U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010-5064

Land Disturbance Associated with Oil and Gas 

Development and Effects of Development-Related 

Land Disturbance on Dissolved-Solids Loads in 

Streams in the Upper Colorado River Basin, 1991, 

2007, and 2025 

Prepared in cooperation with the U.S. Department of the Interior Bureaus of Land Management and 

Reclamation
Cover: Foreground image: Photograph to the north showing a pumping well in the 

Drunkards Wash gas field near Price, Utah. Photograph by Susan G. Buto, August, 2009.

Background image: 2006 National Agricultural Imagery Program image showing oil- and 

gas-related land disturbance near the Green and White Rivers in Uintah County, Utah.
Land Disturbance Associated with Oil 

and Gas Development and Effects of 

Development-Related Land Disturbance on 

Dissolved-Solids Loads in Streams in the 

Upper Colorado River Basin, 1991, 2007, 

and 2025 

By Susan G. Buto, Terry A. Kenney, and Steven J. Gerner

Prepared in cooperation with the U.S. Department of the Interior Bureaus of Land 

Management and Reclamation

Scientific Investigations Report 2010–5064

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

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

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Suggested citation:

Buto, S.G., Kenney, T.A., and Gerner, S.J., 2010, Land disturbance associated with oil and gas development and 

effects of development-related land disturbance on dissolved-solids loads in streams in the Upper Colorado River 

Basin, 1991, 2007, and 2025: U.S. Geological Survey Scientific Investigations Report 2010-5064, 56 p. Available at 

http://pubs.usgs.gov/sir/2010/5064.
iii

Contents

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

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

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

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

Sources of Dissolved Solids ...............................................................................................................5

Estimation of Area Disturbed by Oil and Gas Development ...................................................................5

Review of Oil and Gas Development Plans and Best Management Practices .........................5

Compilation of Oil and Gas Well Data................................................................................................6

Developing a Calibration Dataset to Measure Land Disturbance from Constructing Oil 

and Gas Drill Pads and Resource Roads ............................................................................9

Methods Used to Estimate Land Disturbance Associated with Oil and Gas Development ....9

Description of Methods Used to Estimate Land Disturbance Associated with Oil 

and Gas Drill Pads .......................................................................................................12

Description of Methods Used to Estimate Land Disturbance Associated with Oil 

and Gas Resource Roads............................................................................................12

Description of Methods Used to Estimate Land Disturbance from Past Oil and Gas 

Development .................................................................................................................14

Description of Methods Used to Project Land Disturbance from Future Oil and Gas 

Development .................................................................................................................14

Estimated Current and Projected Future Land Disturbance from Oil and Gas Development.........................................................................................................................................16

Limitations and Considerations of Methodology....................................................................................18

Errors Associated with Well Locations in the 2007 Upper Colorado River Basin Oil and 

Gas Well Dataset...................................................................................................................19

Assessment of Methods Used to Model Land Disturbance from Oil and Gas Drill Pads.......19

Assessment of Methods Used to Model Land Disturbance from Oil and Gas Resource 

Roads.......................................................................................................................................21

Assessment of Methods Used to Project Future Land Disturbance from Oil and Gas 

Development ..........................................................................................................................25

Statistical Assessment of Dissolved-Solids Sources, Loads, and Transport in the Upper 

Colorado River Basin .....................................................................................................................25

Effects of Land Disturbance from Oil and Gas Development on Dissolved-Solids Loads 

in the Upper Colorado River Basin ....................................................................................25

Interpretation of Results....................................................................................................................28

Summary........................................................................................................................................................31

References Cited..........................................................................................................................................33

Appendixes 1 to 5.........................................................................................................................................37
iv

Figures

1. Map showing major oil and gas development areas in the Upper Colorado River 

Basin study area ........................................................................... 2

2. Graph showing the number of oil and gas wells started on Federal lands annually 

in Colorado, New Mexico, Utah, and Wyoming Fiscal Years 1990 to 2007 ......... 3

3. Map showing oil and gas well locations classified as “disturbed” and “not 

disturbed” in the Upper Colorado River Basin, 2007 .................................... 8

4. Map showing location of 76 cells used to create the oil- and gas-related land 

disturbance calibration dataset, Upper Colorado River Basin ........................ 10

5. Map showing digital line graph roads, primary and secondary oil and gas roads, 

and drill pads in a calibration cell near Rifle, Colorado, 2007 ........................ 11

6. Map showing model of oil and gas drill pads and resource roads overlying 

National Aerial Imagery Program imagery, near Rifle, Colorado, 2007 ............... 13

7. Map showing calculated average annual number of new oil and gas wells anticipated in known oil and gas resource areas, Upper Colorado River Basin and 

parts of surrounding area .................................................................. 17

8. Graph showing A, number of oil and gas wells classified as “disturbed” and the 

total estimated area of land disturbed by oil and gas drill pads and B, roads, and C, 

by both drill pads and roads, Upper Colorado River Basin, 1991, 2007, and 2025 ...... 18

9. Pie chart showing percentage of oil and gas wells classified as “disturbed” by 

Surface Management Agency or landowner, Upper Colorado River Basin, 2007 ... 19

10. Map showing 2005 National Agricultural Imagery Program imagery for an area 

near Rifle, Colorado, and well locations from the 2007 Upper Colorado River 

Basin oil and gas well dataset ............................................................ 20

11. Graphs showing A, percent difference between modeled and measured land 

disturbance from oil and gas drill pads, B, summary of measured and modeled 

area of land disturbance from oil and gas drill pads, C, distribution of difference 

between modeled and measured land disturbance from oil and gas drill pads, 

and D, correlation between modeled and measured land disturbance from oil 

and gas drill pads in 76 calibration cells, Upper Colorado River Basin, 2007......... 22

12. Graphs showing A, correlation between modeled and measured oil and gas 

resource road length and B, summary of modeled and measured measured 

road length in 76 calibration cells, Upper Colorado River Basin, 2007 ............... 24

13. Map showing location of calibration cells chosen to create the digital line graph 

assessment dataset, Upper Colorado River Basin .................................... 26

14. Map showing location of U.S. Geological Survey stream-monitoring sites with 

dissolved-solids monitoring data used for the 1991 Upper Colorado River Basin 

(UCRB) dissolved-solids SPARROW model and the 2007 exploratory UCRB 

dissolved-solids SPARROW model ...................................................... 27

15. Maps showing Upper Colorado River Basin SPARROW stream network 

indicating the percentage of the total contributing land area for each stream 

reach that was disturbed by oil and gas development in A, 1991 and B, 2007, 

Upper Colorado River Basin ............................................................... 29

16. Maps showing distribution of U.S. Geological Survey stream-monitoring sites 

used to calibrate A, the 1991 Upper Colorado River Basin (UCRB) dissolvedsolids SPARROW model and B, the 2007 exploratory UCRB dissolved-solids 

SPARROW model and the wells classified as “disturbed” in the UCRB oil and 

gas well dataset in 1991 and 2007 ......................................................... 32
v

Tables

1. Average oil and gas drill pad and resource road dimensions reported in reviewed 

Bureau of Land Management National Environmental Policy Act documents for 

states in the Upper Colorado River Basin ................................................ 6

2. Summary of oil and gas development forecasts from Bureau of Land Management resource management plans for the Upper Colorado River Basin ............ 15

3. Percentage of all oil and gas wells classified as “disturbed” and “not disturbed”, 

by Surface Management Agency or landowner, Upper Colorado River Basin, 

2007 .......................................................................................... 19

4. Percentage of the oil and gas wells classified as “disturbed” and the percentage 

of the area in each state contained in the 2007 Upper Colorado River Basin 

study area .................................................................................... 19

5. Area of dissolved-solids source groups defined for the 1991 Upper Colorado River 

Basin (UCRB) dissolved-solids SPARROW model and the 2007 UCRB exploratory 

dissolved-solids SPARROW model ...................................................... 30

6. Representation of dissolved-solids source groups in 1991 Upper Colorado River 

Basin (UCRB) dissolved-solids SPARROW model and 2007 exploratory UCRB 

dissolved-solids SPARROW model calibration reaches .............................. 31

Appendix tables 

1A. Summary of National Environmental Policy Act documents reviewed to 

identify common oil and gas drill pad and resource road dimensions for the 

Upper Colorado River Basin, Utah......................................................... 38

1B. Summary of National Environmental Policy Act documents reviewed to 

identify common oil and gas drill pad and resource road dimensions for the 

Upper Colorado River Basin, Colorado ................................................... 39

1C. Summary of National Environmental Policy Act documents reviewed to 

identify common oil and gas drill pad and resource road dimensions for the 

Upper Colorado River Basin, Wyoming ................................................... 40

2. Summary of Bureau of Land Management Resource Management Plans 

reviewed to identify reasonably foreseeable development scenarios for the 

Upper Colorado River Basin ............................................................... 42

3. Descriptions and water year 2007 dissolved-solids load estimates for 

selected sites in the Upper Colorado River Basin ....................................... 43

4. Sources of dissolved solids in Upper Colorado River Basin streams by 

bounded calibration reach excluding point-source import source group as 

defined for 1991 Upper Colorado River Basin SPARROW model ..................... 46

5. Sources of dissolved solids in Upper Colorado River Basin streams by 

bounded calibration reach excluding point-source import source group as 

defined for exploratory 2007 Upper Colorado River Basin SPARROW model ...... 55

17. Pie chart showing percentage of oil and gas wells classified as “disturbed” in the 

2007 Upper Colorado River Basin (UCRB) oil and gas dataset located on 

UCRB dissolved-solids SPARROW model geologic source groups .................. 33 
vi

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

)

acre 0.004047 square kilometer (km2

)

square mile (mi2

) 2.590 square kilometer (km2)

Volume

barrel (bbl), (petroleum,

1 barrel = 42 gal) 0.1590 cubic meter (m3

)

cubic foot (ft3) 0.02832 cubic meter (m3)

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). 
vii

Abbreviations and Acronyms Used in the Text

(Clarification or additional information given in parentheses) 

ANSI American National Standards Institute 

API American Petroleum Institute 

BLM Bureau of Land Management 

BMP Best Management Practices 

CS Common Status 

DLG Digital Line Graph 

DOQ Digital Orthophoto Quadrangle 

EA Environmental Assessment 

EIS Environmental Impact Statement 

EPCA Energy Policy and Conservation Act 

FY Fiscal Year 

GAP Geographic Area Plan

GIS Geographic Information System 

GPS Global Positioning System 

HUC Hydrologic Unit Code 

LOP Life of Project 

MDP Master Development Plan 

NAIP National Agricultural Imagery Program 

NED National Elevation Dataset (USGS) 

NEPA National Environmental Policy Act of 1969 

NHD National Hydrography Dataset 

NWIS National Water Information System (USGS) 

PLSS Public Land Survey System 

PRISM Precipitation-elevation Regressions on Independent Slopes Model (Oregon 

State University) 

RFD Reasonably Foreseeable Development 

RMP Resource Management Plan 

ROW Right of Way 

SMA Surface Management Agency 

SPARROW Spatially Referenced Regressions on Watershed Attributes (USGS) 

UCRB Upper Colorado River Basin 

U.S. United States 

USBR U.S. Bureau of Reclamation 

USFS U.S. Forest Service 

USGS U.S. Geological Survey 
viii
Land Disturbance Associated with Oil and Gas 

Development and Effects of Development-Related Land 

Disturbance on Dissolved-Solids Loads in Streams in the 

Upper Colorado River Basin, 1991, 2007, and 2025

By Susan G. Buto, Terry A. Kenney, and Steven J. Gerner

Abstract 

Oil and gas resource development in the Upper Colorado 

River Basin (UCRB) has increased substantially since the year 

2000. The UCRB encompasses several significant oil and gas 

producing areas that have the potential for continued oil and 

gas resource development. Land disturbance associated with 

oil and gas resource development is caused by activities 

related to constructing drill pads to contain drilling and well 

maintenance equipment and roads to access the drill pad. Land 

disturbed by oil and gas development has the potential to cause 

increased erosion, stream degradation, habitat fragmentation 

and alteration, and increase public use of areas that may be 

environmentally sensitive. Land disturbance resulting from oil 

and gas resource development has not been monitored and 

mapped on a regional scale in the UCRB. However, 

information on the location and age of oil and gas wells in the 

UCRB is available. These data combined with geographic data 

analysis and modeling techniques were used to estimate the 

total area of disturbed land associated with oil and gas resource 

development in 1991 and in 2007 in the UCRB. Additional 

information about anticipated oil and gas development in the 

UCRB was used to project land disturbance to the year 2025. 

Results of the analysis indicate that approximately 117,500 

acres (183 mi2

) of total land disturbance was associated with 

drill pads and related roads in the UCRB in 1991. The 

estimated area of disturbed land associated with oil and gas 

development increased 53 percent to 179,400 acres (280 mi2) 

in 2007. Projecting oil and gas development through 2025 

results in a potential near doubling of the land GLVWXUEDQFH

to approximately 319,300 acres (500 mi2). 

Estimated land disturbance for 1991 and 2007 were input 

to a contaminant transport model developed for the UCRB 

to assess the statistical significance of energy-related land 

disturbance to contributing dissolved solids to basin streams. 

The statistical assessment was an observational study based 

on an existing model and available water-quality monitoring 

data for the basin. No new data were collected for the 

analysis. The source coefficient calibrated for the disturbed 

lands associated with oil and gas development in 2007 was 

zero, which indicated that estimated land disturbance from 

oil and gas development is not statistically significant in 

explaining dissolved solids in UCRB streams. The lack of 

significance in the contaminant transport modeling framework 

may be due to the amount of available monitoring data, 

the spatial distribution of monitoring sites with respect to 

land disturbance, or the overall quantity of land disturbance 

associated with oil and gas development basin wide. Finally, 

dissolved-solids loads derived from natural landscapes may 

be similar to loads derived from lands disturbed by oil and 

gas resource development. The model recalibration done for 

this study confirms calibration results from Kenney and others 

(2009): the most significant contributor to dissolved solids in 

the UCRB is irrigated agricultural land, which covers an area 

substantially larger than the estimated area disturbed by oil 

and gas development and is subjected to artificially applied 

water. 

Introduction 

The inland sedimentary basins of the United States 

contain significant sources of oil and natural gas (U.S. Bureau 

of Land Management, 2006). Federal onshore lands contain an estimated 20 percent of the oil and 25 percent of the 

nation’s undiscovered natural gas resources (U.S. Bureau 

of Land Management, 2006). The Bureau of Land Management (BLM) has indicated that the oil and gas industries are 

interested in continuing to develop the Upper Colorado River 

Basin (UCRB; U.S. Bureau of Land Management, 2002). Oil 

and gas development areas in the UCRB include the UintaPiceance Province in northwestern Colorado and northeastern 

Utah, the San Juan Province in northwestern New Mexico and 

southwestern Colorado, the southwestern Wyoming Province, 

and the Paradox Basin in southern Utah and southwestern 

Colorado (fig. 1). 

A significant volume of known and potential oil and gas 

reserves occur in the sedimentary basins in the UCRB. In 

2002, the U.S. Geological Survey (USGS) estimated 21 trillion 

ft3

 of gas, 60 million barrels of oil, and 43 million barrels of 
2 Land Disturbance Associated with Oil and Gas Development

WYOMING

UTAH

COLORADO

ARIZONA

NEW MEXICO

IDAHO

ColoradoColorado

River

ColoradoColorado

River

Green

River

San JuanSan Juan

River

Rifle

Salt Lake City

Evanston

Green River

Price

Grand

Junction

Kayenta Farmington

Page

Gallup

Blanding

Durango

114° 108°

42°

39°

36°

111°

0

0

50

50

100 Miles

100 Kilometers

Base from U.S Census Bureau digital data, 2000 

Hydrography from USGS Enhanced River Reach File 2.0, 2002

Energy development areas from USGS National Oil and Gas assessment data, 1995 and 2002

Hillshade from 30-meter USGS National Elevation Dataset, 1999

Albers Equal Area Conic projection, central meridian at -96°, standard parallels at 29.5° and 

45.5°, latitude of origin at 23°, North American Datum of 1983

Hydrologic Unit Code (HUC) region 14 subbasins not included in UCRB study area

Major energy development areas

Paradox Basin

San Juan Province

Southwestern Wyoming Province

Uinta-Piceance Province

Upper Colorado River Basin (UCRB) 

boundary

Wind River Range

EXPLANATION

Wasatch Mountains

Continental Divide

Great Divide subbasin

Paria 

River 

subbasin

Colorado Plateau

Continental Divide

USGS stream gage 09380000

Lees Ferry

Study area

San Juan Mountains

Figure 1. Major oil and gas development areas in the Upper Colorado River Basin study area.
Introduction 3

natural gas liquids remain undiscovered in the Uinta-Piceance 

Province (U.S. Geological Survey, 2002a). In addition, the 

USGS estimated the San Juan Province could contain about 

50 trillion ft3 of gas, 19 million barrels of oil, and 148 million 

barrels of total natural gas liquids (U.S. Geological Survey, 

2002b). The southwestern Wyoming Province could contain 

84 trillion ft3 of gas, 131 million barrels of oil, and 2.6 billion 

barrels of total natural gas liquids (U.S. Geological Survey, 

2002c). No recent estimates of undiscovered reserves were 

available for the Paradox Basin. Huffman (1995) indicates the 

Aneth field, discovered in the Paradox Basin in 1956, contains 

approximately 1 billion barrels of proven oil reserves. 

The pace of oil and gas development in the UCRB has 

increased substantially since 2000. An average of 4,527 wells 

were started per year on Federal land in the five UCRB states 

in fiscal years 2006 and 2007 (FY, October 1 to September 

30) (U.S. Bureau of Land Management, 2008). An average of 

2,462 wells per year were drilled between FY 2000 and 2005. 

In contrast, an average of 1,284 wells were drilled per year 

in the preceding 10-year period, FY 1990 to 1999. Wyoming 

had the largest increase and the largest number of wells drilled 

since 2000 (fig. 2). According to BLM statistics, two wells 

were started on Federal land in Arizona between FY 1990 and 

2007.

Oil, natural gas, and coal bed methane exploration and 

reserve development occurs on both Federal and non-Federal 

lands in the UCRB. Calculations based on BLM and other 

National digital datasets (U.S. Bureau of Land Management, 

2006; John Reitsma, Bureau of Land Management, written 

commun., October 23, 2007; National Atlas of the United 

States, 2006a,b) indicate that approximately 60 percent of 

UCRB lands are Federally owned. Another 15 percent of lands 

are tribal owned. State-owned lands make up about 3.5 percent 

of the area and approximately 4.5 percent of land in the UCRB 

is split-estate land. Split-estate lands occur when the surface 

and mineral rights are owned by separate entities, usually one 

Federal and one non-Federal. Non-Federal entities include 

private landholders. On split-estate lands, the surface owner 

or managing agency controls the surface uses but the mineral 

estate is the dominant estate (U.S. Bureau of Land Management, 2006). The remaining 17 percent of land is private or 

managed by local governmental entities.

Oil and gas resource development requires construction 

of drill pads for well drilling and operation. A drill pad is a 

level area, usually several acres, that is constructed to provide 

a platform for drilling and then operating and maintaining 

a completed, producing well. A low traffic volume, single 

lane resource road is usually constructed to access each drill 

pad. Roads can erode land, degrade streams, fragment and 

alter habitat and increase public use of an area (U.S. Bureau 

of Land Management, 2007). Drill pads may have similar 

environmental effects. Drill pads and roads can be reclaimed 

Statistics include all public lands except for tribal lands. Data are for entire area of each state and were last updated February 21, 2008

0

500

1,000

1,500

2,000

2,500

3,000

TOTAL NUMBER OF WELLS

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

FISCAL YEAR

Colorado

New Mexico

Utah

Wyoming 

Figure 2. The number of oil and gas wells started on Federal lands annually in Colorado, New Mexico, Utah, and Wyoming Fiscal Years 

1990 to 2007.
4 Land Disturbance Associated with Oil and Gas Development

after the well is abandoned but reclamation may take decades 

to be completed in the arid landscapes of the UCRB. The 

rate at which plant communities recover during reclamation 

partly depends on climatic and vegetation conditions at each 

site. Even moderate disturbance in a site dominated by desert 

scrub can take 60 years to reach predisturbance biomass and 

180 years for reasonable recovery of species diversity, even 

on noncompacted soils (U.S. Bureau of Land Management, 

2009a). 

Salinity in steams, as measured by dissolved-solids 

concentration, can be affected by natural conditions, such 

as geology, precipitation patterns, or land cover, and by 

anthropogenic activities, such as land use and irrigation 

practices. Increased drill pad and road construction in the 

UCRB in recent years has raised concerns that the land 

disturbance associated with oil and gas development could 

increase erosion and soil material transport in the basin. 

Increased erosion and soil material transport has the potential 

to adversely affect water quality and dissolved-solids load in 

the surface waters of the UCRB by increasing the volume of 

readily dissolved mineral salts transported from drill pads and 

roads to streams. 

The USGS Spatially Referenced Regressions on 

Watershed Attributes (SPARROW) surface water-quality 

model relates measured chemical constituents at monitoring 

stations to upland catchment attributes, such as land use, land 

cover, or geology (Smith and others, 1997). The USGS, in 

cooperation with U.S. Department of the Interior—Bureau of 

Reclamation (USBR) and BLM, has developed a dissolvedsolids SPARROW model of the UCRB to assess the sources 

and transport mechanisms of dissolved-solids loads in streams 

throughout the basin (Kenney and others, 2009). Land 

disturbance from oil and gas development in the UCRB has 

been estimated using geographic information system (GIS) 

analysis and modeling techniques. Results from the estimation 

have been input to the UCRB dissolved-solids SPARROW or 

UCRB SPARROW model to assess the statistical significance 

of land disturbance related to oil and gas development on 

dissolved-solids transport in the UCRB.

Purpose and Scope 

Regional-scale compilation, synthesis, and analysis of 

data defining land disturbance related to oil and gas development and its effects on water quality may help to improve 

understanding of the potential cumulative effects of oil and 

gas development in the UCRB. Land disturbance associated 

with oil and gas well drilling is not regularly or consistently 

mapped at state or regional scales in the study area. This report 

consolidates information about oil and gas resource development in the UCRB and uses the information to estimate the 

amount of land disturbance related to energy development 

in the study area. Future potential disturbance was projected 

on the basis of information from BLM resource management 

plans (RMP) and reasonably foreseeable development (RFD) 

scenarios. The statistical significance of estimated current 

oil- and gas-related land disturbance on contributing dissolved 

solids to surface water in the study area was evaluated within 

the USGS SPARROW surface water-quality model for the 

UCRB. 

This report is organized into two major sections. The 

first section of the report describes methods used to model 

the amount of land disturbed by oil and gas development in 

the UCRB and gives the results of land disturbance estimates 

for existing disturbance in 1991 and 2007 and for projected 

future land disturbance by 2025. The second section of the 

report documents the statistical assessment of the contribution 

of oil and gas development-related land disturbance on 

dissolved-solids transport in streams and rivers in the UCRB. 

The statistical assessment was an observational study based 

on an existing UCRB SPARROW model and on available 

water-quality monitoring data for the basin. No new data were 

collected for this analysis.

Description of Study Area

The UCRB drains parts of Arizona, Colorado, New 

Mexico, Utah, and Wyoming (fig. 1). For this study and for 

the earlier SPARROW model described by Kenney and others 

(2009), the UCRB is defined as the contributing drainage 

basin of Hydrologic Unit Code (HUC) region 14 upstream of 

USGS streamflow-gaging station 09380000, Colorado River 

at Lees Ferry, Arizona. The 2,505,000-acre (3,900-mi2) Great 

Divide subbasin (HUC 14040200), northeast of the continental 

divide in Wyoming, is part of HUC 14 but is a closed basin 

and does not contribute runoff to the UCRB. The Great Divide 

subbasin has been excluded from the extent of the UCRB for 

this study. The 914,000-acre (1,400-mi2) Paria River subbasin 

(HUC 14070007) also has been excluded from this study 

because surface-water flows from the subbasin discharge 

below the USGS gage at Lees Ferry, Arizona. The UCRB, for 

the purposes of this study, has a contributing drainage area of 

about 69,200,000 acres (108,000 mi2

). Major river drainages in 

the UCRB include the Green, San Juan, and Colorado Rivers. 

The UCRB is bounded by the Wasatch Mountains in 

northern and central Utah to the west, the San Juan Mountains 

of Colorado and New Mexico to the southeast, and the Wind 

River Range in west-central Wyoming to the north (fig. 1). 

Basin landscapes vary, ranging from high alpine to arid desert. 

Annual precipitation ranges from about 40 inches, mostly as 

snow, near the continental divide to less than 10 inches on the 

Colorado Plateau (PRISM Group, Oregon State University, 

2007). Land cover in the basin is characterized by mixed 

desert scrub and rangeland, irrigated agriculture, and forested 

highlands. The largest urban area in the UCRB is Grand 

Junction, Colorado with a population of approximately 42,000 

according to the 2000 Census (U.S. Census Bureau, 2000). 
Estimation of Area Disturbed by Oil and Gas Development 5

Sources of Dissolved Solids

Geologic formations, particularly sedimentary rocks, are 

the largest natural source of dissolved solids transported to 

streams in the UCRB (Iorns and others, 1965; Liebermann and 

others, 1989; U.S. Department of the Interior, 2003; Anning 

and others, 2007; Kenney and others, 2009). Dissolved solids 

are produced from geologic formations containing soluble 

minerals that are dissolved by surface runoff and groundwater 

flow (Kenney and others, 2009). Saline springs discharge 

substantial quantities of dissolved solids from groundwater 

and may contribute as much as 800,000 tons of dissolved 

solids per year to UCRB streams (U.S. Department of the 

Interior, 2003). Irrigated agricultural lands are the major 

anthropogenic source of dissolved solids in the UCRB 

(Iorns and others, 1965; Liebermann and others, 1989; 

U.S. Department of the Interior, 2003). Irrigation in arid 

environments can alter the natural rate at which solids are 

dissolved and transported to streams. 

Dissolved-solids concentrations in streams differ 

throughout the study area as a result of varying climatic, 

hydrologic, and geologic conditions. A significant 

factor determining the composition of dissolved-solids 

concentrations is the predominant rock types and the soils 

derived from those rock types within a drainage basin. In 

general, sedimentary rock assemblages of Mesozoic and 

Cenozoic age yield the largest volumes of dissolved solids in 

the UCRB (Kenney and others, 2009). The middle and lower 

reaches of the Colorado, Green, and San Juan Rivers are 

underlain by sedimentary rocks that contain soluble minerals 

that have the potential to contribute to dissolved-solids loads 

in the UCRB (Iorns and others, 1965). 

Removing native vegetation and disturbing and 

compacting native soils to construct unpaved, or loose-surface, 

roads and drill pads can increase erosion from both wind and 

water at the disturbed site. Arid-land soils are often stabilized 

by chemical and biological crusts. Even a slight disturbance 

of these crusts can lead to active erosion of a previously stable 

ground surface (Wilshire and others, 1996). Compaction 

of soils from road construction, drill pad construction, and 

vehicular traffic may alter soil structure and thereby reduce 

infiltration capacity, which can increase runoff, erosion, 

and transport of loose soil material. Bare ground associated 

with drill pads and access roads may aid the efficiency of 

dissolved-solids transport from high-yield sedimentary 

assemblages by increasing the total sediment load of runoff 

waters. Dissolved solids are produced from sediment load by 

chemical dissolution of soluble mineral components in the 

sediment during fluid transport of eroded materials. Efforts 

are made to mitigate the potential for erosion from drill pads 

and access roads. BLM construction guidelines suggest, when 

appropriate, trapping well location runoff and sediments by 

using sediment fences or water retention ponds (U.S. Bureau 

of Land Management, 2007). 

Estimation of Area Disturbed by Oil and 

Gas Development

Estimates of land disturbance associated with oil and 

gas resource development in the UCRB were developed in 

several phases. First, documents relating to oil and gas Best 

Management Practices (BMP) and development plans for the 

UCRB were reviewed and information about common oil and 

gas drill pad and resource road construction practices were 

compiled. Second, oil and gas well data from public, statemanaged databases were assembled to create a single dataset 

of well locations for the study area. Information from the 

state databases was used to identify wells that were likely to 

be associated with active land disturbance related to drilling 

and maintaining the well. Third, A GIS-based calibration 

dataset was developed to show the pattern and extent of 

oil and gas-related land disturbance in the study area. The 

calibration dataset was also used to assess the completeness 

and accuracy of existing GIS-based road datasets for the study 

area. Finally, an oil- and gas-related land disturbance model 

for 2007 was created using GIS tools and techniques. The 

modeled disturbance included land disturbance created by the 

construction of drill pads and resource roads. The accuracy of 

the model was evaluated and compared with oil- and gasrelated land disturbance data from the calibration dataset. 

The same methods used to estimate oil- and gas-related land 

disturbance for 2007 were used to estimate oil- and gas-related 

disturbance for 1991 and to project potential land disturbance 

to the year 2025. Each phase is described in detail in the 

remainder of this section.

Review of Oil and Gas Development Plans and 

Best Management Practices 

Proposed drilling and leasing areas on Federal lands are 

subject to an evaluation of potential environmental impact 

under the National Environmental Policy Act of 1969 (NEPA) 

before sites are cleared and drilling commences. NEPA 

requires Federal agencies to assess the environmental effects 

of proposed actions before making decisions (Council on 

Environmental Quality, 2007). Environmental Assessments 

(EA) and Environmental Impact Statements (EIS) related 

to oil and gas development generally outline the number of 

proposed drill pads for a project or lease area and the average 

pad size during initial well development and during the life of 

the project (LOP). EA and EIS documents may also contain 

descriptions of total anticipated resource road length and width 

for the initial well development phase and for the LOP. NEPA 

and other guidance documents were reviewed to identify 

common drill pad and resource road construction practices in 

the UCRB. The information gathered and summarized from 

the reviewed documents was used in conjunction with high 

resolution aerial imagery showing oil- and gas-related land 

disturbance to devise the methods used to estimate the extent 

of land disturbance from oil and gas development described in 

this report.
6 Land Disturbance Associated with Oil and Gas Development

A total of 20 draft and final EIS documents for Utah and 

Wyoming and 8 Master Development Plans (MDP) for 

Colorado were reviewed and summarized (appendixes 1A–C). 

MDPs are EA documents developed by BLM Colorado field 

offices under guidance from onshore oil and gas orders 

implemented jointly by the U.S. Departments of Interior and 

Agriculture (U.S. Forest Service and U.S. Bureau of Land 

Management, 2007). All reviewed documents were obtained 

from the BLM. No EIS or EA directly related to oil and gas 

development and implemented exclusively by the U.S. Forest 

Service (USFS) were evaluated. No EIS or EA for Arizona or 

New Mexico were reviewed. Initial drill pad size reported for 

Colorado, Utah, and Wyoming was approximately 3.9 acres, 

but in-state averages varied widely (table 1). All three states 

indicated that the average drill pad size throughout the LOP 

was 1.5 acres or smaller. The average widths of LOP resource 

roads were less than 30 ft; initial widths were as much as 

60 ft. The larger initial width allows large equipment to access 

the drill pad. The road is partially reclaimed to a narrower 

width after the well is completed. During the draft EIS and EA 

process, several alternative plans are usually suggested with 

one scenario identified as the preferred development plan. 

Resource road and drill pad dimensions summarized in table 1

are based on the preferred alternative proposed in the draft 

document or are based on the final EIS if available. 

Suggested BMPs regarding drill pad and resource road 

construction are outlined in the BLM Gold Book (U.S. Bureau 

of Land Management, 2007) and Manual 9113 (U.S. Bureau 

of Land Management, 1985). The Gold Book recommends 

that drill pads be located in level areas away from narrow 

ridges and steep slopes. The Gold Book further recommends 

that operations be avoided or properly mitigated in riparian 

areas, floodplains, playas, lakeshores, wetlands, and areas 

subject to severe erosion and mass soil movement. Documents 

reviewed for this study recommend that a 500-ft wide buffer 

of undisturbed land will be maintained between construction 

areas and perennial stream channels or open water. The buffer 

area is usually reduced to 100 ft for ephemeral and intermittent 

stream channels. BLM guidelines suggest that resource road 

gradients should not exceed 8 percent except for short lengths 

to minimize the environmental effects of erosion.

Compilation of Oil and Gas Well Data

The location and current status of oil and gas wells in 

the UCRB is maintained in oil and gas well databases by each 

state in the region. Well information is also available from 

private companies that maintain subscription-based oil and 

gas well databases. The privately managed databases have 

restrictions on reuse and dissemination of the data. Because of 

these restrictions, state information held in publicly available 

databases was used in this study as the basis for estimating 

the total area of oil- and gas-related land disturbance in the 

UCRB. Colorado, New Mexico, Utah, and Wyoming maintain 

well records online (Colorado Oil and Gas Conservation 

Commission, 2007; New Mexico Institute of Mining and 

Technology Petroleum Recovery Research Center, 2007; 

Utah Division of Oil, Gas, and Mining, 2007; Wyoming 

Oil and Gas Conservation Commission, 2007). Arizona 

maintains records that are available upon request (Steve 

Rauzi, Arizona Geological Survey, written commun., August 

7, 2007). Records in the databases represent wells permitted 

on state, local, private, Tribal, and Federal lands in each state. 

Well information contained in the state databases includes 

American Petroleum Institute (API) identification numbers, 

the geographic location of the well, and information about the 

well’s status, and spud date. The spud date is the date drilling 

began (Schlumberger Limited, 2009). 

Tabular well data from the state oil and gas databases 

were acquired in the summer of 2007. The data from each state 

was migrated to a new table that was composed of a standard 

set of attributes, including the location of each well, the unique 

API number of the well, the spud date of each well, and the 

current status of the well. Attributes in a table or database 

are columns or fields of information that are used to describe 

the features in the table. Each state well record included an 

alphabetic code used to describe the status of the well. The 

state well status codes were modified before inclusion in the 

Table 1. Average oil and gas drill pad and resource road dimensions reported in reviewed Bureau of Land 

Management National Environmental Policy Act documents for states in the Upper Colorado River Basin.

[A list of reviewed documents is in Appendixes 1A–C. LOP, life of project; ROW, right of way; ft, feet]

State

State average

Utah Colorado Wyoming

Average estimated initial pad size (acres) 2.50 5.00 4.10 3.9

Average estimated LOP pad size (acres) 1.40 1.25 1.50 1.4

Lifetime average pad size by State (acres) 1.95 3.13 2.80 2.6

Average estimated initial ROW width (ft) 32.50 59.00 52.00 47.8

Average estimated LOP ROW width (ft) 21.00 26.00 28.00 25.0

Lifetime average ROW width by State (ft) 26.75 42.50 40.00 36.4
Estimation of Area Disturbed by Oil and Gas Development 7

new table by appending the two letter American National 

Standards Institute (ANSI) state alpha code (U.S. Census 

Bureau, 2008) to the state status code. Appending the state 

ANSI code to the state status code prevented confusion when 

two states used the same set of letters to identify different 

well status conditions. For example, the well status code SP 

identifies a spudded well in the Wyoming state database and 

a plugged and abandoned storage well in the Arizona state 

database. These codes were modified to WY-SP and AZ-SP 

to maintain the state definitions and create unique well status 

codes in the new table. Most of the wells in the state 

databases were either categorized as drilled and completed as 

producing wells, or drilled and abandoned at the time the state 

data were acquired. Some wells in the state databases were 

permitted but not drilled at the time the data were acquired. 

The state databases included spud dates and status 

dates. Status dates could be associated with either database 

maintenance or with the date when the well’s status changed. 

Status date was not clearly defined for any of the state 

databases. The attribute “status date” was maintained in 

the new table to provide temporal information for wells 

where spud dates were missing or incomplete. API numbers 

and well locations expressed in latitude and longitude were 

transferred directly from the state databases to the new

table. Attributes used to identify the disturbance classification 

and location source information for each well were included in 

the new table and determined for this study. 

Each state table was converted to a point feature class 

stored in a geodatabase. A feature class is a dataset, or 

collection of geographic features, that have the same geometry 

type (such as point, line, or polygon), the same attribute 

fields, and the same spatial reference (Environmental Systems 

Research Institute, 2009a). A geodatabase is a database used 

to store, query, and manipulate spatial data (Environmental 

Systems Research Institute, 2009a). Each point in the feature 

class represented a well location based on the latitude, 

longitude, and datum information supplied by the states. 

Latitude or longitude information was missing for over 

2,000 New Mexico well records. The New Mexico database 

included Public Land Survey System (PLSS) township, range, 

and section with each well record. The location of wells with 

incomplete location information was estimated from the PLSS 

information using the BLM township geocoder. The township 

geocoder allows township, range, section, and quarter section 

values to be converted into latitude and longitude (U.S. 

Bureau of Land Management and U.S. Forest Service, 2008a). 

The location returned by the geocoder is the centroid of the 

section or quarter section polygon that is input to the geocoder 

interface. Well locations estimated using the PLSS information 

were identified in the well feature classes in an attribute 

named “location source.” The individual feature classes were 

projected to Albers Equal Area Projection, merged into a 

single feature class, and clipped to the boundary of the study 

area to create the final 2007 UCRB oil and gas well dataset. 

The final well dataset contained 89,282 points representing 

well locations in the study area. 

A simplified common status (CS) code attribute was 

added to the 2007 UCRB oil and gas well dataset and defined 

for four well types: “active”, “inactive”, “abandoned–

disturbed”, and “abandoned–not disturbed.” State status codes 

identifying a well as producing, spudded, or active were 

assigned the CS code “active.” Wells with state status codes 

indicating the well had been permitted but not yet drilled or 

identifying the well as an abandoned location were assigned 

the CS code “inactive.” About 20,000 wells in the 2007 UCRB 

oil and gas well dataset had a state status code indicating 

the well had been plugged and abandoned. CS codes were 

assigned to each plugged and abandoned well location on the 

basis of visual inspection of randomly selected wells plotted 

on top of 2005–2007 1-meter resolution National Agricultural 

Imagery Program (NAIP) imagery (U.S. Department of 

Agriculture, 2006). Land disturbance was clearly visible in 

the NAIP imagery at the locations of most inspected well 

locations drilled in the mid-1970s and later. Land disturbance 

was less evident or absent at older well locations. Wells dated 

from 1975 or later were assigned the CS code “abandoned–

disturbed” on the basis of this observation. Plugged and 

abandoned wells dated before 1975 were coded “abandoned–

not disturbed.” Status date was substituted for spud date when 

assigning the CS code to 30,764 wells because spud dates 

were missing in the source data. Substituting status date for 

spud date assumes that the well’s status date has some relation 

to drilling activity and is not simply related to database 

maintenance activities. Both spud date and status date were 

missing for 7,162 wells in the 2007 UCRB oil and gas well 

dataset and several wells had invalid date information, such 

as 7/1/5003 and 12/1/2402. Plugged and abandoned wells 

with no status or spud date or with invalid status or spud dates 

were assigned the CS code “abandoned–not disturbed.” Lack 

of date information or substitution of dates can affect the 

accuracy of the CS code a well was assigned. 

Common status codes were used to further classify each 

well as “disturbed” or “not disturbed.” For the purposes of 

this study, an oil and gas well that is classified as “disturbed” 

is assumed to be associated with an area of active land 

disturbance related to the drill pad constructed to contain 

drilling equipment and the road used to access the drill pad. 

The land is disturbed by removing the natural vegetation and 

modifying natural topography to accommodate drilling and 

well maintenance activities. The disturbed drill pad area and 

road are maintained for access to the well head if the well 

becomes a producing well. Wells with CS codes “active” or 

“abandoned–disturbed” were classified as “disturbed.” Wells 

with all other CS codes were classified “not disturbed.” In the 

database, 61,780 wells (69 percent of the total) are classified 

as “disturbed” (fig. 3). The 2007 UCRB oil and gas well 

dataset can be downloaded from the USGS at http://water.

usgs.gov/GIS/metadata/usgswrd/XML/sir2010_5064_UCRB_

ogdb.xml.
8    Land Disturbance Associated with Oil and Gas Development

Figure 3.  Oil and gas well locations classified as “disturbed” and “not disturbed” in the Upper Colorado River Basin, 2007. 

Major energy development areas

Paradox Basin

San Juan Province

Southwestern Wyoming Province

Uinta-Piceance Province

Upper Colorado River Basin boundary

Oil or gas well

Classified as “disturbed”

Classified as “not disturbed”

114° 108°

42°

39°

36°

111°

0

0

50

50

100 Miles

100 Kilometers

Base from U.S Census Bureau digital data, 2000

Energy development areas from USGS National Oil and Gas assessment data, 1995 and 2002

Hillshade from 30-meter USGS National Elevation Dataset, 1999

Albers Equal Area Conic projection, North American Datum of 1983

EXPLANATION

WYOMING

UTAH

COLORADO

ARIZONA

NEW MEXICO

IDAHO
Estimation of Area Disturbed by Oil and Gas Development 9

Developing a Calibration Dataset to Measure 

Land Disturbance from Constructing Oil and Gas 

Drill Pads and Resource Roads 

A calibration dataset was developed to help 

systematically measure resource road and drill pad geometry 

across the UCRB, to verify information gathered from BMP 

and development plans, and to calibrate and assess the 

accuracy of the methods used to estimate oil- and gas-related 

land disturbance in the study area described in the report 

section titled “Methods Used to Estimate Land Disturbance 

Associated with Oil and Gas Development.” The extent of 

the calibration data were constrained by 100-km2 (38.6-mi2) 

calibration cells that were randomly selected from a feature 

class containing a continuous grid of cells distributed across 

the study area. To select the calibration cells, 100 randomly 

placed points were produced within the boundaries of the 

continuous grid. The points were created using a GIS tool 

that randomly generates a specified number of points within a 

user-defined area (Environmental Systems Research Institute, 

2009b). No constraint was placed on the number of points 

that could be placed within a single grid cell. Grid cells 

that contained one or more randomly generated points were 

selected as calibration cells. The final selection consisted of 76 

cells, each of which was assigned a unique identifying number 

(fig. 4). 

The land area within each of the 76 calibration cells 

was inspected for visible surface disturbance that could be 

attributed to oil and gas development. Each calibration cell 

was examined on a computer screen against a backdrop of 

2005–2007 NAIP imagery (U.S. Department of Agriculture, 

2006). Sixty of the selected calibration cells contained oil- and 

gas-related land disturbance. The remaining 16 contained 

no land disturbance that could be attributed to oil and gas 

development. 

Land disturbance that could be attributed to oil and 

gas development within the boundaries of each calibration 

cell was manually digitized into the calibration dataset. 

Visible drill pads were digitized into the calibration dataset 

as polygons (fig. 5). The extent of the digitized polygon was 

constrained by the boundary of the calibration cell; therefore, 

only the part of the drill pad inside the calibration cell was 

digitized. Well locations from the UCRB oil and gas database 

were used to help identify bare areas visible in the NAIP 

imagery as oil and gas drill pads. Bare areas that showed 

characteristics common to drill pad construction, such as 

the presence of a pit for containment of drilling fluids or a 

characteristic rectangular shape with a visible access road, 

were digitized even if no well point fell within or near the bare 

area. 

Resource roads were digitized from the road’s origin at 

the edge of the drill pad to the location where the resource 

road intersected an existing road contained in a USGS Digital 

Line Graph (DLG) dataset (fig. 5). DLG data are digital 

representations of cartographic information converted from 

maps and related sources (U.S. Geological Survey, 1996a). 

The DLG data used to represent existing, or baseline, roads 

for this analysis were produced from USGS 1:100,000-scale 

30- by 60-minute topographic quadrangle maps and BLM 

1:100,000-scale planimetric maps. The DLG roads were used 

to represent existing roads for this study to maintain continuity 

with the earlier SPARROW study for the UCRB (Kenney and 

others, 2009), for which the DLG roads were used to calculate 

road densities in the study area. For this study, the DLG 

road datasets were compared with more recent road datasets, 

including the 2001 National land cover data impervious 

surface (Multi-Resolution Land Characteristics Consortium, 

2001) and Bureau of Transportation Statistics roads data 

(U.S. Geological Survey, 2007) and found to be of similar 

resolution and quality. None of the datasets evaluated as 

potential baseline road layers accurately captured the extent of 

the unpaved road network visible in the NAIP imagery in the 

study area. Resource roads were digitized into the calibration 

dataset as lines representing the approximate centerline of the 

road and classified as either primary or secondary oil and gas 

roads (fig. 5). The extent of the digitized line representing 

an oil and gas road was constrained by the boundary of the 

calibration cell so that only the part of the road inside the cell 

was digitized. If the source drill pad was alone or far from 

other drill pads, a single primary resource road was designated 

for the drill pad and other roads directly connected to the drill 

pad were classified as secondary access roads. If the drill pad 

was part of a large network of drill pads, roads that appeared 

to be directly connected in a network and could be used for 

primary access to the drill pads were digitized and classified 

as primary roads. Secondary roads were digitized only when 

directly associated with a drill pad. Additional roads that 

connected with the primary resource road or secondary access 

roads were assumed to have been created by other activities, 

such as recreational driving, grazing access, or short cutting 

between pads, and not directly associated with oil and gas 

development. 

Methods Used to Estimate Land Disturbance 

Associated with Oil and Gas Development 

Land disturbance associated with oil and gas development is not regularly or consistently mapped in the UCRB 

at state or regional scales. Accurately mapping oil- and 

gas-related land disturbance is difficult because of 

the large spatial extent of the study area. Land disturbance 

estimates developed for this study were based on information 

gathered from existing oil and gas well databases, information from EIS and other guidance documents, and observations made from aerial imagery rather than from mapping 

the precise extent and location of all oil and gas-related land 

disturbance in the study area. Estimates of land disturbance 

from drill pads are described in the next section followed by 

a description of the methods used to model land disturbance 

from resource roads.
10 Land Disturbance Associated with Oil and Gas Development

114° 108°

42°

39°

36°

111°

0

0

50

50

100 Miles

Base from U.S Census Bureau digital data, 2000 100 Kilometers Albers Equal Area Conic projection, North American Datum of 1983

Upper Colorado River Basin boundary

100-square-kilometer calibration cell — Number 

refers to unique identifier for each cell

Cell contains land disturbance from oil and gas 

drilling

Cell contains no land disturbance from oil and 

gas drilling

EXPLANATION

WYOMING

UTAH

COLORADO

ARIZONA NEW MEXICO

IDAHO

1833

1796

1775

1755

1717

1662

1676 1683 1653

310

1607

1557

1584

1445

1482

1532

1538

1412

1414

1333

294

1387

1436

1473

1495

1525

1316

1403

1465

1375

1099

1344

1062

1345

1192

1144

1183

1258

1271

797

799 824

837

989

923

1051

785

814

858

905

1033 1010

780

854

887

508

663

611

504 518

566 609

632

274

367

403

404

219

324

391

54 57

203

135

7

1758

Figure 4. Location of 76 cells used to create the oil- and gas-related land disturbance calibration dataset, Upper Colorado River Basin.
Estimation of Area Disturbed by Oil and Gas Development 11

0 0.5 1 1.5 2 Miles

0 10.5 1.5 2 Kilometers

Base from U.S. Census Bureau digital data, 2000

Image from USDA National Agricultural Imagery Program, preliminary compressed county 

mosaic for Garfield County, CO, 2005

Albers Equal Area Conic projection, North American Datum of 1983

100-square-kilometer calibration cell

Drill pad from digitized calibration data

Existing road from U.S. Geological 

Survey digital line graph

Roads from digitized calibration data

Primary oil and gas road

Secondary oil and gas road

EXPLANATION

107°55' 107°50'

39°35'

39°30'

Detail

Figure 5. Digital line graph roads, primary and secondary oil and gas roads, and drill pads in a calibration cell near Rifle, Colorado, 

2007. 
12 Land Disturbance Associated with Oil and Gas Development

Description of Methods Used to Estimate Land 

Disturbance Associated with Oil and Gas Drill 

Pads 

Information from the reviewed NEPA and BMP 

documents and measurements based on the calibration dataset 

were used in conjunction with the UCRB oil and gas well 

dataset to develop estimates of land disturbance from oil and 

gas drill pad construction. A circular buffer was created around 

each well classified as “disturbed” in the 2007 UCRB oil and 

gas well dataset and stored in a GIS feature class. The buffer 

is a circular polygon with the well point at the center of the 

polygon. The radius of the circle is the specified buffer size. 

Areas where buffers overlapped were treated as a single area 

of disturbance. 

A series of differently sized buffer polygons ranging in 

radius from 175.5 to 182.1 ft (53.5 to 55.5 m) were compared 

to the calibration dataset. The selected buffer sizes correspond 

to a drill pad model that ranges in size between 2 and 2.5 

acres. Buffer sizes were selected to correspond with average 

pad sizes reported in reviewed NEPA documents (table 1, 

appendix 1A-1C) and with measurements taken from the 

calibration dataset. The total modeled pad area from each 

tested buffer size was compared with the total pad area 

digitized in the calibration dataset. A 177.2-ft (54-m) radius 

buffer underestimated the total drill pad disturbance measured 

in the calibration dataset by less than 1 percent. The area of 

a circle with a 177.2-ft radius equals 2.26 acres. The area of 

land disturbed by oil and gas drill pads in the UCRB for 2007 

was modeled by applying a 177.2-ft radius buffer to wells in 

the 2007 UCRB oil and gas well dataset that were classified as 

“disturbed” (fig. 6).

Description of Methods Used to Estimate 

Land Disturbance Associated with Oil and Gas 

Resource Roads

BLM road construction guidelines suggest that a single 

resource road should be constructed to access a drill pad. 

Additional roads connected to drill pads may be the result 

of shortcuts created by drilling and well service personnel 

or by recreational driving and off-road vehicle traffic that is 

unrelated to oil and gas development. For this analysis, road 

disturbance from resource roads is assumed to occur on a 

single access road originating at a drill pad and terminating at 

an existing road mapped in the 1:100,000-scale USGS DLG 

roads dataset previously described. 

GIS least-cost distance tools were used to model the 

location of the single, primary resource road used to access 

each oil and gas drill pad. The least-cost path method models 

a path from a source to a destination based on a raster, or cellbased cost surface (Environmental Systems Research Institute, 

2008). The cost surface is created by applying a weight to 

each raster cell. The weight assigned to each cell represents 

the difficulty associated with travel through the cell. Higher 

weights are assigned to cells where travel should be restricted. 

For example, when modeling the fastest route between 

destinations on an existing street network, the cost surface 

may be constructed using existing speed limits as weights. 

Raster cells representing roads with slower speed limits would 

be assigned a higher cost value so that the slowest routes 

correspond with the highest cost of travel. Costs are usually 

based on inherent features in the location (Environmental 

Systems Research Institute, 2008). High costs may be assigned 

to travel on steep slopes or across protected land cover classes, 

such as wetlands or riparian areas, to restrict the location of 

modeled paths. Paths created using this method are GIS-based 

representations of road locations and do not represent actual 

road locations constructed to access drill pads.

Several cost surfaces based on slope or a combination of 

slope and simulated riparian areas were tested for this analysis. 

First, a percent-slope dataset was calculated for the study area 

from 1 arc-second USGS National Elevation Data (NED; U.S. 

Geological Survey, 1999a). The NED is a raster representation 

of elevation. The raster is composed of a grid of square cells 

each of which is assigned a value representing the average 

elevation of the area covered by that cell. A raster cell in the 1 

arc-second NED represents an area approximately 30 m 

(98.4 ft) on each side. The percent-slope dataset was 

reclassified into four separate cost surface datasets. The first 

dataset contained four classes of slope values. Each class was 

assigned an arbitrarily chosen integer value that increased with 

increasing slope. The value assigned to each class represented 

the cost to travel across the raster cell. The next group 

contained seven classes. The final two datasets contained 14 

and 30 classes respectively. Increasing the number of classes 

in the cost surface dataset allowed for finer control over the 

routes created across the cost surface by the model. 

A least-cost path model was created using each of the 

cost surfaces described above. Locations of the oil and gas 

wells classified as “disturbed” in the 2007 UCRB oil and gas 

well database were input to the model as destinations. The 

1:100,000-scale DLG roads data were input to the model as 

the sources so that a path was created to each well location 

from the nearest DLG road along a path calculated by the 

model. The results were visually inspected and compared with 

digitized resource roads from the calibration dataset. In all 

cases, the least-cost path model based on slope cost surfaces 

created paths that meandered in riparian areas and in areas 

with shallow slopes. 

A buffer area around perennial and intermittent stream 

courses was created and combined with the cost surfaces 

to better control the behavior of the cost path model. 

Stream courses mapped in the medium-resolution National 

Hydrography Dataset (NHD; U.S. Geological Survey, 1999b) 

were used to model the riparian areas. The NHD contains 

codes that identify perennial, intermittent, and other types of 

stream courses. Stream lines coded as perennial water courses 

were buffered by 500 ft, and intermittent stream lines were 

buffered by 100 ft. The buffered streams, representing riparian 

areas, were converted to raster format, assigned the highest 

cost value from the slope cost surface, and combined with 
Estimation of Area Disturbed by Oil and Gas Development 13

0 0.5 0.75 Mile

0 0.25 0.5 0.75 Kilometer

Base from U.S. Census Bureau digital data, 2000

Image from USDA National Agricultural Imagery Program, preliminary compressed county 

mosaic for Garfield County, CO, 2005

Albers Equal Area Conic projection, North American Datum of 1983

EXPLANATION

107°55' 107°54'

39°31'

39°30'

0.25

Boundary of oil and gas drill pad created from 177.2-foot radius buffer

Oil and gas resource road modeled using least-cost path method

Road from U.S. Geological Survey digital line graph

Boundary of 100-square-kilometer calibration cell #989

Upper Colorado River Basin oil and gas well dataset

Oil or gas well classified “disturbed”

Oil or gas well classified “not disturbed”

Calibration cell # 989

Detail

Figure 6. Model of oil and gas drill pads and resource roads overlying National Aerial Imagery Program imagery, near Rifle, Colorado, 

2007.
14 Land Disturbance Associated with Oil and Gas Development

the 14- and the 30-class slope cost surfaces. A least-cost path 

model was created for each of the riparian-slope cost rasters. 

The 1:100,000-scale DLG roads were input to the cost path 

model as the source, and the destination was set to the oil and 

gas wells that had been classified as “disturbed” in the 2007 

UCRB oil and gas well dataset. The results were visually 

compared to NAIP imagery and the calibration dataset. Paths 

created from the riparian-slope cost rasters tended to create 

more direct routes from the source road to the destination well. 

The 2007 least-cost path datasets were compared with the total 

length of primary resource roads digitized in the calibration 

dataset. The path dataset based on 30 slope classes combined 

with riparian areas most closely matched the total length of 

primary resource roads measured in the calibration dataset. As 

previously noted, roads created using least-cost path methods 

are representations of the primary resource roads (fig. 5) 

constructed to access drill pads and do not match the exact 

location of actual roads (fig. 6). If a road in the source DLG 

dataset was less than 98.4 ft (30 m) from the well destination, 

no path to the well was calculated in the model because a path 

already existed. Because of this, the total resource road length 

estimate does not take into account resource roads that were 

present in the USGS 1:100,000-scale DLG dataset.

Resource road right of way (ROW) widths were 

measured in selected calibration cells in the study area. 

Measured road widths incorporated all visible disturbance, 

including the main road surface and drainage ditches and 

berms on either side of the primary roadway. The average 

measured ROW width was approximately 35 ft, which 

compares favorably with ROW widths reported in NEPA 

documentation (table 1, appendix 1A-1C). The total area of 

land disturbance associated with oil and gas resource roads for 

2007 in the UCRB was estimated by creating a 17.5-ft buffer 

on both sides of each modeled resource road and summing 

the area of the buffer polygons. A 17.5-ft buffer results in a 

35-ft-wide polygon around the modeled resource road. 

Description of Methods Used to Estimate Land 

Disturbance from Past Oil and Gas Development

Estimates of land disturbance associated with oil and 

gas development through 1991 were required as input to 

the UCRB SPARROW model (Kenney and others, 2009), 

which was calibrated to monitoring data for water year 

1991 (October 1990–September 1991; a water year is the 

12-month period from October 1 through September 30 and 

is designated by the calendar year in which it ends). Land 

disturbance associated with oil and gas development through 

1991 was estimated by identifying wells dated 1991 or earlier 

in the 2007 UCRB oil and gas well dataset. Wells were first 

selected on the basis of spud year or, if the well had no spud 

date, status year. Wells that had no spud or status date or had 

erroneous dates were included in the 1991 estimation. The 

resulting selection contained 48,073 well locations. Status 

codes for these wells were assessed in the same manner as 

that used to assess codes in the 2007 UCRB oil and gas well 

dataset. Each well was assigned a CS code to indicate whether 

the well was classified as “disturbed” or “not disturbed.” 

Wells plugged and abandoned before 1960 were assigned 

CS code “abandoned–not disturbed” and classified “not 

disturbed.” Wells plugged and abandoned between 1960 

and 1991 were assigned CS code “abandoned–disturbed” 

and classified “disturbed.” Wells with no spud or status date 

or with erroneous dates kept their previously assigned CS 

code “abandoned–not disturbed” and were classified “not 

disturbed.” In 1991, 36,483 wells were classified “disturbed” 

and 11,590 wells were classified “not disturbed.” The area 

disturbed by oil and gas drill pads and resource roads in 

1991 was estimated using the same methods as those used to 

estimate land disturbance in 2007. 

Description of Methods Used to Project 

Land Disturbance from Future Oil and Gas 

Development

Oil and gas development on public lands in the western 

United States has increased in the last decade, and will likely 

continue in the UCRB (U.S. Bureau of Land Management, 

2008). The 2007 UCRB oil and gas well dataset and BLM 

forecasts of potential future oil and gas development were 

used to project land disturbance from oil and gas development activities through 2025. RMPs are developed to guide 

management decisions for large areas of Federal land in the 

western United States. RMPs often cover a span of 10 to 15 

years and are usually developed by BLM field offices but may 

also be produced as cooperative agreements between multiple 

land-management stakeholders in a region. An example of a 

cooperative management plan is the San Juan Public Lands 

RMP developed jointly by the USFS and BLM (U.S. Bureau 

of Land Management, 2009b). RMPs commonly include 

RFD documents outlining the amount and types of resource 

extraction activity expected for the life of the RMP. Seventeen 

RMPs were reviewed to estimate future oil and gas development in the UCRB (appendix 2). 

Information from RMPs was integrated into a single 

table identifying the projected development expected 

within the resource area covered by the RMP (table 2). The 

BLM field offices reported RMP information in different 

ways, some offices presenting minimum and maximum 

anticipated development and others presenting a single value 

representing expected development. This study did not revise 

or modify BLM estimates derived from the RMPs but did 

use conservative methods to calculate average anticipated 

development within the study area. RMP estimates were 

usually associated with known resource areas or with USGS 

“plays” identified in the National oil and gas assessment 

(U.S. Geological Survey, 2009). A “play” is a set of known 

or postulated oil and/or gas accumulations sharing similar 

geologic, geographic, and temporal properties (U.S. 

Geological Survey, 1996b). Most of the RMP documents 

examined were published between the years 2000 and 2008. 
Estimation of Area Disturbed by Oil and Gas Development 15

Table 2. Summary of oil and gas development forecasts from Bureau of Land Management resource management plans for the Upper 

Colorado River Basin.

[BLM, Bureau of Land Management; RMP, Resource Management Plan]

Resource area

Anticipated number

of wells reported

in BLM RMP

BLM 

field office RMP date

Length of 

RMP 

(years)

Comments

Minimum Maximum

San Juan Basin (New Mexico 

and Colorado)

12,461 16,615 Farmington, 

Columbine

2001 20 Based on New Mexico estimates of expected subsurface 

completions.

Glenwood Springs-Roan Plateau 2,976 3,691 Glenwood 

Springs

2006 20 Maximum value is based on number of wells in proposed 

alternative. Minimum value is based on number of wells 

estimated in no action alternative. 

Grand Junction operational area 300 1,000 Grand Junction 1985 20 Assumed same drilling densities from 1985 RMP.

Kemmerer gas 2,680 Kemmerer 2008 20 Coal and non-coal gas totals.

Little Snake operational area 3,031 Little Snake 2007 20

Moab operational area 150 600 Moab 2005 15 Sum of all reported areas in Moab field office RMP.

Colorado San Juan public lands 1,185 Multiple - see 

comments

2007 15 San Juan public lands RMP. Covers parts of Dolores, 

Columbine, and Pagosa Springs BLM field offices.

Jonah 500 3,100 Pinedale 2008 20

LaBarge and south central 120 2,000 Pinedale 2008 20 Counts calculated based on 20 to 100 wells per township 

density.

Merna 1,152 2,304 Pinedale 2008 20 Counts calculated based on 1 to 2 wells per 40 acres.

Pinedale Anticline 900 2,450 Pinedale 2008 20

Pinedale coalbed gas 600 Pinedale 2008 20 Based on estimate of 600 wells in low potential areas.

Emery-Book Cliffs-Price 

operational area

940 Price 2004 20 Sum of Book Cliffs/Emery and remainder of Price planning 

area.

Tavaputs Plateau - Price 600 Price 2004 20

Rawlins area 8,822 Rawlins 2008 20

Richfield area 1, 2a, and 3b 94 Richfield 2005 15 Area 4c (potential 360 wells) is largely outside the study 

area and was omitted from these estimates.

LaBarge - Rock Springs west 80 400 Rock Springs 1997 20 Based on Pinedale LaBarge and south-central estimates.

Rock Springs central and east 3,000 Rock Springs 1997 20 Estimate based on density of drilling in Rawlins RMP.

Altamont-Bluebell 425 Vernal 2008 15 Oil, gas, and coalbed gas.

East Tavaputs Plateau 677 Vernal 2008 15

Manila-Clay Basin 42 Vernal 2008 15

Monticello operational area 75 315 Monticello 2008 15 Total of reported values for Paradox fault and fold belt, 

Blanding subbasin, and Monument upwarp.

Monument Butte - Red Wash 4,658 Vernal 2008 15

Tabiona-Ashley Valley 28 Vernal 2008 15

West Tavaputs Plateau 454 Vernal 2008 15

White River operational area 18,200 21,650 White River 2007 20 Oil and gas plus coalbed methane wells included in estimate.

One plan was from 1997 and one from 1985. Oil and gas 

development estimates outlined in older documents were 

included in the analysis with the assumption that development 

activities in these geographic areas would continue 20 more 

years at the pace outlined in the older document. The average 

number of wells reported for each resource area or play was 

calculated from the minimum and maximum number of 

wells reported in each RMP. If no minimum was reported, 

the average was calculated as half the reported number of 

expected wells. In some cases, the expected development was 

reported as the anticipated density of wells within a known 

resource area. These data were converted to an expected 

number of wells on the basis of the total area of anticipated 

development cited in the RMP. The RMP for the Farmington, 

New Mexico, field office area reported development in terms 

of expected subsurface completions. The reported values 

were used with the assumption that each completion would be 

associated with a single drill pad. Calculating the number of 
16 Land Disturbance Associated with Oil and Gas Development

disturbed drill pads using the average number of subsurface 

completions may result in overestimating drill pad densities in 

the geographic area covered by the RMP. 

Existing oil and gas resource areas were identified from 

digital state oil and gas maps (De Bruin, 2002; Chidsey and 

others, 2004; Wray and others, 2005), resource areas from the 

2006 BLM Energy Policy and Conservation Act (EPCA) 

report (U.S. Bureau of Land Management, 2006), and BLM 

township and range polygons (U.S. Bureau of Land 

Management and U.S. Forest Service, 2008b). Known oil and 

gas development areas were selected and cross-referenced 

with the areas reported in the reviewed RMP documents. The 

selected areas were merged with a GIS dataset of leasable land 

parcels from the BLM EPCA report. Merging the selected oil 

and gas development areas with leasable land parcels created a 

dataset which represented resource areas where future oil and 

gas drilling is likely to occur. The resource areas represented 

areas of anticipated activity in the total area reported in the 

RMP and occasionally extended outside the UCRB boundary. 

The average annual number of wells anticipated for each 

resource area was estimated by dividing the calculated average 

number of wells for each resource area by the number of years 

covered by the RMP pertaining to that resource area (table 2). 

The calculated average annual number of wells was used to 

estimate the total number of wells that are projected to be 

drilled in each resource area between 2007 and 2025 (fig. 7). 

To estimate the total cumulative number of wells 

associated with active disturbance that could be expected in 

2015, the 2007 UCRB oil and gas well dataset was modified 

by assuming that disturbance associated with wells in the 

dataset that had been plugged and abandoned between 1975 

and 1983 would be successfully restored to natural or near 

natural conditions between 2007 and 2015. These wells, 

previously assigned CS code “abandoned–disturbed”, were 

selected and assigned CS code “abandoned–not disturbed.” 

Random points representing new wells were generated within 

the resource area polygons. The number of random well 

points generated within a resource area equaled the calculated 

number of wells anticipated for the 8-year period between 

2007 and 2015. The new wells were assigned CS code 

“active” and classified as “disturbed.” The wells were clipped 

to the study area boundary and merged with the modified 2007 

UCRB oil and gas well dataset to create an oil and gas well 

dataset representing an estimated number of oil and gas wells 

in the UCRB projected to 2015. The process was repeated 

in two additional time steps for the periods 2015 to 2020 

and 2020 to 2025. Wells in the 2007 UCRB oil and gas well 

dataset that had state status codes identifying them as plugged 

and abandoned and with CS codes “abandoned–disturbed” 

were reassigned CS code “abandoned–not disturbed” in 5-year 

time steps as the future development scenarios progressed 

forward. Reassignment of CS codes was based on the 

assumption that disturbed land area would be successfully 

reclaimed and that disturbance would no longer be evident 

at well locations more than 30 years old. Disturbance was 

modeled for all wells in the final 2025 dataset using the same 

methods as those used to estimate disturbance for the 2007 

UCRB oil and gas well dataset. Modeled resource roads were 

created from existing DLG roads to the new set of wells 

classified as “disturbed” using the same methods as those used 

to create resource roads for the 2007 UCRB oil and gas well 

dataset. 

Estimated Current and Projected Future Land 

Disturbance from Oil and Gas Development

A total of 36,483 wells were classified as “disturbed” in 

1991. The total modeled pad area (2.26 acres each) associated 

with these wells was about 78,800 acres (123 mi2) 

(fig. 8A). In 2007, 61,780 wells were classified as “disturbed” 

and the modeled disturbance from drill pads increased to 

about 120,400 acres (188 mi2). Disturbance projections based 

on BLM RMPs indicate that the number of wells classified 

as “disturbed” could increase to about 109,500 by 2025, and 

projected land disturbance from constructing new oil and gas 

drill pads could increase to as much as 222,800 acres 

(348 mi2) by 2025. 

The total length of oil and gas resource roads in the 

study area was estimated to be about 9,000 mi in 1991 and 

about 13,500 mi in 2007. The length estimate is based on the 

assumption that a single access road was constructed to each 

well location classified as “disturbed” in the 2007 UCRB 

oil and gas well dataset for those years (fig. 8B). The total 

length of resource roads could increase to 22,500 mi by 2025 

if average anticipated development scenarios are met. The 

modeled resource road length was based on calculating the 

shortest path from a well site classified as “disturbed” to the 

nearest mapped DLG road and pairing each well site with a 

single primary access road. Assuming a 35-ft ROW width, the 

total area disturbed by resource roads associated with wells 

classified as “disturbed” was approximately 38,700 acres 

(60 mi2) in 1991 and was projected to be 58,950 acres (92 mi2) 

by 2007. Road disturbance could increase to 96,500 acres 

(151 mi2) by 2025.

The total modeled area of land disturbance from drill 

pads and roads was 117,500 acres (183 mi2

) for 1991 and 

179,350 acres (280 mi2) for 2007 (fig. 8C). The total area 

disturbed by oil and gas resource development could increase 

to over 319,000 acres (500 mi2) by 2025. The predicted rate 

of growth is linear because the prediction method assumes an 

average number of wells drilled per year calculated from RMP 

averages. Actual yearly disturbance is likely to vary over time 

as resource development varies in response to commodities 

prices and resource demand. 

GIS datasets containing information about Surface 

Management Agency (SMA) and landowners were acquired 

from the BLM and the National Atlas of the United States 

(U.S. Bureau of Land Management, 2006; John Reitsma, 

Bureau of Land Management, written commun., October 

23, 2007; National Atlas of the United States, 2006a, b). The 

datasets were combined to create a single SMA dataset. The 

2007 UCRB oil and gas dataset was merged with the SMA 
Estimation of Area Disturbed by Oil and Gas Development 17

WYOMING

UTAH

COLORADO

ARIZONA

NEW MEXICO

IDAHO

Data from Bureau of Land Management resource 

management plans were used to calculate averages

Average number of wells expected to be 

drilled annually in known resource areas

1 to 25

26 to 50

51 to 100

101 to 200

201 to 400

Greater than 400

Upper Colorado River Basin boundary

114° 108°

42°

39°

36°

111°

0

0

50

50

100 Miles

100 Kilometers

Base from U.S Census Bureau digital data, 2000 

Resource areas from State and Bureau of Land Management digital data, 2002–2008

Hillshade from 30-meter USGS National Elevation Dataset, 1999

Albers Equal Area Conic projection, North American Datum of 1983

EXPLANATION

Figure 7. Calculated average annual number of new oil and gas wells anticipated in known oil and gas resource areas, Upper 

Colorado River Basin and parts of surrounding area.
18 Land Disturbance Associated with Oil and Gas Development

dataset to examine the relation between well locations and 

the SMA. The data show that approximately 48 percent of 

wells classified as “disturbed” were located on BLM managed 

land and 25 percent were on private or assumed private land 

(fig. 9). Assumed private lands are lands within the UCRB 

that had no assigned SMA or landowner in the SMA dataset. 

Bureau of Indian Affairs lands contained 13 percent of the 

wells classified as “disturbed” and approximately 5 percent of 

wells classified as “disturbed” were on split-estate lands. The 

distribution of all wells drilled in the study area, classified as 

“disturbed” and classified as “not disturbed” on each SMA 

compares well to the percentages of well locations classified 

as “disturbed” reported above (table 3).

Well densities are highest in New Mexico, where about 

35 percent of wells classified as “disturbed” are located 

(table 4). About 9 percent of the UCRB area is in New 

Mexico. Approximately 26 percent of wells classified as 

“disturbed” are in Colorado, and about 18 percent of wells 

classified as “disturbed” are in Wyoming. About 36 percent 

and 16 percent of UCRB lands are in Colorado and Wyoming, 

respectively. Approximately 21 percent of the wells classified 

as “disturbed” are in Utah, which comprises about 33 percent 

of the total UCRB land area. Less than 1 percent of wells 

classified as “disturbed” are in Arizona, which is about 6 

percent of the total UCRB area. 

Limitations and Considerations of 

Methodology

The methods described in this report produce estimates 

of current and projected land disturbance from oil and gas 

development and do not map the precise locations and extent 

of all oil- and gas-related land disturbance. This section 

describes limitations of these methods and attempts to assess 

some of the uncertainties associated with the land disturbance 

estimates. Errors in the modeling methods can be related to 

incorrect well locations and dates and classification methods 

that generalized actual conditions on the basis of reported 

well status information. Using a model to create drill pads of 

uniform size may introduce errors because drill pad sizes vary 

spatially and temporally. The method used to estimate the 

impact of resource roads is based on creating modeled paths 

from the source well to an existing road. The paths are only an 

estimate of the length and location of resource roads, and the 

actual length of a road constructed to access an oil or gas well 

may be over- or underestimated. In addition, ROW widths 

used to estimate the total area of resource roads were uniform, 

whereas actual road widths can vary spatially and temporally. 

0

50,000

100,000

150,000

200,000

250,000

ESTIMATED PAST AND PROJECTED LAND

DISTURBANCE FROM DRILL PADS, IN ACRES

0

20,000

40,000

60,000

80,000

100,000

120,000

ESTIMATED PAST AND PROJECTED NUMBER

OF WELLS CLASSIFIED AS “DISTURBED”

A

78,800

120,400

222,800

YEAR

0

20,000

40,000

60,000

80,000

100,000

120,000

ESTIMATED PAST AND PROJECTED

LAND DISTURBANCE FROM

RESOURCE ROADS, IN ACRES

0

5,000

10,000

15,000

20,000

25,000

ESTIMATED PAST AND PROJECTED

LENGTH OF RESOURCE ROADS, IN MILES

B

38,700

58,950

96,500

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

TOTAL ESTIMATED AND PROJECTED

LAND DISTURBANCE FROM DRILL PADS

AND RESOURCE ROADS, IN ACRES 

Disturbance from drill pads (2.26-acre pad area)

Disturbance from resource roads (35-foot right of way)

Number of well locations classified as “disturbed”

Length of resource roads

78,800

120,400

222,800

38,700

58,950

96,500

1991 2007 2025

C

Figure 8. A, Number of oil and gas wells classified as 

“disturbed” and the total estimated area of land disturbed by 

oil and gas drill pads and B, roads, and C, by both drill pads and 

roads, Upper Colorado River Basin, 1991, 2007, and 2025. 
Limitations and Considerations of Methodology 19

Errors Associated with Well Locations in the 

2007 Upper Colorado River Basin Oil and Gas 

Well Dataset

Well locations from the state databases were randomly 

checked and verified against 2005–2007 NAIP imagery but 

no systematic error analysis was made on the source data. 

The actual location of the oil and gas well may vary from 

the reported location because of field conditions at the time 

the well was spudded, map and Global Positioning System 

(GPS) errors at the time the well was sited, or data entry 

errors. For example, in the active oil and gas development 

area near Rifle, Colorado, most wells classified as “disturbed” 

are located in areas where well-pad disturbance is visible and 

most wells classified as “not disturbed” are located in areas 

where pad disturbance is not visible or next to a well classified 

as “disturbed” (fig. 10). Some wells appear to be mislocated 

and some bare areas that may be a drill pad have no well point 

associated with them. Recently permitted wells are likely to be 

sited more accurately than older wells in the database because 

of available GPS technology and rule changes requiring that 

locations submitted during the permitting process are more 

accurate. Location reporting requirements vary by state and 

by the age of the well (Utah Division of Oil, Gas, and Mining, 

2004; Wyoming Oil and Gas Conservation Commission, 2008; 

Colorado Oil and Gas Conservation Commission, 2009).

The method used to model areas disturbed by oil and gas 

development depends on accurate well locations. Although 

the regional estimate of land disturbance is within 1 percent of 

the total land disturbance measured in the calibration dataset, 

locational errors in the 2007 UCRB oil and gas well dataset 

may translate to over- or underestimating the land disturbed 

by oil and gas development at local scales. Imagery dates may 

play a minor role in the error of the estimation. Wells drilled 

after the NAIP imagery was acquired were not digitized into 

the calibration data but would have been included as wells 

classified as “disturbed” in the 2007 UCRB oil and gas well 

dataset and modeled as areas of land disturbance.

Assessment of Methods Used to Model Land 

Disturbance from Oil and Gas Drill Pads

Oil and gas drill pads are not constructed with uniform 

dimensions or areas. State and Federal permitting rules, 

topographic and environmental conditions at the well site, 

construction practices, and equipment requirements dictate 

the actual area and dimensions of drill pads. The estimate of 

land disturbance from oil and gas development described in 

this report relies on a model that created drill pads of uniform 

dimensions that may be larger or smaller than the dimensions 

of the actual disturbed area. Individual drill pads vary in size 

over time as the pad areas are partially reclaimed during the 

production phase of the well and as final reclamation efforts 

take place.

Figure 9. Percentage of oil and gas wells classified as 

“disturbed” by Surface Management Agency or landowner, Upper 

Colorado River Basin, 2007.

Table 3. Percentage of all oil and gas wells classified as 

“disturbed” and “not disturbed”, by Surface Management Agency 

or landowner, Upper Colorado River Basin, 2007.

 Surface Management 

Agency or landowner

Number of wells 

(“disturbed” and 

“not disturbed”)

Percentage of 

total

Bureau of Land Management 42,503 48

Bureau of Indian Affairs/Tribal 12,795 14

Private or no SMA identified 21,379 24

Split estate 4,238 5

State 5,256 6

U.S. Forest Service 2,006 2

Other1 1,105 1

1 Bureau of Reclamation, Fish and Wildlife Service, National Park Service, 

Department of Defense, and local government agencies.

Table 4. Percentage of the oil and gas wells classified as 

“disturbed” and the percentage of the area in each state 

contained in the 2007 Upper Colorado River Basin (UCRB) study 

area.

State

Percentage of 2007 

wells classified 

as “disturbed”

Percentage 

of total area 

of UCRB

Arizona 0.3 6

Colorado 26.2 36

New Mexico 35.2 9

Utah 20.6 33

Wyoming 17.7 16

48

13

25

5

6

2 1

Bureau of Land Management

Bureau of Indian Affairs/Tribal

Private or no surface management agency identified

Split estate

State

U.S. Forest Service

Other*

* Bureau of Reclamation, Fish and Wildlife 

Service, National Park Service, Department 

of Defense, and local government agencies
20 Land Disturbance Associated with Oil and Gas Development

0 0.5 0.75 Mile

0 0.25 0.5 0.75 Kilometer

Base from U.S. Census Bureau digital data, 2000

Image from USDA National Agricultural Imagery Program, preliminary compressed county 

mosaic for Garfield County, CO, 2005

Albers Equal Area Conic projection, North American Datum of 1983

EXPLANATION

107°55' 107°54'

39°31'

39°30'

0.25

Oil or gas well classified as “disturbed”

Oil or gas well classified as “not disturbed” Detail

Figure 10. 2005 National Agricultural Imagery Program imagery for an area near Rifle, Colorado, and well locations from the 2007 

Upper Colorado River Basin oil and gas well dataset. 
Limitations and Considerations of Methodology 21

The total area of modeled drill pads is within less than 

1 percent of the total area of measured drill pads in the 

calibration cells in 2007. Errors vary within individual 

calibration cells (fig. 11A). The average total measured pad 

disturbance for all calibration cells is about 44 acres compared 

with 54 acres in the land disturbance model (fig. 11B). The 

median measured disturbance is 7.2 acres compared with 

7.9 acres in the modeled data. The maximum disturbed area 

from drill pads measured in a calibration cell was 558 acres 

and the maximum modeled area from drill pad disturbance in 

a calibration cell was 665 acres. Disturbed area from drill pads 

was underestimated in 41 of 76 calibration cells and 

overestimated in 24 calibration cells (fig. 11C). No disturbance 

was measured in 16 calibration cells. No disturbance was 

estimated in 11 calibration cells so 5 calibration cells that had 

no measured disturbance contained some estimated 

disturbance. Figure 11D shows the measured pad areas for all 

76 calibration cells compared with the modeled pad areas. The 

data are generally clustered along the linear trend line with a 

few outliers. 

The model underestimated land disturbance from drill 

pads most often in Wyoming and Utah, where disturbance was 

underestimated in 81 percent and 61 percent of the calibration 

cells, respectively. In Colorado, the model underestimated 

drill pad disturbance in 36 percent of the calibration cells, 

overestimated in 36 percent of the calibration cells and was 

correct in 28 percent of the cells. In Arizona, the model 

underestimated disturbance in one of the two cells and 

overestimated it in the other cell. The model overestimated 

drill pad disturbance in all five calibration cells in New 

Mexico. Over- or underestimation of land disturbance from oil 

and gas drill pads may be due to statewide differences in drill 

pad construction practices or to errors in the source databases 

used to site the wells. Overestimation in New Mexico may be 

because of well locations derived from township and range 

information or because a large number of oil and gas wells 

are located in agricultural and urban areas around the city of 

Farmington where mixed land use made land disturbance from 

drill pads difficult to identify in the NAIP imagery.

Large differences between measured and modeled 

land disturbance from drill pads were examined to identify 

reasons for over- or underestimating disturbance. The 

largest differences were in calibration cell #780 (fig. 4). The 

disturbance model assigned 17.5 acres of land disturbance to 

this calibration cell. Calibration cell #780 contained 1.8 acres 

of measured disturbance from drill pads. The cell contained 

13 well locations from the Utah oil and gas database. Two 

wells were undated. The Utah oil and gas database indicated 

that the remaining wells were drilled between 1965 and 

1985. The two undated wells were identified as abandoned 

locations in the source database. Of the 11 drilled wells in this 

calibration cell, disturbed area around only one well drilled in 

1984 was visible in the NAIP imagery. No disturbance could 

be seen near wells located approximately 1.5 mi northwest of 

the 1984 well and spudded between 1977 and 1985. The lack 

of visible disturbance may be due to location or date errors in 

the oil and gas database, differences in the terrain on which 

the wells were sited, differences in the way the drill pads were 

constructed, or differences in reclamation activity and success 

on the drill pads. Lack of visible disturbance may also be 

because wells were never actually drilled at those locations.

The second largest error occurred in calibration cell 

#404, which contained 48 wells from the Colorado oil and 

gas well database. The measured drill pad disturbance in this 

cell was 4.5 acres. Twenty acres were modeled in calibration 

cell #404. Only one well in the calibration cell had a spud 

date and seven wells had neither a spud date nor a status date. 

The earliest status date was 1911 and the latest date was 1990. 

Thirty nine of the wells were classified as “not disturbed” and 

nine were classified as “disturbed” in the 2007 UCRB oil and 

gas well dataset. Five of the wells classified as “disturbed” 

were dated between 1976 and 1985 and located in an area 

where several houses were visible in the NAIP imagery. 

All well locations were within 300 ft of U.S. Highway 160. 

Neither the houses nor any disturbance were visible in digital 

orthophoto quadrangles (DOQ) acquired in the mid-1990s 

(U.S. Geological Survey, 2006). A minor network of roads 

connecting the well sites was visible in the NAIP imagery and 

in the DOQ. The remaining wells classified as “disturbed” 

were distributed throughout the calibration cell. 

Analysis of the differences between modeled and 

measured land disturbance in calibration cells highlights a 

limitation of the method used to estimate drill pad disturbance. 

The disturbance estimation relies on accurate locations, well 

status, and date information in the source oil and gas databases 

and assumes that reclamation activities will be uniformly 

successful across the widely varying landscape of the UCRB. 

Assessment of Methods Used to Model Land 

Disturbance from Oil and Gas Resource Roads

Length of resource roads was modeled using least-cost 

path methods to create a simulated road network. The disturbed area associated with resource roads was estimated by 

applying a uniform ROW width to the simulated roads. The 

following discussion of sources of error in the resource model 

will focus on the total length of measured roads compared 

with the total length of modeled roads because road lengths 

were digitized into the calibration dataset to test the methods 

used to model roads. Actual road area was not measured in the 

calibration data, and the accuracy of the area estimate will not 

be directly assessed. 

The total length of modeled primary resource roads 

within all 76 calibration cells was approximately 395 mi. The 

total length of primary resource roads measured and digitized 

in the calibration cells was 364 mi. The total length of primary 

resource roads estimated by the least-cost path model was 

approximately 8.5 percent more than the total length of 

primary resource roads measured in all calibration cells. As 

with the pad disturbance estimation, the difference between 

modeled and measured primary road lengths varies by 

calibration cell. Measured and modeled road lengths correlate 

well when plotted against each other (fig. 12A). The average 
22 Land Disturbance Associated with Oil and Gas Development PERCENT DIFFERENCE BETWEEN MODELED AND MEASURED DRILL PAD AREA BY CALIBRATION CELL

TOTAL MEASURED LAND DISTURBANCE FROM DRILL PADS BY CALIBRATION CELL, IN ACRES

-200

0

200

400

600

800

1,000

0 100 200 300 400 500 600 700

A 

-100

0

100

200

300

400

500

600

700

800

ACRES

B 

Measured drill

pad disturbance

in calibration cells

Modeled drill

pad disturbance

in calibration cells

Outlying value

Percentile—Percentage of 

analysis equal to or less 

than the indicated value

90th percentile

Mean

75th percentile

Median

25th percentile

10th percentile

measured road length for all calibration cells was 6.5 mi 

compared with 7.1 mi in the least-cost path model (fig. 12B). 

The maximum length of roads measured in a single cell was 

51.6 mi compared with the maximum modeled length of 

57.4 mi. The median measured road length was 2.0 mi 

compared with the median modeled road length of 2.4 mi. 

Although the above analysis indicates that the least-cost 

path model overestimates the total length of resource roads in 

the UCRB, the model likely underestimates the actual impact 

of resource roads in the study area because the model does not 

account for secondary roads created as a result of oil and gas 

development. Thirty seven of the 60 calibration cells that contained visible oil- and gas-related land disturbance contained 

unpaved roads that were digitized as secondary oil and gas 

resource roads. The total length of measured secondary roads 

in these calibration cells varied from as little as 230 ft in a cell 

to as much as 34 mi in a cell. In the 37 calibration cells that 

contained secondary roads, the average length these roads was 

3.5 mi per calibration cell. 

Figure 11. A, Percent difference between modeled and measured land disturbance from oil and gas drill pads, B, summary of 

measured and modeled area of land disturbance from oil and gas drill pads, C, distribution of difference between modeled and 

measured land disturbance from oil and gas drill pads, and D, correlation between modeled and measured land disturbance from oil and 

gas drill pads in 76 calibration cells, Upper Colorado River Basin, 2007. 
Limitations and Considerations of Methodology 23

Figure 11. A, Percent difference between modeled and measured land disturbance from oil and gas drill pads, B, summary of 

measured and modeled area of land disturbance from oil and gas drill pads, C, distribution of difference between modeled and 

measured land disturbance from oil and gas drill pads, and D, correlation between modeled and measured land disturbance from oil and 

gas drill pads in 76 calibration cells, Upper Colorado River Basin, 2007.—Continued FREQUENCY OF OBSERVATION

MODELED AREA OF LAND DISTURBANCE MINUS MEASURED AREA OF LAND DISTURBANCE, IN ACRES

-250-230-210-190-170-150-130-110

-90-70-50-30-10

-1

0

1

1030507090

110130150170190210230250

0

5

10

15

20

25

C 

0 100 200 300 400 500 600

0

100

200

300

400

500

600

700

R2 = 0.8431

(R2, coefficient of determination)

D 

TOTAL MODELED DRILL PAD AREA BY CALIBRATION CELL, IN ACRES

TOTAL MEASURED DRILL PAD AREA BY CALIBRATION CELL, IN ACRES
24 Land Disturbance Associated with Oil and Gas Development

Errors in the location and extent of roads in the DLG 

dataset used as the source of existing roads in the least-cost 

path model could cause the model to over- or underestimate 

the length of resource roads at local scales. The DLG dataset 

was often incomplete, and comparisons to roads visible in the 

NAIP imagery indicated locational errors. A mislocated or 

missing source road in the DLG dataset could affect the total 

length of modeled resource roads by either lengthening or 

shortening the modeled path created to access the drill pad. In 

addition, an unknown length of resource roads was included 

in the DLG dataset as unpaved roads. These roads would 

not have been modeled as resource roads and would not be 

included in the road disturbance estimates. 

Fifteen of the 76 calibration cells described earlier were 

randomly selected (fig. 13) and used to estimate the extent of 

existing resource roads in the DLG data. All visible roads—

resource roads, paved roads, and unpaved local roads visible 

in the NAIP imagery—in these cells were manually digitized 

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70

MEASURED PRIMARY RESOURCE ROAD LENGTH

BY CALIBRATION CELL, IN MILES

MODELED PRIMARY RESOURCE ROAD LENGTH BY CALIBRATION CELL, IN MILES

A

-10

0

10

20

30

40

50

60

70

B 

Outlying value

Percentile—Percentage of 

analysis equal to or less 

than the indicated value

90th percentile

Mean

75th percentile

Median

25th percentile

10th percentile

Measured

primary resource

road length in

calibration cells

Modeled

primary resource

road length in

calibration cells

 RESOURCE ROAD LENGTH, IN MILES

R2 = 0.9078

(R2, coefficient of determination)

Figure 12. A, Correlation between modeled and measured oil and gas resource road length and B, summary of modeled and measured 

resource road length in 76 calibration cells, Upper Colorado River Basin, 2007. 
Statistical Assessment of Dissolved-Solids Sources, Loads, and Transport in the Upper Colorado River Basin 25

into a DLG assessment dataset. Roads in the DLG assessment 

dataset were digitized as the centerline of the road visible 

in the NAIP imagery. Each digitized line was classified as a 

paved road, a local unpaved road, or a resource road. A single 

resource road was designated for each drill pad that had more 

than one road associated with it. All other roads associated 

with the drill pad were classified as local unpaved roads. It 

was also noted whether the digitized road existed in or was 

absent from the DLG dataset. 

Oil and gas resource roads were present in the DLG 

dataset in 10 of the 15 DLG calibration cells. The total length 

of resource roads per calibration cell included in the DLG 

dataset ranged from 0.25 mi to 6.9 mi. The average length of 

resource roads in the 10 DLG calibration cells that contained 

resource roads was 2 mi. Resource roads in the DLG dataset 

are a source of error for the resource road model because these 

roads are omitted from the modeled length of resource roads. 

The total length of all unpaved roads in the model was 

underestimated by 4 percent to 72 percent when compared 

with road lengths measured in the 15 tested calibration cells. 

On average, the total length of unpaved roads mapped in 

the DLG dataset was underestimated by 50 percent when 

compared with the total length of unpaved roads measured 

in the 15 selected calibration cells. Missing or badly located 

roads can affect the route created by the least-cost path model 

and cause the total length of roads actually constructed to 

access a drill pad to be over- or underestimated at local scales. 

Assessment of Methods Used to Project Future 

Land Disturbance from Oil and Gas Development

Projected future land disturbance estimates were based 

on the average number of wells presented in the BLM RMPs. 

Total projected drill pad area may be underestimated if the 

maximum number of wells drilled approaches the maximum 

number of wells in the RMP projections. Conversely, 

disturbance will be overestimated if the expected drilling only 

meets the minimum anticipated number of wells. Resource 

development depends on future energy demands and will 

vary over time. In addition, development projections are often 

based on undiscovered resources and the actual resource may 

be more or less abundant than anticipated. The calculated area 

of land disturbance from oil and gas development was derived 

from GIS-based modeled drill pads, some of which overlapped 

and were treated as a single area. The analysis assumes that 

each well is associated with 2.26 acres of disturbed ground, 

even when multiple wells were drilled on a single drill pad. 

If the total number of discrete drill pads reaches the averages 

calculated from RMP documents and used for this analysis, 

the total disturbed area could be larger than that estimated. 

Future well locations are not actual well locations and were 

only created to simulate potential overall land disturbance 

from future oil and gas development. Well densities in areas 

where simulated wells were created to approximate future 

conditions may be higher than that allowed by state, local, 

and Federal regulations. In addition, BLM RMP data are 

projections of expected activity and may not correctly predict 

the actual development for an area.

Statistical Assessment of DissolvedSolids Sources, Loads, and Transport in 

the Upper Colorado River Basin

The USGS in cooperation with the USBR and the BLM, 

developed a dissolved-solids SPARROW model specific to 

the UCRB for water year 1991 (Kenney and others, 2009). 

The SPARROW surface water-quality model uses a mass 

balanced approach to examine the production and transport of 

instream constituent mass, or flux, on the basis of a nonlinear, 

weighted least-squares regression technique (Schwarz and 

others, 2006). Coefficients for defined load sources, landscape 

transport characteristics, and aquatic transport characteristics 

are derived through iterative calibration with loads from 

stream-monitoring sites. The determined coefficients represent 

average conditions based upon the role each source term and 

characteristic play throughout the basin of interest, assuming 

an unbiased distribution of the monitoring sites used in model 

calibration (Kenney and others, 2009). These coefficients are 

then applied to the SPARROW model, and constituent load 

estimates can be generated for each of the incremental stream 

reaches of the basin of interest. 

The UCRB dissolved-solids SPARROW or UCRB 

SPARROW model was calibrated using dissolved-solids loads 

calculated for 218 stream-monitoring sites (fig. 14). Prediction 

error is approximated at 51 percent (Kenney and others, 

2009). The 11 defined sources for the model were 7 geologic 

source groups, 3 agricultural lands groups, and a point-source 

imports group that was composed of 7 large saline springs and 

6 reservoirs. Six landscape transport characteristics, including 

terms associated with climate, soils, vegetation, and elevation, 

were statistically significant in describing the transport of 

dissolved solids to streams in the UCRB. 

Effects of Land Disturbance from Oil and Gas 

Development on Dissolved-Solids Loads in the 

Upper Colorado River Basin 

The 1991 UCRB SPARROW model was used to assess 

the effects of land disturbance from oil and gas development 

on dissolved-solids loads in the basin. The calibration 

routine of the SPARROW model generates basin-averaged 

coefficients for sources, landscape transport characteristics, 

and aquatic transport characteristics that statistically explain 

the production, transport, and fate of the constituent of 

interest. Modeled land disturbance attributed to oil and gas 

development for 1991 and 2007 was examined as a source of 

dissolved solids in streams in the UCRB. The 1991 UCRB 
26 Land Disturbance Associated with Oil and Gas Development

114° 108°

42°

39°

36°

111°

0

0

50

50

100 Miles

Base from U.S Census Bureau digital data, 2000 100 Kilometers Albers Equal Area Conic projection, North American Datum of 1983

Upper Colorado River Basin boundary

100-square-kilometer areas used to create calibration 

data—Number refers to unique identifier for each cell

Cell used to assess drill pad and resource road land 

disturbance only

Cell used to assess drill pad and resource road land 

disturbance and roads from U.S. Geological Survey 

Digital Line Graph data

1833 EXPLANATION

1796

1775

1755

1717

1662

1676 1683 1653

310

1607

1557

1584

1445

1482

1532

1538

1412

1414

1333

294

1387

1436

1473

1495

1525

1316

1403

1465

1375

1099

1344

1062

1345

1192

1144

1183

1258

1271

797

799 824

837

989

923

1051

785

814

858

905

1033 1010

780

854

887

508

663

611

504 518

566 609

632

274

367

403

404

219

324

391

54 57

203

135

7

1758

WYOMING

UTAH

COLORADO

ARIZONA NEW MEXICO

IDAHO

Figure 13. Location of calibration cells chosen to create the Digital Line Graph assessment dataset, Upper Colorado River Basin. 
Statistical Assessment of Dissolved-Solids Sources, Loads, and Transport in the Upper Colorado River Basin 27

WYOMING

UTAH

COLORADO

ARIZONA NEW MEXICO

IDAHO

Colorado

River

Green

River

Colorado

River

San Juan

River

114° 108°

42°

39°

36°

111°

0

0

50

50

100 Miles

100 Kilometers

Base from U.S Census Bureau digital data, 2000

Hydrography from USGS Enhanced River Reach File 2.0, 2002

Hillshade from 30-meter USGS National Elevation Dataset, 1999

Albers Equal Area Conic projection, North American Datum of 1983

Upper Colorado River Basin boundary

U.S. Geological Survey stream-monitoring site 

used to calibrate SPARROW model

Used only for 1991 model

Used only for 2007 model

Used for both 1991 and 2007 models

EXPLANATION

Figure 14. Location of U.S.Geological Survey stream-monitoring sites with dissolved-solids monitoring data used for the 1991 Upper 

Colorado River Basin (UCRB) dissolved-solids SPARROW model and the 2007 exploratory UCRB dissolved-solids SPARROW model. 
28 Land Disturbance Associated with Oil and Gas Development

SPARROW model (Kenney and others, 2009) and a similar, 

exploratory SPARROW model specific to monitoring data for 

water year 2007 were used for this analysis. The estimated 

total area of land disturbed by oil and gas development was 

calculated for each catchment and stream reach in the UCRB 

SPARROW stream network for 1991 and 2007 as an input to 

the models (fig. 15). A catchment, or contributing area, is the 

land-surface area that contributes flow to a stream segment. 

All runoff from a catchment is discharged from the same 

outlet. 

Annual dissolved-solids loads were available for 218 

monitoring sites for the 1991 UCRB SPARROW model 

compared with 53 monitoring sites for the 2007 model (fig. 14). 

Mean daily and annual dissolved-solids loads for the 53 sites 

were determined by using a multiple linear regression model 

included in the computer model LOADEST (Runkel and others, 

2004) adapted for use with TIBCO Spotfire S+ statistical 

software (TIBCO Software Inc., 2008) (appendix 3). 

Explanatory variables in the regression models included various 

functions of streamflow and time. The LOADEST models were 

calibrated by using dissolved-solids concentration data 

(sometimes estimated from specific-conductance 

measurements) and associated streamflow values obtained from 

the USGS National Water Information System (NWIS) 

database. For each site, a time series of daily mean streamflow 

values was applied to the formulated regression model to 

estimate dissolved-solid loads. 

The land disturbance source input to the UCRB 

SPARROW model included the total area of land disturbance 

estimated for drill pads and resource roads. Including the 

land disturbance source with the defined sources of the 1991 

UCRB SPARROW model increased the source groups to 

12. The 6 landscape transport characteristics applied to the 

original 11 source groups were unchanged. However, different 

combinations of landscape transport characteristics applied to 

the land disturbance source were examined in the 1991 and 

the 2007 SPARROW models. In each of these models, the 

source coefficient estimated for the disturbed lands associated 

with oil and gas development was zero (null). Within the 

framework of the SPARROW model, the coefficient indicates 

that the land area disturbed by oil and gas development was 

not statistically significant in explaining dissolved-solids loads 

in UCRB streams. The other source groups had coefficients 

that were similar to those reported by Kenney and others 

(2009). 

Interpretation of Results

To understand the null result of the effect of land 

disturbance from oil and gas development on dissolvedsolids loads in the UCRB requires a more thorough 

examination of the data network and the limitations of the 

UCRB SPARROW model. The null result indicates that land 

disturbance associated with oil and gas development does 

not contribute to dissolved-solids loads in streams in the 

UCRB. However, this examination of the relation between 

land disturbance associated with oil and gas development and 

dissolved solids is an observational study, not an experimental 

study. The study design was limited to available data that 

may not have been ideal for properly testing the hypothesis 

that land disturbance associated with oil and gas development 

increases dissolved solids in streams in the UCRB. When the 

result of an observational study does not overtly confirm the 

hypothesis, care must be taken when drawing a conclusion. 

As described in detail below, the null result is likely caused by 

the inherent limitations of the data used in the model. Further, 

because SPARROW is a spatially referenced statistical model, 

results are scaled to the data network supporting the model. 

The model results were affected by the available monitoring 

data, distribution of monitoring sites with respect to land 

disturbance, the total area of disturbed lands associated with oil 

and gas development basin wide and within the reaches used 

for model calibration, and the potential yield of dissolved solids 

from disturbed lands compared with the natural yield. 

Total land disturbance associated with oil and gas 

development in the study area was estimated at 117,500 acres 

(183 mi2

) for 1991 and 179,350 acres (280 mi2) for 2007. This 

accounts for 0.17 and 0.26 percent, respectively, of the 108,000 

mi2 in the UCRB. For perspective, the defined sources 

represented in the 1991 UCRB SPARROW model are shown in 

table 5 (Kenney and others, 2009). The smallest represented 

source group in the 1991 UCRB SPARROW model, irrigated 

lands of other lithologies, consisted of 268,800 acres (420 mi2), 

or 0.39 percent of the UCRB. As discussed by Kenney and 

others (2009), the probability was high that the estimated 

coefficient for the irrigated lands of other lithologies group was 

zero (p-value), or insignificant in explaining dissolved solids in 

UCRB streams, but it was retained in the model for continuity. 

The next smallest source group, irrigated sedimentary-clastic 

Mesozoic lands, was 576,000 acres (900 mi2

), roughly three 

times the size of the disturbed lands associated with oil and gas 

development in 2007. The total area of disturbed lands 

associated with oil and gas development modeled in 1991 and 

2007 may be too small for a regional scale model, such as the 

UCRB SPARROW model, to capture their contribution to 

instream dissolved-solids loads. The total land disturbance in 

2025 is projected to be approximately 319,000 acres (500 mi2

), 

an areal extent that is about 19 percent larger than the irrigated 

lands of other lithologies source in the 1991 UCRB SPARROW 

model. It is important to note that substantially more water is 

artificially applied to irrigated lands than naturally falls on the 

disturbed lands associated with oil and gas development in the 

UCRB. Artificially applied water substantially increases the 

production and transport of dissolved solids. Further, transport 

paths from irrigated lands and lands disturbed by oil and gas 

development differ in length. Irrigated lands are generally much 

closer to streams in the UCRB than the lands disturbed by oil 

and gas development. From the exploratory efforts of 

examining land disturbance associated with oil and gas 

development for 1991 and 2007, it is expected that the 

projected 2025 RFD land disturbance would also likely be too 

small to be a significant explanatory variable as a source of 

dissolved solids in streams in the UCRB. 
Statistical Assessment of Dissolved-Solids Sources, Loads, and Transport in the Upper Colorado River Basin 29

108°

42°

39°

36°

111°

0

0

50

50

150 Miles

150 Kilometers

100

100

Base from U.S Census Bureau digital data, 2000 

Hydrography modified from 1:100,000-scale USGS National Hydrography dataset, 2008

Albers Equal Area Conic projection, North American Datum of 1983

Upper Colorado River Basin boundary

Percentage of stream drainage area with land 

disturbance from oil and gas drilling

0.0 to 0.1

0.1 to 0.5

0.5 to 1.0

1.0 to 2.0

2.0 to 3.0

3.0 to 4.0

4.0 to 5.0

5.0 to 10.0

10.0 to 20.0

20.0 to 40.0

EXPLANATION

108°

42°

39°

36°

111°

A

1991

B

2007

Figure 15. Upper Colorado River Basin SPARROW stream network indicating the percentage of the total contributing land area for 

each stream reach that was disturbed by oil and gas development in A, 1991 and B, 2007, Upper Colorado River Basin. 
30 Land Disturbance Associated with Oil and Gas Development

Data for annual dissolved-solids loads were available 

at 218 and 53 monitoring sites during water years 1991 and 

2007, respectively. As explained by Kenney and others (2009), 

within the SPARROW modeling framework these monitoring sites correspond to 218 and 53 unique calibration reaches 

from which SPARROW estimates model coefficients. The 

distribution of model parameters, including sources, within 

the calibration reaches provides some insight as to how well 

each parameter is being represented during the model calibration process. For the 1991 data, the drainage area for calibration reaches ranged from 2,278 acres (3.56 mi2

) to 9,088,000 

acres (14,200 mi2

) and the average area was 316,800 acres 

(495 mi2). For the 2007 data, the drainage area of calibration 

reaches ranged from 12,800 acres (20 mi2) to 14,336,000 acres 

(22,400 mi2) and the average area was 1,305,600 acres 

(2,040 mi2). 

Appendixes 4 and 5 show how the source groups, including land disturbance associated with oil and gas development 

and excluding the point-source imports, were represented 

within each of the calibration reaches. The percentage of the 

calibration reach area represented by each source was computed and the maximum, minimum, mean, and median were 

reported for all non-zero source groups (table 6) for the 1991 

and 2007 data. The maximum percentage of land disturbance 

within a calibration reach was 2.81 percent for the 1991 

data and 0.95 percent for the 2007 data. For both years, the 

maximum percentage of the land disturbance sources is much 

smaller than any other defined sources, which indicates that 

land disturbance associated with oil and gas development 

may not be represented well in the calibration reach data. 

The distribution of stream-monitoring sites used to calibrate 

the 1991 model and the 2007 exploratory model are shown 

in figure 16. Ideally, the monitoring sites would be evenly 

distributed throughout the study area including areas with land 

disturbance from oil and gas development. A lack of streammonitoring sites within areas with land disturbance from oil 

and gas development indicates that the stream-monitoring 

network may have a biased distribution toward areas without 

oil- and gas-related land disturbance such that contributions of 

dissolved solids from disturbed lands are not adequately represented in the model. Inadequate representation may produce a 

null result. 

The potential yield of dissolved solids from land 

disturbed by oil and gas development is a function of the 

natural yield of the local geologic units. Land disturbance on 

high-yield geologic units would contribute more to dissolvedsolids loads than similar disturbance on low-yield geologic 

units. Dissolved-solids yield from geologic units in the UCRB 

SPARROW model are represented by seven geologic source 

groups. Statistically significant coefficients, which represent 

basin-averaged yields, were estimated for each of these seven 

source groups. These yields ranged from 1.26 to 41.9 tons of 

dissolved solids per square mile (Kenney and others, 2009). 

For comparison, the UCRB SPARROW model contained three 

irrigated lands sources with predicted yields of 22.8, 662, 

and 1,180 tons per square mile (Kenney and others, 2009). 

Table 5. Area of dissolved-solids source groups defined for the 1991 Upper Colorado River Basin (UCRB) dissolved-solids SPARROW 

model and the 2007 UCRB exploratory dissolved-solids SPARROW model.

Source group

Total area of source group Percentage of Upper 

Colorado River Basin 1

Acres Square miles

Crystalline and volcanic rocks 2 6,195,200 9,680 8.96

High-yield sedimentary Cenozoic rocks 2 7,872,000 12,300 11.4

Low-yield sedimentary Cenozoic rocks 2 16,448,000 25,700 23.8

High-yield sedimentary Mesozoic rocks 2 8,960,000 14,000 13

Low-yield sedimentary Mesozoic rocks 2 23,168,000 36,200 33.5

High-yield sedimentary Paleozoic and Precambrian rocks 2 2,694,400 4,210 3.89

Low-yield sedimentary Paleozoic and Precambrian rocks 2 3,795,600 5,930 5.5

Irrigated sedimentary-clastic Tertiary lands 2 883,200 1,380 1.3

Irrigated sedimentary-clastic Mesozoic lands 2 576,000 900 0.83

Irrigated lands of other lithologies 2 268,800 420 0.39

Disturbed lands, 1991 3 117,500 183 0.17

Disturbed lands, 2007 4 179,350 280 0.26

1

 Sum of values does not add to 100 percent because data sources overlap.

2

 Value used in 1991 and 2007 models.

3

 Value used in 1991 model.

4

 Value used in 2007 model.
Summary 31

Table 6. Representation of dissolved-solids source groups in 1991 Upper Colorado River Basin (UCRB) dissolved-solids SPARROW 

model and 2007 exploratory UCRB dissolved-solids SPARROW model calibration reaches. 

[Statistical analyses of sources in calibration reaches were done on all non-zero source areas. Max., maximum; Min., minimum]

Irrigated 

sedimentaryclastic

Tertiary

lands

Irrigated 

sedimentaryclastic

Mesozoic

lands 

Irrigated 

lands 

of other

lithologies 

Crystalline 

and volcanic 

rocks 

Sedimentary 

Cenozoic rocks

Sedimentary 

Mesozoic rocks

Sedimentary Paleozoic 

and Precambrian rocks

Land 

disturbance 

associated 

with

oil and gas 

development 

 High-yield Low-yield High-yield Low-yield High-yield Low-yield

Percentage of the calibration reach area

 1991

Max. 15.4 54.6 8.39 100 90.6 100 100 100 98.795 100 2.81

Min. 0.0004 0.001 0.0002 0.017 0.006 0.041 0.007 0.018 0.0020 0.003 0.0008

Mean 1.59 2.309 0.994 42.6 14.2 25.5 16.5 26.5 24.1 9.92 0.167

Median 0.865 0.666 0.350 29.8 4.28 16.4 10.5 15.3 8.76 2.59 0.032

 2007

Max. 14.0 21.9 7.07 98.9 46.8 92.5 44.4 93.0 59.8 32.5 0.947

Min. 0.051 0.018 0.001 0.186 0.004 0.045 0.013 1.26 0.002 0.079 0.001

Mean 1.84 1.80 1.23 34.1 10.1 25.5 12.4 28.0 11.1 5.10 0.199

Median 1.24 0.927 0.706 24.4 6.55 16.8 10.4 14.9 4.31 2.44 0.118

There are a number of possible reasons why the disturbed 

lands associated with oil and gas development were not 

a significant explanatory variable for the production of 

dissolved solids in the UCRB dissolved-solids SPARROW 

model. The null result is likely due to a combination of 

factors and indicates that the UCRB SPARROW model has a 

streamflow data network that probably is not extensive enough 

to fully assess the contribution of dissolved solids from 

land disturbed by oil and gas development. A true test of the 

hypothesis would require more monitoring data representative 

of locations that have significant land disturbance from oil and 

gas development. 

Summary

The Bureau of Land Management (BLM) has identified 

the Upper Colorado River Basin (UCRB) as an area with 

potential for continued oil and gas development on the basis of 

interest expressed by the oil and gas industries. Oil and gas 

development has increased substantially in the UCRB since 

2000. Lands disturbed by oil and gas development can harm 

the environment through erosion, air pollution, stream 

degradation, habitat fragmentation and alteration, and 

increased public use of potentially environmentally sensitive 

areas. Monitoring and mapping land disturbance from oil and 

gas development has not been synthesized on a regional scale 

in the UCRB but data on the location and age of oil and gas 

wells are available from state-maintained databases for the 

five states partly within the UCRB. GIS analysis and modeling 

techniques were used to map the location and estimate the 

The large yields associated with irrigated lands are due to 

the application of water, which increases the dissolution and 

transport of solids to streams. The amount of water applied 

greatly exceeds natural precipitation in these areas.

The seven geologic source groups, which represent the 

natural landscape, are subject to natural precipitation and 

associated weathering that dissolve solids at rates that are 

much smaller than those for irrigated lands. Disturbed lands 

associated with oil and gas development, aside from being 

barren, are similar to the natural landscapes of the UCRB. 

Barren surfaces exposed by construction of drill pads and 

resource roads may provide access to previously unweathered 

materials soon after the initial disturbance. However, with 

time, the yield of these disturbed materials may approach 

that of the surrounding geology. Most of the disturbed 

lands associated with oil and gas development in the UCRB 

are buffered by undisturbed lands containing sparse aridenvironment vegetation types. This vegetation may impede 

the transport of dissolved solids to streams by slowing down 

overland flow of water and sediment, and encouraging 

infiltration. 

Another factor that likely affected the results of the 

UCRB SPARROW model was that about 73 percent of the 

wells classified as “disturbed” in the 2007 UCRB oil and 

gas well dataset were located on one of three low-yield 

sedimentary lithologies of the 1991 UCRB SPARROW model 

(Kenney and others, 2009). Approximately 27 percent of wells 

classified as “disturbed” were located on one of the three highyield sedimentary lithologies (fig. 17). The null result for the 

land disturbance coefficient in the UCRB SPARROW model 

would in this case represent the effects of the location of much 

of the oil and gas land disturbance on low-yield geologic units.
32 Land Disturbance Associated with Oil and Gas Development

total area of land disturbed by oil and gas resource 

development up to 2007 in the UCRB. Additional information 

about anticipated oil and gas development in the UCRB was 

used to project disturbance estimates to 2025. The disturbance 

estimate indicates that there was approximately 120,400 acres 

of land disturbance from drill pads in 2007. An additional 

58,950 acres of disturbance associated with 13,500 miles of 

resource roads were estimated for 2007. Projected disturbance 

for 2025 nearly doubles the total pad disturbance to 222,800 

108°

42°

39°

36°

111°

0

0

50

50

150 Miles

150 Kilometers

100

100

Base from U.S Census Bureau digital data, 2000 

Albers Equal Area Conic projection, North American Datum of 1983

Upper Colorado River Basin boundary

Well classified as “disturbed”, 1991

Well classified as “disturbed”, 2007

U.S. Geological Survey stream-monitoring 

site used to calibrate SPARROW model

Used only for 1991 model

Used only for 2007 model

Used for both 1991 and 2007 models

EXPLANATION

108°

42°

39°

36°

111°

A

1991

B

2007

Figure 16. Distribution of U.S. Geological Survey stream-monitoring sites used to calibrate the A, 1991 Upper Colorado River Basin 

(UCRB) dissolved-solids SPARROW model and the B, 2007 exploratory UCRB dissolved-solids SPARROW model and the wells classified 

as “disturbed” in the UCRB oil and gas well dataset in 1991 and 2007.

acres. Road disturbance projected for 2025 could be more than 

96,500 acres for as much as 22,500 miles of new resource 

roads.

The U.S. Geological Survey, in cooperation with the 

Bureau of Reclamation and the BLM, developed a dissolvedsolids SPARROW model specific to the UCRB (Kenney and 

others, 2009). The UCRB dissolved-solids SPARROW model 

was calibrated using 1991 dissolved-solids loads from 218 

stream-monitoring sites. Estimated land disturbance data from 
References Cited 33

References Cited

Anning, D.W., Bauch, N.J., Gerner, S.J., Flynn, M.E., 

Hamlin, S.N., Moore, S.J., Schaefer, D.H., Anderholm, 

S.K., and Spangler L.E., 2007, Dissolved solids in basinfill aquifers and streams in the southwestern United States: 

U.S. Geological Survey Scientific Investigations Report 

2006-5315, 168 p., available at http://pubs.usgs.gov/

sir/2006/5315/.

Chidsey, T.C., Wakefield, S., Hill, B.G., and Hebertson, M., 

2004, Oil and gas fields map of Utah: Utah Geological 

Survey Map 203DM, CD-ROM. 

Colorado Oil and Gas Conservation Commission, 2007, 

Colorado Oil and Gas Information System (COGIS), 

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Wells

located on

low-yield

sedimentary

lithologies

72.75 percent

Wells

located on

high-yield

sedimentary

lithologies

27.25 percent

Figure 17. Percentage of oil and gas wells classified as 

“disturbed” in the 2007 Upper Colorado River Basin (UCRB) oil and 

gas dataset located on UCRB dissolved-solids SPARROW model 

geologic source groups.

1991 and 2007 were input to the UCRB SPARROW model to 

assess the significance of energy-related land disturbance on 

contributing dissolved solids to basin streams. The statistical 

analysis was an observational study that used existing data to 

assess the relation between land disturbance from oil and gas 

resource development and dissolved-solids load in the UCRB. 

In each of the model years, the source coefficient estimated for 

the lands disturbed by oil and gas development was zero. The 

coefficient indicated that the estimated area of lands disturbed 

by oil and gas development was not statistically significant as 

a contributor of dissolved solids in UCRB streams. 

The lack of significance of disturbed lands in the 

SPARROW modeling framework may be due to the amount 

of available monitoring data, the spatial distribution of 

monitoring sites with respect to land disturbance, and the 

overall quantity of disturbed lands associated with oil and 

gas development basin wide and within calibration reaches. 

Finally, dissolved-solids loads from natural landscapes may 

be similar to loads derived from lands disturbed by resource 

extraction activity. The most significant contributor to 

dissolved solids in the UCRB is irrigated agriculture, which 

covers an area substantially larger than the estimated area of 

disturbed lands by oil and gas development and is subjected to 

large amounts of artificially applied water.
34 Land Disturbance Associated with Oil and Gas Development

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wo/st/en/info/newsroom/Energy_Facts_07/statistics.html. 

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home/index.shtm.
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2009 at http://soswy.state.wy.us/RULES/rules/6913.pdf.
36 Land Disturbance Associated with Oil and Gas Development
Appendixes 1 to 5
38 Land Disturbance Associated with Oil and Gas Development Appendix 1A. Summary of National Environmental Policy Act documents reviewed to identify common oil and gas drill pad and resource road dimensions for the Upper Colorado River Basin, Utah. [EIS, Environmental Impact Statement; ft, foot; LOP, life of project; NR, not reported; ROW, right of way] EIS Number UT-080-06-240 UT-080-06-329 UT-080-05-322 UT-080-06-253 UT-080-07-671 UT-080-06-076 UT-080-03-0300V UT-080-06-099 EIS Name Kerr-McGee Bonanza Gasco Wilkin Ridge unit Gasco Riverbend unit Kerr-McGee Love unit Enduring Resources Saddletree draw leasing and Rock house development proposal 1 Enduring Resources West Bonanza area natural gas development Resource Development Group - Uinta Basin natural gas project EOG Resources North Alger natural gas expansion Number of wells 95 54 49 125 60 131 423 44 Number of pads 95 54 49 125 24 131 423 44 Road length (miles) 43.6 21.4 11 43 8.4 33.7 125 13.7 Pipeline length (miles) 77 33 15 82 NR 60 125 13.7 Number of compressor stations

2 0 0 1 NR 4 1 NR

Pads

Initial pad size (acres) 2.5 3.7 3.7 2.5 2 2 1.19 2.5

LOP pad size (acres) 2 1 NR NR 1 NR NR NR 2.2

Roads

Average new ROW (ft) 50 30 30 30 30 30 30 30

Average LOP ROW (ft) 30 NR NR 15 18 NR NR NR

Website 3

http://www.

blm.gov/utah/vernal/bonanzaea.htm

http://www.

blm.gov/utah/vernal/wilkinridgea.htm

http://www.

blm.gov/utah/vernal/gascorev.html

http://www.blm.

gov/utah/vernal/loveea.html

http://www.blm.

gov/utah/vernal/rockhouse671.htm

http://www.blm.gov/

utah/vernal/nepa.html

http://www.blm.

gov/utah/vernal/rdgfinal.htm

http://www.

blm.gov/utah/vernal/northalger.html

1 The proposed alternative includes wells that will be drilled from existing pads or multiple wells drilled from a single pad.2 If the well becomes a producing well, drill pads are reclaimed to a smaller size after drilling operations are complete.3 Documents that are no longer available online can be obtained upon request to the Bureau of Land Management.
Appendixes 1 to 5 39

Appendix 1B. Summary of National Environmental Policy Act documents reviewed to identify common oil and gas drill pad and resource road dimensions for the Upper Colorado River Basin, Colorado.[EIS, Environmental Impact Statement; GAP, Geographic Area Plan; LOP, life of project; NR, not reported; ROW, right of way; ft, foot]

EIS Number CO-140-2005-134 CO-140-2005-113 CO-140-2006-045 CO-140-2007-115 CO-140-05-009 CO-140-05-047 CO-140-2004-081 CO-140-2006-050

EIS Name

Grant Gulch GAP 

environmental 

assessment - 

EnCana Oil 

and Gas 1

Orchard Unit 

GAP - 

EnCana Oil 

and Gas 1

Rulison 

GAP - 

EnCana Oil 

and Gas 1

Pete and Bill 

Creek GAP - 

Noble Energy 1

Castle Springs 

GAP - 

Windsor 

Energy LLC 1

Wheeler to 

Webster GAP - 

Williams Production 

Natural Gas 1

Grass Mesa GAP 

- EnCana Oil 

and Gas 1

South Parachute 

GAP - 

EnCana 

Oil and Gas 1

Number of wells 97 65 68 42 98 213 100 139

Number of pads 17 7 12 4 18 59 16 26

Road length (miles) 8.27 5.8 6 3 7 NR NR NRPipeline length (miles) 8.27 5.9 6.4 3 7 NR NR NRNumber of compressor 

stations

0 0 0 0 1 NR NR NR

Pads

Initial pad size (acres) 6.70 6.5 4.6 6 3.26 2.5 6 4.15

LOP pad size (acres) 2 1 1 1.5 2 1.5 0.5 1 1.5

Roads

Average new ROW (ft) 60 60 75 75 Variable 30 38 75

Average LOP ROW (ft) 30 30 25 25 18 NR 30 25

Website 3

http://www.blm.

gov/co/st/en/fo/gsfo/GSFO_MasterPlansOfDevelopment.html

http://www.blm.

gov/co/st/en/fo/gsfo/GSFO_MasterPlansOfDevelopment.html

http://www.blm.

gov/co/st/en/fo/gsfo/GSFO_MasterPlansOfDevelopment.html

http://www.blm.

gov/co/st/en/fo/gsfo/GSFO_MasterPlansOfDevelopment.html

http://www.blm.

gov/co/st/en/fo/gsfo/GSFO_MasterPlansOfDevelopment.html

http://www.blm.

gov/co/st/en/fo/gsfo/GSFO_MasterPlansOfDevelopment.html

http://www.blm.

gov/co/st/en/fo/gsfo/GSFO_MasterPlansOfDevelopment.html

http://www.blm.

gov/co/st/en/fo/gsfo/GSFO_MasterPlansOfDevelopment.html

1 The proposed alternative includes wells that will be drilled from existing pads or multiple wells drilled from a single pad.2 If the well becomes a producing well, drill pads are reclaimed to a smaller size after drilling operations are complete.3 Documents that are no longer available online can be obtained upon request to the Bureau of Land Management.
40 Land Disturbance Associated with Oil and Gas Development Appendix 1C. Summary of National Environmental Policy Act documents reviewed to identify common oil and gas drill pad and resource road dimensions for the Upper Colorado River Basin, Wyoming. [EIS, Environmental Impact Statement; ft, foot; LOP, life of project; NA, not available; NR, not reported; ROW, right of way] EIS Number WY-040-EA00-094 WY-040-EA03-187 WY-040-EA03-186 WY-040-EADESFT04 WY-040-EA04-008 WY-040-EA04-007 EIS Name Vermillion Basin natural gas exploration and development Copper Ridge shallow gas exploration and development Little Monument natural gas Desolation Flats natural gas field development 1 Pacific Rim shallow oil and gas exploration Bitter Creek shallow oil and gas exploration Number of wells 56 89 31 385 120 61 Number of pads 56 89 31 361 120 61 Road length (miles) 28 22.25 NR 542 35.64 NR Pipeline length (miles) 28 66.75 NR 361 50.64 NR Number of compressor stations NR 1 NR 4 5 NR Pads Initial pad size (acres) 3.8 2 1.8 4 1.1 3 LOP pad size (acres) 2 1 1 1 1.5 0.2 1 Roads Average new ROW (ft) 55 60 55 50 30 NR Average LOP ROW (ft) 32 30 NR 50 14 NR Website 3

http://www.blm.gov/

wy/st/en/info/NEPA/rsfodocs/vermbasin.html

http://www.blm.gov/wy/

st/en/info/NEPA/rsfodocs/copperridge.html

http://www.blm.gov/wy/st/

en/info/NEPA/rsfodocs/littlemonument.html

http://www.blm.gov/

wy/st/en/info/NEPA/rfodocs/desflats.html

http://www.blm.gov/wy/st/

en/info/NEPA/rsfodocs/pacificrim.html

http://www.blm.gov/

wy/st/en/info/NEPA/rsfodocs/bittercreek.html

1 The proposed alternative includes wells that will be drilled from existing pads or multiple wells drilled from a single pad.2 If the well becomes a producing well, drill pads are reclaimed to a smaller size after drilling operations are complete.3 Documents that are no longer available online can be obtained upon request to the Bureau of Land Management.
Appendixes 1 to 5 41

Appendix 1C. Summary of National Environmental Policy Act documents reviewed to identify common oil and gas drill pad and resource road dimensions for the Upper Colorado River Basin, Wyoming.—Continued[EIS, Environmental Impact Statement; ft, foot; LOP, Life of project; NA, not available; NR , not reported; ROW, right of way]

EIS Number WY-040-EA05-161 WY-040-EA03-211 WY-040-CDWIIROD WY-JIDPEIS-06 WY-EIS00-018 NA

EIS Name Monell enhanced oil recovery project Lower Bush Creek coalbed methane exploration 1 Continental Divide- Wamsutter II natural gas project Jonah infill drilling project Pinedale Anticline oil and gas exploration and development project Pinedale Anticline oil and gas exploration supplemental EIS 1

Number of wells 126 22 2,130 3,100 900 4,399

Number of pads 126 20 2,130 3,100 900 250

Road length (miles) 32 10.14 1,065 485 366 NRPipeline length (miles) 132 NR 1,065 465 120 NRNumber of compressor 

stations

1 NR 3 NR 4 NR

Pads

Initial pad size (acres) 2 1.39 2.6 3.8 3.7 20

LOP pad size (acres) 2 1 0.7 0.8 0.9 1.4 7.5

Roads

Average new ROW (ft) 60 30 50 73 55 See original EIS

Average LOP ROW (ft) 30 12 27 29 NR NR

Website 3

http://www.blm.gov/

wy/st/en/info/NEPA/rsfodocs/monell.html

http://www.blm.gov/

wy/st/en/info/NEPA/rsfodocs/lowerbush.html

http://www.blm.gov/

wy/st/en/info/NEPA/rfodocs/cd_wamsutter.html

http://www.blm.gov/

wy/st/en/info/NEPA/pfodocs/jonah.html

http://www.blm.gov/

wy/st/en/info/NEPA/pfodocs/anticline.html

http://www.blm.gov/

wy/st/en/info/NEPA/pfodocs/anticline/seis.htm

1 The proposed alternative includes wells that will be drilled from existing pads or multiple wells drilled from a single pad.2 If the well becomes a producing well, drill pads are reclaimed to a smaller size after drilling operations are complete.3 Documents that are no longer available online can be obtained upon request to the Bureau of Land Management.
42 Land Disturbance Associated with Oil and Gas Development

Appendix 2. Summary of Bureau of Land Management Resource Management Plans reviewed to identify reasonably foreseeable 

development scenarios for the Upper Colorado River Basin.

[BLM, Bureau of Land Management; EIS, Environmental Impact Statement; FO, Field Office; RMP, Resource Management Plan]

State Area Date of RMP Date accessed

Status 

when 

accessed

Website1

Colorado BLM Little Snake FO January 2007 January 16, 2009 Approved http://www.blm.gov/co/st/en/fo/lsfo/plans/rmp_

revision/rmp_docs.html

Colorado BLM White River FO November 2007 January 16, 2009 Final http://www.blm.gov/co/st/en/BLM_Programs/land_

use_planning/rmp/white_river/documents.html

Colorado BLM Glenwood 

Springs FO

October 2007 January 16, 2009 Final http://www.blm.gov/pgdata/etc/medialib/blm/co/

programs/land_use_planning/rmp/kfo-gsfo/

documents.Par.8480.File.dat/GSFO_AMSFinal_103107.pdf

Colorado Glenwood Springs 

FO, Roan Plateau 

geographic area

August 2006 January 16, 2009 Final http://www.blm.gov/co/st/en/BLM_Programs/

land_use_planning/rmp/roan_plateau/documents/

final_rmpa_eis.html

Colorado San Juan public lands 

geographic area

December 2006 January 16, 2009 Draft EIS http://ocs.fortlewis.edu/forestPlan/reports.asp

Colorado BLM Grand 

Junction FO

November 1985 January 16, 2009 Final http://www.blm.gov/co/st/en/BLM_Programs/land_

use_planning/rmp/archived/grand_junction.html

New Mexico BLM Farmington FO - 

San Juan Basin, New 

Mexico

July 2001 January 16, 2010 Final http://www.blm.gov/pgdata/etc/medialib/blm/nm/

field_offices/farmington/farmington_planning/

ffo_rmp_docs.Par.59812.File.dat/RFD.pdf

Utah BLM Vernal FO October 2008 January 13, 2009 Approved http://www.blm.gov/ut/st/en/fo/vernal/planning/rmp/

rod_approved_rmp.html

Utah BLM Monticello FO November 2008 January 15, 2009 Approved http://www.blm.gov/ut/st/en/fo/monticello/planning/

Monticello_Resource_Management_Plan.html

Utah BLM Price FO August 2002 January 15, 2009 Draft EIS http://www.blm.gov/ut/st/en/fo/price/planning/

Resource_Management_Plan/Draft_EIS.html

Utah BLM Moab FO August 2005 January 16, 2009 Complete http://www.blm.gov/pgdata/etc/medialib/blm/ut/moab_

fo/rmp/background_documents.Par.44906.File.dat/

MoabFinalRFDwithMaps.pdf

Utah BLM Kanab FO July 2008 January 16, 2009 Approved http://www.blm.gov/ut/st/en/fo/kanab/planning/

proposed_rmp_feis.html

Utah BLM Richfield FO August 2008 January 16, 2009 Proposed RMP/

Final EIS

http://www.blm.gov/pgdata/etc/medialib/blm/ut/

richfield_fo/planning/rmp/August_8__2008.

Par.20741.File.dat/Vol-III_Appendix-12_RichfieldFEIS_RFD.pdf

Wyoming BLM Pinedale FO November 2008 January 13, 2009 Approved http://www.blm.gov/rmp/wy/pinedale/documents_

RFD.html

Wyoming BLM Kemmerer FO August 2008 January 13, 2009 Draft EIS http://www.blm.gov/rmp/kemmerer/feis.htm

Wyoming BLM Rawlins FO December 2008 January 13, 2009 Approved http://www.blm.gov/rmp/wy/rawlins/documents.html

Wyoming BLM Rock Springs 

FO - Green River 

Resource Area

August 1997 January 13, 2009 Approved http://www.blm.gov/pgdata/etc/medialib/blm/wy/

programs/planning/rmps.Par.20275.File.dat/

greenriver-rmp.pdf

1

 Documents that are no longer available online can be obtained upon request to the originating agency
Appendixes 1 to 5 43

Appendix 3. Descriptions and water year 2007 dissolved-solids load estimates for selected sites in the Upper Colorado River Basin.[Dissolved-solids load estimates determined using a multiple linear regression model included in the computer model LOADEST (Runkel and others, 2004). Horizontal datum is North American Datum of 1983; NGVD 29, National Geodetic Vertical Datum of 1929; NAVD 88, North American Vertical Datum of 1988; AZ, Arizona; CO, Colorado; SEP, standard error of prediction; UT, Utah; WY, Wyoming; —, no data]

Site 

identification 

number

Site name Decimal latitude Decimal longitude

Altitude 

of gage/ 

land 

surface 

(feet above 

datum)

Altitude 

datum

Hydrologic 

Unit Code

Drainage 

area, in 

square 

miles

Estimates of dissolved-solids load during 

water year 2007, in tons

Mean 

daily 

load

95-percent confidence 

interval for mean daily load 

SEP of 

mean 

daily 

load

Annual 

load Lower 

bound 

Upper 

bound

09032000 Ranch Creek near Fraser, CO 39.9500 -105.7656 8,660 NGVD 29 14010001 19.9 0.69 0.61 0.79 0.05 253

09034250 Colorado River at Windy Gap, near 

Granby, CO

40.1083 -106.0042 7,790 NGVD 29 14010001 789 29.9 27.5 32.4 1.26 10,900

09058000 Colorado River near Kremmling, CO 40.0367 -106.4400 7,320 NGVD 29 14010001 2,380 330 307 354 11.9 121,00009063000 Eagle River at Red Cliff, CO 39.5083 -106.3667 8,654 NGVD 29 14010003 70.0 10.6 10.4 10.9 0.13 3,89009066510 Gore Creek at mouth near Minturn, 

CO

39.6094 -106.4478 7,730 NGVD 29 14010003 102 25.2 23.3 27.2 0.98 9,200

09081000 Roaring Fork River near Emma, CO 39.3733 -107.0839 6,470 NGVD 29 14010004 853 291 281 301 5.14 106,00009083800 Crystal River below Carbondale, CO 39.4080 -107.2303 6,120 NAVD 88 14010004 350 185 180 189 2.42 67,400

09085000 Roaring Fork River at Glenwood 

Springs, CO

39.5436 -107.3295 5,721 NGVD 29 14010004 1,450 766 745 788 11.2 280,000

09095500 Colorado River near Cameo, CO 39.2391 -108.2662 4,814 NGVD 29 14010005 8,050 3,620 3,520 3,720 49.1 1,320,00009107000 Taylor River at Taylor Park, CO 38.8603 -106.5667 9,340 NGVD 29 14020001 128 16.1 15.5 16.7 0.30 5,87009112200 East River below Cement Creek near 

Crested Butte, CO

38.7842 -106.8709 8,440 NGVD 29 14020001 238 85.0 80.8 89.5 2.23 31,000

09112500 East River at Almont, CO 38.6644 -106.8481 8,006 NGVD 29 14020001 289 101 97.9 104 1.52 36,80009113980 Ohio Creek above mouth near 

Gunnison, CO

38.5878 -106.9314 7,770 NGVD 29 14020002 161 16.6 14.4 19.0 1.17 6,040

09114500 Gunnison River near Gunnison, CO 38.5419 -106.9498 7,655 NGVD 29 14020002 1,010 186 176 196 5.20 67,80009119000 Tomichi Creek at Gunnison, CO 38.5217 -106.9409 7,629 NGVD 29 14020003 1,060 69.4 64.6 74.4 2.49 25,30009128000 Gunnison River below Gunnison 

Tunnel, CO

38.5292 -107.6489 6,526 NGVD 29 14020002 3,970 293 275 313 9.71 107,000

09132500 North Fork Gunnison River near 

Somerset, CO

38.9258 -107.4342 6,280 NGVD 29 14020004 526 93.8 80.7 108 7.06 34,200

09146020 Uncompahgre River near Ouray, CO 38.0433 -107.6831 7,600 NGVD 29 14020006 77.0 76.0 73.8 78.2 1.13 27,70009146200 Uncompahgre River near Ridgway, 

CO

38.1839 -107.7459 6,878 NGVD 29 14020006 149 141 133 149 4.04 51,500

09152500 Gunnison River near Grand Junction, 

CO

38.9833 -108.4506 4,628 NGVD 29 14020005 7,930 2,950 2,770 3,140 95.2 1,080,000
44 Land Disturbance Associated with Oil and Gas Development Appendix 3. Descriptions and water year 2007 dissolved-solids load estimates for selected sites in the Upper Colorado River Basin.—Continued [Dissolved-solids load estimates determined using a multiple linear regression model included in the computer model LOADEST (Runkel and others, 2004). Horizontal datum is North American Datum of 1983; NGVD 29, National Geodetic Vertical Datum of 1929; NAVD 88, North American Vertical Datum of 1988; AZ, Arizona; CO, Colorado; SEP, standard error of prediction; UT, Utah; WY, Wyoming; —, no data] Site identification number Site name Decimal latitude Decimal longitude Altitude of gage/ land surface (feet above datum) Altitude datum Hydrologic Unit Code Drainage area, in square miles Estimates of dissolved-solids load during water year 2007, in tons Mean daily load 95-percent confidence interval for mean daily load SEP of mean daily load Annual load Lower bound Upper bound 09163500 Colorado River near Colorado-Utah State Line 39.1328 -109.0271 4,325 NGVD 29 14010005 17,800 7,320 7,060 7,580 132 2,670,000 09169500 Dolores River at Bedrock, CO 38.3103 -108.8854 4,940 NGVD 29 14030002 2,020 154 121 193 18.5 56,100 09171100 Dolores River near Bedrock, CO 38.3569 -108.8334 4,910 NGVD 29 14030002 2,150 314 254 383 33.0 114,000 09180000 Dolores River near Cisco, UT 38.7972 -109.1951 4,165 NGVD 29 14030004 4,580 711 609 825 55.0 260,000 09180500 Colorado River near Cisco, UT 38.8105 -109.2934 4,090 NGVD 29 14030005 24,100 7,660 7,220 8,130 232 2,800,000 09196500 Pine Creek above Fremont Lake, WY 43.0305 -109.7702 7,450 NGVD 29 14040102 75.8 3.35 3.22 3.48 0.06 1,220 09211200 Green River below Fontenelle Reservoir, WY 42.0210 -110.0498 6,378 NGVD 29 14040103 4,280 512 493 533 10.2 187,000 09217000 Green River near Green River, WY 41.5164 -109.4490 6,060 NGVD 29 14040106 14,000 688 661 716 13.9 251,000

09229500 Henrys Fork near Manila, UT 41.0125 -109.6729 6,060 NGVD 29 14040106 520 117 69.9 183 29.0 42,500

09239500 Yampa River at Steamboat Springs, 

CO

40.4830 -106.8324 6,695 NGVD 29 14050001 568 66.7 48.2 90.1 10.7 24,400

09247600 Yampa River below Craig, CO 40.4808 -107.6142 6,100 NGVD 29 14050001 1,750 466 300 691 100 170,00009251000 Yampa River near Maybell, CO 40.5027 -108.0334 5,900 NGVD 29 14050002 3,410 610 517 716 50.8 223,00009258980 Muddy Creek below Young Draw, 

near Baggs, WY

41.0682 -107.6316 6,270 NGVD 29 14050004 — 12.1 7.53 18.4 2.79 4,410

09260050 Yampa River at Deerlodge Park, CO 40.4516 -108.5251 5,600 NGVD 29 14050002 7,660 768 656 893 60.6 280,000

09261000 Green River near Jensen, UT 40.4094 -109.2354 4,758 NGVD 29 14060001 29,700 2,960 2,370 3,650 327 1,080,00009302000 Duchesne River near Randlett, UT 40.2103 -109.7814 4,756 NGVD 29 14060003 3,790 348 323 374 12.95 127,00009304200 White River above Coal Creek, near 

Meeker, CO

40.0050 -107.8253 6,400 NGVD 29 14050005 648 177 166 189 5.80 64,600

09304800 White River below Meeker, CO 40.0133 -108.0931 5,928 NGVD 29 14050005 1,020 406 382 430 12.4 148,00009306200 Piceance Creek below Ryan Gulch, 

near Rio Blanco, CO

39.9211 -108.2976 6,070 NGVD 29 14050006 506 42.3 40.5 44.2 0.96 15,400

09306222 Piceance Creek at White River, CO 40.0780 -108.2365 5,730 NGVD 29 14050006 652 67.2 64.4 70.1 1.45 24,50009306255 Yellow Creek near White River, CO 40.1686 -108.4012 5,535 NGVD 29 14050006 262 8.68 8.18 9.19 0.26 3,170
Appendixes 1 to 5 45

Appendix 3. Descriptions and water year 2007 dissolved-solids load estimates for selected sites in the Upper Colorado River Basin.—Continued[Dissolved-solids load estimates determined using a multiple linear regression model included in the computer model LOADEST (Runkel and others, 2004). Horizontal datum is North American Datum of 1983; NGVD 29, National Geodetic Vertical Datum of 1929; NAVD 88, North American Vertical Datum of 1988; AZ, Arizona; CO, Colorado; SEP, standard error of prediction; UT, Utah; WY, Wyoming; —, no data]

Site 

identification 

number

Site name Decimal latitude Decimal longitude

Altitude 

of gage/ 

land 

surface 

(feet above 

datum)

Altitude 

datum

Hydrologic 

Unit Code

Drainage 

area, in 

square 

miles

Estimates of dissolved-solids load during 

water year 2007, in tons

Mean 

daily 

load

95-percent confidence 

interval for mean daily load 

SEP of 

mean 

daily 

load

Annual 

load Lower 

bound 

Upper 

bound

09306290 White River below Boise Creek, near 

Rangely, CO

40.1797 -108.5654 5,395 NGVD 29 14050007 2,530 503 479 527 12.4 183,000

09306500 White River near Watson, UT 39.9789 -109.1787 4,947 NGVD 29 14050007 4,020 569 516 626 28.1 208,000

09314500 Price River at Woodside, UT 39.2639 -110.3465 4,600 NGVD 29 14060007 1,540 220 188 256 17.4 80,40009315000 Green River at Green River, UT 38.9861 -110.1512 4,040 NGVD 29 14060008 44,900 3,590 3,230 3,980 194 1,310,00009328500 San Rafael River near Green River, 

UT

38.8583 -110.3701 4,190 NGVD 29 14060009 1,630 291 — — — 106,000

09352900 Vallecito Creek near Bayfield, CO 37.4775 -107.5437 7,906 NGVD 29 14080101 72.5 16.2 15.3 17.1 0.46 5,920

09359020 Animas River below Silverton, CO 37.7903 -107.6676 9,200 NGVD 29 14080104 146 140 138 143 1.34 51,20009371492 Mud Creek at State Highway 32, near 

Cortez, CO

37.3128 -108.6612 5,765 NGVD 29 14080202 33.6 36.1 34.0 38.3 1.10 13,200

09371520 McElmo Creek above Trail Canyon 

near Cortez, CO

37.3267 -108.7007 5,690 NGVD 29 14080202 234 202 187 218 7.98 73,700

09372000 McElmo Creek near Colorado-Utah 

State Line

37.3242 -109.0157 4,890 NGVD 29 14080202 346 209 202 216 3.50 76,300

09379500 San Juan River near Bluff, UT 37.1469 -109.8648 4,048 NGVD 29 14080205 23,000 1,590 1,390 1,810 108 580,00009380000 Colorado River at Lees Ferry, AZ 36.8647 -111.5882 3,106 NGVD 29 14070006 112,000 15,100 14,900 15,400 141 5,520,000
46 Land Disturbance Associated with Oil and Gas Development Appendix 4. Sources of dissolved solids in Upper Colorado River Basin streams by bounded calibration reach excluding point-source import source group as defined for 1991 Upper Colorado River Basin SPARROW model. [All measurements are in square miles] Calibration reach labeled by downstream monitoring site number Drainage area of calibration reach Irrigated sedimentary- clastic Tertiary lands Irrigated sedimentary- clastic Mesozoic lands Irrigated lands of other lithologies Crystalline and volcanic rocks High- yield sedimentary Cenozoic rocks Low- yield sedimentary Cenozoic rocks High- yield sedimentary Mesozoic rocks Low- yield sedimentary Mesozoic rocks High- yield sedimentary Paleozoic and Precambrian rocks Low- yield sedimentary Paleozoic and Precambrian rocks Land disturbance associated with oil and gas development 09010500 53.8 0 0 0 52.7 0 0.173 0.920 0 0 0 0.00 09024000 27.6 0 0 0 27.6 0 0 0 0 0 0 0.00 09025000 28.2 0 0 0 28.2 0 0 0 0 0 0.078 0.00 09025400 7.25 0.034 0 0.081 7.11 0 0.139 0 0 0 0 0.00 09026500 32.9 0 0 0 32.2 0 0 0 0.787 0 0.001 0.00 09032000 20.0 0 0 0 19.8 0 0.222 0 0 0 0 0.00 09032100 6.28 0 0 0 6.28 0 0 0 0 0 0 0.00 09034250 614 14.8 2.64 5.42 332 147 85.5 24.9 8.90 0 15.9 0.005 09034500 36.0 0.934 0.011 0.043 0.737 32.6 2.44 0.146 0 0 0.097 0.00 09034900 6.12 0 0 0 6.12 0 0 0 0 0 0 0.00 09035500 10.3 0 0 0 10.3 0 0 0 0 0 0 0.00

09035700 18.9 0 0 0 18.9 0 0 0 0 0 0 0.00

09035800 8.86 0 0 0 8.86 0 0 0 0 0 0 0.00

09035900 27.7 0 0 0 27.7 0 0 0 0 0 0 0.00

09036000 17.8 0 0 0.106 17.8 0 0 0 0 0 0 0.00

09037500 94.3 0.876 0.272 0.988 75.7 2.99 10.3 0 3.76 0 1.54 0.00

09038500 9.02 0.191 0 0 1.23 1.65 6.14 0 0 0 0 0.00

09039000 44.7 0 0 0.004 39.8 4.45 0.530 0 0 0 0 0.00

09041090 148 0.207 6.11 0.257 22.9 11.1 19.5 54.9 37.8 0 2.02 0.00

09041500 146 0.875 6.10 2.01 36.1 5.07 26.3 39.3 35.5 0.658 3.45 0.00

09046490 42.5 0 0 0 24.3 0 0 0.461 1.93 15.8 0 0.00

09046600 80.9 0 0 0 54.3 0 0 11.0 9.98 3.57 2.03 0.00

09047500 58.1 0 0 0 57.1 0 0 1.04 0 0 0 0.00

09047700 9.39 0 0 0 9.39 0 0 0 0 0 0 0.00

09050100 86.6 0 0 0 56.7 0.407 0 0 0 29.6 0 0.00

09050700 51.3 0 0 0 33.9 5.54 0 7.59 3.66 0 0.602 0.00
Appendixes 1 to 5 47

Appendix 4. Sources of dissolved solids in Upper Colorado River Basin streams by bounded calibration reach excluding point-source import source group as defined for 1991 Upper Colorado River Basin SPARROW model.—Continued[All measurements are in square miles]

Calibration 

reach 

labeled by 

downstream 

monitoring 

site number

Drainage 

area of 

calibration 

reach 

Irrigated 

sedimentaryclastic 

Tertiary 

lands 

Irrigated 

sedimentaryclastic 

Mesozoic 

lands 

Irrigated 

lands 

of other 

lithologies 

Crystalline 

and 

volcanic 

rocks 

Highyield 

sedimentary 

Cenozoic 

rocks 

Lowyield 

sedimentary 

Cenozoic 

rocks 

Highyield 

sedimentary 

Mesozoic 

rocks 

Lowyield 

sedimentary 

Mesozoic 

rocks 

Highyield 

sedimentary 

Paleozoic 

and 

Precambrian 

rocks 

Lowyield 

sedimentary 

Paleozoic 

and 

Precambrian 

rocks 

Land 

disturbance 

associated 

with oil 

and gas 

development 

09051050 19.3 0 0 0 18.3 0 0 0.985 0.028 0 0 0.00

09052000 16.0 0 0.014 0 15.3 0 0 0.005 0.756 0 0 0.00

09052400 8.66 0 0 0 8.54 0 0 0 0.124 0 0 0.00

09052800 14.5 0 0 0 12.4 0 1.91 0.191 0.058 0 0 0.00

09054000 15.3 0 0 0 14.5 0.123 0.669 0 0 0 0 0.00

09055300 12.0 0 0 0 10.6 0.275 0.546 0 0.573 0 0 0.00

09057500 163 1.75 2.93 2.85 77.5 3.00 9.66 50.4 18.5 0 3.81 0.00

09057520 61.6 0 1.95 0 16.2 0 0.945 10.5 32.7 1.19 0 0.00

09058000 379 21.7 5.25 4.92 80.5 134 105 16.6 32.9 0.090 9.60 0.00

09058500 12.8 0 0 0 10.8 0 0 0 0 2.05 0 0.00

09058610 3.56 0 0 0 0.148 0 0.100 0 0.008 3.31 0 0.00

09058700 3.58 0 0 0 0.620 0 0.188 0 0 2.77 0 0.00

09058800 3.60 0 0 0 3.25 0 0 0 0.038 0.312 0 0.00

09059500 70.5 0.146 0 0.269 10.7 0 7.63 4.14 19.9 28.1 0 0.00

09060550 72.9 0 0 0 56.4 0 1.58 0 8.42 6.52 0 0.00

09060770 128 1.19 9.35 1.05 22.9 0 10.6 0 78.1 16.6 0 0.014

09063000 76.0 0 0 0 28.0 0.055 0 0 0 45.4 2.50 0.00

09063200 9.69 0 0 0 0.585 0 0.828 0 0 8.27 0 0.00

09063400 14.1 0 0 0 0.937 0 0.487 0 0 12.7 0 0.00

09063900 6.48 0 0 0 6.48 0 0 0 0 0 0 0.00

09064500 51.9 0 0 0 51.0 0.433 0 0 0 0.390 0 0.00

09064600 34.4 0 0 0 21.4 0 0 0 0 13.0 0 0.00

09065100 34.8 0 0 0.008 33.5 0 0 0 0 1.30 0 0.00

09065500 14.6 0 0 0.003 14.3 0 0.006 0 0 0.307 0 0.00

09066000 12.5 0 0 0 3.55 0 0.842 0 0 8.09 0 0.00

09066100 5.65 0 0 0.050 5.63 0 0 0 0 0.026 0 0.00
48 Land Disturbance Associated with Oil and Gas Development Calibration reach labeled by downstream monitoring site number Drainage area of calibration reach Irrigated sedimentary- clastic Tertiary lands Irrigated sedimentary- clastic Mesozoic lands Irrigated lands of other lithologies Crystalline and volcanic rocks High- yield sedimentary Cenozoic rocks Low- yield sedimentary Cenozoic rocks High- yield sedimentary Mesozoic rocks Low- yield sedimentary Mesozoic rocks High- yield sedimentary Paleozoic and Precambrian rocks Low- yield sedimentary Paleozoic and Precambrian rocks Land disturbance associated with oil and gas development 09066150 6.19 0 0 0.059 4.83 0 0 0 0 1.13 0.237 0.00 09066200 6.12 0 0 0.021 4.07 0 0 0 0 1.99 0.061 0.00 09066300 6.01 0 0 0.019 1.79 0 0 0 0 4.18 0.043 0.00 09066310 26.0 0 0 0.956 1.90 0 4.39 0 0 18.5 1.15 0.00 09066400 8.49 0 0 0 4.05 0 0 0 0 4.44 0 0.00 09067000 14.8 0 0 0 8.68 0 0 0 0 6.16 0 0.00 09067005 73.7 0.082 0 0.843 7.32 0 5.50 0 0 58.8 2.09 0.00 09070000 549 0.057 1.45 14.8 91.4 0 24.6 35.9 77.0 296 24.6 0.00 09070500 773 1.81 10.5 4.31 209 0.183 89.8 35.5 191 247 0.615 0.00 09071300 6.83 0 0 0 0.320 0 0 0 0 6.51 0 0.00

09071750 137 0 0 0.147 17.0 0 5.89 0 0.096 114 0 0.00

09073300 76.3 0 0 0.029 76.3 0 0 0 0 0 0 0.00

09073400 29.8 0 0 0.158 27.2 0 0 0 0 2.64 0 0.00

09074000 41.7 0 0 0.04 39.8 0 0 0 0 1.93 0 0.00

09074800 32.3 0 0 0 18.1 0 0 0 0 14.2 0 0.00

09075700 35.8 0 0 0 7.92 0 0 0 0 27.9 0 0.00

09080400 223 0.062 0 0.211 146 2.85 2.40 0 0 72.5 0 0.00

09081600 169 0.004 0.132 0.118 33.7 0 6.56 21.2 57.2 50.0 0 0.00

09085000 833 3.93 16.1 32.6 197 0.207 109 19.9 172 296 39.2 0.049

09085100 24.4 0.016 0 0.077 5.25 0 0.277 0 0 18.9 0 0.00

09086000 9.53 0 0.002 0.011 0 0 0 0 1.07 8.46 0 0.00

09086470 91.3 0 0 0.022 1.13 0 0 0 0 90.2 0 0.00

09089500 64.5 0.217 0 0 0.123 0 59.5 4.91 0 0 0 0.004

09093700 1,180 47.1 7.97 16.6 16.6 144 630 49.7 101 194 49.0 2.30

09095500 623 10.2 0 3.18 0 285 307 16.7 6.75 0 7.38 0.535

09105000 592 22.1 3.80 23.0 184 77.3 286 10.7 14.6 0 19.5 0.712

Appendix 4. Sources of dissolved solids in Upper Colorado River Basin streams by bounded calibration reach excluding point-source import source group as defined for 1991 Upper Colorado River Basin SPARROW model.—Continued[All measurements are in square miles]
Appendixes 1 to 5 49

Calibration 

reach 

labeled by 

downstream 

monitoring 

site number

Drainage 

area of 

calibration 

reach 

Irrigated 

sedimentaryclastic 

Tertiary 

lands 

Irrigated 

sedimentaryclastic 

Mesozoic 

lands 

Irrigated 

lands 

of other 

lithologies 

Crystalline 

and 

volcanic 

rocks 

Highyield 

sedimentary 

Cenozoic 

rocks 

Lowyield 

sedimentary 

Cenozoic 

rocks 

Highyield 

sedimentary 

Mesozoic 

rocks 

Lowyield 

sedimentary 

Mesozoic 

rocks 

Highyield 

sedimentary 

Paleozoic 

and 

Precambrian 

rocks 

Lowyield 

sedimentary 

Paleozoic 

and 

Precambrian 

rocks 

Land 

disturbance 

associated 

with oil 

and gas 

development 

09106150 172 1.19 0.559 0.236 4.86 1.04 34.8 124 5.54 0 0.916 0.151

09107000 129 0 0 0.239 118 0.045 0 0 0 6.81 3.60 0.00

09107500 44.5 0 0 0 42.9 0.110 0 0 0 0.279 1.19 0.00

09109000 81.9 0 0 0.360 62.8 2.66 0 0 0 9.52 6.91 0.00

09110000 223 0 0.232 0.709 155 0 0 0 8.53 59.3 0.794 0.00

09112500 290 2.14 4.57 10.4 68.1 0 17.3 21.9 108 67.1 6.87 0.00

09114500 245 15.9 9.35 5.87 96.6 0 73.4 28.7 39.6 0 6.74 0.004

09118450 334 5.93 0 9.27 298 0 24.4 0 6.41 0 5.28 0.00

09119000 727 15.4 4.90 8.72 505 0.044 48.9 0 135 38.5 0 0.00

09124500 340 0.649 0 1.65 310 0.592 24.9 0 0 0 4.47 0.00

09126000 67.2 0 0 0 53.8 0 13.5 0 0 0 0 0.00

09128000 1,490 8.87 4.53 8.17 1,220 22.4 141 2.00 98.3 0 4.34 0.00

09128500 43.6 0.001 0.232 0 20.9 0 5.60 0 17.1 0 0 0.00

09132500 525 11.1 0.344 1.44 104 3.27 299 98.0 16.1 0 5.28 0.079

09134000 41.8 0 0.142 0 8.28 0 5.67 15.7 12.1 0 0 0.00

09135900 66.9 0.069 2.38 2.17 15.8 2.86 13.4 9.58 18.5 0 6.78 0.00

09143000 27.7 0 0 0 19.0 1.17 7.36 0.002 0 0 0.114 0.004

09143500 14.9 0 0.156 1.25 5.89 0.736 0.717 1.99 0.163 0 5.39 0.005

09144250 951 13.9 73.4 39.0 91.3 9.71 156 103 518 0 73.1 0.008

09146200 149 0.274 3.29 4.25 87.6 0 12.0 0 29.8 10.1 9.81 0.00

09147000 97.6 2.30 4.55 0.161 23.7 0 20.1 0 53.7 0 0.001 0.00

09147025 18.1 0.096 1.40 0.0475 0.208 0 1.91 0 16.0 0 0 0.00

09147500 183 1.44 3.63 1.30 55.7 0 50.2 0 72.6 1.14 3.26 0.00

09149500 667 33.0 39.0 30.9 1.49 0.290 128 1.86 489 0 47.1 0.015

09152500 1,170 3.89 14.0 13.9 51.1 2.91 50.5 139 899 6.78 20.1 0.041

09153290 17.7 0 9.67 0 0 0 0 0 17.7 0 0 0.022

Appendix 4. Sources of dissolved solids in Upper Colorado River Basin streams by bounded calibration reach excluding point-source import source group as defined for 1991 Upper Colorado River Basin SPARROW model.—Continued[All measurements are in square miles]
50 Land Disturbance Associated with Oil and Gas Development Calibration reach labeled by downstream monitoring site number Drainage area of calibration reach Irrigated sedimentary- clastic Tertiary lands Irrigated sedimentary- clastic Mesozoic lands Irrigated lands of other lithologies Crystalline and volcanic rocks High- yield sedimentary Cenozoic rocks Low- yield sedimentary Cenozoic rocks High- yield sedimentary Mesozoic rocks Low- yield sedimentary Mesozoic rocks High- yield sedimentary Paleozoic and Precambrian rocks Low- yield sedimentary Paleozoic and Precambrian rocks Land disturbance associated with oil and gas development 09163500 1,170 11.4 53.5 35.5 20.6 51.2 119 346 575 0 60.0 1.59 09165000 105 0 0 0 13.7 0 5.01 6.72 41.8 37.7 0.529 0.00 09166500 399 0 2.76 0.540 16.1 0.520 0 64.1 286 32.2 0 0.005 09166950 69.3 0 0.241 0 0.166 0.263 0 0 68.8 0 0 0.00 09169500 1,450 2.88 6.91 0.027 4.53 0 41.5 140 1,240 17.3 10.6 0.204 09171100 122 4.34 0.086 0.427 0 0 37.0 23.9 44.1 8.06 8.81 0.00 09172500 309 0.196 5.51 1.06 80.8 0.111 20.1 13.1 182 12.4 0 0.00 09177000 1,190 0 43.4 0 16.7 0.482 15.1 24.7 1,130 5.18 0.042 0.081 09180000 928 2.60 1.35 0.635 71.3 0.116 37.2 252 489 7.51 71.3 0.016 09180500 1,530 2.44 2.74 0.998 36.4 235 94.9 407 758 0.029 0 5.88

09184000 74.5 0 0.496 0 3.46 0 1.68 0 65.0 0 4.31 0.006

09186500 30.8 0 0 0 4.97 0 7.42 0 18.4 0 0 0.00

09209400 3,830 365 0.274 13.4 610 149 2,190 0.413 341 154 392 9.00

09211200 370 7.50 0.716 0 0 118 111 14.8 111 9.22 5.43 0.675

09215550 1,130 21.0 0 0.288 83.6 456 550 0.891 0.198 0 44.5 0.274

09216050 600 13.0 0 0 0 492 107 0 0 0 0 0.141

09217000 3,800 0.215 0 0 0 1,470 1,360 702 269 0 0 8.14

09224700 2,980 144 3.94 0.350 0 209 2,020 149 384 21.6 206 3.76

09234500 2,400 37.4 8.38 4.24 0.418 619 1,150 13.2 157 56.5 402 0.858

09235600 24.7 0 0 0 0 0 11.4 0 1.84 0.066 11.4 0.00

09237450 207 5.01 14.9 3.05 26.0 0.492 83.0 0.346 93.7 0 3.67 0.00

09237500 20.5 0.255 0 0 2.86 0 16.5 0 1.08 0 0 0.00

09238900 26.0 0 0 0 26.0 0.066 0 0 0 0 0 0.00

09239500 313 5.40 0.810 4.32 186 0.623 87.1 8.78 24.9 0 6.20 0.016

09240900 123 0 0.026 0.210 112 0 0.271 0 8.67 0 2.67 0.00

09241000 93.3 1.12 0.018 0.206 37.6 0 40.6 0 14.1 0 1.07 0.00

Appendix 4. Sources of dissolved solids in Upper Colorado River Basin streams by bounded calibration reach excluding point-source import source group as defined for 1991 Upper Colorado River Basin SPARROW model.—Continued[All measurements are in square miles]
Appendixes 1 to 5 51

Calibration 

reach 

labeled by 

downstream 

monitoring 

site number

Drainage 

area of 

calibration 

reach 

Irrigated 

sedimentaryclastic 

Tertiary 

lands 

Irrigated 

sedimentaryclastic 

Mesozoic 

lands 

Irrigated 

lands 

of other 

lithologies 

Crystalline 

and 

volcanic 

rocks 

Highyield 

sedimentary 

Cenozoic 

rocks 

Lowyield 

sedimentary 

Cenozoic 

rocks 

Highyield 

sedimentary 

Mesozoic 

rocks 

Lowyield 

sedimentary 

Mesozoic 

rocks 

Highyield 

sedimentary 

Paleozoic 

and 

Precambrian 

rocks 

Lowyield 

sedimentary 

Paleozoic 

and 

Precambrian 

rocks 

Land 

disturbance 

associated 

with oil 

and gas 

development 

09242500 243 6.25 6.66 1.59 103 0 45.5 15.1 74.8 0 5.21 0.00

09243700 24.7 0 0.238 0 0 0 0 21.9 2.86 0 0 0.007

09243900 17.7 0 0.058 0 0 0 0 17.7 0 0 0 0.00

09245000 67.8 0 0.094 0 0.986 0 14.7 24.3 27.8 0 0 0.012

09246920 40.3 1.10 0 0 0.116 0 40.1 0 0 0 0 0.011

09247600 952 19.0 12.0 0.015 38.6 78.4 260 379 195 0 1.24 0.534

09249750 458 0.207 10.7 0 23.9 0 53.4 161 220 0 0 0.166

09250507 20.1 0 0.193 0 0 0 0 19.2 0.910 0 0 0.078

09251000 776 6.28 8.72 0.031 0.149 31.6 269 288 180 5.67 0.991 0.246

09253000 252 1.86 0.561 0.710 124 0 96.0 14.2 14.6 0 2.53 0.006

09255000 151 2.19 1.94 0 7.78 14.5 106 7.45 15.4 0 0 0.00

09260000 3,630 39.2 3.61 0.133 89.5 668 2,350 370 109 5.43 38.6 4.12

09260050 517 6.98 0.099 0 0 30.8 369 20.7 60.0 26.5 9.68 0.045

09261000 2,430 4.41 0.244 0.425 13.2 428 944 39.2 167 401 435 1.54

09261700 87.5 0 0.108 0 0 0 30.8 7.53 7.86 30.0 11.3 0.00

09266500 101 0 0 0 0 0 42.0 0 0.382 11.6 47.3 0.00

09275500 63.0 0 0.013 0 0 0 23.5 11.1 28.4 0 0 0.004

09276600 26.9 0 0.134 0 0 0 5.17 2.90 0.490 14.8 3.57 0.00

09277500 268 9.06 0.417 0.677 0 0 64.3 22.3 51.0 45.5 85.1 0.014

09277800 101 0 0 0 0 0 0.143 0 0.327 0 100 0.00

09278000 16.3 0 0 0 0 0 0.093 0 0.261 5.20 10.7 0.00

09279000 35.8 0.075 0 0 0 0 7.02 1.85 0.294 12.0 14.7 0.00

09279100 83.2 0.160 0 0 0 0 47.8 3.64 18.2 7.11 6.44 0.029

09279150 30.3 1.88 0 0 0 0 30.3 0 0.020 0 0 0.117

09285000 214 0 0 0 0 10.9 149 9.98 31.5 11.1 0.918 0.03

09285900 159 0.144 0 0 0 25.3 134 0 0 0 0 0.018

Appendix 4. Sources of dissolved solids in Upper Colorado River Basin streams by bounded calibration reach excluding point-source import source group as defined for 1991 Upper Colorado River Basin SPARROW model.—Continued[All measurements are in square miles]
52 Land Disturbance Associated with Oil and Gas Development Calibration reach labeled by downstream monitoring site number Drainage area of calibration reach Irrigated sedimentary- clastic Tertiary lands Irrigated sedimentary- clastic Mesozoic lands Irrigated lands of other lithologies Crystalline and volcanic rocks High- yield sedimentary Cenozoic rocks Low- yield sedimentary Cenozoic rocks High- yield sedimentary Mesozoic rocks Low- yield sedimentary Mesozoic rocks High- yield sedimentary Paleozoic and Precambrian rocks Low- yield sedimentary Paleozoic and Precambrian rocks Land disturbance associated with oil and gas development 09286100 31.4 0 0 0 0 0 8.00 13.3 10.1 0 0 0.00 09286700 47.1 0 0 0 0 0 12.5 16.7 17.9 0 0 0.005 09288000 119 2.61 0 0 0 0 112 6.64 0.989 0 0 0.016 09288180 350 3.21 0.948 0 0 115 214 0.087 20.9 0 0 0.106 09288400 140 0.045 0.002 0 0 0 118 0 21.9 0 0 0.634 09289500 77.8 0 0 0 0 0 0 0 0 0 77.8 0.00 09292500 139 0.189 0 0 0 0 22.3 0 0.297 4.85 112 0.004 09295000 763 33.2 14.8 10.6 0 41.5 547 0.747 75.7 7.78 90.3 1.83 09299500 124 0.167 0 0.058 0 0 16.0 0 0.610 3.55 104 0.005 09302000 1,010 87.8 30.8 29.9 0 0 544 8.97 118 13.4 322 2.70

09303000 259 0.010 0 1.29 93.0 0.601 69.7 0 37.6 52.7 5.57 0.00

09303300 52.6 0 0 0 30.0 0.114 0.208 0 0 22.2 0 0.00

09303400 75.8 0 0 0 22.6 0 0.211 0 0 53.0 0 0.00

09304000 51.7 0.060 0 1.87 8.91 0 16.0 0 0 22.5 4.34 0.00

09304200 208 0.588 0.458 1.83 3.21 0.863 11.2 0 34.0 158 0.704 0.00

09304500 113 1.88 5.91 0 0 0 6.38 18.6 83.5 4.54 0 0.026

09304800 264 6.88 5.75 0 0 31.5 78.7 85.2 51.7 16.6 0 0.086

09306007 177 1.23 0.093 0 0 28.8 119 21.1 7.46 0.984 0 0.088

09306200 328 3.57 0 0 0 7.27 321 0 0 0 0 0.299

09306222 146 1.37 0 0 0 11.0 135 0 0 0 0 0.116

09306242 31.7 0 0 0 0 14.3 17.4 0 0 0 0 0.03

09306255 231 0.285 0 0 0 34.8 196 0 0 0 0 0.021

09306290 593 4.04 0.301 0.284 0 151 190 79.4 125 43.1 4.39 0.303

09306500 1,370 2.11 1.25 0 0 382 219 607 137 20.8 0 8.50

09310000 17.0 0 0 0 0 13.0 1.72 2.30 0 0 0 0.00

09310500 47.3 0 0 0 0 24.7 0 22.3 0.309 0 0 0.007

Appendix 4. Sources of dissolved solids in Upper Colorado River Basin streams by bounded calibration reach excluding point-source import source group as defined for 1991 Upper Colorado River Basin SPARROW model.—Continued[All measurements are in square miles]
Appendixes 1 to 5 53

Calibration 

reach 

labeled by 

downstream 

monitoring 

site number

Drainage 

area of 

calibration 

reach 

Irrigated 

sedimentaryclastic 

Tertiary 

lands 

Irrigated 

sedimentaryclastic 

Mesozoic 

lands 

Irrigated 

lands 

of other 

lithologies 

Crystalline 

and 

volcanic 

rocks 

Highyield 

sedimentary 

Cenozoic 

rocks 

Lowyield 

sedimentary 

Cenozoic 

rocks 

Highyield 

sedimentary 

Mesozoic 

rocks 

Lowyield 

sedimentary 

Mesozoic 

rocks 

Highyield 

sedimentary 

Paleozoic 

and 

Precambrian 

rocks 

Lowyield 

sedimentary 

Paleozoic 

and 

Precambrian 

rocks 

Land 

disturbance 

associated 

with oil 

and gas 

development 

09312600 93.7 0 0 0 0 84.2 8.24 1.28 0 0 0 0.004

09313000 302 0 0.678 0 0 175 0 123 4.33 0 0 0.111

09315000 6,800 61.3 62.9 0.03 0 2,790 1,850 474 1,530 69.6 76.6 15.0

09326500 141 0 0 0 0 90.2 0.684 34.4 2.84 0 13.1 0.00

09328500 1,520 20.5 26.4 0 0 199 121 360 773 8.73 59.2 0.631

09329050 24.7 0 0 0 11.4 0.249 9.93 0 0.006 0 3.10 0.00

09330000 739 12.5 10.7 2.56 444 1.44 206 4.92 66.8 0 15.9 0.017

09330230 447 2.90 1.56 0.643 33.7 0 72.9 86.1 225 9.79 19.5 0.019

09333500 2,950 12.0 2.54 0 30.3 73.9 229 394 2,190 0.095 30.5 0.554

09337000 67.8 0 0 0 37.4 0 19.3 0 10.5 0 0.610 0.011

09337500 258 1.35 0.480 0 15.8 18.4 96.5 8.25 118 0 0.622 0.085

09339900 65.8 0.135 0.291 0.064 54.0 0 3.31 2.08 5.07 0 1.37 0.00

09342500 215 1.78 4.68 0.416 139 0 30.7 38.2 7.89 0 0 0.009

09346000 176 1.24 2.21 0.042 66.3 0 46.7 38.0 25.3 0 0 0.104

09346400 797 2.98 10.8 0 80.5 0 102 276 338 0 0 0.296

09349800 654 1.23 9.27 2.25 132 0 59.4 70.3 348 36.7 7.06 0.04

09352900 80.3 0 0 0 51.8 0 0.036 0 0 5.40 23.1 0.00

09354500 439 18.0 24.1 5.06 105 4.82 72.9 20.5 173 48.4 14.0 2.09

09355000 58.6 1.60 14.8 0.159 0 0 21.3 0 36.7 0 0.609 0.567

09355500 748 12.3 0.664 0 0 9.66 719 0 18.9 0 0 7.47

09361500 701 0.003 0.473 8.20 271 1.43 5.05 25.0 42.9 311 44.9 0.00

09363500 401 14.6 25.8 7.62 34.3 43.7 67.0 63.3 134 45.5 13.3 2.88

09364500 269 10.1 0.017 0 0 161 105 0 2.30 0 0 7.57

09365000 2,590 41.8 0.039 0 0 880 1,700 0 8.48 0 0 53.5

09367500 586 6.89 15.5 19.1 8.05 89.9 41.9 285 104 9.29 47.8 4.63

09368000 5,070 19.2 42.9 0 4.32 583 262 2,510 1,720 1.63 0 12.8

Appendix 4. Sources of dissolved solids in Upper Colorado River Basin streams by bounded calibration reach excluding point-source import source group as defined for 1991 Upper Colorado River Basin SPARROW model.—Continued[All measurements are in square miles]
54 Land Disturbance Associated with Oil and Gas Development Calibration reach labeled by downstream monitoring site number Drainage area of calibration reach Irrigated sedimentary- clastic Tertiary lands Irrigated sedimentary- clastic Mesozoic lands Irrigated lands of other lithologies Crystalline and volcanic rocks High- yield sedimentary Cenozoic rocks Low- yield sedimentary Cenozoic rocks High- yield sedimentary Mesozoic rocks Low- yield sedimentary Mesozoic rocks High- yield sedimentary Paleozoic and Precambrian rocks Low- yield sedimentary Paleozoic and Precambrian rocks Land disturbance associated with oil and gas development 09371000 528 0 14.3 4.49 4.31 0.231 0 337 176 0.746 9.38 0.140 09371002 25.5 3.93 0.102 0 1.51 0 9.19 2.86 11.9 0 0 0.00 09371010 1,130 1.38 3.41 0 22.2 17.4 21.2 218 847 0 3.08 3.20 09371500 230 8.09 46.2 0 0.589 0.052 16.6 9.90 203 0 0 0.029 09372000 116 0 3.03 0 4.99 0 2.10 4.53 105 0 0 0.05 09378170 8.46 0 0 0 2.33 0 0.055 0 6.07 0 0 0.00 09378200 19.3 0 0 0 2.70 0 0.454 0 16.2 0 0 0.00 09378630 4.52 0 0 0 0.756 0 0 0 3.77 0 0 0.00 09379500 8,110 1.81 67.4 0 49.3 169 187 1,530 5,410 88.1 681 11.2 09380000 14,200 2.36 6.91 0.03 102 46.2 546 1,660 9,850 285 1,750 3.30 Appendix 4. Sources of dissolved solids in Upper Colorado River Basin streams by bounded calibration reach excluding point-source import source group as defined for 1991 Upper Colorado River Basin SPARROW model.—Continued [All measurements are in square miles]
Appendixes 1 to 5 55

Calibration 

reach 

labeled by 

downstream 

monitoring 

site number

Drainage 

area of 

calibration 

reach

Irrigated 

sedimentaryclastic 

Tertiary 

lands 

Irrigated 

sedimentaryclastic 

Mesozoic 

lands 

Irrigated 

lands of 

other 

lithologies 

Crystalline 

and 

volcanic 

rocks 

Highyield 

sedimentary 

Cenozoic 

rocks 

Lowyield 

sedimentary 

Cenozoic 

rocks 

Highyield 

sedimentary 

Mesozoic 

rocks 

Lowyield 

sedimentary 

Mesozoic 

rocks 

High-yield 

sedimentary 

Paleozoic 

and 

Precambrian 

rocks 

Low-yield 

sedimentary 

Paleozoic 

and 

Precambrian 

rocks 

 Disturbed 

lands

associated 

with oil 

and gas 

development 

09032000 20 0 0 0 19.8 0 0.222 0 0 0 0 0

09034250 770 14.9 2.64 5.5 486 147 85.8 25.9 9.68 0 16 0.005

09058000 1,590 26.6 22.6 11.2 756 201 184 193 178 50.8 23.2 0

09063000 76 0 0 0 28 0.055 0 0 0 45.4 2.5 0

09066510 102 0.082 0 1.37 40.6 0 6.29 0 0 53 2.02 0

09081000 856 0.796 9.29 13.7 394 3.06 19.6 0.113 106 308 24.3 0

09083800 349 0.185 3.24 2.85 67 0 60.2 36.9 87.4 94.5 3.13 0.054

09085000 236 3.02 3.69 16.7 84.3 0 38.4 4.19 35.3 62 11.8 0

09095500 3,980 60.7 29.2 41 575 430 1,140 147 483 1,120 83.2 11.9

09107000 129 0 0 0.239 118 0.045 0 0 0 6.81 3.6 0

09112200 242 0.122 3.35 7.99 60.3 0 9.49 21.2 80.2 66.3 4.25 0

09112500 47.9 2.02 1.22 2.39 7.74 0 7.84 0.68 28.3 0.76 2.62 0

09113980 162 9.72 8.73 3.17 46.6 0 63.6 28.7 19.6 0 3.7 0.004

09114500 433 6.22 0.856 3.77 310 2.77 9.82 0 28.6 69.1 11.9 0

09119000 1,060 21.3 4.89 18 803 0.044 73.3 0 141 38.5 5.28 0

09128000 1,900 9.52 4.53 9.82 1,590 23 180 2 98.3 0 8.81 0

09132500 525 11.1 0.344 1.44 104 3.27 299 98 16.1 0 5.28 0.209

09146020 82.4 0 0.02 0 69.6 0 0 0 3.79 6.27 2.76 0

09146200 66.9 0.274 3.27 4.25 18 0 12 0 26 3.8 7.05 0

09152500 3,280 54.8 139 88.8 293 17.7 439 271 2,100 7.91 156 0.299

09163500 1,950 34.7 67.5 58.7 209 130 440 481 613 0 80.4 4.02

09169500 2,020 2.88 9.91 0.567 34.5 0.783 46.5 211 1,630 87.2 11.1 0.36

09171100 122 4.34 0.086 0.427 0 0 37 23.9 44.1 8.06 8.81 0.01

09180000 2,430 2.8 50.2 1.7 169 0.709 72.4 290 1,800 25.1 71.3 0.564

09180500 1,530 2.44 2.74 0.998 36.4 235 94.9 407 758 0.029 0 5.12

09196500 75.9 0 0 0 74.2 0 0 0 0 0 1.65 0

09211200 4,130 372 0.99 13.4 535 267 2,300 15.3 452 164 396 18.8

Appendix 5. Sources of dissolved solids in Upper Colorado River Basin streams by bounded calibration reach excluding point-source import source group as defined for exploratory 2007 Upper Colorado River Basin SPARROW model.[All measurements are in square miles]
56 Land Disturbance Associated with Oil and Gas Development Appendix 5. Sources of dissolved solids in Upper Colorado River Basin streams by bounded calibration reach excluding point-source import source group as defined for exploratory 2007 Upper Colorado River Basin SPARROW model.—Continued [All measurements are in square miles] Calibration reach labeled by downstream monitoring site number Drainage area of calibration reach Irrigated sedimentary- clastic Tertiary lands Irrigated sedimentary- clastic Mesozoic lands Irrigated lands of other lithologies Crystalline and volcanic rocks High- yield sedimentary Cenozoic rocks Low- yield sedimentary Cenozoic rocks High- yield sedimentary Mesozoic rocks Low- yield sedimentary Mesozoic rocks High-yield sedimentary Paleozoic and Precambrian rocks Low-yield sedimentary Paleozoic and Precambrian rocks Disturbed lands associated with oil and gas development 09217000 5,540 34.2 0 0.288 83.6 2,420 2,020 703 269 0 44.5 16.5 09229500 528 33 2.08 3.73 0 15 280 2.1 40.3 18.9 171 0.241 09239500 567 10.7 15.7 7.37 240 1.18 187 9.13 120 0 9.87 0.026 09247600 1,560 27.5 19.1 2.02 292 78.4 401 458 323 0 10.2 1.05 09251000 1,250 6.49 19.6 0.031 24 31.6 322 469 401 5.67 0.991 1.14 09258980 1,010 2.13 0.285 0 0 272 429 246 59.8 0.771 0 8.04 09260050 3,550 48.1 5.92 0.844 222 441 2,500 166 140 31.2 50.8 4.9 09261000 7,300 153 10.5 1.28 13.6 1,240 3,840 199 670 460 883 12.2 09302000 3,800 139 47.1 41.2 0 193 2,060 98.1 396 125 928 7.49 09304200 647 0.658 0.458 4.98 158 1.58 97.3 0 71.6 308 10.6 0 09304800 377 8.76 11.7 0 0 31.5 85.1 104 135 21.2 0 0.263

09306200 506 4.8 0.093 0 0 36.1 440 21.1 7.46 0.984 0 1.48

09306222 146 1.37 0 0 0 11 135 0 0 0 0 0.302

09306255 262 0.285 0 0 0 49.1 213 0 0 0 0 0.443

09306290 593 4.04 0.301 0.284 0 151 190 79.4 125 43.1 4.39 1.05

09306500 1,370 2.11 1.25 0 0 382 219 607 137 20.8 0 12.9

09314500 1,730 14.9 25.9 0 0 414 121 286 911 0 0 5.15

09315000 5,720 46.4 37.8 0.03 0 2,670 1,810 345 636 111 135 37

09328500 1,660 20.5 26.4 0 0 290 122 394 776 8.73 72.3 1.64

09352900 80.3 0 0 0 51.8 0 0.036 0 0 5.4 23.1 0

09359020 164 0 0 0 146 0 0 0 3.56 10.5 3.99 0

09371492 33.2 4.65 1.81 0 0.589 0 9.67 2.59 20.4 0 0 0

09371520 205 3.44 44.9 0 0 0.052 6.93 7.32 191 0 0 0.032

09372000 108 0 2.57 0 4.99 0 2.1 4.53 96.9 0 0 0.055

09379500 22,400 139 237 47.4 832 1,960 3,460 5,410 9,420 531 819 124

09380000 18,800 31.1 22.7 3.23 683 140 1,190 2,150 12,500 295 1,820 2.38

Buto, Kenney, and Gerner—Land Disturbance Associated with Oil and Gas Development and Effects of Development-Related Land Disturbance on DissolvedSolids Loads in Streams in the Upper Colorado River Basin, 1991, 2007, and 2025—Scientific Investigations Report 2010–5064