Location of Rogers Mesa, Delta County, Colorado.

Introduction 3
Table 1. Selected sources of hydrologic data for water-supply reports.

[Data sources: CDSS, Colorado Decision Support System; CDPHE, Colorado Department of Public Health and Environment; CGS, Colorado Geological Survey; CRS, Colorado Revised Statutes; DWR, Colorado Division of Water Resources; USDA, U.S. Department of Agriculture; USGS, U.S. Geological Survey]

Data source Type of data Data format Website (hyperlink) Access date

CDSS Consumptive use and irrigated crop 

type and areas 

Geospatial and 

tabular

http://cdss.state.co.us/DNN/Gunnison/tabid/56/

Default.aspx

03/15/2007

CDPHE Water-quality standards Documents http://www.cdphe.state.co.us/ 03/15/2007

CGS Geologic and water-resources maps 

and reports

Documents http://geosurvey.state.co.us/ 03/15/2007

CRS Statutes Document http://www2.michie.com/colorado/lpext.

dll?f=templates&fn=fs-main.htm&2.0.

03/15/2007

Delta County Parcels and subdivisions Geospatial http://www.deltacounty.com/index.asp?ID=70 03/15/2007

DWR Documents Documents http://water.state.co.us/

http://165.127.23.116/website/lttools/

03/15/2007

DWR Well data1 Tabular http://water.state.co.us/ 03/15/2007

DWR Water-rights data Tabular http://water.state.co.us/ 03/15/2007

USDA Soils Geospatial http://datagateway.nrcs.usda.gov/NextPage.

aspx

USDA Digital ortho photography Geospatial http://165.221.201.14/NAIP.html 03/15/2007

USGS Land-surface altitude Geospatial http://seamless.usgs.gov/ 09/11/2006

USGS Geologic and water-resources maps 

and reports

Geospatial http://ngmdb.usgs.gov/ngmdb/

http://infotrek.er.usgs.gov/pubs/

09/29/2006

09/29/2006

USGS Ground-water and water-quality 

data

Tabular http://waterdata.usgs.gov/co/nwis/ 03/15/2007

1

Available for purchase from the Colorado Division of Water Resources. Limited well data may be accessed at the Colorado Division of Water Resources 

website at http://water.state.co.us/ using an online map-based search engine.

4 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

was based on sparse data from the National Water Information System and from the Delta County Environmental Health 

Division and comparison with Federal and State drinkingwater standards for public water supplies. Potential effects of 

ground-water withdrawals on discharge across the boundary 

of the aquifer were estimated for a range of distances from 

a hypothetical pumping center to the aquifer boundary. An 

analytical method was used to estimate potential effects of 

pumping wells for a hypothetical subdivision on discharge 

from the Rogers Mesa aquifer. Definitions of technical and 

regulatory terms are provided in the glossary at the back of 

this report.

Acknowledgments

The cooperation of landowners, who allowed access 

to their property during field reconnaissance, is gratefully 

acknowledged. Paul Healy, Coordinator of the Delta County 

Geographic Information section, provided geospatial data 

for water-provider service areas and platted subdivisions 

that were used in this study. Ken Nordstom, Director of 

the Delta County Environmental Health Division, provided 

water-quality data for selected sites on Rogers Mesa. Wayne 

Schieldt, Division Engineer for Water Division 4 (Gunnison 

River Basin) of the Colorado Division of Water Resources, 

and staff in Montrose, Colo., facilitated compilation of well 

data. Judith Thomas (USGS) compiled data from the DWR 

well files and conducted the field reconnaissance of Rogers 

Mesa.

Background and Review of Subdivision WaterSupply Plans and Reports

Preparation of a water-supply plan for a subdivision that 

proposes the use of ground water as the water supply requires 

consideration of hydrogeologic conditions in addition to the 

determination of the legal availability of the water. A watersupply report, prepared by an engineer, geologist, or hydrologist is an important component of the water-supply plan for 

a proposed subdivision. In some cases, where water will be 

provided by a municipality, water district, or public supply, 

a water-supply report may not be required. The water-supply 

report presents evidence that water of suitable quality will 

be available to provide a dependable (sustainable) water 

supply for the proposed subdivision when fully developed. 

This section of the report summarizes the legal definition of a 
Introduction 5

subdivision; the administrative rules for submission, referral, 

and review of subdivision water-supply plans and reports; and 

types of well permits for domestic supplies.

Definition of a Subdivision

Colorado Revised Statutes (CRS) Section 30–128–10(10)

(a) defines a subdivision or subdivided land as any parcel of 

land which is to be used for condominiums, apartments, or any 

other multiple-dwelling units or which is divided into two or 

more parcels. The DWR does not apply the subdivision rules 

to parcels that are 35 acres or more in extent. Subdivisions 

with parcels that are less than 35 acres in extent that were 

created after June 1, 1972, unless specifically exempted by the 

county, are subject to the subdivision rules.

Requirements of Subdivision Water-Supply Plans

The basic requirements for a subdivision water-supply 

plan, whether the proposed source is ground or surface water, 

are defined by CRS Section 30–28–133(3)(d). This statute 

requires that a water-supply plan provide evidence that a water 

supply is available (legally and physically) and is adequate in 

terms of quality, quantity, and sustainability for the proposed 

subdivision. The evidence must include but is not limited to 

the following items:

1. Evidence of ownership or right of acquisition or use of 

existing and proposed water rights;

2. Evidence of historic use and estimated yield of claimed 

water rights;

3. Evidence of amenability of existing water rights to a 

change in use;

4. Evidence that a willing public or private water supplier 

can and will supply water to the proposed subdivision, 

stating the amount of water available for use within the 

subdivision and the feasibility of extending service to that 

area; and

5. Evidence that the water supply is potable.

When the proposed water supply is ground water from individual on-lot wells, the wells must be permitted and are subject to 

administrative rules and policies of the DWR.

Administrative Rules for Subdivisions and Well 

Permits

The DWR has established administrative rules when 

the proposed water supply for a subdivision is ground water 

supplied by individual residential wells (Division of Water 

Resources, 2006). Criteria that determine the type of well 

permit that can be issued for individual wells in subdivisions include the date that the subdivision was created; other 

appropriations within the stream-aquifer system; the tributary 

status of the ground water; and, in some parts of Colorado, 

whether the wells are located in a designated basin (Colorado 

Division of Water Resources, 2005).

A designated basin is an area, established by the 

Colorado Ground Water Commission in accordance with 

CRS 37–90–106. A designated basin is an area in which 

ground water is not available to or required for fulfillment 

of decreed surface-water rights or that is not adjacent to a 

continuously flowing stream and in which ground-water 

withdrawals constituted the principal water usage for at 

least 15 years preceding the date of the first hearing on the 

proposed designation of the basin (Colorado Division of Water 

Resources, 2006). Currently (2007), all designated basins in 

Colorado are located in the eastern part of the state (Colorado 

Division of Water Resources, 2006).

The two different classes of well permits in Colorado 

are (1) permits for wells that are not administered under the 

priority system (exempt well permits) and (2) permits for 

wells that are administered under the priority system (nonexempt well permits). Water uses are limited by the conditions 

of approval stated on the well permit when it is issued. In 

most cases, permits for exempt wells limit the pumping rate to 

15 gal/min or less and limit the annual appropriation, depending on the uses of the water. Generally, permits for domesticand-livestock (domestic) and household-use-only (residential) 

wells require nonevaporative ISDS, such as standard septic 

tank and leach field systems. Water that infiltrates into the 

subsurface from an ISDS is assumed to return to the same 

stream drainage system in which the well is located. Except in 

a few cases, an exempt well permit is not issued where either 

a municipality or a water district can provide water to the 

property. In most cases, no more than one exempt well permit 

is issued for a single lot.

Several types of uses are allowed for exempt wells, 

including commercial-exempt, domestic, residential, and 

unregistered existing wells (Colorado Division of Water 

Resources, 2006). A permit for an exempt domestic well may 

be obtained for 35-acre or larger parcels, where the proposed 

well will be the only well on the tract. Parcels that are at least 

35 acres in extent are not considered under the subdivision 

rules. A permit for an exempt domestic well may be obtained 

for tracts of land that are less than 35 acres if the surface 

drainage system is not overappropriated or if the well will 

produce from deep (nontributary) ground water. Depending on the provisions under which the well permit is issued, 

an exempt domestic well may be able to serve up to three 

single-family dwellings, irrigate 1 acre or less of lawn and 

garden, and provide water for an individual’s domestic animals 

and livestock. A permit for an exempt household-use-only 

(residential) well may be obtained by the owner of a lot in a 

subdivision that was created prior to June 1, 1972, or if the 

parcel was created by an exemption to the subdivision laws by 

the local county planning authority.

Residential wells that are located in subdivisions created 

after June 1, 1972, or those that are located in parcels that 
6 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

were not created by an exemption to the subdivision laws by 

the local county planning authority, generally are permitted as 

nonexempt residential wells. An augmentation plan may be 

required for nonexempt residential wells that are located in an 

overappropriated stream-aquifer system.

The purpose of an augmentation plan is to offset stream 

depletions caused by the withdrawal of tributary ground water 

by nonexempt wells. Ground water is considered tributary 

if its withdrawal will deplete the flow of a surface stream by 

one-tenth of one percent or more of the rate of withdrawal in 

100 years. Ground water is considered nontributary to surface 

streams if its withdrawal will deplete the flow of a surface 

stream by less than one-tenth of one percent of the rate of 

withdrawal in 100 years. The intent of an augmentation plan is 

to prevent material injury to decreed water rights by replacing the consumptive use of water from nonexempt wells. New 

nonexempt wells in overappropriated areas of the State may 

be required to replace any out-of-priority stream depletions in 

time, place, amount, and quality by having augmentation water 

available. The augmentation plan must be approved before the 

DWR grants approval to the water-supply plan for a proposed 

subdivision. A plan for augmentation generally is not required 

in Colorado if the stream-aquifer system is not overappropriated. Development of an augmentation plan usually requires 

the services of a water-resource engineer and, possibly, a water 

attorney. More information about subdivision and well-permit 

rules, tributary ground water, and augmentation plans can be 

obtained from the DWR Web site at http://water.state.co.us/.

A stream-depletion analysis is done to determine if 

ground water is tributary to a stream and to calculate the 

potential stream depletion that would result from the proposed 

ground-water diversions for the subdivision. A computer 

program that calculates stream depletion that results from 

well pumping is available from the Integrated Decision 

Support Group at Colorado State University at http://www.ids.

colostate.edu/index.html?/projects/idsawas/.

Administrative rules of the DWR (Colorado Division of 

Water Resources, 1986) and some counties in Colorado limit 

proposed ground-water appropriations of nontributary ground 

water from an aquifer by limiting the annual volume of diversions to a percentage of the estimated volume of ground water 

stored in the aquifer. Typically, the DWR limits the annual 

volume of appropriation of nontributary ground water to a 

maximum of 1 percent per year of ground water that is stored 

in the aquifer in which the well will be completed and that 

underlies the parcel of land in which the well will be located. 

This planned rate of depletion is referred to as the “100-year 

rule.” If the volume of ground water stored in a nontributary 

aquifer is small, planned depletion effectively restricts the 

minimum size of parcels. For example, assuming that the 

annual appropriation needed for a residential well is 0.3 acre-ft 

and the available storage is 10 ft of water (per unit area) in a 

nontributary aquifer, a lot size of 3 acres would be required 

under the 100-year rule to provide 0.3 acre-ft/yr of water 

[0.3 acre-ft/yr / (10 ft X 0.01/yr) = 3 acres]. In some Colorado 

counties, the annual volume of pumping from nontributary 

aquifers is limited to an amount equal to 0.33 percent per 

year of nontributary ground water that is stored in the aquifer 

in which the well will be completed and that underlies the 

parcel of land in which the well will be located. This planned 

rate of storage depletion is referred to as the “300-year rule.” 

Both the 100-year and 300-year rules assume that the rates of 

ground-water withdrawal from a nontributary aquifer are not 

sustainable. Neither rule considers changes in recharge to or 

discharge from the aquifer that may result from reductions in 

water levels in the aquifer. If ground-water withdrawals do 

not induce additional recharge or capture other discharge, the 

aquifer will be dewatered (mined) to a point at which water 

may no longer be available to wells. A water-supply plan 

based on ground water from a non-renewable aquifer also 

needs to incorporate alternative renewable water resources 

that provide a sustainable water supply for future generations 

(Colorado Division of Water Resources, 2005).

Referral and Review of Subdivision WaterSupply Plans

Colorado Revised Statutes Section 30–28–136 defines 

the referral and review process for subdivision water-supply 

plans. Initially, the county reviews the preliminary watersupply plan and submits it to the DWR. The DWR is required 

by CRS Section 30–28–136(2) to review and comment on 

the water-supply plan within 21 days of submission by the 

county commissioners. An extension to the 21-day period 

may be granted for review of a water-supply plan for certain 

circumstances and with agreement of the county and the applicant. The DWR provides an opinion to the Board of County 

Commissioners concerning (1) the potential injury to decreed 

water rights caused by diversions to supply the proposed 

subdivision and (2) the adequacy of the proposed water supply. 

Policies of the DWR about review of a water-supply plan are 

defined in a memorandum from the State Engineer (Colorado 

Division of Water Resources, 2005 [http://water.state.co.us/

pubs/policies/memo_subdivisions.pdf]).

The preliminary water-supply plan includes the following 

components:

1. Expected water requirements (total demand and consumptive use) at full development of the subdivision for all 

anticipated water uses;

2. A water-supply report defining the legal and physical 

availability and sustainability of the water supply for the 

proposed subdivision;

3. Evidence of ownership or right of use of existing water 

rights;

4. Evaluation of potential material injury to all existing and 

proposed water rights that could result from proposed 

water use in the subdivision, which includes the cumulative effect of withdrawals of all on-lot wells at full development of the subdivision;
Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 7

5. A completed water-supply information summary form 

listing the proposed uses; and 

6. A 7.5-minute USGS topographic map with the boundaries 

of the proposed subdivision plotted as described by the 

metes and bounds description.

Subdivision Water-Supply Reports

A subdivision water-supply report defines both the legal 

and the physical characteristics of the water supply for a 

proposed subdivision. Definition of the legal availability of 

the water supply is based on compilation of existing water 

rights and is outside the scope of this report. A water lawyer 

generally prepares evidence of the legal availability of the 

water supply. A water-resources engineer generally prepares 

evidence of the physical availability and sustainability of the 

water supply. The Colorado Revised Statutes and administrative rules of the DWR do not explicitly define what evidence 

of the physical availability and sustainability of a water supply 

for a proposed subdivision is adequate.

For purposes of this report, ground-water availability 

means that a sufficient quantity of ground water of suitable 

quality can be obtained from wells or springs for the intended 

use of the water. Even if ground water is physically available in an aquifer, its use may be restricted to prevent injury 

to senior water rights. Ground-water use from nontributary 

aquifers also may be restricted to limit aquifer depletion and 

from tributary aquifers to prevent or mitigate stream depletion. 

Ground-water sustainability is defined as the development 

and use of ground water in a manner that can be maintained 

for an indefinite time without causing unacceptable consequences (Alley and others, 1999). Unacceptable consequences 

could include depletion of streamflow, depletion of aquifer 

storage, drying of springs and wetlands, and changes in water 

quality. Knowledge of the volume of ground-water storage 

and the water budget is needed to determine the sustainability 

of a ground-water supply. The sustainability of a groundwater supply can vary in response to short-term, seasonal, 

and long-term changes in recharge and discharge conditions. 

Development of a sustainable ground-water supply requires 

an understanding of the effects of development on long-term 

recharge and discharge conditions and the interaction of the 

aquifer with other parts of the hydrologic system.

The only three possible sources of water discharged by 

a well are ground-water storage, ground-water discharge, 

and additional recharge. Ground water cannot be withdrawn 

from an aquifer without affecting at least one of those three 

sources. The amount of ground water available for sustained 

use depends on more than the volume that can be extracted 

for use; it is a complex function of the aquifer’s hydraulic and 

storage properties, boundary conditions, withdrawal rates, 

well locations, and the sources of ground water discharged by 

wells.

Availability, Sustainability, and 

Suitability of Ground Water on Rogers 

Mesa

This section of the report provides examples of hydrologic analyses and data that may be needed for a water-supply 

report for a proposed subdivision that plans the use of individual wells for its water supply. Types of analyses and data that 

can be used in subdivision water-supply reports are described 

in this section. An example of preliminary analyses and data 

for a water-supply report for a hypothetical subdivision on 

Rogers Mesa is then presented. The list of types of analyses 

and data can be used as a checklist in preparing and reviewing 

subdivision water-supply reports. The preliminary analysis 

includes a stream-depletion analysis of the proposed groundwater withdrawals for a hypothetical subdivision.

“The foundation of any good ground-water analysis, 

including those analyses whose objective is to propose and evaluate alternative management strategies, 

is the availability of high-quality data” (Alley and 

others, 1999).

Because the analysis of ground-water conditions on 

Rogers Mesa presented in this report is based primarily on 

available data, which may not be of high quality, it should 

be considered preliminary. Suggestions for the collection of 

additional data and the analyses of data that would improve 

the understanding of ground-water conditions on Rogers Mesa 

also are included in this section.

Types of Analyses and Data for Use in 

Subdivision Water-Supply Reports

A water-supply report defines the availability, sustainability, and suitability of a proposed ground-water supply. A 

water-supply report may not be required in a water-supply 

plan if the water supply will be provided by an existing municipal or quasi-municipal water provider (Colorado Division of 

Water Resources, 2000). Determining the physical availability 

of a ground-water supply requires a hydrologic analysis to 

estimate the amount of water in ground-water storage and to 

determine if the aquifer will yield sufficient water to wells or 

springs for the intended use. Determining the sustainability of 

a proposed ground-water supply requires an understanding of 

how recharge to and discharge from the aquifer occur and how 

recharge and discharge may be affected by changes in land and 

water uses. The suitability of ground water for a residential 

supply depends primarily on the water’s physical properties 

and chemical and biological characteristics. The determination 

of suitability should be based on analyses of water samples 

from the aquifer and from potential sources of recharge to the 

aquifer.
8 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

Subdivision regulations adopted by a board of county 

commissioners pursuant to CRS 30–28–133 require subdividers to submit data, surveys, analyses, studies, plans, and 

designs to the board of county commissioners. Although 

the requirements for a water-supply report are not defined 

explicitly, CRS 30–28–133(3)(d) states that adequate evidence 

that a water supply that is sufficient in terms of quality, 

quantity, and dependability will be available to ensure an 

adequate supply of water for the type of subdivision. The 

following analyses likely will be needed in a water-supply 

report for a proposed subdivision to meet the requirements of 

CRS 30–28–133(3)(d):

1. Evaluation of local ground- and surface-water resources 

on a system-wide basis to understand the potential 

effects of changes in ground-water use on the availability 

(quantity) and sustainability (dependability) of the water 

resources; 

2. Evaluation of the potential material injury to decreed 

water rights that could be caused by pumping of the 

proposed wells at full development of the subdivision 

(Colorado Division of Water Resources, 2000); and

3. A hydrogeologic analysis of the ground-water/surfacewater system, including 

a. a conceptual model of the hydrologic system,

b. aquifer geometry, boundary conditions, and 

hydraulic and storage properties,

c. a water budget, and

d. water-quality characteristics.

If existing data are not adequate, data collection will be needed 

to define the availability, sustainability, and suitability of the 

proposed ground-water supply. This data collection could 

require installation of test and monitoring wells, aquifer tests, 

measurement of water levels, and collection of water samples 

to determine physical properties and chemical and biological 

characteristics of water in the aquifer.

The types of analyses and data that may be needed for a 

water-supply report for a subdivision that proposes the use of 

ground water from individual on-lot wells are listed in table 2 

(modified from Alley and others, 1999, table 2). Table 2 can 

be used as a checklist by subdivision developers in preparation 

of water-supply reports and by land-use officials as criteria to 

evaluate subdivision water-supply reports. Not all types of data 

listed in table 2 may be needed for a subdivision water-supply 

report. For example, if ground water is not affected by infiltration from the surface or diversion of surface water for irrigation, water-budget components related to irrigation may be 

irrelevant. Data and analyses related to stream depletion and 

infiltration from the surface may not be necessary if ground 

water is nontributary.

A conceptual model describes geologic and hydrologic 

factors that control the occurrence and flow of ground water, 

including recharge and discharge conditions. For water-supply 

reports, the study area may be greater than the extent of the 

proposed subdivision. Where practical, the extent of the study 

area coincides with hydrologic boundaries, such as streams 

or other natural boundaries. For regionally extensive aquifers, 

the study area boundary encompasses those areas that may be 

affected directly by proposed ground-water diversions. The 

hydrogeologic setting is a part of the conceptual model that 

describes the climate, topography, surface and subsurface 

geologic and hydrologic conditions, and current and proposed 

land and water uses. Aquifer geometry, if not previously 

defined, is mapped to define the aquifer’s lateral extent and 

thickness, and the aquifer’s relation with other aquifers and 

confining units. Maps of the depths to or altitudes of the 

bottom and top of the aquifer and of water levels in the aquifer 

are needed. Aquifer boundary conditions define where and 

how water flows into or out of an aquifer. Where practical, 

the boundary conditions are defined at physical boundaries, 

such as geologic features or streams. Reilly (2001) provides 

a detailed discussion of conceptualization and mathematical 

treatment of boundary conditions. The hydraulic and storage 

properties define the ability of an aquifer or confining unit to 

transmit and store water. Knowledge of an aquifer’s hydraulic 

and storage properties and their variability is needed to calculate flow and storage in the aquifer, to estimate potential well 

yields, to evaluate the effects of pumping or other changes 

in recharge and discharge conditions, and, if the aquifer is 

hydraulically connected to a stream, to calculate stream depletion. A water budget is an accounting of inflow, outflow, and 

storage changes of water for an aquifer. Because many of the 

components in a water budget are not measured routinely or 

cannot be measured directly, a water budget also includes the 

cumulative errors in the estimated components of the budget. 

A ground-water flow model may be needed to determine 

ground-water availability and sustainability and to predict 

potential effects of proposed pumping in complex systems. 

The water quality (physical, chemical, and biological) characteristics define the suitability of the ground water for domestic 

supply. Results from analyses of samples can be compared 

with drinking-water standards to establish the suitability of the 

water supply.

Example of Preliminary Analyses and Data for a 

Subdivision Water-Supply Report

A brief field reconnaissance and publicly accessible 

data (table 1) were used for this preliminary analysis of 

ground water on Rogers Mesa. If existing data are sparse, 

more intensive field investigations may be needed to prepare 

water-supply reports for subdivisions in other areas in Delta 

County. Detailed geologic mapping, drilling and installation 

of test wells, measurement of water levels and spring and well 

discharge, aquifer tests, and collection of water samples from 

springs and wells may be needed to define the availability, 

sustainability, and suitability of a ground-water supply for a 

proposed subdivision.
Table 2. Types of analyses and data that may be needed for subdivision water-supply reports [modified from Alley and others, 1999].

[--, may not be needed; X, may be needed]

Analysis Data type Confined 

aquifer

Unconfined 

aquifer

Hydrogeologic setting

Aquifers and confining units X X

Land use X X

Physiographic setting and topography X X

Regional stratigraphy and geologic structure X X

Stratigraphy and lithology X X

Surface-water features, including irrigation canals and agricultural drains X X

Aquifer geometry and 

boundary conditions

Aquifer extent and boundary conditions X X

Topography X X

Depths to tops and bottoms of aquifers and confining units X X

Well and spring locations X X

Seeps and wetlands X X

Water levels X X

Saturated thickness -- X

Thickness of unsaturated zone -- X

Hydraulic and storage 

properties

Hydraulic conductivity -- X

Transmissivity X --

Specific yield X X

Storage coefficient or specific storage X --

Specific retention X X

Specific capacity and yields of wells X X

Water budget

Surface inflow -- X

Surface outflow -- X

Subsurface inflow X X

Subsurface outflow X X

Recharge from losing streams X X

Discharge to gaining streams X X

Infiltration of irrigation return flow -- X

Infiltration from individual sewage disposal systems -- X

Infiltration of precipitation -- X

Surface-water application, irrigated areas -- X

Ground-water application, irrigated areas -- X

Consumptive use, irrigated areas by crops -- X

Consumptive use, nonirrigated areas -- X

Leakage to and from vertically adjacent units X X

Discharge to agricultural drains and tail-water pits -- X

Discharge from wells X X

Discharge to springs, seeps, and wetlands X X

Water quality Physical properties and chemical and biological characteristics of surface water X X

Physical properties and chemical and biological characteristics of ground water X X

Aquifer depletion Pumping rate, saturated thickness, and specific yield X X

Stream depletion Aquifer properties, pumping rate, and well and stream locations X X

Well interference Aquifer properties, pumping rate, and well locations X X

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 9
10 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

Availability

The physical availability of ground water for subdivision water supply on Rogers Mesa is limited by the volume 

of water stored in the aquifer, the ability of wells to extract 

a sufficient quantity of ground water for residential use, and 

the effects that additional ground-water use will have on the 

subsurface and surface environment. The following section of 

the report is a preliminary analysis of ground-water availability on Rogers Mesa that was based on publicly available data. 

A more complete analysis of ground-water availability likely 

would require the collection of additional data.

Hydrogeologic Setting of Rogers Mesa

The study area, Rogers Mesa, is about 15 mi east of 

Delta, Colo. (fig. 1). The boundary of the study area (fig. 2) 

encompasses an area of 7, 641 acres or about 12 mi2. The 

population of Rogers Mesa is estimated to be about 800 to 

1,000 on the basis of the number of domestic and residential wells and active water taps. Irrigated agriculture is 

the principal land use on Rogers Mesa. About 5,651 acres 

of cropland, grass pasture, and orchards were irrigated in 

the study area during 2000 (Colorado Division of Water 

Resources and Colorado Water Conservation Board, 2007). 

The estimated area of platted subdivisions on or partially on 

Rogers Mesa (fig. 2) is about 4,792 acres (Paul Healy, Delta 

County, Colorado, electronic commun., 2007), of which about 

2,756 acres also was identified as irrigated land in 2000.

Rogers Mesa is a relatively flat-topped upland that is 

covered with alluvial-fan deposits and underlain by sedimentary rocks. The altitude of the land surface at the head of the 

alluvial fan on Rogers Mesa is about 6,000 ft, and the altitude 

of the land surface atop the scarp at the toe of the alluvial fan 

is about 5,400 ft (fig. 1). The land surface of Rogers Mesa 

slopes southward toward the North Fork Gunnison River 

Valley at about 150 ft/mi (fig. 2). Local surface relief from the 

edge of Rogers Mesa to the North Fork Gunnison River Valley 

is about 150 to 200 ft and to the Leroux Creek Valley is about 

100 to 150 ft (fig. 2).

The North Fork Gunnison River Valley to the south, 

Leroux Creek Valley to the east, and Big Gulch to the west of 

Rogers Mesa are cut into the northerly dipping sedimentary 

rocks, which are of Cretaceous-Jurassic age (fig. 3; modified 

from Day and others, 1999). South flowing streams deposited 

a Quaternary age alluvial fan on an erosional surface (angular 

unconformity) on top of the sedimentary rocks. Continued 

erosion by the streams removed some of the alluvial-fan 

deposits and cut narrow valleys into the underlying sedimentary rocks, forming the steep scarps between Rogers Mesa 

and the North Fork Gunnison River and Leroux Creek valleys. 

Generally, these steep scarps limit the contact and hydraulic 

connection of the alluvial-fan deposits with recent alluvium 

along these streams.

The alluvial-fan deposits consist of a heterogeneous 

mixture of unconsolidated sediments that includes clay, silt, 

sand, gravel, cobbles, and boulders (fig. 4). Thickness of 

the alluvial-fan deposits, as estimated from reported depths 

to shale or sandstone from drillers’ logs, ranges from 32 to 

255 ft. Many of the cobbles and boulders in the alluvial-fan 

deposits were eroded from basalt on Grand Mesa (fig. 1). 

Where saturated, the alluvial-fan deposits are referred to in 

this report as the “Rogers Mesa aquifer.” The Rogers Mesa 

aquifer is an unconfined aquifer.

The Cretaceous-age Mancos Shale, which underlies most 

of Rogers Mesa, is a relatively impermeable regional confining unit with an estimated hydraulic conductivity of about 

3x10-4 ft/d (Lazear, 2006) to 1.4 ft/d (Weigel, 1987). The 

Mancos Shale is exposed or thinly covered by slope deposits at the edge of Rogers Mesa. Weathered Mancos Shale is 

exposed along Big Gulch to the west and northwest of Rogers 

Mesa. The Mancos Shale, where not removed by erosion, 

separates the alluvial-fan deposits from the Cretaceous-age 

Dakota Sandstone and Burro Canyon Formation. Near the 

southwestern part of Rogers Mesa, the Mancos Shale thins 

and the alluvial-fan deposits may directly overlie the Dakota 

Sandstone and Burro Canyon Formation. Locally, the Dakota 

Sandstone and Burro Canyon Formation are important aquifers 

in western Colorado (Topper and others, 2003) but reportedly 

yield only small quantities of water to wells near Rogers Mesa. 

Additional field investigations are needed to determine the 

lateral extent of the Mancos Shale in the southwestern part of 

Rogers Mesa, where the Dakota Sandstone and Burro Canyon 

Formation may directly underlie the base of the Rogers Mesa 

aquifer. The Morrison and Wanakah Formations and the 

Entrada Sandstone (Jurassic-age sedimentary rocks) crop out 

in the North Fork Gunnison River Valley south of Rogers 

Mesa (Day and others, 1999) and likely are not in contact with 

the alluvial-fan deposits on Rogers Mesa (fig. 3).

Climate

The climate of the Rogers Mesa area is semiarid with the 

potential for evaporation and transpiration (evapotranspiration) 

to exceed precipitation in every month of the year (fig. 5). 

A meteorological station (HOT01; fig. 6), which is part of 

the Colorado Agricultural Meteorological (COAGMET) 

network, is located on Rogers Mesa at the Colorado State 

University Experiment Station. The COAGMET network is 

operated by the Colorado Climate Center at Colorado State 

University and is used to estimate local reference evapotranspiration (consumptive use) by crops. Consumptive use is the 

amount of water evaporated from soil and transpired by plants. 

Reference evapotranspiration is the hypothetical evapotranspiration or consumptive use of water by a well-watered crop 

of alfalfa. Reference evapotranspiration is calculated using 

an energy balance equation, the 1982 Kimberly Penman 

equation for alfalfa (Wright, 1982), and local measurements 

of relative humidity, precipitation, solar radiation, wind speed, 

and air and soil temperatures. Data from the COAGMET 

network can be accessed at http://ccc.atmos.colostate.

edu/%7Ecoagmet/. Average annual precipitation during 
3

5 4

2 1

2 3

3 4 3 5 3 3

2 8

2 6

2 7

2 1

3 2

2 9

2 2

2 0

8

3 6

2 4

2 5

9 1 0 11 1 2

1 9

3 0

6

1 4 1 3

3 1

7

1 5

 No water company service

 Rogers Mesa Domestic Water Company

 Lazear Domestic Water Company

 Irrigation

 Livestock

 Monitoring hole/well

 Residential

Highline

Di tch

Fire M ou n tai n Canal

5,400

5,900

5,500

5,600

5,700

5,800

5,300

5,300

6,300

5,700

5,600

5,500

5,600

5,900

R O G E R S M E S A

Big

Gulch

Stingley Gulch

Livestock well

Isom Ditch

Big Gulch Ditch

Fleming Ditch

Isom Ditch

Little Mary Ditch

Leroux Creek Ditch

Jessie Ditch

Permitted wells, December 31, 2004

5,500

6,000

Area platted for subdivision development,

 June 2007

Topographic contour—Shows altitude of land surface. Contour

 interval 100 feet. North American Vertical Datum of 1988

Diversion structure—Shows location and 

 name of surface-water diversion

Springs, 2007

 Spring with decreed water right

 Other spring or seep

Water company service area, June 2007

Approximate extent of Rogers Mesa aquifer

Irrigation canal or ditch

Little Mary Ditch

 Commercial

 Domestic

 Fishery

 Geothermal

T. 14 S.

T. 15 S.

R. 93 W. Universal Transverse Mercator projection, Zone 13

North American Datum of 1983

0 1 2 MILES

0 1 2 KILOMETERS

38°49’

38°48’

38°47’

38°46’

107°49’ 107°48’ 107°47’ 107°46’ 107°45’

EXPLANATION

Leroux

Creek

North

Fork

Gunnison River

107°44’

Figure 2. Generalized topography, subdivisions, water company service areas, springs, and wells, Rogers Mesa, Delta County, 

Colorado.

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 11
Figure 3. Generalized surface geology and configuration of the base of the aquifer (the contact of alluvial-fan deposits with shale 

or sandstone) on Rogers Mesa, Delta County, Colorado.

3

5 4

2 1

2 3

3 4 3 5 3 3

2 8

2 6

2 7

2 1

3 2

2 9

2 2

2 0

8

3 6

2 4

2 5

9 1 0 11 1 2

1 9

3 0

6

1 4 1 3

3 1

7

1 5

5,300

Riverside

Cemetary

Highline Ditch

Surface geology Bedrock contour—Shows altitude of base of aquifer. Contour interval

 20 feet. Hachures indicate depression. North American Vertical

 Datum of 1988

Approximate axis of buried valley

Irrigation canal or ditch

Control point—Shows location of control point used to estimate altitude

 of base of aquifer. North American Datum of 1988 

Altitude of stream—Shows approximate location where stream crosses 

 index topographic contour. Number is altitude, in feet. North American 

 Vertical Datum of 1988

Outcrop (shown in figure 4)

 Unconsolidated sediments

 Alluvium

 Gravels and alluviums

 Sedimentary rocks

 Mancos Shale

 Dakota Sandstone and Burro Canyon 

 Formation

 Morrison and Wanakah Formations and 

 Entrada Sandstone

Approximate extent of Rogers Mesa aquifer

Fire Mountain

Canal

T. 14 S.

T. 15 S.

R. 93 W. Universal Transverse Mercator projection, Zone 13

North American Datum of 1983

0 1 2 MILES

0 1 2 KILOMETERS

38°49’

38°48’

38°47’

38°46’

107°49’ 107°48’ 107°47’ 107°46’ 107°45’

EXPLANATION

North

Fork

Gunnison River

107°44’

R O G E R S M E S A

Leroux Creek

Fire Mountain Canal

12 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado
Figure 4. Contact of alluvial deposits with weathered Mancos Shale near Riverside Cemetery, Rogers Mesa, Delta 

County, Colorado. Riverside Cemetary is at top of hill and Leroux Creek is at base of slope. Approximate location shown in 

figure 3. Photograph by Judith Thomas, U.S. Geological Survey.

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 13

irrigation years 1999–2006 at station HOT01 was about 0.87 ft 

and ranged from about 0.6 ft in irrigation year 2003 to about 

1 ft in irrigation year 2005. (An irrigation year begins November 1 of the previous calendar year and ends October 31 of the 

calendar year.) Average annual reference evapotranspiration 

during irrigation years 1999–2006 was about 4.7 ft and ranged 

from about 4.2 ft during irrigation year 2006 to 5.2 ft during 

irrigation year 2000. The difference between average annual 

precipitation and average annual reference evapotranspiration 

during irrigation years 1999–2006 was a deficit of about 3.8 ft. 

This deficit represents the minimum amount of irrigation 

water that would be needed by a well-watered crop of alfalfa. 

The annual deficit between precipitation and reference evapotranspiration ranged from 3.2 ft in irrigation year 2005 to 4.5 ft 

in irrigation year 2000.

Soils

Soils on Rogers Mesa are developed on the alluvial-fan 

deposits and are moderately permeable (fig. 6). The saturated 

vertical hydraulic conductivity of soils at depths of 3 to 5 ft on 

Rogers Mesa generally ranges from 4.23 to 14.11 micrometers 

per second (μm/s), which is equivalent to about 1.2 to 4 ft/d 

(U.S. Department of Agriculture, Natural Resources Conservation Service, 2007a). Because the hydraulic conductivity 

of soils is measured or estimated perpendicular to the land 

surface, it is an estimate of the vertical hydraulic conductivity 

of the soil. The available water capacity of the soils at depths 

of 3 to 5 ft on Rogers Mesa is variable and averages about 

8 percent (U.S. Department of Agriculture, Natural Resources 

Conservation Service, 2007a). Available water capacity is the 

difference between the soil water content at field capacity and 

the wilting point (U.S. Department of Agriculture, Natural 

Resources Conservation Service, 2007b). Field capacity is 

the amount of moisture that remains in a soil after free water 

in the pores has drained into the underlying unsaturated soil. 

Field capacity is measured as the ratio of the weight of water 

in the soil to the oven-dry weight of the soil. For permeable 

soils of medium texture, the time required for drainage to field 

capacity is about 2 or 3 days after a substantial rain or irrigation. The wilting point is the moisture content (the ratio of 

the weight of water in the soil to the oven-dry weight of the 
Figure 5. Mean monthly precipitation and estimated reference evapotranspiration 

at meteorological station HOT01, Rogers Mesa, Delta County, Colorado, May 21, 

1998, through December 31, 2006. MONTHLY MEAN, IN INCHES

0

1

2

3

4

5

6

7

8

9

10

Precipitation

Reference evapotranspiration

January

February

March

April

May

June

July

August

September

October

November

December

14 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

soil) at which plants cannot extract water from the soil (U.S. 

Department of Agriculture, Natural Resources Conservation 

Service, 2007c). The available water capacity commonly is 

expressed as a fraction of an inch of water per inch (or per 

foot) of soil but also can be expressed as a dimensionless ratio. 

The available water capacity is approximately equivalent to 

the specific retention (fig. 6) of the porous media (Lohman and 

others, 1972).

The estimated clay content of soils on Rogers Mesa, at 

depths of 3 to 5 ft, ranges from 18 to 28 percent by volume 

(U.S. Department of Agriculture, Natural Resources Conservation Service, 2007a). Assuming the clay content in the soil at 3 

to 5 ft is similar to that in the underlying alluvial-fan deposits, 

the alluvial-fan deposits would be described as a clayey sand 

and gravel. The infiltration of precipitation and irrigation 

water applied to the land surface likely is inhibited by clay 

within the soil and the unsaturated zone overlying the water 

table. As water infiltrates through the unsaturated zone, clay 

provides sites for ion exchange that may affect the chemical 

composition of the water as it percolates to the water table.

Irrigation

Irrigated agriculture is the principal land use on Rogers 

Mesa. Surface water is diverted from the North Fork Gunnison River by the Fire Mountain Canal, from Leroux Creek by 

the Highline Ditch and Leroux Creek Ditch, and by several 

smaller ditches to irrigate about 5,572 acres on Rogers Mesa 

(Colorado Division of Water Resources and Colorado Water 

Conservation Board, 2007). The Fire Mountain Diversion 

Dam and Canal were built primarily from 1949 to 1953. The 

diversion for the Fire Mountain Canal is located on the North 

Fork Gunnison River about 17 mi upstream from Rogers 

Mesa (fig. 1). The Fire Mountain Canal ranges from 4 ft 

wide, where it is concrete lined, to 10 ft wide, where it is clay 

lined. Maximum capacity of the Fire Mountain Canal is about 

100 ft3/s where it crosses Leroux Creek onto Rogers Mesa 

(Bureau of Reclamation, 2006). The Highline Ditch diverts 

water from Leroux Creek about 6 mi north of Rogers Mesa 

(fig. 1). Locations of diversion structures for Big Gulch Ditch, 

Fleming Ditch, Isom Ditch, Jessie Ditch, Leroux Creek Ditch, 

and Little Mary Ditch are shown in figure 7. Ground water 
Figure 6. Estimated vertical hydraulic conductivity and specific retention of soils derived from alluvial-fan deposits, Rogers Mesa, 

Delta County, Colorado. [Data modifed from U.S. Department of Agriculture, Natural Resources Conservation Service, 2007.]

HOT01

 1.2 to 4

3

5 4

2 1

2 3

3 4 3 5

3 3

2 8

2 6

2 7

2 1

3 2

2 9

2 2

2 0

8

3 6

2 4

2 5

9 1 0 11 1 2

1 9

3 0

6

1 4 1 3

3 1

7

1 5

T. 14 S.

T. 15 S.

R. 93 W. Universal Transverse Mercator projection, Zone 13

North American Datum of 1983

0 1 2 MILES

0 1 2 KILOMETERS

38°49’

38°48’

38°47’

38°46’

107°49’ 107°48’ 107°47’ 107°46’ 107°45’

North

Fork

Gunnison River

107°44’

R O G E R S M E S A

Leroux Creek

Fire Mountain

Canal Fire Mountain Canal

Highline Ditch

EXPLANATION

 Hydraulic conductivity, 

 vertical (feet per day)

 Specific retention

 (percent)

 0 to 0.06

 0.12 to 0.4

 1.2 to 4

 1.2 to 4

 13 to 16

 0

 Not defined

 4 to 5

 7 to 9

Soil properties at 3- to 5-foot depth Approximate extent of Rogers Mesa aquifer

Irrigation canal or ditch

Colorado Agricultural Meteorological

 Network Station HOT01

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 15
Figure 7. Irrigated cropland, pasture, and orchards, and locations of canals, ditches, diversion structures, irrigation wells, and 

selected springs on Rogers Mesa, Delta County, Colorado, 2000.

Leroux Creek Ditch

Jessie Ditch

Isom Ditch

Little Mary Ditch

2 wells

2 springs

0.03

0.15

0.05

0.05

1

1

0.05

0.05

0.1

0.33

2

0.44 0.05

0.05

0.25

0.25

0.25

0.1

0.1

0.33

Fleming

Ditch

Isom Ditch

Big Gulch Ditch

 Grass pasture

 Fruit orchard

 Small grains

Not irrigated with surface water

 Corn

 Alfalfa

Ditch diversion structure

Spring—Shows location of springs. Number

 is decreed rate, in cubic feet per second

Irrigated with surface water Approximate extent of Rogers Mesa aquifer

Irrigation canal or ditch

Irrigation well

5 3 4

2

1

2 3

3 4 3 5

3 3

2 8

2 6

2 7

2 1

3 2

2 9

2 2

2 0

8

3 6

2 4

2 5

9 1 0 11 1 2

1 9

3 0

6

1 4 1 3

3 1

7

1 5

T. 14 S.

T. 15 S.

R. 93 W. Universal Transverse Mercator projection, Zone 13

North American Datum of 1983

0 1 2 MILES

0 1 2 KILOMETERS

38°49’

38°48’

38°47’

38°46’

107°49’ 107°48’ 107°47’ 107°46’ 107°45’

North

Fork

Gunnison River

107°44’

R O G E R S M E S A

Fire Mountain

Canal Fire Mountain Canal

Highline Ditch

EXPLANATION

Leroux Creek

16 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado
Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 17

from wells also may be used to irrigate an estimated 723 acres 

on Rogers Mesa; however, no records of diversion by irrigation wells on Rogers Mesa are available. As of December 

2004, only 21 wells in the DWR well file had a primary or 

secondary use for irrigation on Rogers Mesa (fig. 7).

 In 2000, the principal crops irrigated on Rogers Mesa 

included about 3,991 acres of grass pasture, about 931 acres 

of fruit orchards, about 633 acres of alfalfa, about 14 acres 

of corn, and about 3.4 acres of small grains (fig. 7; Colorado 

Division of Water Resources and Colorado Water Conservation Board, 2007). The estimated area of lawns and gardens 

irrigated with ground water from domestic wells is about 

78 acres.

Residential Water Supplies

Lazear Domestic Water Company and Rogers Mesa 

Domestic Water Company (fig. 2) have a combined 430 active 

water taps and annually import a total of 32.9 Mgal or about 

101 acre-ft of water for use on Rogers Mesa. The source of 

water for the Lazear Domestic Water Company is ground 

water from the aquifer along the North Fork Gunnison River 

(Colorado Department of Health and Environment, 2004) and 

for the Rogers Mesa Domestic Water Company is surface 

water from Leroux Creek (U.S. Environmental Protection Agency, 2007a). In 2004, there were 98 domestic and 

40 residential (household use only) wells with permits on 

Rogers Mesa (fig. 2). There also were permits for 21 irrigation wells, 3 commercial wells, and 1 stock well. In addition, 

20 springs on Rogers Mesa have decreed water rights (fig. 7).

Because the study area does not have a centralized 

sewage treatment system, sanitary wastes are treated and 

disposed of by using ISDS. Assuming that the 430 active water 

taps and the 98 domestic, 40 residential, and the 3 commercial wells dispose of wastewater by using ISDS, an estimated 

571 ISDS are located on Rogers Mesa. Nonconsumptive water 

use from 571 systems is assumed to return to the aquifer (to 

recharge the aquifer) by infiltration from the leach fields of the 

ISDS. No quantitative studies of consumptive use of residential water have been done in the Rogers Mesa area; however, 

nonconsumptive use of water by Colorado residences using 

ISDS is estimated to range from 84 to 93 percent (Ralf Topper, 

Colorado Geological Survey, written commun., 2007; http://

dnr.state.co.us/NR/rdonlyres/C9D61BC3-26A6-418B-A179-

4856C941B03D/0/TopperMemoWaterUsebyIndividualSewageSystems5707.doc). Nonconsumptive use of residential water 

supplies on Rogers Mesa was assumed to be 90 percent of 

in-house water use.

Aquifer Boundary Conditions

Boundary conditions for Rogers Mesa aquifer are 

relatively simple. The lower boundary, the base of the aquifer, 

which is the contact of the alluvial-fan deposits with the 

Mancos Shale, Dakota Sandstone, or Burro Canyon Formation, is a no-flow (specified flow of zero) boundary. The upper 

boundary, the water table, is a specified flow boundary across 

which the aquifer is recharged by downward infiltration of 

water through the unsaturated zone. The lateral boundaries 

of the aquifer generally are specified head (head-dependent 

flow) boundaries across which flow is variable, depending on 

the transmissivity of the aquifer and the hydraulic gradient 

at the boundary. Locally, flows across the lateral boundaries 

of the aquifer are concentrated at lows in the basal surface of 

the aquifer, where ground water discharges to the surface at 

springs and seeps. In some areas along the lateral boundaries, the aquifer grades into soil and slope deposits and ground 

water discharges through the soil and slope deposits. Groundwater discharge areas along the lateral boundary of the aquifer 

commonly are indicated by the occurrence of water-loving 

plants, such as cattails and willows, or by salt encrustation on 

the land surface.

Lower Boundary—Base of the Aquifer

The generalized configuration of the base of the aquifer, 

the lower no-flow boundary of the aquifer, is shown in 

figure 3. The map of the base of the aquifer (fig. 3) was 

prepared using drillers’ logs for 105 wells from the DWR well 

database. Although about 30 percent of the drillers’ logs did 

not report a depth to shale or sandstone, it was assumed that 

all wells were drilled to shale or sandstone. The altitudes of 

the land surface at the control points for the bedrock surface 

were estimated from a national elevation dataset (U.S. Geological Survey, 2007). The altitudes of the base of the aquifer 

(the bedrock surface) at the control points were calculated by 

subtracting the reported depth to shale, sandstone, or, if the 

depth to shale or sandstone was not reported, the total well 

depth from the estimated altitude of the land surface at the 

well. Kriging, a geostatistical interpolation method, as implemented in Environmental Systems Research Inc. (1999–2005) 

ESRI ArcMap 9.1, was used to estimate the altitude of the 

bedrock surface (the base of the aquifer) between control 

points and to estimate the standard error of the estimated 

surface. Kriging was used to contour the generalized configuration of the base of the aquifer rather than manual contouring 

because of errors in point values that result from the accuracy 

of well locations. Manual contouring methods require that 

contour lines honor all data values; thus, contour lines must 

pass between points that are larger than the contour value 

and points that are smaller. Kriging, as implemented in ESRI 

ArcMap, interpolates a grid surface from the point values. 

When two or more point values fall within a grid cell, the 

mean value of the point values in the grid cell is used. Use of 

a mean value in kriging can result in contour lines that appear 

not to honor all data points. Because the locations of wells in 

the DWR well files generally were reported by 40-acre tracts 

within sections, two or more wells may have the same reported 

location even though they actually could be separated by more 

than 1,800 ft.

The bedrock surface (fig. 3) generally slopes to the south 

toward the North Fork Gunnison River. Upslope deflections 

in the contour lines indicate the presence of buried channels 
18 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

in several locations. Generally, the altitude of the base of 

the aquifer is greater than the altitude of the land surface in 

adjacent valleys; thus, the Rogers Mesa aquifer essentially 

is a perched aquifer. However, the altitude of the base of the 

aquifer in the southwest quarter, sec. 23, T. 14 S., R. 93 W., 

may be lower than the altitude of Leroux Creek to the east, 

which implies that locally the Rogers Mesa aquifer is hydraulically connected with Leroux Creek.

Upper Boundary—Water Table

The upper boundary of the aquifer, the water table, 

receives recharge through the unsaturated zone and is a 

specified flow boundary. The water table will fluctuate with 

changes in the rates of infiltration of recharge and pumping 

of nearby wells. The altitude of the water table (fig. 8) was 

estimated from the reported depth to water for 115 wells from 

the DWR well database. The altitudes of the water table at 

the wells were calculated by subtracting the reported depth 

to water from the estimated altitude of the land surface from 

the national elevation dataset (U.S. Geological Survey, 2007). 

Kriging also was used to estimate the altitude of the water 

table between control points and to estimate the standard 

error of the estimated surface. Because the reported depths to 

water that were used to estimate the altitude of the water table 

are from a wide range of dates (October 13, 1964, through 

February 28, 2006), figure 8 should be considered only an 

approximation of the water-table surface. Undoubtedly, variations of recharge and discharge during 1964–2006 would have 

caused the water table to fluctuate. Ideally, water levels used 

to prepare a map of the water table would be contemporaneous 

measurements.

Lateral Boundaries—Aquifer Extent

The lateral extent of the Rogers Mesa aquifer initially 

was assumed to coincide with the extent of “older alluviums 

and gravels” as mapped by Day and others (1999; fig. 3). The 

lateral extent of the aquifer (fig. 8) was modified on the basis 

of drillers’ logs, field reconnaissance, and topographic expression. Detailed field mapping of the contact of the alluvial-fan 

deposits with the sedimentary rocks could improve definition 

of the aquifer’s lateral extent and the altitude of the base of the 

aquifer.

Where water-table contours (fig. 8) are perpendicular 

to the lateral boundaries of an isotropic aquifer, the hydraulic gradient across the boundary is zero and there is no flow 

across the boundary. For practical purposes, where watertable contours are perpendicular to an aquifer boundary, the 

boundary can be considered a specified no-flow boundary. 

Because the predominant slope of the base of the Rogers 

Mesa aquifer is toward the south, no-flow boundaries occur 

locally on the southern sides of gullies that are eroded through 

the alluvial-fan deposits. Where water-table contours (fig. 8) 

are not perpendicular to the lateral boundary of the aquifer, 

ground water is flowing across the boundary and the boundary 

is a specified head boundary. The water table in the Rogers 

Mesa aquifer adjacent to Leroux Creek Valley generally slopes 

easterly, indicating a potential for subsurface flow towards 

Leroux Creek. The water table in the southwest quarter of 

sec. 23, T. 14 S., R. 93 W., slopes away from Leroux Creek 

Valley toward the aquifer, indicating that this reach of Leroux 

Creek may be losing water to the Rogers Mesa aquifer. Confirmation of a hydraulic connection between Leroux Creek and 

the Rogers Mesa aquifer would require more detailed field 

mapping and test drilling.

Hydraulic and Storage Properties

Ideally, the hydraulic and storage properties of an aquifer 

are determined by controlled tests, referred to as “aquifer 

tests.” In the absence of aquifer tests, however, the hydraulic 

and storage properties of an aquifer often are estimated using 

available data from drillers’ pumping tests, pump-installation 

tests, and lithologic logs. Drillers’ pumping tests and pumpinstallation tests can be used to estimate the specific capacity 

of wells and the relative hydraulic properties of an aquifer. 

When results from aquifer tests and laboratory tests of cores 

are not available, the storage properties of an aquifer can be 

estimated from lithology of the deposits or rocks. The storage 

properties (porosity, specific yield, and specific retention) 

of the Rogers Mesa aquifer were estimated on the basis of 

lithologic descriptions from drillers’ logs and specific yield 

and specific retention values for similar geologic materials 

(Robson, 1993).

The specific capacity of a well is the ratio of the pumping 

rate and the drawdown caused by pumping. Drawdown is the 

water-level change, the difference between the static water 

level prior to pumping and the water level at some time after 

pumping began. The specific capacity of a well can be used 

to estimate aquifer transmissivity. However, aquifer transmissivity generally is underestimated by the specific capacity of 

a well because specific capacity of a well may be substantially affected by well construction and development, the 

pumping rate, and duration of the test. Drillers’ pumping 

tests and pump-installation tests often are used to estimate 

the specific capacity of wells but are subject to large errors. 

The principal sources of error in drillers’ pumping tests and 

pump-installation tests likely are inaccurate measurements of 

well discharge, static water level, and pumping water level. 

If the wells in an area have similar construction characteristics, however, analyses of drillers’ pumping tests and pumpinstallation tests may provide an estimate of the relative 

hydraulic characteristics of the aquifer.

Data were available from drillers’ pumping tests of 

99 wells and from pump-installation tests for 67 wells 

completed in the Rogers Mesa aquifer; 60 of the wells had 

both drillers’ pumping and pump-installation tests. The 

estimated specific capacity of the wells was calculated by 

dividing the reported pumping rate by the difference between 

the reported static and pumping water levels. The statistical 

distributions of estimated specific capacity for two classes of 

wells, small-capacity wells with reported pumping rates of 
3

5 4

2 1

2 3

3 4 3 5

3 3

2 8

2 6

2 7

2 1

3 2

2 9

2 2

2 0

8

3 6

2 4

2 5

9 1 0 11 1 2

1 9

3 0

6

1 4 1 3

3 1

7

1 5

5,800

5,600

5,600

5,500

5,500

5,700

5,400

5,400

5,500

 10 to 20

 20 to 30

 30 to 40

 40 to 50

 Less than 10

 No data

Standard error of estimated

 altitude (feet)

Approximate extent of Rogers Mesa aquifer

Water table—Shows line of equal altitude of water table. Contour interval 20 feet.

 North American Vertical Datum of 1988

Irrigation canal or ditch

Spring with decreed water right

Other spring or seep—Shows location of spring or seep from the U.S. Geological

 Survey National Water Information System

Control point—Shows location of control point used to estimate altitude of water

 table, in feet. North American Vertical Datum of 1988

Altitude of stream—Shows approximate location where stream crosses index

 topographic contour. Number is altitude, in feet. North American Vertical Datum 

 of 1988

EXPLANATION

T. 14 S.

T. 15 S.

R. 93 W. Universal Transverse Mercator projection, Zone 13

North American Datum of 1983

0 1 2 MILES

0 1 2 KILOMETERS

38°49’

38°48’

38°47’

38°46’

107°49’ 107°48’ 107°47’ 107°46’ 107°45’

North

Fork

Gunnison River

107°44’

R O G E R S M E S A

Fire Mountain Canal

Highline Ditch

Leroux Creek

Figure 8. Generalized configuration and altitude of the water table, and locations of springs, Rogers Mesa, Delta County, Colorado.

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 19
20 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

less than 50 gal/min and large-capacity wells with reported 

pumping rates of 50 gal/min or greater, are shown in figure 9. 

The common reporting unit for specific capacity of gallons 

per minute per foot (gal/min/ft) of drawdown was converted 

to consistent units of cubic feet per day per foot of drawdown 

[(ft3/d)/ft]. The consistent units of cubic feet per day per foot 

[(ft3/d)/ft] is dimensionally equivalent to units of square feet 

per day (ft2/d).

For small-capacity wells, obvious differences exist 

between specific-capacity values estimated on the basis of 

drillers’ pumping tests and those estimated on the basis of 

pump-installation tests (fig. 9). The median estimated specificcapacity value from pump-installation tests of small capacity 

wells of 361 (ft3/d)/ft (1.88 (gal/min)/ft) was about 4 times 

greater than the median value from drillers’ pumping tests of 

96 (ft3/d)/ft (0.5 (gal/min)/ft). The difference in the estimated 

values may result from additional well development, differences in pumping methods, and differences in measurement 

of pumping rates and static and pumping water levels. Drillers’ pumping tests commonly are done as the well is being 

developed by the use of a bailer. Pump-installation tests generally are done after well development and by the use of a well 

pump.

The estimated specific-capacity values from six tests of 

large-capacity wells ranged from about 500 to 21,700 (ft3/d)/ft 

(about 2.7 to 113 (gal/min)/ft) and had a median value of 

about 3,200 ft3/d/ft (about 16.6 (gal/min)/ft). The estimated 

specific-capacity values from drillers’ pumping tests and 

pump-installation tests of large-capacity wells were nearly 

identical. The ninefold difference between the median 

estimated specific capacity values from pump-installation tests 

of small- and large-capacity wells (fig. 9) may result from 

differences in well construction and development. Although a 

specific-capacity test is done to test the capacity of a well to 

yield water, the specific capacities of wells often are used to 

estimate aquifer transmissivity when aquifer-test results are 

not available (Theis, 1963; Lohman, 1979; Driscoll, 1986). 

Because specific-capacity tests are affected by test conditions, 

well construction, and well development, they often underestimate the transmissivity of the aquifer.

The transmissivity of an aquifer is a measure of the 

ability of an aquifer to transmit water through a unit width 

of an aquifer under a unit hydraulic gradient (Lohman and 

others, 1972). Though spoken of as a property of the aquifer, 

it also embodies the saturated thickness of the aquifer and the 

density and viscosity of the ground water. The transmissivity of the Rogers Mesa aquifer has not been determined by 

aquifer test. On the basis of the estimated specific capacity 

of wells completed in the aquifer, the estimated transmissivity of the Rogers Mesa aquifer ranges from a few hundred to 

20,000 or more ft2/d. Because transmissivity is the product of 

the saturated thickness and the hydraulic conductivity of the 

aquifer, variations in hydraulic conductivity and in saturated 

thickness can result in large variability of aquifer transmissivity.

Hydraulic conductivity is defined as the volume of water 

at the existing kinematic viscosity that will move in unit time 

under a unit hydraulic gradient through a unit area measured 

at right angles to the direction of flow (Lohman and others, 

1972). Although hydraulic conductivity can vary with direction of measurement, in this report the hydraulic conductivity 

of the aquifer is assumed isotropic in the horizontal plane. 

The horizontal hydraulic conductivity of the Rogers Mesa 

aquifer was estimated by dividing the estimated aquifer 

transmissivity, which was estimated on the basis of drillers’ 

pumping and pump-installation tests, by the saturated thickness of the aquifer. The saturated thickness of the aquifer was 

estimated by subtracting the reported static water level from 

the reported depth to shale, sandstone, or, if the depth to shale 

or sandstone was not reported, the reported total well depth. 

Estimated horizontal hydraulic conductivity values ranged 

from less than 1 to about 350 ft/d and had a median of about 

6 ft/d. A horizontal hydraulic conductivity of 6 ft/d is near the 

low range of hydraulic conductivity for fine-grained or silty 

sand (Freeze and Cherry, 1979, table 2.2, p. 29) and likely is 

smaller than the hydraulic conductivity typical for the silty 

sand and gravel (alluvial-fan deposits) on Rogers Mesa. The 

horizontal hydraulic conductivity values of the Rogers Mesa 

aquifer likely are greater than the values estimated from the 

drillers’ pumping and pump-installation tests. The range of 

hydraulic conductivity for silty sand and gravel is approximately 0.1 to 500 ft/d (Freeze and Cherry, 1979, table 2.2, 

p. 29). On the basis of the water-budget analysis (discussed 

later in this report) and the lithology of the alluvial-fan deposits, the median horizontal hydraulic conductivity of the Rogers 

Mesa aquifer likely is nearer to the upper range of hydraulic 

conductivity values for silty sand and gravel and is underestimated by drillers’ pumping and pump-installation tests.

The vertical hydraulic conductivity of the Rogers Mesa 

aquifer, as estimated from the hydraulic conductivity of soils 

at 3- to 5-ft depths (U.S. Department of Agriculture, Natural 

Resources Conservation Service, 2007a), is about 1.2 to 4 ft/d. 

The large difference between the estimated horizontal and 

vertical hydraulic conductivities of the Rogers Mesa aquifer 

is typical of alluvial deposits. The heterogeneity and bedded 

nature of alluvial deposits, including alluvial-fan deposits, 

imparts a strong anisotropy to average properties of large 

volumes of an aquifer (Freeze and Cherry, 1979, p. 148). 

Aquifer tests and laboratory tests of core samples from the 

alluvial-fan deposits are needed to better define the transmissivity, hydraulic conductivity, and storage properties of 

the aquifer but are relatively expensive to conduct and often 

difficult to interpret.

For the most part, lithologic descriptions of subsurface 

materials from driller’s logs are subjective and too general 

to be useful in estimating vertical variations in grain size of 

the alluvial-fan deposits. The alluvial-fan deposits consist of 

a mixture of particles of various sizes that range in diameter 

from less than 0.02 millimeter (clay and silt) to greater than 

1 meter (boulders). Slichter (1899; as cited in Lohman, 1979) 
Figure 9. Estimated specific capacity for small- and large-capacity wells, Rogers 

Mesa, Delta County, Colorado.

Drillers’ pumping test

Pump-installation test

ESTIMATED SPECIFIC CAPACITY, IN CUBIC FEET PER DAY PER FOOT OF DRAWDOWN

SMALL CAPACITY

Pumping rate less than

 50 gallons per minute

LARGE CAPACITY

Pumping rate 50 gallons

 per minute or more

Interquartile range (IQR)

Median

Far outlier (data value more 

 than 3 times the IQR outside

 the quartile)

n = 61

n = 93

n = 6 n = 6

n, number of tests

1

10

100

1,000

10,000

Outlier (data value equal or

 less than 3 and more than 

 1.5 times the IQR outside 

 the quartile)

25th percentile

75th percentile

75th percentile 

plus 1.5 times 

interquartile range

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 21

demonstrated that the range of porosity for spherical particles 

of equal size ranges from about 0.26 to 0.48. Because alluvialfan deposits are heterogeneous mixtures of different sized 

particles, the porosity of the alluvial-fan deposits likely is 

near the lower end of the range of porosity for equal-sized 

spheres and is assumed to be 0.3. With respect to water, the 

porosity of an aquifer consists of two parts: pores that will 

drain by gravity (specific yield) and those that will not drain 

by gravity (specific retention). The specific yield of an aquifer 

is the ratio of the volume of water in an aquifer that will drain 

by gravity to the total volume of the aquifer (Lohman and 

others, 1972). The specific retention of an aquifer is the ratio 

of the volume of water that is retained in the aquifer against 

the force of gravity to the total volume of the aquifer (Lohman 

and others, 1972). Assuming a porosity of 0.3 and that specific 

retention equals 0.08 (the available water capacity of soils 

on Rogers Mesa at 3- to 5-ft depths; U.S. Department of 

Agriculture, Natural Resources Conservation Service, 2007a), 

the specific yield of the Rogers Mesa aquifer is an estimated 

0.22 (0.3–0.08 = 0.22). Aquifer tests and laboratory tests of 

core samples could better define the storage properties of the 

aquifer.

Saturated Thickness and Aquifer Storage

Saturated thickness of the Rogers Mesa aquifer (fig. 10) 

was estimated as the difference between the altitude of the 

water table (fig. 8) and the altitude of the base of the aquifer 

(fig. 3). Saturated thickness was not estimated for about 

10 percent of the areal extent of the aquifer, primarily near the 

edges of the aquifer, because there were too few well data to 

define the water table and the bedrock surfaces. The estimated 

saturated thickness ranged from a minimum of about 18 ft to 

a maximum of about 130 ft. In some areas on Rogers Mesa, 

the aquifer is saturated near the contact of the alluvial-fan 

deposits with the underlying sedimentary rock, as indicated 

by the occurrence of seeps and springs, but in some areas, the 

alluvial-fan deposits are unsaturated at the contact with the 

underlying sedimentary rock (fig. 4).

The volume of saturated aquifer was estimated by 

subtracting the altitude of the base of the aquifer (fig. 3) 

from the altitude of the water table (fig. 8) and multiplying by the area of the aquifer. The area of the aquifer was 

determined by dividing the areal extent of the aquifer into 

blocks or cells, each about 164 ft by 164 ft, then summing 
22 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

the saturated volumes of all grid cells within the areal extent 

of the aquifer. The estimated volume of saturated aquifer 

is about 1.52 x1010 ft3 (15.2 billion cubic feet). The volume 

of water in storage in the aquifer equals the product of the 

volume of saturated aquifer and the estimated porosity (0.3) 

of the aquifer. The estimated volume of water in storage in 

the aquifer is about 4.56 x109 ft3 (1.52 x1010 ft3 * 0.3 = 4.56 

x109 ft3) or about 104,700 acre-ft. Assuming a specific yield 

of about 0.22 and a specific retention of about 0.08, about 

76,800 acre-ft of water could drain from the Rogers Mesa 

aquifer by gravity and about 27,900 acre-ft would be held 

(retained) against the force of gravity.

The volume of unsaturated aquifer above the water 

table, including the soil zone, was estimated by subtracting 

the altitude of the water table (fig. 8) from the altitude of the 

land surface. The estimated volume of unsaturated alluvialfan deposits and soils on Rogers Mesa is about 1.89 x1010 ft3

. 

Assuming a specific retention of 0.08, a minimum of about 

1.51 x109 ft3 (1.89 x1010 ft3 * 0.08 = 1.51 x109 ft3) or about 

34,700 acre-ft of water is retained between the land surface 

and the water table. Assuming a specific yield of 0.22, the 

amount of unsaturated pore space between the land surface 

and the water table is about 4.16 x109 ft3 (1.89 x1010 ft3 * 0.22 

= 4.16 x109 ft3) or about 95,450 acre-ft.

Well Yields

The reported yields (pumping rates) of wells on Rogers 

Mesa range from less than 1 to 500 gal/min (fig. 11) and 

generally are adequate for residential supplies. The median 

reported yield for commercial and residential (small-capacity) 

wells was 15 gal/min (fig. 11). However, results from drillers’ 

pumping tests and pump-installation tests (fig. 10) indicate 

that many of the small-capacity wells on Rogers Mesa cannot 

maintain pumping rates of 15 gal/min for long periods. The 

typical volume of water permitted for self-supplied in-house 

use in Colorado is 0.3 acre-ft/yr (Colorado Division of Water 

Resources, 2006). A well capable of producing 15 gal/min 

could withdraw 0.3 acre-ft/yr while pumping less than 

20 minutes per day. Pumping rates for domestic and residential wells of only a few gallons per minute also can yield an 

adequate supply for in-house use. An estimated 76,800 acre-ft 

of ground water is physically available for withdrawal within 

the boundaries of the Rogers Mesa aquifer and well yields 

generally are adequate to supply in-house water use. However, 

increased ground-water pumping may not be sustainable 

and ultimately could decrease the volume of ground water 

discharged to seeps, springs, and streams, and could decrease 

the saturated thickness at and yields of existing wells.

Sustainability

For a subdivision’s water supply to be sustainable, the 

rate of withdrawal cannot exceed the capture of additional 

recharge and other discharge from the aquifer. Recharge and 

discharge conditions of the aquifer must be quantified so the 

potential effects of increased pumping by new wells can be 

anticipated. A water budget is an accounting of the flow in and 

out and the change in storage of water in a hydrologic system. 

A water budget provides a preliminary means of evaluating 

the relative importance of recharge and discharge processes. 

However, a water budget is only a preliminary evaluation 

and cannot be used to predict when and where the effects of 

additional ground-water withdrawals will occur. A numerical ground-water flow model may be needed to evaluate the 

sustainability of a ground-water supply and the potential 

effects of additional pumping on the hydrologic system.

Water Budget

A water budget is based on the principle of conservation 

of mass—inflow minus outflow equals change in storage. The 

inflow and outflow components of a water budget often are 

estimated because much of the data needed to prepare a water 

budget are not readily available. Although a water budget 

is an estimate and has unknown error, the development of a 

water budget helps focus attention on the interconnectedness 

of a hydrologic system and the relative contribution of the 

various components of the system. A hydrologic system, as 

used in this report, includes both surface and subsurface water 

and the processes by which water is exchanged between the 

atmosphere, surface, and subsurface.

A quasi-steady-state water budget was prepared for 

Rogers Mesa as part of the evaluation of the sustainability of 

the aquifer. A quasi-steady-state condition means that inflow 

approximately equals outflow and there is no substantial 

change in ground-water storage. Although inflow, outflow, 

and ground-water storage of Rogers Mesa vary seasonally, the 

average water budget for Rogers Mesa for periods greater than 

a few years in duration likely approximates a quasi-steadystate condition. Surface water diverted from the North Fork 

Gunnison River and Leroux Creek for irrigation on Rogers 

Mesa is the principal source of recharge to the aquifer and 

was relatively constant during irrigation years 1999–2006. 

Although the use of ground water for irrigation is not 

measured, it is relatively small in comparison to the use of 

surface water for irrigation. However, few long-term waterlevel data or records of spring discharge from the Rogers Mesa 

aquifer are available to confirm the assumption of quasisteady-state conditions.

The estimated annual water budget for Rogers Mesa 

(table 3) was prepared for average annual conditions during 

irrigation years 1999–2006. The period 1999–2006 was 

selected for estimating the water budget from Rogers Mesa 

because meteorological data were available to estimate 

consumptive use (evapotranspiration) from irrigated land. The 

irrigation year was used in the water budget because surfacewater diversions in Colorado are reported on that basis. The 

water budget for Rogers Mesa includes estimates of inflows to 

and outflows from the land surface and the aquifer. The water 

budget was used to estimate recharge to the aquifer from the 

surface and to estimate discharge at the aquifer boundaries. 
Figure 10. Generalized saturated thickness of the Rogers Mesa aquifer, Delta County, Colorado.

 20 to 40

 40 to 60

60

40

80

10 0

60

6

8 0

40

40

40

60

80

40

60

40

A'

4

40

40

60

40

A

B

C

B'

C'

80

A A'

0

60

80

0

60

60

100

3

5 4

2 1

2 3

3 4 3 5

3 3

2 8

2 6

2 7

2 1

3 2

2 9

2 2

2 0

8

3 6

2 4

2 5

9 1 0 11 1 2

1 9

3 0

6

1 4 1 3

3 1

7

1 5

EXPLANATION

Saturated thickness (feet)

 No data

 18 to 20

 100 to 120

 120 to 130

 60 to 80

 80 to 100

Approximate extent of Rogers Mesa aquifer

Line of section—Shows location of section used for 

 estimate of subsurface flow. Letters are section name

Saturated thickness contour—Shows line of equal

 saturated thickness. Contour interval 20 feet

Irrigation canal or ditch

T. 14 S.

T. 15 S.

R. 93 W. Universal Transverse Mercator projection, Zone 13

North American Datum of 1983

0 1 2 MILES

0 1 2 KILOMETERS

38°49’

38°48’

38°47’

38°46’

107°49’ 107°48’ 107°47’ 107°46’ 107°45’

North

Fork

Gunnison River

107°44’

R O G E R S M E S A

Fire Mountain Canal

Highline Ditch

Leroux Creek

Fire Mountain

Canal

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 23
24 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

The water-budget estimates of recharge to and discharge from 

the aquifer were used with Darcy’s law (Lohman and others, 

1972, eq. 2) to estimate the average hydraulic conductivity of 

the aquifer.

Surface Inflow

The principal sources of inflow to the surface on Rogers 

Mesa are surface-water diversions from the North Fork Gunnison River and Leroux Creek for irrigation of crops (alfalfa, 

corn, and small grains), grass pasture, and orchards. Irrigation with ground water and precipitation also are sources of 

inflow to the surface. Because the amounts of surface-water 

diversions are reported to the DWR at the points of diversion, the reported amounts of diversions can include water 

used upstream from Rogers Mesa and conveyance losses 

that occur between the points of diversion and Rogers Mesa. 

Conveyance loss refers to the water that is lost by evaporation, 

evapotranspiration, seepage, and spillage, as irrigation water 

travels from its source to the irrigated field (Price, 1995). 

Reported amounts of monthly diversions to Fire Mountain 

Canal and Highline Ditch were decreased on the basis of the 

proportion of the area on Rogers Mesa irrigated with water 

from each system to the total irrigated area for each system. 

The estimated amount of diversions by Fire Mountain Canal 

and Highline Ditch to Rogers Mesa also were decreased for 

conveyance losses that occur upstream from Rogers Mesa. 

Published estimates of conveyance losses from irrigation 

canals and ditches are not available for the study area. The 

estimated amounts of diversions that were delivered by Fire 

Mountain Canal to Rogers Mesa were decreased by 25 percent 

for upstream conveyance losses; similarly, the estimated 

amounts of surface-water diversions that were delivered by 

Highline Ditch to Rogers Mesa were decreased by 10 percent 

for upstream conveyance losses. Conveyance losses were 

not estimated for the other ditches (table 3) that divert water 

for irrigation on Rogers Mesa. The mean (average) of the 

estimated annual diversions for irrigation on Rogers Mesa 

during irrigation years 1999–2006 was about 34,311 acre-ft 

(table 3). Variability in estimated annual diversions to Rogers 

Mesa during 1999–2006 was relatively small, as indicated 

by the standard deviation for estimated annual surface-water 

diversions of about 6,162 acre-ft. The minimum of estimated 

annual diversions for irrigation on Rogers Mesa during irrigation years 1999–2006 was 21,153 acre-ft, during irrigation 

year 2002, and the maximum was 40,190 acre-ft, during irrigation year 2005. Fire Mountain Canal, Highline Ditch, and 

Leroux Creek Ditch (fig. 1) are estimated to have supplied, 

on average, about 89 percent of the surface water diverted to 

Rogers Mesa (table 3).

An estimated 976 acre-ft/yr of ground water may be used 

to irrigate an estimated 723 acres of cropland and pasture on 

Rogers Mesa, and an estimated 294 acre-ft/yr of ground water 

may be used to irrigate an estimated 78 acres of lawn and 

garden on Rogers Mesa. However, ground-water use for irrigation on Rogers Mesa generally is not measured or reported 

and field investigations are needed to corroborate estimated 

ground-water use for irrigation.

Average annual precipitation during irrigation years 

1999–2006 at station HOT01 was about 0.87 ft (10.4 in.). 

Assuming uniform precipitation on the 7,641-acre study area, 

the volume of precipitation averages about 6,647 acre-ft/yr. 

About 4,916 acre-ft of the annual precipitation occurs 

on irrigated cropland and pasture and the remainder, 

1,731 acre-ft, occurs on nonirrigated land.

Surface Outflow

The largest components of outflow from the surface in 

the water budget for Rogers Mesa are infiltration of irrigation 

water and precipitation through the soil and unsaturated zone 

to the water table and the consumptive use (evapotranspiration) of water by irrigated crops, grass pasture, and orchards 

(table 3). Other minor outflows from the surface include 

consumptive use from lawns and gardens; and evapotranspiration from non-irrigated land, riparian areas, and ponds. 

Because infiltration of irrigation water and precipitation is not 

measured, it was estimated as the difference between inflow to 

and other outflows from the surface.

Monthly consumptive use of water by crops, grass 

pasture, and orchards during irrigation years 1999–2006 

was estimated for irrigated areas on Rogers Mesa (Colorado 

Division of Water Resources, and Colorado Water Conservation Board, 2007) from the following information:

1. Daily reference evapotranspiration rates from measurements at COAGMET meteorological station HOT01 

(location shown in figure 6) were available online at 

http://ccc.atmos.colostate.edu/~coagmet/; 

2. Seasonal crop coefficients (Broner, 1993, table 4); and

3. Geographic information system (geospatial) data for 

irrigated areas in 2000 from the Colorado Decision 

Support Systems website (http://cdss.state.co.us/DNN/

GIS/tabid/67/Default.aspx).

Daily consumptive use was calculated for each crop type 

as the product of daily reference evapotranspiration rate and 

the seasonal crop coefficient. Monthly consumptive use of 

water was calculated by summing the daily values by month. 

The estimates of monthly consumptive use for each crop type 

were summed for each irrigation year from 1999 through 

2006. The annual rates of consumptive use were multiplied by 

the estimated acreage for each crop to estimate average annual 

consumptive use during irrigation years 1999 through 2006 

(table 3). Estimates that are more precise might be achieved by 

calculating consumptive use on a daily basis and incorporating 

soil-moisture conditions to estimate daily infiltration below the 

root zone.

Evapotranspiration was estimated to consume about 

92 percent of precipitation on non-irrigated land. During the 

growing season, April through October, rates of evapotranspiration greatly exceed rates of precipitation (fig. 5) and there is 
Figure 11. Reported yields of wells, Rogers Mesa, Delta County, Colorado.

Irrigation wells

Commercial and residential wells

Primary use of water 

1

10

100

REPORTED WELL YIELD, IN GALLONS PER MINUTE

Interquartile range (IQR)

Median

Far outlier (data value more 

 than 3 times the IQR outside

 the quartile)

Outlier (data value equal or

 less than 3 and more than 

 1.5 times the IQR outside 

 the quartile)

Median

n = 93 

75th percentile plus 1.5 times IQR n = 16

25th percentile 

minus 1.5 times IQR

75th percentile 

plus 1.5 times IQR

25th percentile

25th percentile 

minus 1.5 times 

IQR

75th percentile

25th percentile

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 25

little potential for recharge from infiltration of precipitation. 

Published estimates of ground-water recharge from precipitation are not available for the study area. Precipitation during 

November through March averaged about 0.25 ft (3 inches). 

Although monthly evapotranspiration during November 

through March of irrigation years 1999–2006 generally 

exceeded precipitation, it was assumed that part of the precipitation during November through March infiltrates below the 

soil zone and recharges the aquifer. Recharge from infiltration 

of precipitation is an assumed 0.07 ft/yr or about 8 percent of 

annual precipitation.

Evapotranspiration by vegetation in riparian areas and 

evaporation from ponds was estimated. Riparian (vegetated) 

area along surface drainages was estimated from a geographic 

information system coverage of hydrologic features and a 

digital image of Rogers Mesa from the National Agricultural Imagery Project (U.S. Department of Agriculture, Farm 

Service Agency, 2007) to be about 10 acres. Areas of ponds 

were estimated from the geographic information system coverage of hydrologic features to be about 10.5 acres. The difference between average annual reference evapotranspiration and 

precipitation of 3.8 ft/yr was assumed to equal the evapotranspiration rate from riparian vegetation and ponds. Annual 

evapotranspiration from riparian areas and evaporation from 

ponds was estimated as the product of area and the assumed 

evapotranspiration rate.

Infiltration of water from the surface to the water table 

was estimated as the difference between the volume of water 

applied naturally by precipitation and artificially by irrigation 

to the surface and the volume consumed by evapotranspiration. 

The combined volume of surface water and ground water for 

irrigation and precipitation on irrigated and nonirrigated land, 

ponds, and riparian areas during irrigation years 1999–2006 

averaged 42,228 acre-ft/yr (table 3). The combined volume of 

estimated consumptive use from the land surface, including 

consumptive use from irrigated land and evapotranspiration 

from nonirrigated land, riparian areas, and ponds, averaged 

11,461 acre-ft/yr during that same period (table 3). The 

difference between the volume of water applied to the surface 

(surface inflow) and that consumed by evapotranspiration 

(surface outflow) averaged 30,767 acre-ft/yr during irrigation years 1999–2006 and is assumed to equal ground-water 

recharge from the surface.

Ground-Water Inflow

Ground-water inflow to the Rogers Mesa aquifer consists 

of infiltration from the surface (30,767 acre-ft/yr), infiltration 

in the subsurface from ISDS, and subsurface inflow. Infiltration from the surface was an estimated 30,767 acre-ft/yr 

during irrigation years 1999–2006. Infiltration in the subsurface from ISDS was assumed to equal 90 percent of in-house 
Table 3. Estimated average annual water budget for Rogers Mesa, Delta County, Colorado, November 1998 through October 2006.

—Continued

[--, not applicable; <, less than]

Water-budget components Number of sites Estimated area 

(acres)

Average 

annual rate 

(feet per year)

Average 

annual volume 

(acre-feet)

Surface inflow

Surface-water diversions (structure number)

Big Gulch Ditch (4000915) -- 144 7.7 1,109

Fire Mountain Canal (4001133) -- 3,489 7.9 20,573

Fleming Ditch (4000922) -- 29 16.9 490

Highline Ditch (4000923)1 -- 857 7.9 6,072

Isom Ditch (4000925) -- 61 8.5 521

Jessie Ditch (4000929) -- 252 4.7 1,176

Leroux Creek Ditch (4000926) -- 685 5.9 4,014

Little Mary Ditch (4000927) -- 56 6.4 356

Ground-water irrigation

Cropland 21 723 1.35 976

Lawn and garden 80 78 3.8 294

Precipitation, irrigated land, and 

lawn and garden

-- 5,651 .87 4,916

Precipitation, nonirrigated land -- 1,990 .87 1,731

Subtotal 42,228

Surface outflow

Streamflow (assumed) 0

Consumptive use, irrigated land

Alfalfa -- 633.6 –2.3 –1,451

Corn -- 13.9 –2.2 –30

Grass pasture -- 3,991.4 –1.6 –6,346

Orchard -- 930.9 –2.0 –1,834

Small grains -- 3.4 –1.9 –6

Consumptive use, lawn and garden -- 78 –1.6 –124

Evapotranspiration, non-irrigated land -- 1,990 –0.8 –1,592

Evapotranspiration from riparian areas -- 10 –3.8 –38

Evapotranspiration from ponds -- 10.5 –3.8 –40

Subtotal –11,461

Surface inflow minus surface outflow 30,767

26 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado
Table 3. Estimated average annual water budget for Rogers Mesa, Delta County, Colorado, November 1998 through October 2006.

—Continued

[--, not applicable; <, less than]

Water-budget components Number of sites Estimated area 

(acres)

Average 

annual rate 

(feet per year)

Average 

annual volume 

(acre-feet)

Ground-water inflow

Infiltration from the surface2 30,767

Infiltration, individual sewage disposal 

systems 

571 -- 0.27 119

Subsurface inflow from north -- -- -- 4,491

Subsurface inflow from Leroux Creek -- -- -- 533

Subtotal 35,910

Ground-water outflow

Estimated pumpage

Commercial wells 3 -- –.3 –1

Domestic wells including 78 acres of 

irrigated lawn and garden

98 -- –3.0 –298

Residential wells 40 -- –.3 –12

Irrigation wells3 21 723 –1.35 –976

Livestock well 1 -- -- 1

Subsurface outflow (excluding discharge of 

springs with decreed rates)

-- -- -- –27,822

Springs with decreed rates 20 -- -- –6,800

Subtotal –35,910

Change in ground-water storage (ground-water inflow minus ground-water outflow) 0

1

Reported diversions by the Fire Mountain Canal and Highline Ditch were reduced for upstream water use and conveyance loss.

2

Infiltration from the surface was estimated as the difference between surface inflow and surface outflow. 

3

The average annual volume of water pumped by irrigation wells was estimated from decreed rates of diversion.

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 27
28 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

water use for 3 commercial, 98 domestic, and 40 residential 

wells, and for the 430 active water taps. Estimated infiltration from ISDS in the subsurface was about 119 acre-ft/yr. 

Although the volume of recharge from ISDS is relatively small 

in comparison with other water-budget components, infiltration of effluent from ISDS could affect the quality of ground 

water.

Subsurface flow equals the product of aquifer width 

(perpendicular to flow), saturated thickness, hydraulic 

conductivity, hydraulic gradient, and time. Subsurface 

inflow into the Rogers Mesa aquifer from the north (fig. 10, 

Section A–A’) was estimated for steady flow as the product of 

saturated cross-sectional area, an assumed average hydraulic 

conductivity of 107 ft/d, hydraulic gradient, and the cosine 

of the estimated angle between the water-table contours and 

section A–A’. The assumed average hydraulic conductivity 

value for the Rogers Mesa aquifer (107 ft/d) was the value 

needed to balance subsurface flow in the water budget. The 

cosine of the angle between the water-table contours and 

segments of section A–A’ was included in the computation 

because section A–A’ is not parallel to the water table contours 

(fig. 8). By definition, the hydraulic gradient is in the direction 

of maximum decrease in head (Lohman and others, 1972), 

which is perpendicular to water table contours in an isotropic 

aquifer. Estimated subsurface flow across section A–A’ was 

535,925 ft3/d or about 4,491 acre-ft/yr.

Leroux Creek, North Fork Gunnison River, and Big 

Gulch have cut through the alluvial-fan deposits into 

sedimentary rocks and as a result, their valley floors generally are topographically lower than the base of the Rogers 

Mesa aquifer. Therefore, the boundary of the Rogers Mesa 

aquifer generally is a discharge boundary at which ground 

water discharges at seeps and springs or into slope deposits. However, in the southwest quarter of sec. 23, T. 14 S, 

R. 93 W., the base of the aquifer likely is at a lower altitude 

than Leroux Creek (fig. 3), and Leroux Creek may be losing 

water to the aquifer. The water-table surface (fig. 8) in that 

area also indicates a potential for flow from Leroux Creek into 

the aquifer along a 1,350-ft long stream reach. Streamflow loss 

from Leroux Creek to the aquifer was estimated as the product 

of an estimated 1,350-ft long stream reach, a saturated aquifer 

thickness of 40 ft (fig. 10), an assumed average hydraulic 

conductivity of 107 ft/d, and a hydraulic gradient of 0.011, to 

be about 63,610 ft3/d or 533 acre-ft/yr. However, the accuracies of the altitudes of the base of the aquifer (fig. 3) and of the 

water table (fig. 8) are inadequate to confirm a direct hydraulic 

connection between the stream and aquifer. Additional field 

investigations are needed to confirm streamflow loss from 

Leroux Creek to the aquifer. Streamflow loss to the aquifer of 

this magnitude possibly could be measured for low streamflow 

rates.

Ground-Water Outflow

Ground water pumped by wells represents a relatively 

small portion of total ground-water outflow from Rogers Mesa 

aquifer. Ground-water outflow from the Rogers Mesa aquifer 

is primarily subsurface outflow at the aquifer boundary and 

discharge to springs and seeps.

In 2004, 98 domestic wells, 40 residential wells, 

21 irrigation wells, 3 commercial wells, and 1 livestock well 

had permits to pump water from the Rogers Mesa aquifer. 

Ground-water withdrawals are not routinely monitored or 

reported. Estimated ground-water withdrawal by permitted 

wells from Rogers Mesa aquifer was about 1,290 acre/ft/yr 

(table 3).

Assuming that there was no long-term change in groundwater storage during irrigation years 1999–2006, subsurface 

flow toward the downgradient boundaries of the aquifer equals 

the average infiltration to the water table plus subsurface 

inflow from the north (fig. 10, section A–A’) and from Leroux 

Creek minus ground-water withdrawals by wells. Using this 

assumption, subsurface flow toward the downgradient boundaries of the aquifer and including estimated discharge to 

springs is an estimated 34,622 acre-ft/yr (about 48 ft3/s).

Subsurface flow through sections B–B’ and C–C’

(fig. 10) toward the downgradient boundaries of the aquifer 

was estimated as the product of saturated cross-sectional 

areas, hydraulic gradients, and hydraulic conductivity. The 

saturated cross-sectional areas (the product of aquifer width 

and saturated thickness) of sections B–B’ and C–C’ were 

about 195,000 and 1,089,000 ft2, respectively; the average 

hydraulic gradients perpendicular to sections B–B’ and C–C’

were 0.02 and 0.018, respectively; and the average hydraulic 

conductivity was an assumed 107 ft/d. Combined subsurface flow through sections B–B’ and C–C’ was an estimated 

21,800 acre-ft/yr. The estimated flow through sections B–B’

and C–C’ is less than the estimated 34,622 acre-ft/yr of 

subsurface outflow from the aquifer because net recharge 

(infiltration from the surface minus well discharge) downgradient from sections B–B’ and C–C’ is about 12,822 acre-ft/yr.

The assumed hydraulic conductivity of 107 ft/d that was 

used to estimate subsurface flow for the Rogers Mesa aquifer 

is substantially larger than the median hydraulic conductivity 

of 6 ft/d that was estimated from drillers’ pumping tests and 

pump-installation tests but is within the range of plausible 

values for unconsolidated sand and gravel (Freeze and Cherry, 

1979, table 2.2, p. 29). Aquifer tests are needed to determine 

the hydraulic properties of the Rogers Mesa aquifer. The 

average hydraulic conductivity value of 107 ft/d is a relative 

value; if the components of the water budget, especially infiltration from the surface, can be estimated more precisely, the 

average hydraulic conductivity value for the aquifer also can 

be estimated more precisely.

Ground-Water Storage

Although the volume of water stored in the Rogers Mesa 

aquifer likely varies seasonally with changes in recharge and 

discharge, seasonal changes in storage could not be evaluated 

because no long-term water-level data are available for the 

aquifer. The estimated volume of ground water stored in the 
Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 29

saturated part of the aquifer is about 107,000 acre-ft, but only 

part of that water could be withdrawn by wells. An estimated 

37,000 acre-ft of water also is retained in the unsaturated zone 

by capillary forces.

Water-Budget Errors

Errors in the individual components of the water budget 

for Rogers Mesa (table 3) likely are large and increase uncertainty in the evaluation of the availability and sustainability of 

ground water on Rogers Mesa. Because errors in individual 

components of a budget are additive, they are propagated 

through the budget when it is used to estimate other components, such as ground-water recharge and discharge. The 

largest errors in the ground-water budget for Rogers Mesa 

result primarily from errors in the estimated volume of irrigation water applied to the land surface and in estimates of 

consumptive use of water by irrigated crops, grass pasture, and 

orchards.

Uncertainty in estimated recharge to the aquifer can be 

decreased if errors in the other components of the budget can 

be decreased. Although diversions by Fire Mountain Canal, 

Highline Ditch, and Leroux Creek Ditch are measured at their 

points of diversion, actual deliveries of surface-water diversions to Rogers Mesa are not reported. When the diversion 

point is distant from the place of water application, estimates 

of conveyance loss and use of water outside the study area 

introduce unknown errors in the estimated amount of water 

delivered to Rogers Mesa.

Suitability

The suitability of ground water from individual residential wells for domestic use in a subdivision is a function of 

the physical, chemical, and biological characteristics of the 

water. Data from numerous sites in the Rogers Mesa area 

are available from the National Water Information System 

(NWIS); however, results are limited principally to measurements of physical properties of water and selenium concentrations. Analytical results in the NWIS for physical properties 

and concentrations of major ions, nutrients, and selected trace 

constituents were available for only six ground-water wells 

on Rogers Mesa (table 4). Analytical results for another four 

ground-water wells (domestic or residential wells) on Rogers 

Mesa (table 4) were available from the Delta County Environmental Health Division. Data from the NWIS are available at 

http://waterdata.usgs.gov/co/nwis/. Values of physical properties and concentrations of selected chemical constituents in 

ground water from Rogers Mesa aquifer are included in a 

reconnaissance report on the ground-water resources in North 

Fork Gunnison River Basin (Ackerman and Brooks, 1986).

Collection of ground-water samples by the USGS for 

biological analyses is not routine, and few data are available 

for the study area in published reports or publicly accessible databases. The Delta County Environmental Health 

Division reviews subdivision proposals for adequacy of private 

drinking-water supplies. Testing is required to prove that the 

water is a safe potable supply (Delta County Environmental 

Health Division, 2007). The Colorado Department of Public 

Health and Environment (2002) provides information about 

the safety of drinking water from wells and a list of certified 

laboratories that can test water samples. Bacteriologic sample 

containers are available at the Delta County Environmental 

Health Division office to sample water for contamination.

Values of physical properties and concentrations of 

selenium in surface-water samples are included in table 4 

because those results represent the quality of water diverted 

from streams for irrigation and, in some areas, the quality of 

ground water discharged from the aquifer to surface drainages. Specific conductance of water is a function of the 

concentration and types of dissolved ions in the water and 

is an indicator of the salinity or dissolved-solids content of 

water (Hem, 1985). The variability of specific conductance 

of surface-water samples in the Rogers Mesa vicinity is large. 

Specific conductance values of surface-water samples range 

from 135 μS/cm (Fire Mountain Canal at Leroux Creek) to 

2,650 μS/cm (Big Gulch at Highway 92; table 4). Concentrations of dissolved solids in ground water discharged from the 

Rogers Mesa aquifer towards Big Gulch likely are increased 

by evapotranspiration of water from the soils and by dissolution of minerals the water contacts in the subsurface, as 

indicated by the presence of salt crusts and saline soils along 

Big Gulch. Studies by the Bureau of Reclamation indicate that 

salt loading occurs when seepage from irrigation conveyance 

systems and irrigation return flow passes through highly saline 

soils and the underlying Mancos Shale (Bureau of Reclamation, 2007).

Results for ground-water samples from Rogers Mesa 

(table 4) were compared with Colorado’s drinking-water 

standards (Colorado Department of Public Health and 

Environment, 2005) for selected physical properties and 

chemical constituents. On the basis of these few comparisons, 

ground water from Rogers Mesa aquifer is considered suitable 

for domestic use with a few exceptions. The pH of a sample 

from Doughty Springs (table 4, site-identification number 

384611107453000) was 6.3 standard units, which is below 

the acceptable range of 6.5 to 8.5 standard units. Concentrations of dissolved solids exceed the U.S. Environmental 

Protection Agency Secondary Maximum Contaminant Level 

(SMCL) of 500 mg/L (Colorado Department of Public Health 

and Environment, 2005, table 3–1) for 11 of 12 ground-water 

samples from Rogers Mesa aquifer (table 4). SMCLs are 

non-enforceable guidelines regulating contaminants that may 

cause cosmetic effects (such as skin or tooth discoloration) 

or aesthetic effects (such as taste, odor, or color) in drinking water (U.S. Environmental Protection Agency, 2007b). 

Concentrations of dissolved sulfate exceed the SMCL of 

250 mg/L for 3 of 12 ground-water samples (table 4). Without 

treatment, the large concentrations of dissolved solids, as 

much as 1,250 mg/L, and sulfate, as much as 633 mg/L, may 

limit the use of ground water from Rogers Mesa for drinkingwater supplies.
Table 4. Values of physical properties and concentrations of selected chemical constituents in ground and surface water from Rogers Mesa and vicinity, Delta County, 

Colorado.—Continued[The local names are modified from local names in the U.S. Geological Survey National Water Information System. μS/cm, microsiemens per centimeter; °C, degree Celsius; mg/L, milligrams per liter; NWIS, National Water Information System; GW, ground water; --, no value; DCEHD, Delta County Environmental Health Department; SW, surface water; μg/L, micrograms per liter; <, less than; yellow shading indicates that value exceeds secondary drinking-water standard; pink shading indicates that value exceeds primary drinking-water standard; BD, less than method detection limit. Drinking-water standards are available online at http://www.cdphe.state.co.us/regulations/waterqualitycontroldivision/100301primarydrinkingwater.pdf]

Site identification 

number or station 

name

Local name

Latitude

 (decimal 

degrees)

Longitude

 (decimal 

degrees)

Site

type

Source of

data

Sample 

date

pH 

(standard 

units)

Specific 

conductance 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

as calcium 

carbonate 

(mg/L)

Dissolved 

solids, sum of 

constituents 

(mg/L)

Ground water

384611107453000 Doughty Springs 38.76970669 107.75894817 Spring NWIS 19800626 6.3 4,700 14 -- --384620107455001 Tommy Dowell Spring 38.77220664 107.76450390 Spring NWIS 19770818 7.6 910 13 320 612384621107455601 SC01509303DDB1 38.77248440 107.76617062 Spring NWIS 19780330 8 825 14 350 636384632107460300 SC01509303DBD1 38.77553991 107.76811513 Spring NWIS 19780609 -- 949 13 340 628384656107444401 Seep near Delta Fish 

Hatchery

38.78220666 107.74617013 Seep NWIS 19981014 8.1 748 13.7 -- --

384707107455201 SC01509303AAA1 38.78526201 107.76505951 Well NWIS 19790323 -- 680 13.5 -- --384735107470501 SC01409333ADC1 38.79303960 107.78533794 Well NWIS 19770818 7.6 910 13 360 647384744107441301 SC01409336BAC1 38.79554002 107.73755896 Spring NWIS 19790323 7.5 875 13.5 420 772384753107435601 Seep area in draw below 

Highway 92

38.79804010 107.73283669 Seep NWIS 20001205 8.2 851 7.9 -- --

384800107442201 SC01409325CCD1 38.79998435 107.74005900 Well NWIS 19790323 7.6 875 9 -- --384801107454201 SC01409326CCC1 38.80026182 107.76228170 Well NWIS 19780415 7.5 860 14.5 310 683384809107464501 SC01409327CCC1 38.80248394 107.77978225 Well NWIS 19790323 7.8 900 9 -- --384842107444201 T14SR93W026ADD 

Well near 3300 Road

38.81165072 107.74561465 Well NWIS 20000620 7.5 1,710 14.1 770 1,250

384854107474501 SC01409328BBA1 38.81498369 107.79894956 Well NWIS 19780331 7.5 535 13 280 381384855107450101 Seep along Leroux 

Creek above Duke Ditch

38.81526167 107.75089250 Seep NWIS 20000620 8 1,400 12.4 -- --

384912107482601 Lower seep area along 

Stingley Gulch

38.81987248 107.80769985 Seep NWIS 20001206 7.8 883 3.2 -- --

384918107481801 Seep on right bank of 

Stingley Gulch

38.82151136 107.80547756 Seep NWIS 20001206 7.7 2,190 2.9 -- --

30 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado
Table 4. Values of physical properties and concentrations of selected chemical constituents in ground and surface water from Rogers Mesa and vicinity, Delta County, 

Colorado.—Continued[The local names are modified from local names in the U.S. Geological Survey National Water Information System. μS/cm, microsiemens per centimeter; °C, degree Celsius; mg/L, milligrams per liter; NWIS, National Water Information System; GW, ground water; --, no value; DCEHD, Delta County Environmental Health Department; SW, surface water; μg/L, micrograms per liter; <, less than; yellow shading indicates that value exceeds secondary drinking-water standard; pink shading indicates that value exceeds primary drinking-water standard; BD, less than method detection limit. Drinking-water standards are available online at http://www.cdphe.state.co.us/regulations/waterqualitycontroldivision/100301primarydrinkingwater.pdf]

Site identification 

number or station 

name

Local name

Latitude

 (decimal 

degrees)

Longitude

 (decimal 

degrees)

Site

type

Source of

data

Sample 

date

pH 

(standard 

units)

Specific 

conductance 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

as calcium 

carbonate 

(mg/L)

Dissolved 

solids, sum of 

constituents 

(mg/L)

Ground water—Continued

AG1 3176 L Road 38.814889 107.768860 Well DCEHD -- 7.8 720 -- 318 535JTH1 3144 Highway 92 38.800153 107.770896 Well DCEHD -- 7.9 831 -- 297 624LCA1 1096 3250 Road 38.813052 107.753332 Well DCEHD -- 7.28 700 -- 195 678LF1 1125 3080 Road 38.820951 107.786510 Well DCEHD -- 7.49 1,120 -- -- 784

Surface water

384756107490801 Big Gulch at Highway 92 38.79887271 107.81950568 Stream NWIS 19990512 7.7 2,650 14.5 -- --384756107490801 Big Gulch at Highway 92 38.79887271 107.81950568 Stream NWIS 19990831 7.8 2,140 15.8 -- --384756107490801 Big Gulch at Highway 92 38.79887271 107.81950568 Stream NWIS 19991109 8.2 1,320 8.3 -- --384756107490801 Big Gulch at Highway 92 38.79887271 107.81950568 Stream NWIS 20000314 8.6 1,140 7.3 -- --384842107443901 Leroux Creek at 3300 

Road

38.81165074 107.74478131 Stream NWIS 20000314 8.6 1,010 10.6 -- --

384842107443901 Leroux Creek at 3300 

Road

38.81165074 107.74478131 Stream NWIS 20000620 8.4 1,210 17.5 -- --

384853107451201 Jessie Ditch at 3250 and 

L Roads

38.81470611 107.75394815 Diversion NWIS 20000725 8.2 626 15.8 -- --

384854107450201 Leroux Creek above 

Duke Ditch Diversion

38.81498389 107.75117029 Stream NWIS 20000328 8.5 933 13.9 -- --

384854107450201 Leroux Creek above 

Duke Ditch Diversion

38.81498389 107.75117029 Stream NWIS 20000620 8.4 1,010 17 -- --

384910107482701 Stingley Gulch above 

Big Gulch

38.81953915 107.80800541 Stream NWIS 20001206 8.3 1,250 5.2 -- --

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 31
Table 4. Values of physical properties and concentrations of selected chemical constituents in ground and surface water from Rogers Mesa and vicinity, Delta County, 

Colorado.—Continued[The local names are modified from local names in the U.S. Geological Survey National Water Information System. μS/cm, microsiemens per centimeter; °C, degree Celsius; mg/L, milligrams per liter; NWIS, National Water Information System; GW, ground water; --, no value; DCEHD, Delta County Environmental Health Department; SW, surface water; μg/L, micrograms per liter; <, less than; yellow shading indicates that value exceeds secondary drinking-water standard; pink shading indicates that value exceeds primary drinking-water standard; BD, less than method detection limit. Drinking-water standards are available online at http://www.cdphe.state.co.us/regulations/waterqualitycontroldivision/100301primarydrinkingwater.pdf]

Site identification 

number or station 

name

Local name

Latitude

 (decimal 

degrees)

Longitude

 (decimal 

degrees)

Site

type

Source of

data

Sample 

date

pH 

(standard 

units)

Specific 

conductance 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

as calcium 

carbonate 

(mg/L)

Dissolved 

solids, sum of 

constituents 

(mg/L)

Surface water—Continued

384914107460601 Jessie Ditch Diversion, 

Leroux Creek

38.82053930 107.76894864 Diversion NWIS 20000328 8.3 1,860 10.1 -- --

384915107460801 Leroux Creek above 

Jessie Ditch Diversion

38.82081707 107.76950421 Stream NWIS 20000620 8 2,570 14.7 -- --

384919107481601 Stingley Gulch at West 

Draw

38.82192802 107.80492199 Stream NWIS 20001206 8 1,410 7.1 -- --

384937107463801 Leroux Creek below 

Fire Mountain Canal

38.82692806 107.77783783 Stream NWIS 20000620 8.3 2,020 16.6 -- --

384938107463601 Fire Mountain Canal at 

Leroux Creek

38.82720584 107.77728226 Diversion NWIS 20000620 8.1 135 13.7 -- --

384942107463701 Leroux Creek Diversion at Fire Mountain 

Canal

38.82831694 107.77756005 Diversion NWIS 20000328 8.6 1,340 11.2 -- --

384944107463601 Leroux Creek above 

Fire Mountain Canal

38.82887248 107.77728226 Stream NWIS 20000620 8.5 1,320 13.1 -- --

32 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado
Table 4. Values of physical properties and concentrations of selected chemical constituents in ground and surface water from Rogers Mesa and vicinity, Delta County, 

Colorado.—Continued[The local names are modified from local names in the U.S. Geological Survey National Water Information System. μS/cm, microsiemens per centimeter; °C, degree Celsius; mg/L, milligrams per liter; NWIS, National Water Information System; GW, ground water; --, no value; DCEHD, Delta County Environmental Health Department; SW, surface water; μg/L, micrograms per liter; <, less than; yellow shading indicates that value exceeds secondary drinking-water standard; pink shading indicates that value exceeds primary drinking-water standard; BD, less than method detection limit. Drinking-water standards are available online at http://www.cdphe.state.co.us/regulations/waterqualitycontroldivision/100301primarydrinkingwater.pdf]

Site identification 

number or station 

name

Local name Sample date Calcium (mg/L) Mag- nesium (mg/L) Potassium (mg/L) Sodium (mg/L)

Acid 

neutralizing 

capacity, as 

calcium 

carbonate 

(mg/L)

Alkalinity, 

as 

calcium 

carbonate 

(mg/L)

Bicarbonate 

(mg/L)

Carbonate 

(mg/L)

Chloride 

(mg/L)

Fluoride 

(mg/L)

Silica 

(mg/L)

Sulfate 

(mg/L)

Ground water

384611107453000 Doughty Springs 19800626 -- -- -- -- -- -- -- -- -- -- -- --

384620107455001 Tommy Dowell 

Spring

19770818 59 41 16.0 78 340 -- 420 0 5 0.70 36.0 160

384621107455601 SC01509303DDB1 19780330 60 48 17.0 85 350 -- 430 0 6.3 .60 39.0 160384632107460300 SC01509303DBD1 19780609 61 45 16.0 85 340 -- 420 0 5.9 .90 40.0 160384656107444401 Seep near Delta Fish 

Hatchery

19981014 -- -- -- -- -- -- -- -- -- -- -- --

384707107455201 SC01509303AAA1 19790323 -- -- -- -- -- -- -- -- -- -- -- --384735107470501 SC01409333ADC1 19770818 47 59 19.0 77 340 -- 420 0 7.9 .60 35.0 190384744107441301 SC01409336BAC1 19790323 86 50 13.0 92 340 -- -- -- 13 50 38.0 260384753107435601 Seep area in draw 

below Highway 92

20001205 -- -- -- -- -- -- -- -- -- -- -- --

384800107442201 SC01409325CCD1 19790323 -- -- -- -- -- -- -- -- -- -- -- --384801107454201 SC01409326CCC1 19780415 64 37 12.0 110 340 -- 410 0 6.4 .50 35.0 210384809107464501 SC01409327CCC1 19790323 -- -- -- -- -- -- -- -- -- -- -- --384842107444201 T14SR93W026ADD 

Well near 3300 Road

20000620 110 120 11.1 104 -- 348 -- -- 9.62 0.76 41.5 633

384854107474501 SC01409328BBA1 19780331 56 34 7.7 19 250 -- 310 0 2.1 1.10 35.0 71384855107450101 Seep along Leroux 

Creek above Duke Ditch

20000620 -- -- -- -- -- -- -- -- -- -- -- --

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 33
Table 4. Values of physical properties and concentrations of selected chemical constituents in ground and surface water from Rogers Mesa and vicinity, Delta County, 

Colorado.—Continued[The local names are modified from local names in the U.S. Geological Survey National Water Information System. μS/cm, microsiemens per centimeter; °C, degree Celsius; mg/L, milligrams per liter; NWIS, National Water Information System; GW, ground water; --, no value; DCEHD, Delta County Environmental Health Department; SW, surface water; μg/L, micrograms per liter; <, less than; yellow shading indicates that value exceeds secondary drinking-water standard; pink shading indicates that value exceeds primary drinking-water standard; BD, less than method detection limit. Drinking-water standards are available online at http://www.cdphe.state.co.us/regulations/waterqualitycontroldivision/100301primarydrinkingwater.pdf]

Site identification 

number or station 

name

Local name Sample date Calcium (mg/L) Mag- nesium (mg/L) Potassium (mg/L) Sodium (mg/L)

Acid 

neutralizing 

capacity, as 

calcium 

carbonate 

(mg/L)

Alkalinity, 

as 

calcium 

carbonate 

(mg/L)

Bicarbonate 

(mg/L)

Carbonate 

(mg/L)

Chloride 

(mg/L)

Fluoride 

(mg/L)

Silica 

(mg/L)

Sulfate 

(mg/L)

Ground water—Continued

384912107482601 Lower seep area along 

Stingley Gulch

20001206 -- -- -- -- -- -- -- -- -- -- -- --

384918107481801 Seep on right bank of 

Stingley Gulch

20001206 -- -- -- -- -- -- -- -- -- -- -- --

AG1 3176 L Road -- 50 47 16.3 44 -- 347 -- -- -- 0.095 -- 78JTH1 3144 Highway 92 -- 28 55 14 52 -- 328 -- -- -- -- -- 98LCA1 1096 3250 Road -- -- -- 32 294 -- 410 -- -- -- .088 -- 148LF1 1125 3080 Road -- -- -- -- -- -- BD -- -- -- -- -- 500

Surface water

384756107490801 Big Gulch at Highway 92 19990512 -- -- -- -- -- -- -- -- -- -- -- --384756107490801 Big Gulch at Highway 92 19990831 -- -- -- -- -- -- -- -- -- -- -- --384756107490801 Big Gulch at Highway 92 19991109 -- -- -- -- -- -- -- -- -- -- -- --384756107490801 Big Gulch at Highway 92 20000314 -- -- -- -- -- -- -- -- -- -- -- --384842107443901 Leroux Creek at 3300 

Road

20000314 -- -- -- -- -- -- -- -- -- -- -- --

384842107443901 Leroux Creek at 3300 

Road

20000620 -- -- -- -- -- -- -- -- -- -- -- --

384853107451201 Jessie Ditch at 3250 

And L Roads

20000725 -- -- -- -- -- -- -- -- -- -- -- --

34 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado
Table 4. Values of physical properties and concentrations of selected chemical constituents in ground and surface water from Rogers Mesa and vicinity, Delta County, 

Colorado.—Continued[The local names are modified from local names in the U.S. Geological Survey National Water Information System. μS/cm, microsiemens per centimeter; °C, degree Celsius; mg/L, milligrams per liter; NWIS, National Water Information System; GW, ground water; --, no value; DCEHD, Delta County Environmental Health Department; SW, surface water; μg/L, micrograms per liter; <, less than; yellow shading indicates that value exceeds secondary drinking-water standard; pink shading indicates that value exceeds primary drinking-water standard; BD, less than method detection limit. Drinking-water standards are available online at http://www.cdphe.state.co.us/regulations/waterqualitycontroldivision/100301primarydrinkingwater.pdf]

Site identification 

number or station 

name

Local name Sample date Calcium (mg/L) Mag- nesium (mg/L) Potassium (mg/L) Sodium (mg/L)

Acid 

neutralizing 

capacity, as 

calcium 

carbonate 

(mg/L)

Alkalinity, 

as 

calcium 

carbonate 

(mg/L)

Bicarbonate 

(mg/L)

Carbonate 

(mg/L)

Chloride 

(mg/L)

Fluoride 

(mg/L)

Silica 

(mg/L)

Sulfate 

(mg/L)

Surface water—Continued

384854107450201 Leroux Creek above 

Duke Ditch Diversion

20000328 -- -- -- -- -- -- -- -- -- -- -- --

384854107450201 Leroux Creek above 

Duke Ditch Diversion

20000620 -- -- -- -- -- -- -- -- -- -- -- --

384910107482701 Stingley Gulch above 

Big Gulch

20001206 -- -- -- -- -- -- -- -- -- -- -- --

384914107460601 Jessie Ditch Diversion, Leroux Creek 20000328 -- -- -- -- -- -- -- -- -- -- -- --384915107460801 Leroux Creek above 

Jessie Ditch Diversion

20000620 -- -- -- -- -- -- -- -- -- -- -- --

384919107481601 Stingley Gulch at 

West Draw

20001206 -- -- -- -- -- -- -- -- -- -- -- --

384937107463801 Leroux Creek below 

Fire Mountain Canal

20000620 -- -- -- -- -- -- -- -- -- -- -- --

384938107463601 Fire Mountain Canal 

at Leroux Creek

20000620 -- -- -- -- -- -- -- -- -- -- -- --

384942107463701 Leroux Creek Diversion at Fire Mountain Canal 20000328 -- -- -- -- -- -- -- -- -- -- -- --384944107463601 Leroux Creek above 

Fire Mountain Canal

20000620 -- -- -- -- -- -- -- -- -- -- -- --

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 35
Table 4. Values of physical properties and concentrations of selected chemical constituents in ground and surface water from Rogers Mesa and vicinity, Delta County, 

Colorado.—Continued[The local names are modified from local names in the U.S. Geological Survey National Water Information System. μS/cm, microsiemens per centimeter; °C, degree Celsius; mg/L, milligrams per liter; NWIS, National Water Information System; GW, ground water; --, no value; DCEHD, Delta County Environmental Health Department; SW, surface water; μg/L, micrograms per liter; <, less than; yellow shading indicates that value exceeds secondary drinking-water standard; pink shading indicates that value exceeds primary drinking-water standard; BD, less than method detection limit. Drinking-water standards are available online at http://www.cdphe.state.co.us/regulations/waterqualitycontroldivision/100301primarydrinkingwater.pdf]

Station or

 site identification 

number or

 name

Local name Sample date

Nitrite plus 

nitrate, as 

nitrogen 

(mg/L)

Orthophosphate, as 

phosphorus 

(mg/L)

Orthophosphate 

(mg/L)

Phosphorus 

(μg/L)

Iron 

(μg/L)

Manganese 

(μg/L)

Selenium 

(μg/L)

Ground water

384611107453000 Doughty Springs 19800626 -- -- -- -- -- -- 0384620107455001 Tommy Dowell Spring 19770818 2.10 10 0.06 -- <10 <10 --384621107455601 SC01509303DDB1 19780330 1.50 20 .06 -- 20 <10 6384632107460300 SC01509303DBD1 19780609 1.60 80 .06 -- 80 <10 --384656107444401 Seep near Delta Fish 

Hatchery

19981014 -- -- -- -- -- -- 1

384707107455201 SC01509303AAA1 19790323 -- -- -- -- -- -- --384735107470501 SC01409333ADC1 19770818 1.00 10 .12 -- <10 <10 --384744107441301 SC01409336BAC1 19790323 3.20 20 .12 0.030 20 <10 6384753107435601 Seep area in draw below Highway 92 20001205 -- -- -- -- -- -- 2.4384800107442201 SC01409325CCD1 19790323 -- -- -- -- -- -- --384801107454201 SC01409326CCC1 19780415 1.10 40 .06 -- 40 <10 2384809107464501 SC01409327CCC1 19790323 -- -- -- -- -- -- --384842107444201 T14SR93W026ADD 

Well near 3300 Road

20000620 1.63 -- -- -- -- <1.0 20.1

384854107474501 SC01409328BBA1 19780331 .38 20 .03 -- 20 <10 4384855107450101 Seep along Leroux 

Creek above Duke Ditch

20000620 -- -- -- -- -- -- 9.4

384912107482601 Lower seep area along 

Stingley Gulch

20001206 -- -- -- -- -- -- 3

384918107481801 Seep on right bank of 

Stingley Gulch

20001206 -- -- -- -- -- -- 73.2

36 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado
Table 4. Values of physical properties and concentrations of selected chemical constituents in ground and surface water from Rogers Mesa and vicinity, Delta County, 

Colorado.—Continued[The local names are modified from local names in the U.S. Geological Survey National Water Information System. μS/cm, microsiemens per centimeter; °C, degree Celsius; mg/L, milligrams per liter; NWIS, National Water Information System; GW, ground water; --, no value; DCEHD, Delta County Environmental Health Department; SW, surface water; μg/L, micrograms per liter; <, less than; yellow shading indicates that value exceeds secondary drinking-water standard; pink shading indicates that value exceeds primary drinking-water standard; BD, less than method detection limit. Drinking-water standards are available online at http://www.cdphe.state.co.us/regulations/waterqualitycontroldivision/100301primarydrinkingwater.pdf]

Station or

 site identification 

number or

 name

Local name Sample date

Nitrite plus 

nitrate, as 

nitrogen 

(mg/L)

Orthophosphate, as 

phosphorus 

(mg/L)

Orthophosphate 

(mg/L)

Phosphorus 

(μg/L)

Iron 

(μg/L)

Manganese 

(μg/L)

Selenium 

(μg/L)

Ground water—Continued

AG1 3176 L Road -- 1.63 -- -- -- -- -- BDJTH1 3144 Highway 92 -- -- -- -- -- -- -- --LCA1 1096 3250 Road -- 1.11 -- -- -- -- -- BDLF1 1125 3080 Road -- -- -- -- -- -- -- --

Surface water

384756107490801 Big Gulch at Highway 92 19990512 -- -- -- -- -- -- 9384756107490801 Big Gulch at Highway 92 19990831 -- -- -- -- -- -- 8384756107490801 Big Gulch at Highway 92 19991109 -- -- -- -- -- -- 7384756107490801 Big Gulch at Highway 92 20000314 -- -- -- -- -- -- 7384842107443901 Leroux Creek at 3300 

Road

20000314 -- -- -- -- -- -- 4.5

384842107443901 Leroux Creek at 3300 

Road

20000620 -- -- -- -- -- -- 13.7

384853107451201 Jessie Ditch at 3250 

and L Roads

20000725 -- -- -- -- -- -- 10.4

384854107450201 Leroux Creek above 

Duke Ditch Diversion

20000328 -- -- -- -- -- -- 3.5

384854107450201 Leroux Creek above 

Duke Ditch Diversion

20000620 -- -- -- -- -- -- 7.9

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 37
Table 4. Values of physical properties and concentrations of selected chemical constituents in ground and surface water from Rogers Mesa and vicinity, Delta County, 

Colorado.—Continued[The local names are modified from local names in the U.S. Geological Survey National Water Information System. μS/cm, microsiemens per centimeter; °C, degree Celsius; mg/L, milligrams per liter; NWIS, National Water Information System; GW, ground water; --, no value; DCEHD, Delta County Environmental Health Department; SW, surface water; μg/L, micrograms per liter; <, less than; yellow shading indicates that value exceeds secondary drinking-water standard; pink shading indicates that value exceeds primary drinking-water standard; BD, less than method detection limit. Drinking-water standards are available online at http://www.cdphe.state.co.us/regulations/waterqualitycontroldivision/100301primarydrinkingwater.pdf]

Station or

 site identification 

number or

 name

Local name Sample date

Nitrite plus 

nitrate, as 

nitrogen 

(mg/L)

Orthophosphate, as 

phosphorus 

(mg/L)

Orthophosphate 

(mg/L)

Phosphorus 

(μg/L)

Iron 

(μg/L)

Manganese 

(μg/L)

Selenium 

(μg/L)

Surface water—Continued

384910107482701 Stingley Gulch above 

Big Gulch

20001206 -- -- -- -- -- -- 6.9

384914107460601 Jessie Ditch Diversion, 

Leroux Creek

20000328 -- -- -- -- -- -- 89.4

384915107460801 Leroux Creek above 

Jessie Ditch Diversion

20000620 -- -- -- -- -- -- 53.2

384919107481601 Stingley Gulch at West 

Draw

20001206 -- -- -- -- -- -- 4.9

384937107463801 Leroux Creek below 

Fire Mountain Canal

20000620 -- -- -- -- -- -- 140

384938107463601 Fire Mountain Canal at 

Leroux Creek

20000620 -- -- -- -- -- -- <.7

384942107463701 Leroux Creek Diversion at Fire Mountain 

Canal

20000328 -- -- -- -- -- -- 8

384944107463601 Leroux Creek above 

Fire Mountain Canal

20000620 -- -- -- -- -- -- 7.2

38 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado
Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 39

The concentration of selenium in a ground-water sample 

from a seep along Stingley Gulch, in the northwestern part 

of Rogers Mesa, was 73.2 μg/L (table 4, site identification 

number 384918107481801) and exceeds the State of Colorado 

maximum contaminant level of 50 μg/L (Colorado Department 

of Public Health and Environment, 2005, table 2–3).

Concentrations of dissolved total nitrogen (nitrite plus 

nitrate, as nitrogen) ranged from 0.38 to 3.2 mg/L and were 

less than the maximum contaminant level of 10 mg/L for 

total nitrogen (Colorado Department of Public Health and 

Environment, 2005, table 2–3) in all ground-water samples 

(table 4). Excessive concentrations of total nitrogen in ground 

water can indicate contamination from surface sources, such 

as animal wastes, chemical fertilizers, and effluent from ISDS 

(Hem, 1985, p. 125). Background concentrations of nitrite 

plus nitrate, as nitrogen, in ground water that is unaffected 

by surface sources typically are less than 2 mg/L (Nolan and 

others, 1998).

Hardness, as calcium carbonate, ranged from 195 to 

770 mg/L for ground-water samples from Rogers Mesa aquifer 

(table 4). Water that has hardness (as calcium carbonate) 

concentrations greater than 180 mg/L is classified as “very 

hard” water (Hem, 1985). Water softeners commonly are used 

to decrease hardness to acceptable levels (less than 80 mg/L of 

hardness).

The maximum contaminant levels are enforceable 

standards, and the SMCLs are nonenforceable guidelines for 

public water supplies. Neither maximum contaminant levels 

nor SMCLs apply to individual domestic supplies (Colorado 

Department of Public Health and Environment, 2005). The 

use of drinking-water standards in this report is merely for 

comparison. It is the responsibility of the well owner or user to 

ensure that their drinking-water supply is safe. Drinking-water 

regulations, including drinking-water standards, are available 

at http://www.cdphe.state.co.us/regulations/waterqualitycontro

ldivision/100301primarydrinkingwater.pdf. Information about 

water supplies for private well owners and users is available 

from the Colorado Department of Public Health and Environment at http://www.cdphe.state.co.us/wq/drinkingwater/

PrivateWellInformation.html.

Because many of the ground-water samples from Rogers 

Mesa were collected from seeps and springs near discharge 

areas for the aquifer, concentrations of dissolved solids and 

sulfate likely are greater than is expected in ground water 

from areas near sources of recharge. Concentrations of some 

dissolved constituents tend to increase as water flows though 

an aquifer because of geochemical reactions and the long 

contact time of the water with geologic materials. Because 

many of the ground-water samples that were used in this study 

were collected during the 1970s and 1980s, additional groundwater samples are needed to confirm the suitability of ground 

water for subdivision water supplies.

Potential Hydrologic Effects of Ground-Water 

Use for Hypothetical Subdivisions

As subdivisions are developed on Rogers Mesa, the 

change in land use from irrigated agriculture to residential 

use could have unanticipated effects. Additional pumping for 

subdivision water supplies will decrease ground-water storage 

and discharge to seeps, springs, and subsurface flow at the 

lateral boundaries of the aquifer but likely will not increase 

recharge. If the 2,756 acres of irrigated land on Rogers Mesa 

that currently (2007) also is platted for subdivision development (fig. 2) were developed as 1-acre residential lots with 

no outside water use, recharge of the Rogers Mesa aquifer 

could decrease by an estimated 14,000 acre-ft/yr. If the water 

that has been used to irrigate that 2,756 acres is not used to 

recharge the aquifer, ground-water storage will decrease and, 

eventually, discharge from the aquifer to seeps, springs, and 

subsurface flow will decrease by about 14,000 acre-ft/yr.

For purposes of demonstration, the potential hydrologic 

effects of ground-water use for a hypothetical subdivision on 

Rogers Mesa were approximated using analytical equations. 

The potential effects of pumping on nearby wells (well 

interference), depletion of ground-water storage, and capture 

of ground-water discharge were considered for an idealized 

aquifer. Analyses that incorporated the spatial variability of 

an aquifer’s transmissivity, specific yield, boundaries, and 

recharge and discharge conditions were beyond the scope of 

this study and likely would require the use of a numerical 

model of ground-water flow.

The following conditions were assumed for the analyses 

of the potential effects of pumping wells in a hypothetical 

subdivision:

1. The hypothetical subdivision included 100 contiguous 

1-acre lots with water supplied by individual residential 

wells; 

2. Individual wells were assumed to be pumped at a rate of 

35.8 ft3/d (about 268 gal/d or 0.186 gal/min) to supply 

0.3 acre-ft/yr for each lot;

3. Pumping of the 100 wells was continuous and simultaneous;

4. The consumptive-use rate for in-house use of water was 

assumed to be 10 percent of the pumping rate with 

90 percent of pumpage returned to the aquifer through 

infiltration of ISDS effluent;

5. The idealized aquifer was unconfined, homogeneous, 

isotropic, and infinite in extent;

6. Saturated thickness of the aquifer was 46 ft;
40 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

7. Transmissivity of the aquifer was 4,922 ft2/d;

8. Specific yield of the aquifer was 0.22;

9. Wells were fully penetrating the aquifer;

10. Infiltration of recharge from the surface was unaffected by 

pumping of wells; and

11. The lateral boundary of the aquifer represented a fully 

penetrating stream.

Effects of Pumping on Nearby Wells

A concern of planners in evaluating subdivision plans 

is the effect that lot size may have on the sustainability of 

individual wells. When wells are closely spaced (lot sizes are 

small), pumping of nearby wells could decrease (interfere 

with) the supply of water available to other nearby wells. 

Well interference may decrease the saturated thickness and 

transmissivity of the aquifer at nearby wells. Water levels 

decrease (drawdown) in an aquifer as a well is pumped, with 

the drawdown greatest near the pumped well. The amount of 

drawdown is a function of the pumping rate, the duration of 

pumping, the distance from the pumped well, and the transmissivity and storage properties of the aquifer.

Theis (1935) developed an equation for analysis of 

the time-dependent response of a ground-water system to a 

pumping well in a confined aquifer. The Theis equation generally is used to analyze aquifer-test data (in an analytical mode) 

to determine the hydraulic and storage properties of confined 

aquifers. The Theis equation also can be used to predict 

drawdown due to pumping (in a predictive mode) when the 

aquifer transmissivity and storage coefficient are known.

The Theis equation cannot be integrated directly but 

its value is given by the following equation (Lohman, 1979, 

eq. 44, p. 15):

s = Q/4πT [-0.577216 – loge u + u – u2/(2x2!) 

+ u3/(3x3!) - ∙∙∙],

where

u = r2S / (4Tt) (2)

and the drawdown (s) at some radial distance (r) is caused by 

constant withdrawal (Q) of ground water by a fully penetrating well of infinitesimal diameter for a period of duration (t) 

from a homogeneous and isotropic confined aquifer with a 

transmissivity (T) and a storage coefficient (S). The value of 

the series in the brackets on the right-hand side of equation 1, 

[-0.577216 – loge u + u – u2/(2x2!) + u3/(3x3!) - ∙∙∙], commonly 

is referred to as “the well function or W(u).” Values of W(u) 

for values of u (eq. 2) from 10-15 to 9.9 are given by Lohman 

(1979, table 4, p. 16) or can be approximated using a computer 

spreadsheet as described by Halford and Kuniansky (2002).

Although the Theis equation is strictly valid only for 

confined aquifers, it also can be used for analysis of aquifer 

tests of unconfined aquifers. The storage coefficient (S) in 

equation 2 is assumed to equal the specific yield (Sy) when 

ground water is unconfined. If the measured drawdown during 

an aquifer test of an unconfined aquifer is a substantial portion 

of its initial saturated thickness, the measured drawdown 

should be corrected for the decrease in transmissivity that is 

caused by drawdown. The correction to measured drawdown, 

when ground water is unconfined, is given by the following 

equation (Jacob, 1963):

s’ = s – (s2/2b), (3)

where

s’ is the corrected drawdown (the equivalent 

drawdown for confined conditions), 

s is the measured drawdown for unconfined 

conditions, and 

b is the initial saturated thickness of the 

unconfined aquifer.

The drawdown predicted with equation 1 is the 

drawdown that would occur in a confined aquifer, an aquifer 

with constant transmissivity. The predicted drawdown is less 

than the actual drawdown that would occur in an unconfined 

aquifer. When drawdown in an unconfined aquifer is predicted 

using equation 1, it should be corrected with the following 

equation:

s’’ = b – (b2-2bs’)0.5, (4)

where 

s’’ is the predicted drawdown in an unconfined 

aquifer and 

s’ is the predicted drawdown in a confined 

aquifer. 

Equation 4 is only valid when s’/b is less than 0.5.

Drawdown predicted for a single well pumping from an 

aquifer with a transmissivity of 4,922 ft2/d, a specific yield of 

0.22, and an initial saturated thickness of 46 ft, and at a rate 

of 35.8 ft3/d is relatively small at distances of more than a few 

feet from the pumped well. The theoretical drawdown of water 

levels in the aquifer at distances of 1 to 25,000 ft was calculated for a constant pumping rate of 3,580 ft3

/d for pumping 

periods of 1, 10, and 100 years (fig. 12). The pumping rate of 

3,580 ft3/d used in the example is equivalent to the combined 

discharge of 100 residential wells, each pumping at a rate of 

35.8 ft3/d. Note that the x-axis in figure 12 is a logarithmic 

scale and that the y-axis is inverted. Theoretical drawdown at 

a distance of 209 feet from a pumped well after 100 years of 

constant pumping at a rate of 3,580 ft3/d is about 0.62 ft. (The 

distance between wells at the center of adjacent 1-acre lots is 

approximately 209 ft.) Because drawdown is proportional to 

pumping rate, the drawdown at a distance of 209 feet from 

a well pumped at a constant rate of 35.8 ft3/d for 100 years, 

(1)
THEORETICAL DRAWDOWN, IN FEET

RADIAL DISTANCE FROM PUMPED WELL, IN FEET

1 10 100 1,000 10,000

0

0.5

1 

1.5

Pumping rate = 3,580 cubic feet per day

Transmissivity = 4,922 square feet per day

Specific yield = 0.22

ELAPSED TIME = 1 YEAR

ELAPSED TIME = 10 YEARS

ELAPSED TIME = 100 YEARS Approximate distance between centers of 1-acre lots

Theoretical drawdown in 

nearby well after 100 years 

of pumping

Figure 12. Relation between theoretical drawdown and radial distance in an idealized unconfined 

aquifer for a constant pumping rate and elapsed times of 1, 10, and 100 years.

Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 41

is about 0.0062 ft. For the hypothetical conditions assumed 

for this analysis, the pumping of individual residential wells 

is not likely to cause significant drawdown in nearby wells. 

However, if the transmissivity and specific yield of the Rogers 

Mesa aquifer are substantially different from the values used 

in this analysis, drawdown could be larger or smaller than 

were predicted for the idealized aquifer.

Analytical equations can be used in simple situations that 

involve only a few wells and simple boundary conditions to 

predict the effects that pumping a well will have on groundwater levels. The effects of pumping in complex situations 

that involve many pumping wells with variable pumping 

rates, long periods of time, and complex aquifer and boundary conditions can be predicted more readily using numerical 

models of ground-water flow.

Depletion of Ground-Water Storage

Because of the small rates of withdrawal by residential 

wells, depletion of ground-water storage in an unconfined 

aquifer with a specific yield of 0.22 would be relatively 

small. Assuming residential use of ground-water withdrawal 

is 0.3 acre-ft/yr per 1-acre lot, and consumptive use of that 

water is 10 percent and infiltration of effluent from ISDS is 

90 percent of in-house use, the net withdrawal will be only 

0.03 acre-ft/yr. Assuming a specific yield of 0.22, the change 

in water level at the lot associated with the net withdrawal of 

0.03 acre-ft/yr per 1-acre lot is about 0.14 ft/yr [0.03 acre-ft/yr 

÷ 1 acre ÷ 0.22 ≈ 0.14 ft/yr].

The potential effects to ground-water storage from 

changes in historic land and water use may be of greater 
42 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

concern than the small withdrawals of ground water by 

residential wells if the changes in land use decrease infiltration from the surface. If a subdivision is created from land 

that was formerly irrigated and that land is not irrigated after 

the subdivision is built, infiltration from the surface on that 

land will decrease substantially and likely result in substantial 

decreases in water levels, affecting both ground-water storage 

and discharge from the aquifer. Changes in irrigation practices 

that result in decreased infiltration (recharge) also can result in 

depletion of ground-water storage and, eventually, discharge 

from the aquifer.

Capture of Ground-Water Discharge

When streams and aquifers are hydraulically connected, 

withdrawal of ground water will deplete flow of surface 

streams, either by capture of surface water from streams or 

by capture of ground water that would discharge to streams. 

In Colorado, ground water is considered tributary to a stream 

if withdrawal of ground water by a well will deplete the flow 

of a surface stream by 0.1 percent or more of the withdrawal 

rate in 100 years (CRS 37–90–103, available online at http://

www2.michie.com/colorado/lpext.dll?f=templates&fn=fsmain.htm&2.0). The direct hydraulic connection of the Rogers 

Mesa aquifer to streams is limited because the North Fork 

Gunnison River and Leroux Creek generally are topographically lower than the base of the Rogers Mesa aquifer (fig. 3). 

However, subsurface discharge of ground water across the 

boundaries of the Rogers Mesa aquifer and discharge of 

ground water to seeps and springs likely reach surface streams. 

Thus, ground water in the Rogers Mesa aquifer could be 

considered tributary water. Direct capture of streamflow from 

Leroux Creek by pumping from the Rogers Mesa aquifer 

possibly could occur in the southwest quarter of sec. 23, 

T. 14 S., R. 93 W., where the base of the Rogers Mesa aquifer 

may be lower in altitude than Leroux Creek (fig. 3).

Except for the segment of the aquifer boundary along 

Leroux Creek Valley, where the base of the Rogers Mesa 

aquifer may be lower in altitude than Leroux Creek, the lateral 

boundaries of Rogers Mesa aquifer are drains. A drain is a 

head-dependent flow boundary that only discharges water 

from an aquifer, such as a spring. Where the aquifer boundary 

is a head-dependent flow boundary, ground-water withdrawals 

from the aquifer eventually will decrease saturated thickness 

and hydraulic gradient at the boundary and, consequently, 

ground-water discharge across the boundary of the aquifer. 

Where the Rogers Mesa aquifer is hydraulically connected 

to alluvium along Leroux Creek, ground-water withdrawals 

from the aquifer may either decrease flow from Rogers Mesa 

aquifer to the alluvium or induce flow from the alluvium and 

stream to the aquifer. If sufficient ground-water discharge 

across the boundary is captured and additional flow of water 

from outside the boundary cannot physically be captured, the 

aquifer may become unsaturated at the boundary and flow 

across that part of the boundary will cease. In either case, 

ground-water withdrawals from the Rogers Mesa aquifer 

eventually will reduce streamflow.

The amount and timing of stream depletion depend 

upon the integrated effects of irregular impermeable boundaries, stream meanders, aquifer properties and their areal 

variation, distance from the stream, and imperfect hydraulic 

connection between the aquifer and the stream (Jenkins, 

1968). The DWR has adopted the Alluvial Water Accounting 

System (AWAS) to calculate stream depletion resulting from 

ground-water withdrawals. The AWAS software was developed by the Integrated Decision Support Group at Colorado 

State University, Fort Collins, Colo., and is available for 

download at http://www.ids.colostate.edu/projects/idsawas. 

This computer program calculates stream depletions by using 

either the stream-depletion-factor method (Jenkins, 1968) or 

an analytical stream-depletion method developed by DWR 

(Schroeder, 1987). The latter method uses analytical equations 

described by Glover (1977). AWAS can be used to analyze 

historic stream depletion and to forecast future stream depletion. Stream depletion can be calculated by using either daily 

or monthly time steps for an idealized aquifer. The analytical 

equation solved by AWAS (Schroeder, 1987) is based on the 

following assumptions: 

1. The aquifer is isotropic, homogeneous, of uniform thickness, and infinite in extent;

2. Drawdown is negligible when compared to the aquifer 

thickness and the transmissivity does not change with 

time;

3. The water table is initially flat;

4. Water temperatures are constant;

5. Water is released instantaneously from storage;

6. The stream is straight, infinite in length, and fully penetrates the aquifer;

7. The pumping rate is constant for any pumping period; and

8. The diameter of the well is negligible.

Other analytical models (Barlow and Moench, 1999; 

Butler and Tsu, 2001; Butler and others, 2001; Hunt, 1999 

and 2003) have been developed to estimate aquifer parameters 

from pumping tests when stream depletion occurs. The AWAS 

model was selected as the DWR standard after a detailed 

analysis and review (Ray Bennett, Colorado Water Conservation Board, written commun., 2006, accessed March 13, 

2007, at http://water.state.co.us/pubs/presentations/rbennett_

handout_090606.pdf).

Sophocleous and others (1995) compared results of 

analytical solutions of stream depletion with results from 

numerical models of ground-water flow (MODFLOW, 

McDonald and Harbaugh, 1988) and concluded that the three 

most important assumptions affecting analyses of stream 
Availability, Sustainability, and Suitability of Ground Water on Rogers Mesa 43

depletion were streambed conductance, partial penetration of 

streams, and aquifer heterogeneity. They noted that analytical models of stream depletion consistently overestimated 

stream depletion when conditions did not meet assumptions 

of the analytical solutions. The most important differences 

between the Rogers Mesa aquifer and the idealized aquifer 

are that the Rogers Mesa aquifer is anisotropic, heterogeneous, and variable in thickness, and that the boundary of 

the aquifer is not linear. The anisotropy, heterogeneity, and 

variable thickness may cause substantial differences between 

actual and predicted stream depletion, particularly if the 

variability in properties is spatially correlated. The boundary 

of Rogers Mesa aquifer is a drain and reasonably represents 

a fully penetrating boundary. However, stream depletion at 

that boundary of Rogers Mesa aquifer principally would 

consist of the capture of ground-water discharge to the surface 

and not the capture of streamflow. Because the boundary of 

Rogers Mesa aquifer is not a straight line, as assumed by the 

stream-depletion model, the effects of a pumping well could 

impinge on the aquifer boundary at multiple points and in all 

directions; thus, stream depletion could be greater than that 

predicted by the stream-depletion model.

The AWAS model requires the specification of a streamdepletion factor. The stream-depletion factor (sdf) is equivalent to the time, in days, at which stream depletion equals 

28 percent of the pumping rate. The stream-depletion factor 

(Jenkins, 1968) is calculated from the distance of the well 

from the stream and the transmissivity and specific yield of the 

aquifer, as follows:

sdf = a2∙Sy/T, (5)

where 

a is the distance of the well from the stream, 

Sy is the specific yield, and 

T is the transmissivity.

The stream-depletion analytical model (AWAS) was used 

to evaluate the potential effects of ground-water pumping 

from the Rogers Mesa aquifer on discharge across the aquifer 

boundaries. Transmissivity of the aquifer was assumed to be 

4,922 ft2/d and specific yield was assumed to be 0.22. The 

stream-depletion factor was calculated for various distances 

from a well to a boundary. The volume of stream depletion 

is calculated by AWAS for each time step of a user-specified 

prediction period. A monthly time step and a prediction 

period of 100 yrs were used for this analysis. Because the 

rate of stream depletion is proportional to the specified rate 

of withdrawal by the well, stream depletion may be expressed 

as a ratio of the stream-depletion rate and pumping rate. This 

ratio is independent of the rate of withdrawal and is dependent only on the distance of the well from the stream and the 

transmissivity and specific yield of the aquifer. For ease of 

data input, a pumping rate of 1 acre-ft per month was assumed 

for this analysis. Assuming a consumptive use of 10 percent 

of in-house water use, a monthly withdrawal of 1 acre-ft is 

approximately the monthly consumptive use by 400 residential 

wells, each pumping at a rate of 35.8 ft3/d.

Stream depletion (flow-boundary depletion) was calculated for hypothetical pumping wells at distances of 1,000, 

3,000, 7,500, 15,000, and 25,000 ft from a flow boundary. The 

distance of 25,000 ft is the approximate maximum distance 

across the Rogers Mesa aquifer. The ratios of the annual 

volume of flow-boundary depletion to the annual volume of 

ground-water withdrawal for these distances during the 100-yr 

prediction period are shown as a series of curves in figure 13. 

Note that the x-axis in figure 13 is on a logarithmic scale. 

For the assumed aquifer specific yield and transmissivity, 

the proportion of ground-water withdrawal that is captured 

boundary flow would exceed 0.1 percent of the pumping rate 

within about 4 yrs of the onset of pumping (fig. 13) by a well 

anywhere within the boundary of the Rogers Mesa aquifer. 

Thus, water in the Rogers Mesa aquifer likely would be 

considered tributary ground water. Therefore, new subdivisions on Rogers Mesa that propose the use of nonexempt wells 

completed in the Rogers Mesa aquifer likely would require an 

augmentation plan (Colorado Division of Water Resources, 

2006). Although analytical models of stream depletion provide 

a preliminary evaluation of the potential effects of groundwater withdrawals on streamflows, a numerical model of 

ground-water flow may provide better estimates of stream 

depletion caused by pumping. Numerical models of groundwater flow could be designed to incorporate aquifer anisotropy 

and heterogeneity, multiple pumping wells, and boundary 

conditions that are more realistic.

Suggestions for Collection and Analyses of 

Additional Data

This preliminary analysis of availability, sustainability, 

and suitability of ground water on Rogers Mesa primarily used 

publicly available data. The evaluation could be improved 

with the collection of additional data and the development of 

a numerical model of ground-water flow. The following list of 

data-collection and analyses activities, if implemented, could 

substantially improve the analyses of availability, sustainability, and suitability of ground water on Rogers Mesa for 

subdivision water supplies:

1. Detailed field mapping is needed to define the lateral 

boundaries of the aquifer, to identify ground-water discharge areas, and to determine accurate horizontal and 

vertical coordinates of existing springs and wells, and 

could decrease errors in hydrogeologic maps;

2. Measurement of conveyance losses and ground- and 

surface-water application to irrigated areas, determination 

of local crop coefficients, and the use of soil-moisture 

conditions could decrease errors in the water budget and 

improve estimates of recharge to and the hydraulic and 

storage properties of Rogers Mesa aquifer;
RATIO OF BOUNDARY-FLOW DEPLETION TO GROUND-WATER WITHDRAWAL, IN PERCENT

ELAPSED TIME SINCE PUMPING BEGAN, IN YEARS

1 10 100

0

10

20

30

40

50

60

70

80

90

100

Distance = 15,000 feet

Distance = 25,000 feet

Distan

ce

=

1

,000

fe

et

Distance

= 3

,000 feet Distance = 7,500 feet

Aquifer properties:

Specific yield = 0.22

Transmissivity = 4,922 square feet per day

Figure 13. Relation between depletion of boundary flow to ground-water withdrawal, distance of 

pumped well from flow boundary, and elapsed time since pumping began in an idealized aquifer.

44 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

3. Water-level measurements are needed to define seasonal 

variability of ground-water storage and to improve maps 

of the water table:

4. Aquifer tests and specific-capacity tests of wells are 

needed to decrease uncertainty in estimates of aquifer 

properties;

5. Determination of the physical properties (pH, specific 

conductance, and temperature) and chemical character-

istics of ground water in recharge and discharge areas 

and of surface water diverted into the area could improve 

evaluation of the suitability of the water for residential 

use; and 

6. Numerical models of ground-water flow could improve 

evaluations of the potential effects of changes in land and 

water use on the water budget, aquifer storage, stream 

depletion, and well interference.
Summary 45

Summary

The population of the Western United States is forecast 

to increase substantially during the next few decades. The 

population of Delta County, Colo. (fig. 1), is projected to 

increase by 79 to 105 percent, from about 28,000 in 2000 to 

between 50,200 to 57,500 in 2030. A substantial portion of 

that increase in population likely will reside in subdivisions 

that rely on residential wells for water supply. In Colorado, 

water-supply plans for new subdivisions must demonstrate 

the availability, sustainability, and suitability of the water 

supply. Because ground-water conditions in Colorado are 

highly variable and often are not well defined, developers and 

approving agencies need criteria to define and evaluate what 

data and analyses are needed to define the availability, sustainability, and suitability of ground water as the water supply for 

a proposed subdivision. A preliminary analysis of the groundwater resources of Rogers Mesa, Delta County, Colorado, was 

done by the U.S. Geological Survey, in cooperation with Delta 

County, to demonstrate the use of available data to define the 

availability, sustainability, and suitability of ground water for a 

hypothetical subdivision.

A list is provided of the types of analyses and data 

needed for preparation of a water-supply report for a proposed 

subdivision, when ground water is the proposed supply. These 

analyses and data provide a minimum level of detail needed 

to demonstrate the physical availability, sustainability, and 

suitability of ground water for a proposed subdivision’s water 

supply. The legal availability of a proposed water supply is not 

addressed in this report.

Publicly available data from the Colorado Division of 

Water Resources, the Colorado Decision Support System, the 

Colorado Agricultural Meteorological Network, Delta County, 

the U.S. Geological Survey, and other sources were used to 

prepare a preliminary evaluation of ground-water resources for 

Rogers Mesa. Maps of the altitude of the base of the aquifer, 

the water table, and the saturated thickness of the Rogers Mesa 

aquifer were prepared from data from the well files of the 

Division of Water Resources. A field reconnaissance was done 

to better define the lateral extent of the aquifer and to locate 

potential ground-water discharge areas.

Hydraulic properties of the aquifer were estimated 

from drillers’ pumping tests and pump-installation tests. 

Estimated transmissivity of the aquifer ranges from a few 

hundred to more than 20,000 square feet per day. Estimated 

specific yield and specific retention of the aquifer are 0.22 and 

0.08, respectively. Horizontal hydraulic conductivity of the 

aquifer, as estimated from drillers’ pumping tests and pumpinstallation tests, ranged from less than 1 foot per day to about 

350 feet per day. Average horizontal hydraulic conductivity, as 

estimated from the water budget, was 107 feet per day.

Ground-water storage in the aquifer was estimated to be 

about 107,000 acre-feet. A preliminary water budget for the 

aquifer was used to estimate recharge to the aquifer. During 

November 1998 through October 2006, infiltration of precipitation and irrigation water to the aquifer averaged 30,767 acrefeet per year. Although ground water is physically available in 

the Rogers Mesa aquifer to supply additional residential wells, 

its use may be limited by administrative rules of the Colorado 

Division of Water Resources.

On the basis of an evaluation of sparse water-quality 

data, relatively large concentrations of dissolved solids 

and sulfate and hardness may limit use of ground water for 

residential supplies. The U.S. Environmental Protection 

Agency Secondary Maximum Contaminant Level (SMCL) 

for dissolved solids of 500 milligrams per liter was exceeded 

in 11 of 12 samples and the SMCL for dissolved sulfate of 

250 milligrams per liter was exceeded in 3 of 12 samples. The 

maximum concentration of total nitrogen (nitrite plus nitrate, 

as nitrogen) in ground water was 3.2 milligrams per liter. 

Concentrations of total nitrogen typically were less than the 

background concentration, which is less than 2 milligrams per 

liter, and do not indicate substantial contamination from potential surface sources of nitrogen.

A preliminary stream-depletion analysis indicates that 

ground water in Rogers Mesa aquifer is tributary water. Thus, 

augmentation plans likely would be required for the development of ground water from nonexempt wells for proposed 

subdivisions on Rogers Mesa. The potential effects to groundwater recharge and storage from changes in historic land and 

water use from irrigated agriculture to residential land use may 

be of greater concern than the small withdrawals of ground 

water by residential wells.

Uncertainty in the water budget and the hydraulic and 

storage properties of the aquifer could be decreased with the 

collection of additional data, including accurate locations and 

altitudes of wells. Better estimates of surface-water deliveries for irrigation and crop-consumptive use could improve 

estimates of ground-water recharge. Better estimates of 

aquifer transmissivity and specific yield are needed for use in 

water-budget and stream-depletion analyses of Rogers Mesa. 

Numerical models of ground-water flow could improve evaluations of the potential effects of changes in land and water use 

on the water budget, aquifer storage, stream depletion, and 

well interference.
46 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

References Cited

Ackerman, D.J., and Brooks, Tom, 1986, Reconnaissance 

of ground-water resources in North Fork Gunnison River 

Basin, southwestern Colorado: U.S. Geological Survey 

Water-Resources Investigations Report 85-4230, 21 p.

Alley, W.M., Reilly, T.E., and Franke, O.L., 1999, Sustainability of ground-water resources: U.S. Geological Survey 

Circular 1186, 79 p., available online at http://pubs.usgs.

gov/circ/circ1186/

Barlow, P.M., and Moench, A.F., 1999, WTAQ—A computer program for calculating drawdowns and estimating 

hydraulic properties for confined and water-table aquifers: 

U.S. Geological Survey Water-Resources Investigations 

Report 99-4225, 74 p.

Bates, R.L., and Jackson, J.A., eds., 1980, Glossary of geology 

(2d ed.): Falls Church, Va., American Geological Institute, 

749 p.

Broner, I., 1993, Irrigation scheduling—The water balance 

approach: Colorado State University Extension, Fort Collins, Colo., Cops Online Fact Sheets, no. 4.707, available 

online at http://www.ext.colostate.edu/Pubs/crops/04707.

html

Bureau of Reclamation, 2006: Paonia Project Colorado: 

accessed March 6, 2007, at http://www.usbr.gov/dataweb/

html/paonia.html

Bureau of Reclamation, 2007, Colorado River Basin salinity 

control program, Lower Gunnison River Basin Unit, Colorado: accessed September 7, 2007, at http://www.usbr.gov/

dataweb/html/lowergun.html

Butler, J.J., Jr., and Tsu, Ming-Shou, 2001, Mathematical 

derivation of drawdown and stream depletion produced by 

pumping in the vicinity of a finite-width stream of shallow penetration: Kansas Geological Survey Open-File 

Report 2000–8, 8 p.

Butler, J.J., Jr., Zlotnik, V.A., and Tsou, M.S, 2001, Drawdown 

and stream depletion produced by pumping in the vicinity of a finite width stream of shallow penetration: Ground 

Water, v. 39, no. 5, p. 651–659.

Colorado Climate Center, 2007, Understanding plant water 

use: Fort Collins, Colo., available online at http://ccc.atmos.

colostate.edu/~coagmet/extended_etr_about.php#4

Colorado Department of Local Affairs, 2006, Population totals 

for Colorado Counties: accessed May 17, 2007, at http://

www.dola.state.co.us/dlg/demog/pop_cnty_forecasts.html

Colorado Department of Public Health and Environment, 

2002, Drinking water from household wells: Denver, Colo., 

24 p., available online at http://www.cdphe.state.co.us/wq/

drinkingwater/PrivateWellInformation.html

Colorado Department of Public Health and Environment, 

2004, Source water assessment report—ground water 

sources, Lazear Domestic WC, Public water system ID: 

CO0115467, Lazear, Colo., Delta County: available online 

at http://emaps.dphe.state.co.us/website/SWAP_Summary/

Counties/Delta/115467-Lazear_Domestic_WC_GW.pdf

Colorado Department of Public Health and Environment, 

2005, Primary drinking water regulations (5 CCR 1003–1, 

amended January 19, 2005, effective March 30, 2005): 

Denver, Colo., 247 p., available online at http://www.cdphe.

state.co.us/regulations/waterqualitycontroldivision/100301p

rimarydrinkingwater.pdf

Colorado Division of Water Resources, 1986, Statewide nontributary ground water rules, 2 CCR 402–7: Denver, Colo., 

17 p., accessed February 21, 2006, at http://water.state.

co.us/pubs/rule_reg/nontributary.pdf

Colorado Division of Water Resources, 2000, Descriptive 

clarification A, water wells in proposed housing subdivisions: Denver, Colo., 4 p., accessed November 2, 2006, at 

http://water.state.co.us/pubs/policies.asp

Colorado Division of Water Resources, 2005, State Engineer’s 

action on proposed water supplies for land use actions: 

Denver, Colo., 12 p., accessed February 21, 2006, at http://

water.state.co.us/pubs/policies/memo_subdivisions.pdf

Colorado Division of Water Resources, 2006, Guide to Colorado well permits, water rights, and water administration, 

March 2006: Denver, Colo., 20 p., accessed March 8, 2007, 

at http://water.state.co.us/pubs/wellpermitguide.pdf

Colorado Division of Water Resources, 2007, Water rights 

terminology: Denver, Colo., accessed February 26, 2007, at 

http://water.state.co.us/wateradmin/terms.asp

Colorado Division of Water Resources and Colorado Water 

Conservation Board, 2007, Colorado’s Decision Support 

Systems: Denver, Colo., accessed March 8, 2007, at http://

cdss.state.co.us/DNN/Home/tabid/36/Default.aspx
References Cited 47

Colorado Water Conservation Board, 2004, Statewide water 

supply initiative: Denver, Colo., accessed February 21, 

2006, at http://cwcb.state.co.us/SWSI/PhaseIReport.htm

Day, W.C., Green, G.N., Knepper, D.H., Jr., and Phillips, R.C., 

1999, Spatial geologic data model for the Gunnison, Grand 

Mesa, Uncompahgre National Forests mineral assessment 

area, southwestern Colorado, and digital data for the Leadville, Montrose, Durango, and Colorado parts of the Grand 

Junction, Moab, and Cortez 1 degree x 2 degrees geologic 

maps: U.S. Geological Survey Open-File Report 99–427, 

accessed February 27, 2007, at http://pubs.er.usgs.gov/

usgspubs/ofr/ofr99427

Delta County Environmental Health Division, 2007, Drinking 

water: Delta, Colo., accessed January 15, 2007, at http://codeltacounty2.civicplus.com/index.asp?NID=108

Driscoll, F.G., 1986, Groundwater and Wells (2nd ed.): Johnson Division, St. Paul, Minn., 1021 p.

Environmental Systems Research Inc., 1999–2005, ArcMap, 

version 9.1.

Freeze, R.A., and Cherry, J.A., 1979, Groundwater: Englewood Cliffs, N.J., Prentice-Hall, Inc., 604 p.

Glover, R.E., 1974, Transient groundwater hydraulics: Colorado state University, Department of Civil Engineering, Fort 

Collins, Colo. 413 p.

Glover, R.E., 1977, Ground-water movement: U.S. Bureau of 

Reclamation, Engineering Monograph No. 31, 76 p.

Gutentag, E.D., Heimes, F.J., Krothe, N.C., Luckey, R.R., and 

Weeks, J.B., 1984, Geohydrology of the High Plains aquifer 

in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, and Texas: U.S. Geological Survey 

Professional Paper 1400–B, 63 p.

Halford, K.J., and Kuniansky, E.L., 2002, Documentation of 

spreadsheets for the analysis of aquifer-test and slug-test 

data: U.S. Geological Survey Open-File Report 2002–197, 

51 p., available online at http://pubs.usgs.gov/of/2002/

ofr02197/

Hem, J.D., 1985, Study and interpretation of the chemical 

characteristics of natural water (3rd ed.): U.S. Geological 

Survey Water-Supply Paper 2254, 263 p.

Hunt, B., 1999, Unsteady stream depletion from ground-water 

pumping: Ground Water, v. 37, no. 1, p. 98–102.

Hunt, B., 2003, Unsteady stream depletion when pumping 

from semiconfined aquifers: Journal of Hydrologic Engineering, v. 8, no. 1, p. 12–19.

Jacob, C.E., 1963, Determining the permeability of water-table 

aquifers, in Bentall, Ray, compiler, Methods of determining 

permeability, transmissibility, and drawdown: U.S. Geological Survey Water-Supply Paper 1536–I, p. 245–271.

Jenkins, C.T., 1968, Techniques for computing rate and volume of stream depletion by wells: Ground Water, v. 6, no. 2, 

p 37–46.

Lazear, G.D., 2006, Evidence for deep groundwater flow and 

convective heat transport in mountainous terrain, Delta 

County, Colorado, USA: Hydrogeology Journal, v. 14, 

no. 8, p. 1582–1598.

Lohman, S.W., and others, 1972, Definitions of selected 

ground-water terms—Revisions and conceptual refinements: U.S. Geological Survey Water-Supply Paper 1988, 

21 p.

Lohman, S.W, 1979, Ground-water hydraulics: U.S. Geological Survey Professional Paper 708, 70 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.

Nolan, B.T., Ruddy, B.C., Hitt, K.J., and Helsel, D.R., 1998, 

A national look at nitrate contamination in ground water: 

Water Conditioning and Purification, v. 39, no. 12, p. 76–79.

Price, D.H., 1995, The cultural effects of conveyance loss in 

gravity-fed irrigation systems: Ethnology, v. 34, p. 273–291.

Robson, S.G., 1993, Techniques for estimating specific yield 

and specific retention from grain-size data and geophysical 

logs from clastic bedrock aquifers: U.S. Geological Survey 

Water-Resources Investigations Report 93–4198, 19 p.

Reilly, T.E., 2001, System and boundary conceptualization 

in ground-water flow simulation: U.S. Geological Survey 

Techniques of Water-Resources Investigations book 3, 

chap. B8, 29 p.

Slichter, C.S., 1899, Theoretical investigation of the motions 

of ground water: U.S. Geological Survey 19th Annual 

Report, pt. II–C, p. 295-384.

Schroeder, D.R., 1987, Analytical stream depletion model: 

Colorado Division of Water Resources, Denver, Colo., 

1 computer disk.

Sophocleous, Marios, Koussis, Antonis, Martin, J.L., and 

Perkins, S.P., 1995, Evaluation of simplified stream-aquifer 

depletion models for water-rights administration: Ground 

Water, v. 33, no. 4, p. 579–588.
48 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

Templin, W.A., Herbert, R.A., Stainaker, C.B., Horn, Marilee, and Solley, W.B., 2007, National handbook of recommended methods for water data acquisition, chapter 11: 

U.S. Geological Survey, accessed September 6, 2007 at 

http://pubs.usgs.gov/chapter11/

Theis, C.V., 1935, The relation between lowering of the piezometric surface and the rate and duration of discharge of a 

well using ground-water storage: American Geophysical 

Union Transactions, v. 16, p. 519–524.

Theis, C.V., 1963, Estimating the transmissibility of a watertable aquifer from the specific capacity of a well, in Bentall, 

Ray, complier, Methods of determining permeability, transmissibility, and drawdown: U.S. Geological Survey WaterSupply Paper 1545–C, p. 101–105.

Thrush, P.W., compiler, 1968, A dictionary of mining, mineral, 

and related terms: U.S. Department of the Interior, Bureau 

of Mines, 1269 p.

Topper, Ralf, Spray, K.L., Bellis, W.H., Hamilton, J.L., and 

Barkmann, P.E., 2003, Groundwater atlas of Colorado: 

Colorado Geological Survey Special Publication 53, 210 p.

U.S. Department of Agriculture, Farm Service Agency, 

2007, National agriculture imagery program: available at 

http://165.221.201.14/NAIP.html

U.S. Department of Agriculture, Natural Resource Conservation Service, 2007a, Soil Survey Geographic (SSURGO) 

database for Paonia area, Colorado, parts of Delta, Gunnison, and Montrose Counties: accessed March 7, 2007, at 

http://soildatamart.nrcs.usda.gov/

U.S. Department of Agriculture, Natural Resources Conservation Service, 2007b, National soil survey handbook, 

title 430–VI: available at http://soils.usda.gov/technical/

handbook/

U.S. Department of Agriculture, Natural Resource Conservation Service, 2007c, Glossary of terms: accessed March 13, 

2007 at http://soils.usda.gov/sqi/concepts/glossary.html

U.S. Environmental Protection Agency, 2007a, Safe drinking 

water information system; accessed May 24, 2007, at http://

oaspub.epa.gov/enviro/sdw_report_v2.first_table?pws_i

d=CO0115685&state=CO&source=Purch_surface_

water&population=840&sys_num=0

U.S. Environmental Protection Agency, 2007b, Drinking water 

standards: available online at http://www.epa.gov/safewater/

creg.html

U.S. Geological Survey, 1989, Subsurface-water flow and 

solute transport—Federal glossary of selected terms: U.S. 

Geological Survey, Office of Water Data Coordination, 

August 1989, 38 p.

U.S. Geological Survey, 2007, USGS national elevation dataset: available online at http://seamless.usgs.gov/

Waskom, R., and Neibauer, M., 2004, Glossary of water 

terminology: Colorado State University Extension Fact 

Sheet 4.717, available online at http://www.ext.colostate.

edu/pubs/crops/04717.html

Weigel, J.F., 1987, Selected hydrologic and physical properties 

of Mesozoic formations in the Upper Colorado River Basin 

in Arizona, Colorado, Utah, and Wyoming; excluding the 

San Juan Basin: U.S. Geological Survey Water-Resources 

Investigations Report 86–4170, 68 p.

Wright, J.L., 1982, New evapotranspiration crop coefficients: 

Journal of Irrigation andDrainage Division, American Society of Civil Engineers, v. 108, p. 57–74.
Glossary

A

alluvial fan A low, outspread, relatively flat 

to gently sloping mass of loose rock material, shaped like an open fan or a segment of 

a cone, deposited by a stream (especially in a 

semiarid region) at the place where it issues 

from a narrow mountain valley upon a plain 

or broad valley, or where a tributary stream is 

near or at its junction with the main stream, 

or wherever a constriction in a valley abruptly 

ceases or the gradient of the stream suddenly 

decreases; it is steepest near the mouth of the 

valley where its apex points upstream, and 

it slopes gently and convexly outward with 

gradually decreasing gradient (Bates and 

Jackson, 1980, p. 16).

alluvium (alluvial deposit) Clay, silt, sand, 

and gravel, or other rock materials transported 

by water and deposited in comparatively 

recent geologic time as sorted or semi-sorted 

sediments in riverbeds, estuaries, and flood 

plains, and in fans deposited by running water 

at the bases of mountain slopes (Thrush, 

1968).

anisotropic A condition in which a property 

varies with the direction of measurement at a 

point.

aquifer A geologic formation, group of formations, or part of a formation that contains 

sufficient saturated permeable material to 

yield significant quantities of water to wells 

and springs (Lohman and others, 1972).

aquifer test A controlled field test designed 

to determine the hydraulic or storage properties or both of an aquifer, associated confining 

units, or both (modified from U.S. Geological 

Survey, 1989).

augmentation plan In Colorado, a plan 

approved by the water court to protect senior 

water rights from the depletion of streamflow 

caused by new diversions. An augmentation 

plan may involve (1) storing junior water 

when in priority and releasing that water 

when a river call comes on; (2) purchasing 

stored water from federal entities or others for 

release when a river call comes on; or 

(3) purchasing senior irrigation water rights 

and changing the use of those rights to offset 

the injury to the stream from new uses (Colorado Division of Water Resources, 2007).

available water capacity (soil) The volume 

of water that should be available to plants if 

the soil, inclusive of fragments, was at field 

capacity. Available water capacity is approximately equal to specific retention. It commonly is estimated as the amount of water 

held between field capacity and the wilting 

point, with corrections for salinity, fragments, and rooting depth (U.S. Department of 

Agriculture, Natural Resources Conservation 

Service, 2007b).

C

capture The decrease in discharge plus the 

increase in recharge that results from a change 

in ground-water discharge to wells. Capture 

may occur as decreases in ground-water 

discharge to surface-water bodies (stream 

depletion), springs and seeps, or the component of evapotranspiration derived from the 

saturated zone, or as increases in infiltration 

from surface-water bodies (Lohman and others, 1972).

cone of depression A depression of the 

potentiometric surface in the shape of an 

inverted convex cone that develops around a 

well that is being pumped (U.S. Geological 

Survey, 1989).

confining unit (bed or zone) A geologic 

formation, group of formations, or part of 

a formation of impermeable or distinctly 

less permeable material bounding one or 

more aquifers; a general term that replaces 

the terms aquitard, aquifuge, and aquiclude 

(Lohman and others, 1972, p. 5).

consumptive use That part of water that 

is evaporated, transpired, incorporated into 

products or crops, consumed by humans or 

livestock, or otherwise removed from the 

immediate water environment. Also referred 

to as water consumption or water consumed 

(Templin and others, 2007).

conveyance loss Water that is lost as it 

is conveyed from its source to the irrigated 

field. The factors that lead to conveyance loss 
50 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

include evaporation, evapotranspiration, seepage, and spillage (Price, 1995).

D

drainable ground water The volume of 

drainable water in an aquifer equals the 

product of volume of saturated aquifer and 

the specific yield of the aquifer (Gutentag and 

others, 1984). Generally, not all the drainable 

water in an aquifer can be recovered for use. 

The volume that can be recovered is dependent on site-specific hydrogeologic conditions, well construction, costs of recovery, and 

water quality considerations.

E

exempt well In Colorado, an exempt well 

is a well from which the use of water is not 

subject to the administrative rules of prior 

appropriation (Colorado Division of Water 

Resources, 2006). For additional information, 

see sections 37-92-602 and 37-90-105 of the 

Colorado Revised Statutes at http://www.state.

co.us/gov_dir/leg_dir/olls/colorado_revised_

statutes.htm.

F

field capacity (soil) The soil moisture 

content just after the soil has drained following a period of rain and humid weather, 

after a spring thaw, or after heavy irrigation, 

expressed as the ratio of the weight of water 

to the weight of the soil plus the weight of 

the water. An approximation of soil moisture 

content at field capacity commonly is made 

in the laboratory using 1/3-bar moisture 

percentage for clayey and loamy soil materials and 1/10-bar for sandy materials (U.S. 

Department of Agriculture Natural Resources 

Conservation Service, 2007b).

G

ground water, confined Ground water that 

is under pressure significantly greater than 

atmospheric, its upper limit is the bottom of a 

bed of distinctly lower hydraulic conductivity 

than that of the material in which the confined 

water occurs (Lohman and others, 1972).

ground water, perched Ground water that 

is unconfined but that is separated from 

an underlying body of ground water by an 

unsaturated zone. Its water table is a perched 

water table. It is held up by a perching bed 

whose permeability is so low that water 

percolating downward through it is not able 

to bring water in the intervening unsaturated 

zone above atmospheric pressure (Lohman 

and others, 1972).

ground water, unconfined Ground water in 

an aquifer that has a water table (Lohman and 

others, 1972).

ground-water availability The amount of 

ground water that is available for use, which 

does not cause unacceptable changes in the 

subsurface and surface environment. Estimation of the amount of ground water that is 

available for use requires (1) an evaluation of 

ground and surface water on a systemwide 

basis, including the amounts of water available from changes in ground-water recharge, 

from changes in ground-water discharge, and 

from changes in storage for different levels 

of water consumption; and (2) an evaluation 

of the effects that changes in ground-water 

use will have on the subsurface and surface 

environments (Alley and others, 1999).

ground-water suitability The suitability of 

ground water for specific uses may be limited 

by the physical properties and chemical and 

bacteriological characteristics of the water. 

The Colorado Department of Public Health 

and Environment (2005) and U.S. Environmental Protection Agency (2007b) have 

established standards for drinking water from 

public supplies. The suitability of water from 

individual private wells is not subject to these 

drinking-water standards.

ground-water sustainability Ground-water 

sustainability is defined as the development 

and use of ground water in a manner that 

can be maintained for an indefinite time 

without causing unacceptable consequences 

(Alley and others, 1999). Ultimately, the 

public should determine the tradeoff between 

ground-water use and changes to the environment.

H

head, static The height above a standard 

datum of the surface of a column of water 

(or other liquid) that can be supported by the 

static pressure at a given point (Lohman and 

others, 1972).

heterogeneous A condition in which 

the properties of a geologic formation or 

an aquifer are not uniform in structure or 
Glossary 51

composition. Heterogeneity primarily is a 

function of the geologic environments under 

which the rock was formed and under which it 

has been altered.

homogeneous A condition in which the 

properties of a geologic formation or an aquifer are uniform in structure or composition.

hydraulic conductivity The volume of 

water at the existing kinematic viscosity that 

will move in unit time under a unit hydraulic 

gradient through a unit area measured at right 

angles to the direction of flow (Lohman and 

others, 1972, p. 4). Hydraulic conductivity is 

not only a property of the porous media but 

includes the properties of the fluid (kinematic 

viscosity) and the acceleration due to gravity. 

The standard unit for hydraulic conductivity 

is cubic foot per day per square foot. In this 

report, the mathematically reduced form, foot 

per day, is used for convenience. If hydraulic 

conductivity is independent of the direction of 

measurement, the porous medium is isotropic, 

but if it varies with direction of measurement, 

the porous medium is anisotropic. In most 

alluvial sediments, hydraulic conductivity is 

generally greatest parallel to bedding and least 

perpendicular to bedding.

hydraulic gradient The change in static 

head per unit of distance in a given direction. 

If not specified, the direction generally is 

understood to be that of the maximum rate of 

decrease in head (Lohman and others, 1972, 

p. 8).

I

irrigation year The irrigation year begins 

November 1 of one calendar year and ends 

on October 31 of the following calendar year. 

The irrigation year is used for purposes of 

reporting and recording annual diversions of 

water for irrigation (Waskom and Neibauer, 

2004).

isotropic A condition in which a property is 

independent of the direction of measurement 

at a point (Lohman and others, 1972, p. 9).

N

nonexempt well In Colorado, a nonexempt 

well is a well from which the use of water 

is subject to the administrative rules of prior 

appropriation (Colorado Division of Water 

Resources, 2006). For additional information 

see sections 37–92–602 and 37–90–105 0f the 

Colorado Revised Statutes at http://www.state.

co.us/gov_dir/leg_dir/olls/colorado_revised_

statutes.htm.

nontributary ground water (aquifer) Ground 

water is considered nontributary if it is outside 

the boundaries of any designated groundwater basins in existence on January 1, 

1985, and its withdrawal will not deplete the 

flow of a natural stream at an annual rate 

greater than one-tenth of one percent of the 

annual rate of withdrawal within one hundred years. The determination of whether 

ground water is nontributary or tributary 

shall be based on aquifer conditions existing 

at the time of permit application (Colorado 

Revised Statute 37–90–103, available online 

at http://www2.michie.com/colorado/lpext.

dll?f=templates&fn=fs-main.htm&2.0).

O

out of priority Diversion of water is governed by the priority system in which the priority is based on both the initial appropriation 

date and the adjudication date of a water right, 

as confirmed by the water court. The senior 

water rights holder has the right to divert 

water from a common source before a junior 

water rights holder. When a junior water 

rights holder diverts water from the common 

source before the senior water rights holder 

that diversion is ”out of priority” (Colorado 

Division of Water Resources, 2006).

P

porosity A property of a rock or soil 

containing interstices or voids. Porosity is 

expressed as the ratio of the volume of voids 

to the volume of the rock or soil, as either a 

decimal fraction or a percentage. A related 

term is effective porosity, which refers to the 

amount of interconnected pore space available 

for fluid transmission (Lohman and others, 

1972, p. 10).

potentiometric surface A surface that represents the static head and that is defined by the 

levels to which water will rise in tightly cased 

wells. Where head varies appreciably with 

depth, a potentiometric surface is meaningful only if it defines the static head along a 

specified surface or stratum in the aquifer. 

More than one potentiometric surface may be 

required to define the three-dimensional 
52 Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado

distribution of head in an aquifer. The water 

table is a particular potentiometric surface 

(Lohman and others, 1972, p. 11).

R

reference evapotranspiration Reference 

evapotranspiration is the estimated consumptive use of water by well-watered alfalfa 

under local weather conditions. The reference 

evapotranspiration value that is provided by 

the Colorado Agricultural Meteorological 

network is computed using local meteorological measurements and a reference equation for 

alfalfa (Wright, 1982). Reference evapotranspiration values for other crops are adjusted 

using a crop coefficient. Reference evapotranspiration values are for conditions during 

which soil moisture is greater than 50 percent 

of field capacity. If soil moisture is less than 

50 percent of field capacity, a soil coefficient 

value can be applied in addition to the crop 

coefficient (Colorado Climate Center, 2007).

S

saturated hydraulic conductivity (soil) Saturated hydraulic conductivity is the amount of 

water that would move vertically through a 

unit area of saturated soil in unit time under 

unit hydraulic gradient (U.S. Department of 

Agriculture Natural Resource Conservation 

Service, 2007b).

specific retention The ratio of (1) the 

volume of water which a rock or soil, after 

being saturated, will retain against the pull of 

gravity to (2) the volume of the rock or soil 

(Lohman and others, 1972).

specific storage The ratio of volume of 

water released from or taken into storage per 

unit surface area per unit change in head in 

a compressible ground-water body (Lohman 

and others, 1972).

specific yield The ratio of (1) the volume of 

water which a rock or soil, after being saturated, will yield by gravity to (2) the volume 

of the rock or soil (Lohman and others, 1972).

storage coefficient The volume of water 

an aquifer releases from or takes into storage per unit surface area of the aquifer per 

unit change in head. In a confined aquifer, 

the water derived from storage with decline 

in head comes from expansion of the water 

and compression of the aquifer; similarly, 

water added to storage with a rise in head is 

accommodated by compression of the water 

and expansion of the aquifer. In an unconfined 

aquifer, the storage coefficient is virtually 

equal to specific yield (Lohman and others, 

1972).

stream depletion The capture by a well 

of surface water from a stream or subsurface water that normally would discharge 

to a stream. Stream depletion means either 

direct depletion of stream flow or reduction 

of ground-water flow to the stream (Jenkins, 

1968).

subdivision Any parcel of land in Colorado, which is to be used for condominiums, 

apartments, or any other multiple-dwelling 

units, or which is divided into two or more 

parcels, separate interests, or in common, 

unless exempted (Colorado Division of Water 

Resources, 2007).

system of prior appropriation The use of 

water in Colorado is governed by what is 

known as the prior appropriation system. 

This system of water allocation controls 

who uses how much water, the types of uses 

allowed, and when those waters can be used. 

A simplified way to explain this system is 

often referred to as the priority system or 

“first in time, first in right.” The first person 

to appropriate water and apply that water to 

use has the first right to use that water within 

a particular stream system. This person, after 

receiving a court decree verifying their priority status, then becomes the senior water right 

holder and that water right must be satisfied 

before any other water rights are filled (Colorado Division of Water Resources, 2006).

T

transmissivity The rate at which water of 

the prevailing kinematic viscosity is transmitted through a unit width of an aquifer under a 

unit hydraulic gradient (Lohman and others, 

1972, p. 13). Though spoken of as a property 

of the aquifer, it also embodies the saturated 

thickness of the aquifer and the properties of 

the contained liquid.

tributary water Water that is connected 

to a natural stream system by either surface 

or underground flows (Colorado Division 

of Water Resources, 2006). Ground water 

located outside the boundaries of any des-
Glossary 53

ignated ground-water basins in existence on 

January 1, 1985, the withdrawal of which will 

within one hundred years, deplete the flow of 

a natural stream at an annual rate of one-tenth 

of one percent or more of the annual rate of 

withdrawal is considered tributary. The deter-

mination of whether ground water is non-

tributary or tributary shall be based on aquifer 

conditions existing at the time of permit appli-

cation (Colorado Revised Statute 37-90-103, 

available online at http://www2.michie.com/

colorado/lpext.dll?f=templates&fn=fs-main.

htm&2.0). W

water table The potentiometric surface in 

an unconfined aquifer at which the pressure is 

atmospheric (Lohman and others, 1972).

wilting point (soil) The amount of water 

held too tightly in soil for commonly grown 

crops to extract (U.S. Department of Agricul-

ture, Natural Resources Conservation Service, 

2007c). 
Publishing support provided by:

Helena Publishing Service Center

For more information concerning this publication, contact:

Director, Colorado Water Science Center

U.S. Geological Survey

Box 25046, MS 415

Denver Federal Center

Lakewood, Colorado 80225

(303) 236-5900

Or visit the Colorado Water Science Center Web site at:

http://co.water.usgs.gov/

Watts—Availability, Sustainability, and Suitability of Ground Water, Rogers Mesa, Delta County, Colorado—Scientific Investigations Report 2008–5020

Printed on recycled paper 9 7

8 14113 21311