U.S. Department of the Interior

U.S. Geological Survey

Proceedings of a USGS Workshop on Facing Tomorrow’s 

Challenges Along the U.S.-Mexico Border—Monitoring, 

Modeling, and Forecasting Change Within the ArizonaSonora Transboundary Watersheds

Circular 1322
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Proceedings of a USGS Workshop on Facing Tomorrow’s 

Challenges Along the U.S.-Mexico Border—Monitoring, 

Modeling, and Forecasting Change Within the ArizonaSonora Transboundary Watersheds

Edited by Laura M. Norman, Derrick D. Hirsch, and A. Wesley Ward

Circular 1322

U.S. Department of the Interior

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

Dirk Kempthorne, Secretary

U.S. Geological Survey

Mark D. Myers, Director

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

This report and any updates to it are available online at:

http://pubs.usgs.gov/circ/1322/

For product and ordering information:

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

Telephone: 1–888–ASK–USGS

For more information on the USGS—the Federal source for science about the Earth,

its natural and living resources, natural hazards, and the environment:

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

Telephone: 1–888–ASK–USGS

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

endorsement by the U.S. Government.

Suggested citation: Norman, L.M., Hirsch, D.D., Ward, A.W., eds., 2008, Proceedings of a 

USGS Workshop on Facing Tomorrow’s Challenges along the U.S.-Mexico Border—Monitoring, 

Modeling, and Forecasting Change Within the Arizona-Sonora Transboundary Watersheds

U.S. Geological Survey Circular 1322, 63 p.

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

copyright owners to reproduce any copyrighted material contained within this report.

Cataloging-in-Publication data are on file with the Library of Congress

Produced in the Western Region, Menlo Park, California

Manuscript approved for publication, January 23, 2008

Text edited by Tracey L. Suzuki

Layout and design by Stephen L. Scott

FRONT COVER

Images of the U.S.-Mexico border. Central photo: Stretch of the Rio Grande drying up in February 2003 in the Big 

Bend National Park, Texas (USGS photo by John Klein). Insert photos (clockwise from upper right): (1) Rangelands looking south into Mexico from the eastern edge of the San Rafael Valley, south of the Huachuca Mountains, 

Arizona (USGS photo by Bruce Gungle); (2) border fencing at California coast (photo by Chris Lukinbeal, Arizona State 

University); (3) vehicle barrier, Coronado National Memorial at the International Boundary with Mexico ((USGS photo 

by Bruce Gungle); (4) artwork on the border wall at Nogales, Sonora, Mexico (photo by Gigi Owen, University of Arizona); (5) view from Castlerock of street and houses in colonia of historic Bisbee, Arizona (USGS photo by Laura Norman). Banner photo: Panoramic view of the twin cities of Nogales, Arizona, and Nogales, Sonora, Mexico (photo by 

Chris Lukinbeal, Arizona State University).
Contents

Introduction

Introduction to the Workshop Proceedings......................................................................................1

 Laura M. Norman, Derrick D. Hirsch, and A. Wesley Ward

The U.S.-Mexico Field Coordinating Committee—Who We Are and What We Do ...................5

 Diana M. Papoulias

Interdisciplinary Science in Support of Environmental Health Along the 

 U.S.-Mexico Border—Using Map Tools to Understand Linkages 

 Between the Environment and Human Health ............................................................................7

 Jim Stefanov, Diana M. Papoulias, Jean Parcher, and Ric Page

Surficial and Bedrock Materials, Mineral Resources, and Natural Hazards

How an Integrated State-Federal Geoscience Information Network Can Be 

 Applied in the Borderlands.............................................................................................................9

 M. Lee Allison and Linda Gundersen

Mapping Surficial Geology in the Border Region of Big Bend National

 Park, Texas ......................................................................................................................................11

 Margaret E. Berry

Geologic Map Compilation of the U.S.-Mexico Border.................................................................13

 Floyd Gray, Jaime Castro Escarrega, and William R. Page

Floodplain Lakes and Their Relation to Alluviation Cycles in the 

 Lower Colorado River....................................................................................................................17

 Daniel V. Malmon, Tracey J. Felger, Keith A. Howard

Binational Geologic Mapping in the Lower Rio Grande of Southern Texas, 

 United States, and Northern Tamaulipas, Mexico....................................................................19

 William R. Page, Helen Folger, Bernard Hubbard, Jim Stefanov, and 

 Matthew D. Merrill

Populations, Urban Growth, Infrastructure Health, and Land-Use Change

 Lessons Learned from the Salton Sea—Potential Impact of Dust Emission 

 to Both Air Quality and Human Health........................................................................................21

 Pat Chavez, Jana Ruhlman, Miguel Velasco, Rian Bogle, John Vogel, and 

 JoAnn Isbrecht

Use of Remote Sensing to Detect and Map Temporal and Spatial Vegetation 

 Dynamics to Help Map Landscape Erosion Vulnerability—Mojave Desert and 

 Moloka’i, Hawai’i............................................................................................................................23

 Pat Chavez, JoAnn Isbrecht, Miguel Velasco, and Rian Bogle

CHIPS—A New Way to Monitor Colonias Along the U.S.-Mexico 

 Border...............................................................................................................................................25

 Delbert G. Humberson and Jean W. Parcher

An Approach to Prevent Nonpoint-Source Pollutants and Support Sustainable 

 Development in the Ambos Nogales Transboundary Watershed..........................................29

 Laura M. Norman, D. Phillip Guertin, and Mark Feller

The Potential of Binational Land-Cover-Change Detection Procedures for 

 Use along the U.S.-Mexico Border .............................................................................................31

 Zachary D. Wilson and Jean W. Parcher

Comparison of Contemporary Land-Cover Trends Among the Sonoran 

 Basin and Range, Madrean Archipelago, and Chihuahuan Deserts 

 Ecoregions.......................................................................................................................................35

 Jana Ruhlman, Leila Gass, and Barry Middleton

Role of Environmental Indicators in Determining Impacts, Ecosystem Preservation, 

and Climate Change

The San Pedro River—A Case Study for Examining Past Landscape Change and

 Forecasting Hydrological and Biological Response to Urban Growth and Land-

 Use Change .....................................................................................................................................37

 William G. Kepner, Kenneth G. Boykin, Darius J. Semmens, David C. Goodrich, 

 Christopher J. Watts, and D. Phillip Guertin

III
Contemporary Digital Land-Cover Mapping for the American Southwest—

 The Southwest Regional Gap Analysis Project.........................................................................39

 John Lowry, William G. Kepner, Kenneth G. Boykin, Kathryn A. Thomas, 

 Donald L. Schrupp, and Pat Comer

Stopover Ecology and Habitat Utilization of Migrating Land Birds in Colorado 

 River Riparian Forests of Mexico and the Southwestern United States ..............................41

 Charles van Riper III

Salton Sea Ecosystem—Issues and Status of Restoration Planning.........................................43

 Harvey L. Case, III and Douglas A. Barnum

Quality and Quantity of Water Resources

Geologic Framework, Hydrologic Monitoring, and Land-Use Change in the 

 Willcox and Douglas Basins, Southeast Arizona......................................................................45

 James Callegary, Kurt Schonauer, and Alice Konieczki

Automated Geospatial Watershed Assessment (AGWA)—A GIS-Based Hydrologic 

 Modeling Tool for Watershed Assessment and Analysis........................................................47

 D. Phillip Guertin, David C. Goodrich, William G. Kepner, Darius J. Semmens, 

 Mariano Hernandez, Shea Burns, Averill Cate, Lainie Levick and Scott N. Miller

Causes and Consequences of Monsoonal Flooding in Nogales, Sonora ..................................49

 Hans Huth and Dr. Craig Tinney

Sustainability of Water Resources in the Sierra Vista Subwatershed, Arizona—

 Implications of a Cross-Boundary Aquifer.................................................................................53

 James M. Leenhouts and Bruce Gungle

Front-Row View of Federal Water Lawmaking Shows Process Works—

 U.S.-Mexico Transboundary Aquifer Assessment Act Pondered, Passed, 

 and Signed.......................................................................................................................................55

 Sharon Megdal

Appendixes

1. List of Participants...........................................................................................................................57

2. Workshop Agenda...........................................................................................................................59

IV
1

Borderland Setting

The international border between the United States and 

Mexico runs from the California/Baja California Norte to Texas/

Tamaulipas (fig. 1). The length of the border from west to east is 

almost 2,000 miles. The areas north and south of the border are 

usually referred to as the “Borderlands”; however, there is no 

consensus as to the exact area encompassed by the Borderlands. 

The U.S. Environmental Protection Agency (2006) defines the 

Borderlands as a zone 100-kilometers wide (approximately 

62-miles), the U.S. Department of Housing and Urban Development (2007) defines the Borderlands as a zone 150-miles wide, 

and Woodward and Durall (1996) describe the Borderlands in 

terms of watershed boundaries.

The border in the Eastern part, from El Paso, Tex., to the 

Gulf of Mexico, follows the Rio Grande. The border in the 

Western part, from the Pacific coast to El Paso, is composed of 

straight, surveyed line segments that randomly cross watershed 

boundaries. In the Western region of the Borderlands, water 

flows north and (or) south across the international border with 

Mexico into the interior of each country. Therefore, mutual 

dependencies exist in terms of potential vulnerability, and 

impacts on natural resources exist on both sides of the border.

Natural Setting

The Borderlands terrain comprises steeply rising mountain 

ranges separated by broad, wide valleys and desert basins, such 

as the northern Chihuahuan Desert, the Sonoran Desert, and 

parts of the Mojave Desert. Deeply cut arroyos (dry rivers), 

canyons, mesas, and broad alluvial fans are prominent features. 

Copper, silver, gold, and other metals occur in the region.

The border climate varies from Mediterranean in the 

coastal areas to hot and arid or semiarid in the inland areas. In 

the Sonoran Desert of Arizona, climate is characterized by hot 

summers and cool, mild winters. Droughts are common. 

Hydrologically, surface-water features in the Borderlands 

include springs, ephemeral and intermittent streams, and water 

pockets. Transborder rivers commonly flow through deep, 

steep-walled canyons, forming riparian environments that provide a stark comparison to the adjacent desert landscape. Natural hazards, such as flooding, are prominent in the Borderlands. 

Short, intense, convective thunderstorms are common during 

the summer monsoon season. 

The varieties of precipitation, landscape, and soil types in 

the Borderlands have led to the development of habitats that 

support thousands of species of plants and animals with high 

biodiversity. Vegetation is taller and lusher in riparian areas than 

in the dryer uplands, and these riparian areas provide important nesting and feeding habitat, as well as corridors for animal 

movement. 

Workshop

Competition for water resources, habitats, and urban areas 

in the Borderlands has become an international concern. In the 

United States, Department of Interior Bureaus, Native American 

Tribes, and other State and Federal partners rely on the U.S. 

Geological Survey (USGS) to provide unbiased science and 

leadership in the Borderlands region. Consequently, the USGS 

hosted a workshop, “Facing Tomorrow’s Challenges along the 

U.S.-Mexico Border,” on March 20-22, 2007, in Tucson, Ariz., 

focused specifically on monitoring, modeling, and forecasting 

change within the Arizona-Sonora Transboundary Watersheds. 

Goals of Workshop

The two-day scientific workshop drew State, university, and 

Federal scientists together to discuss current and potential interdisciplinary research that would address the complex human 

and environmental issues that manifest themselves in the Borderlands. The goal of the workshop was to provide a venue to 

pursue research initiatives and to document science issues and 

priorities. The workshop was intended to compliment and build 

on an internal USGS border-strategy meeting held in El Paso, 

Tex., in spring 2006, at which a small group of scientists from 

the USGS met to synthesize a collective-science strategy for the 

USGS to guide U.S.-Mexico border research. 

1

U.S. Geological Survey, 520 N. Park Ave., Suite 355, Tucson, AZ 85719.

2

U.S. Geological Survey, 2255 N. Gemini Drive, Flagstaff, AZ 86001.

3

U.S. Geological Survey, 520 N. Park Ave., Suite 106A, Tucson, AZ 85719.

Introduction to the Workshop Proceedings

By Laura M. Norman1 , Derrick D. Hirsch2 , and A. Wesley Ward3
2 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

!"#$%&'()'"#$%&'#()*%+)#,)&-.)/01023.4'$#)5#67.60

Figure 1. Location map of the U.S.-Mexico Border.

Workshop Themes

The 2007 workshop program was formatted based on 

USGS research conducted in four topical areas, categorized and 

presented under the following themes:

• Surficial and Bedrock Materials, MineralResources, 

and Natural Hazards,

• Populations, Urban Growth, Infrastructure Health, 

and Land-Use Change,

• Role of Environmental Indicators in Determining 

Impacts, Ecosystem Preservation, and Climate Change, 

 and

• Quality and Quantity of Water Resources.

Part of the workshop was designed to identify new multi

disciplinary scientific-research needs and to develop 

USGS research priorities in keeping with the Bureau 

Science Strategy themes of Water Availability, Climate 

Change, Human Health, Natural Hazards, Energy and 

Minerals, and Ecosystems. A field trip to Nogales, Ariz., 

on the day after the workshop introduced participants to 

some of the environmental issues faced by residents 

along the border (fig. 2). 

Workshop Findings

Environmental and health problems along the U.S.-Mexico 

border are plentiful, yet identifiable and manageable. Issues 

of unmanaged urban growth, exponentially growing populations, and rapidly diminishing resources were at the forefront of 

the workshop. Some of the specific human and environmental 

issues along the U.S.-Mexico border that were identified as 

research priorities include:

1. Air Pollution—Among the problems requiring attention is levels of particulate matter that exceed U.S. Federal airquality standards. Sources of particulate matter include unpaved 

roads and parking lots, vehicle emissions, burning garbage 

and wood, and deforested hillsides, all of which contribute to 

poor air quality and related health effects. Airborne-sediment 

transport is affected by vehicular traffic, foot traffic, and wind 

transport; it is in these areas that the highest concentrations of 

atmospheric particulate matter (dust) are observed (see abstracts 

by Berry; Chavez and others; Gray and others; Norman and 

others).

2. Colonias—Urbanization has consequences on infrastructure, erosion, flooding, the airshed, the watershed, and human 

health. Unplanned colonias and squatter settlements have poor 

housing conditions and nonexistent or below-adequate levels of 

services, water supply, sanitation, electricity, roads, and drainage (Norman and others, 2004). Mapping conditions along the 

border can help local residents to attract earmarked funding to 

these areas (see abstract by Humberson and Parcher).

3. Endangered Species Habitat—Many species (some 

endangered) cross the international border frequently as 

they range within their borderland habitats, for example, the 

cactus pygmy owl and Sonoran pronghorn in Arizona; flat-
3

tailed horned lizard and Peninsular Ranges bighorn sheep in 

California; jaguar and Mexican gray wolves in New Mexico; 

and ocelot in Texas. Artificial barriers can harm wildlife by 

blocking critical migration corridors and destroying valuable 

habitat. Mapping of land use, vegetation, riparian areas, and 

habitats for monitoring purposes is invaluable to the U.S.-

Mexico border (see abstracts by Case and Barnum; Chavez 

and others; Kepner and others; Lowry and others; Malmon 

and others; Page and others; Ruhlman and others; Wilson and 

Parcher; van Riper).

4. Erosion—Arid lands are known for supporting specially 

adapted vegetation and animal populations. When disturbed, 

the land and life that it supports takes a long time to return to a 

fully-natural state. Disturbed land is vulnerable to erosion and 

landslides. Urbanization, especially, has led to devegetation and 

erosion of the land. Bare hillslopes have higher rates of surface 

runoff and lower rates of water infiltration into the soil than 

hillslopes covered with natural grasses (see abstracts by Berry; 

Gray and others; Huth and Tinney; Norman and others).

5. Flooding and Natural Disasters—Seasonal monsoon 

flooding affects low-lying areas throughout the Borderlands. For 

example, in Ambos Nogales, where many major streets follow 

the course of natural waterways, landslides caused by rushing 

waters damage homes and streets. In some cases, these catastrophic floods have destroyed people’s livelihoods and homes 

and have taken lives (see abstracts by Berry; Gray and others; 

Huth and Tinney; Malmon and others; Norman and others).

6. High Population Growth—Southern Arizona and northern Mexico have high human-population growth rates. There 

is a need to better understand the short-term and long-term 

impacts this rapid population growth has on changes in water 

demand and on patterns of water use in the basins. An ecological strain is created largely by the rapidity of economic and 

population growth coupled with gaps in the supply and (or) the 

ability of available economic, technical, and human resources 

to monitor and protect the environment. Accurate monitoring 

of resources available to incoming populations in the sensitive 

Borderlands area is in high demand (see abstracts by Allison 

and Gunderson; Humberson and Parcher; Kepner and others; 

Norman and others; Stefanov and others).

7. Human Health—Human health problems in the Borderlands relate in part to air pollution, inadequate water and sewage 

treatment, or improper management of pesticides, and hazardous wastes. Elderly and children are especially at risk. Waterborne and respiratory diseases are a particular concern to local 

residents (see abstracts by Chavez and others; Page and others; 

Stefanov and others).

8. Water Quality—Water-quality data for the Borderlands 

area are limited, especially where rivers cross the international 

boundary and along stretches of rivers downstream of the effluent discharge from wastewater-treatment plants. In both in 

the U.S. and Mexico, potential chemical contaminants from 

industrial sources and biological contaminants from sewage and 

wastewater discharges are inadequately monitored. The poor 

quality of available water supplies increases vulnerability to 

drought, especially for domestic users (see abstracts by Berry 

and others; Callegary and others; Gray and others; Guertin and 

others; Huth and Tinney; Kepner and others; Megdal; Norman 

and others; Page and others).

9. Water Quantity—A better understanding of the water 

budget is needed for borderland watersheds, including quantification of water derived from potential snowpack, surface and 

ground-water flows, evapotranspiration rates, and water lost to 

pumping. In addition, if mines are reopened due to world market 

Figure 2. Photograph taken from Nogales, Ariz., showing the International border fencing 

(diagonal from northwest to southeast) and adjacent housing, built on a hillslope, in Nogales, 

Sonora, Mexico (photo by Leslie Gordon).

!"#$%&'()'"#$%$&'()#*%(+,-*.'$/*0$&(1,23*4'5673*2#$85-&*%#,*9-%,'-(%5$-(1*:$';,'

.,-<5-&*=;5(&$-(1*.'$/*-$'%#,(2%*%$*2$>%#8,2%?*(-;*(;@(<,-%*#$>25-&3*:>51%*$-*(*#51121$),3

5-*0$&(1,23*A$-$'(3*B,C5<$*=)#$%$*:D*E,215,*F$';$-?7

*+%,-.+/'!"01"0#-

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Introduction
4 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

demands, there could be an additional strain on water supplies 

that currently are allocated for other uses or are critical to habitat 

(see abstracts by Callegary and others; Gray and others; Guertin 

and others; Leenhouts and Gungle; Malmon and others; Megdal).

As a result of the workshop, several new research projects 

are being developed to address priority issues in the transborder 

watersheds of the lower Colorado River, the Upper Santa Cruz 

River, the San Pedro River and Douglas Basin, the lower Rio 

Grande, the area surrounding El Paso/Juarez, and in Big Bend 

National Park. The research projects build on the wide array 

of ongoing USGS activities described in the abstracts in this 

report. The abstracts are not inclusive of every USGS borderland study, but they are representative of the projects the USGS 

is conducting in the region.

Acknowledgments

This workshop and publication would not have been possible 

without the support of Anne E. Kinsinger, USGS Western Regional 

Director. Extra effort and initiative contributed by the workshop’s 

steering committee, which included not only the editors of this publication, but also dedicated representatives from each of the disciplines 

at the USGS, including Edwin Pfeifer, Floyd Gray, Charles van 

Riper, Nick Melcher, and Bruce Gungle, made this workshop a success. Additionally, Jean Parcher’s contributions to the organization of 

the workshop were instrumental in the flow of our sessions.

References Cited

Norman, L.M., Parcher, J.W., and Lam, A.H., 2004, 

Monitoring colonias along the U.S.-Mexico border: U.S. 

Geological Survey Fact Sheet, FS 2004-3070, [http://erg.

usgs.gov/isb/pubs/factsheets/fs307004.html, last accessed 

October 17, 2007].

U.S. Department of Housing and Urban Development, 

2007, Community development block grant—Colonias, 

[http://www.hud.gov/offices/cpd/communitydevelopment/

programs/colonias/cdbgcolonias.cfm, last accessed 

October 17, 2007].

U.S. Environmental Protection Agency, 2006, U.S.-

Mexico border 2012 framework, [http://www.epa.gov/

usmexicoborder/intro.htm, last accessed October 17, 

2007].

Woodward , D.G., and Durall, R.A., 1996, United StatesMexico border area, as delineated by a shared-water 

resources perspective: Department of the Interior Fact 

Sheet 1, 4 p.
5

The U.S.-Mexico Field Coordinating Committee (FCC) 

was chartered in 1994. It consists of seven bureaus within the 

Department of the Interior (DOI)—the Bureau of Indian Affairs, 

the Bureau of Land Management, Bureau of Reclamation, 

Minerals Management Service, National Park Service, U.S. 

Fish and Wildlife Service, and the U.S. Geological Survey. Each 

bureau has a representative who serves on the FCC leadership 

team along with the FCC Chair and Vice-Chair. The regional 

environmental officers of the Office of the Secretary of the Interior and an international-affairs representative from the Secretary’s Office in Washington, D.C., are ex officio members. FCC 

membership is comprised of DOI employees with an interest in, 

or responsibility for, resource management or resource activities 

along the U.S.-Mexico border. Participation by bureau personnel is in addition to the other duties of their positions. Expenses 

are borne by the participating bureaus. 

The FCC accomplishes its work on the U.S.-Mexico border 

through biannual meetings, information sharing, and work 

groups established to address specific subjects. The FCC also 

facilitates contacts among those who have an interest in naturaland cultural-resource issues along the border. Important border 

relationships include those with Federal, Tribal, State, and local 

governments on both sides of the border concerning programs, 

projects, and activities affecting the border area. By assisting the member bureaus in building partnerships and enlisting 

volunteers, the FCC advances its objectives of improved communication, coordinated activity, and implementation of the best 

conservation practices in the border area. 

The U.S.-Mexico Field Coordinating Committee—Who We Are 

and What We Do

By Diana M. Papoulias1

1

U.S. Geological Survey, 4200 New Haven Road, Columbia, MO 65201.
6 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

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7

The diverse, fragile ecosystems of the borderlands have 

been pushed beyond sustainable levels due to rapid population 

growth and land-use changes. Water shortages and pollution, 

poor air quality, increased soil salinities, residual pesticides, 

and heavy-metal contaminants are some of the many stressors 

that are degrading the quality of life in the borderlands. The 

relationship between human health and environmental quality 

challenges public officials, medical professionals, and resource 

managers on both sides of the border in their efforts to provide 

for and maintain healthy communities.

To better understand the relationship between environmental and human health, the USGS’s “Border Environmental 

Health Initiative” (BEHI; fig. 1) created an Internet Map Service (IMS) with binational-georeferenced data. BEHI’s goal is 

to have seamless integration of borderwide datasets, at regional 

and local scales, that can lend an understanding of the linkages 

between the condition of the physical environment and publichealth issues.

The Border Environmental Health Initiative Internet Map 

Service is available at http://borderheath.cr.usgs.gov/.

Collaborative Partnerships

An interdisciplinary USGS team identifies biologic, geologic, hydrologic, environmental, public-health, and demographic datasets for incorporation into the binational IMS. This 

team works in collaboration with other Federal, State, and local 

agencies, including nongovernmental and universities in both 

the United States and Mexico. Project success and the reliability 

of these binational scientific databases are dependent on these 

mutually beneficial partnerships.

Examples of cooperative partnerships that utilize the scientific data and research include the following. 

Environmental Protection Agency/Secretaría de Medio 

Ambiente y Recursos Naturales Border 2012—The Border 

2012 Environmental Health Indicators Working Group focuses 

on developing metrics to measure changes in human health as a 

result of improvements to sanitation, and air and water-quality 

in the border region. The USGS is cooperating with this group 

to develop a binational water quality geodatabase for the region 

and to use geospatial data for reporting environmental activities. 

Natural Heritage Institute, University of Texas, and 

Instituto Mexicano de Technogía del Agua—Through the Rio 

Grande Physical Assessment Project, the USGS is collaborating with U.S. and Mexican partners to build a water-resources 

database as the foundation of an advanced hydrologic-planning 

model of the entire Rio Grande Basin. The USGS is verifying 

binational land use and surface- and ground-water data, and is 

validating model results. 

Southwest Consortium of Environmental Resources 

Program (SCERP)— The USGS is partnering with SCERP to 

further our respective missions and to enhance interaction and 

cooperation with border research and policy programs. A first 

joint activity was to co-host a binational GIS summit. 

Housing and Urban Development Colonia Database—

The goal of this project is to provide the baseline data necessary to identify the need for Federal aid to improve the living 

conditions for residents of the many unincorporated settlements, 

known as colonias, found along the U.S.-Mexico border. In 

conjunction with partners, the USGS is providing geographic 

and demographic data to facilitate prioritization of community 

development and infrastructure investment.

Data Assimilation and Integration

USGS scientists strive to preserve the accuracy and associated attributes of the data during production of the IMS. Rigorous efforts have been made to seamlessly integrate U.S. and 

Mexican geospatial datasets along common themes to analyze 

environmental issues relative to human health.

The procedures are documented in Federal Geographic 

Data Committee-compliant metadata files and in procedural 

papers that define the differences in scale, scope, definition of 

terms, and methods of data collection between the two countries.

Interdisciplinary Science in Support of Environmental Health 

along the U.S.-Mexico Border—Using Map Tools to Understand 

Linkages Between the Environment and Human Health

By Jim Stefanov1, Diana Papoulias2, Jean Parcher3, and Ric Page4

1

U.S. Geological Survey, 8027 Exchange Dr., Austin, TX 78754.

2

U.S. Geological Survey, 4200 New Haven Rd., Columbia, MO 65201.

3

U.S. Geological Survey, 8027 Exchange Dr., Austin, TX 78754.

4

U.S. Geological Survey, Box 25046, Denver Federal Center, MS 980, 

Denver, CO 80225.
8 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

Accomplishments to Date

Methods for building binational geospatial data and constructing integrated databases were developed during the BEHI 

pilot phase for the Lower Rio Grande Valley (Subregion 8), 

which extends from Falcon Reservoir to the lower part of the 

Laguna Madre, Tex. The IMS for this data-rich area includes 

remotely sensed imagery and anthropogenic and environmental 

datasets at a large scale (1:24,000). A similar suite of datasets at 

equivalent scales is being integrated for all subregions beginning with Subregion 7, which extends along the Rio Grande 

from Amistad Reservoir to Falcon Reservoir. Applying similar methodology border-wide, regional datasets at medium- 

(1:250,000-scale) and low-resolution (1:2M scale) have been 

integrated to form the basic geospatial framework and to be 

displayed in the IMS. These border-wide datasets provide the 

platform upon which the comprehensive and subregion-specific 

datasets will subsequently be overlaid and will also assure compatibility at temporal and spatial scales.

Web-Site Features

Maps and Data— The IMS provides users with binational 

datasets and the tools to manipulate them over the Internet by 

using a browser. The interface allows users to zoom in to areas 

of interest and select a combination of layers appropriate to 

their focus. Users can select an initial view of the entire border 

region or a particular subregion, and use the tools available to 

customize the view.

Data Layers— Data layers are grouped under the major 

themes of anthropology, hydrology, transportation, biology, geology, imagery, elevation, land use, and infectious disease. The 

numerous data layers within these themes are detailed with a 

description, metadata, and minimum- and maximum-view table 

extents. By means of the Web mapping-service protocols, users 

may incorporate available layers into their own geospatial analyses.

Static Map Library— This feature provides users with 

ready-made maps of common views and themes. These maps 

can be easily integrated into custom presentations.

Data Tables— Additional information about the specific 

data used in the layers is provided in tabular form.

Collaborative Opportunities

An anticipated outcome of this project is an increased 

opportunity to collaborate with scientific researchers in the 

public health, natural resources, and environmental protection fields to apply the BEHI datasets and the IMS to address 

specific public- and environmental-health issues. The vision of 

the USGS is that such collaborations could ultimately expand 

the breadth and depth of the datasets available and allow more 

sophisticated analysis of border health issues, ultimately leading 

to a healthier border environment.

Figure 1. The USGS Border Environmental Health Initiative (BEHI) encompasses the entire U.S.–Mexico border, an area defined 

as 161,000 square miles; it is partitioned into eight subregions based on watersheds as delineated by Woodward and Duvall (1996).
9

National Geoscience Information Network 

In early 2007, the United States geological surveys agreed 

to the development of a National Geoscience Information Network that is distributed, interoperable, uses open-source standards and common protocols, respects and acknowledges data 

ownership, fosters communities of practice to grow, and develops new web services and clients. A common approach enhances 

the nations geoscience community’s ability to coordinate with 

other countries. Such an approach could greatly facilitate analysis, monitoring, and modeling among disparate agencies and 

disciplines along the U.S.-Mexico Borderlands region.

Geological surveys have unique resources and missionspecific requirements that include the gathering, archiving, and 

dissemination of data. Together these data represent one of the 

largest, most extensive long-term information resources on the 

geology of the U.S. Currently, however, these data are available in disparate systems, which require time and resources to 

explore, extract, and reformat. By using modern information 

technology and a virtual “service-oriented architecture” that provides common discovery tools and standards, the surveys and the 

general science community will benefit in multiple ways. First, 

online data and other informational products from each survey 

will be more readily available to the world audience and will be 

more valuable because they will be interoperable. Second, data 

and applications from external sources, such as the USGS’ more 

than 1,000 databases, catalogues, and inventories will be readily 

accessed and integratable with each participating survey’s own 

data system. Third, a large, federated data network will create 

inestimable opportunities for the broader community, including 

academia and the private sector, to build applications utilizing 

this huge data resource, and to integrate it with other data. The 

breadth and depth of survey-based data are so large that they 

constitute one of the largest, if not the largest, data resources in 

the geosciences, in essence, a national data “backbone.” 

By demonstrating national cooperation for data access and 

interoperability among the Federal and State geological surveys, 

the network also could serve as a model for broader cooperation 

in geoinformatics across the entire Earth-science community and 

other scientific disciplines, especially those with a geospatial 

aspect. We intend to coordinate the development of this network 

with other efforts, including the National Science Foundation’s 

“Cyberinfrastructure Vision for 21st Century Discovery” and the 

emerging international efforts in informatics. This “community 

of practice” approach means that we will learn, develop, evolve, 

and coordinate the building of the network with each other and 

our partners. When completed, we envision a scenario where 

any user may go to a geological survey, or other participating 

Web site, enter a distributed science-data catalog, (for example, 

through a simple piece of software served on each geological 

survey’s Web site) and view available data for a specific state 

and adjacent states if desired. Because all these data will use 

a common mark-up language, the user can immediately select 

and download the needed data and load them into any number 

of applications, including in-house, freeware, and proprietary 

commercial products. The original data source would be credited 

with the download. 

Vision for a National Geoscience Information Network—

To achieve this vision of a coordinated network, the surveys 

have agreed to the following principles and activities to be 

undertaken in the next few years. 

• Develop a coordinated, national geoscience framework 

to access and integrate state-survey and USGS-information 

 resources (data bases, maps, publications, methods, 

applications, and data services).

• Function as a “community of practice” in development of 

geoinformatics and the geoscience network. 

• Develop prototypes (pilots, test beds) to show proof of 

 concept, to determine realistic levels of effort, and to 

compare costs and benefits while providing immediate 

benefits in the form of user services. 

• Build the network through an iterative and evolutionary 

process. 

• The basic architecture of the network should be distributed 

and leverage existing systems, map services, and data with 

local autonomy, by using standards to enable interoperabiity. 

• Review, test, and adopt standards and protocols for 

developing the system (including metadata). 

How an Integrated State-Federal Geoscience Information 

Network Can Be Applied in the Borderlands

By M. Lee Allison1 and Linda Gundersen2

1

Arizona Geological Survey, 416 W. Congress St., Ste. 100, Tucson, AZ 

85701. 2

U.S. Geological Survey, 12201 Sunrise Valley Dr., MS 911, Reston, VA 

20192. 
10 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

• New and existing systems should communicate with an 

open source (for example, Open Geospatial Consortiumbased) protocol to promote interoperability. 

• Test and consider accepting GeoSciML (geoscience 

mark-up language) as a protocol and consider proposing it 

as a standard to the Federal Geographic Data Committee 

(FGDC). 

• Recognize that there are priority data for which we have 

mission requirements and inherent partnerships amongst 

the geological surveys. 

• Encourage Web clients and services to be developed, 

 and facilitate participation and implementation by others in 

a manner that meets their own business model and needs. 

• Reduce philosophical and cultural barriers that impede 

system development. 

• Adhere to a code of conduct that respects and acknowl

edges data ownership and the work of others. Respect 

intellectual property and data provenance, use “branding” 

in data services to acknowledge data sources. Develop 

usage measurements and utilize them with Web clients and 

services.

• Develop a database-citation format.

• Acknowledge that geological surveys need to recognize 

interoperable, Web-enabled information resources as part 

their mission. The surveys also must seek partnerships to 

leverage resources, develop, and implement the vision.
11

Big Bend National Park lies within the U.S.-Mexico border 

region of western Texas. Surficial deposits within the park are 

being mapped as part of a collaborative effort among the USGS, 

the National Park Service, and academia to produce a new 

1:100,000-scale geologic map of the park to use as a framework 

for land and resource management. Surficial deposits cover 

a large part of the park, but were not mapped in detail on the 

existing map (Maxwell and others, 1967, Univ. Texas Pub. 

6711; 1:62,500 scale). Our mapping subdivides these deposits 

by genesis and relative age into active (latest Holocene) tributary wash and river deposits (Qaw); young (Holocene to latest 

Pleistocene) river deposits (Qyw); young alluvial (fan, pediment, and stream) deposits, undifferentiated (Qya); intermediate 

(late to middle Pleistocene) river deposits (Qiw); intermediate 

alluvial (fan, pediment, and stream) deposits, undifferentiated 

(Qia); old (middle to early Pleistocene) river deposits (Qow); 

old alluvial (fan, pediment, and stream) deposits, undifferentiated (Qoa); very old (early Pleistocene and Pliocene) alluvium 

(QTa); slope deposits consisting of colluvium aprons and 

colluvial-fan deposits (Qc); rock-fall deposits (Qrf); landslide 

deposits (Qls); eolian sand (Qe); and mixed eolian and alluvial 

deposits (Qea). Units Qyw, Qya, Qiw, and Qia are further subdivided by age where criteria for division are evident and units 

are large enough to map separately at a 1:100,000 map scale. 

River (axial) deposits are differentiated from other types of alluvial deposits mainly along the Rio Grande, where morphological distinctions are pronounced. Terraces along this portion of 

the Rio Grande typically are underlain by coarse-gravel deposits 

comprised of subrounded to well-rounded clasts. Soil carbonate accumulation on the terraces tends to be greater than that in 

corresponding fan and pediment alluvium due to subtle textural 

differences that may influence the way water moves through the 

soils.

To expedite mapping over the park’s large area (3,242 

km2

), surficial geologic units are interpreted from aerial 

photography, satellite imagery, and topographic data, and are 

digitally mapped on color-infrared orthophoto images with 

1-meter ground resolution. Surface morphology, tone, relative height above modern stream channel, and map pattern are 

used to interpret surficial geology from the imagery. Maps are 

printed on a topographic base and field checked, at which time 

soil, weathering, and pavement characteristics are used to refine 

interpretation of mapping units. 

General characteristics of young alluvial deposits (Qy, 

Holocene to latest Pleistocene) include some preservation of 

original morphology (channel, and bar-and-swale or meanderscroll topography), and low relative height above stream channels. Pavement, varnish, and soil carbonate ranges from weak 

or no development, to densely packed and uniform pavement 

with well-varnished clasts and stage I soil-carbonate morphology. Intermediate-age alluvial deposits (Qi, late to middle 

Pleistocene) typically have surfaces that are relatively planar, 

partly incised, and slightly rounded at the edges at intermediate relative height. Pavement ranges from weakly developed 

to densely packed and uniform with well-varnished clasts. 

Soils typically have stage I-II carbonate morphology in the 

younger-intermediate age deposits and stage III-IV carbonate 

morphology in the older-intermediate age deposits. Old alluvial 

deposits (Qo, middle to early Pleistocene) typically have surfaces that are dissected into ridge and ravine topography (thick 

gravel deposits) or form generally planar remnants (thin gravel 

deposits) high above adjacent valley floors. Pavement ranges 

from weakly developed to moderately packed and uniform 

with moderately-varnished clasts; soils typically have weak 

to moderately cemented stage IV carbonate morphology. Very 

old alluvium (QTa, early Pleistocene and Pliocene), typically 

with the highest relative height, is deeply eroded and dissected. 

Where preserved, soils have stage III to IV carbonate horizons 

as much as 2-m thick. 

The wide variety of surficial deposits in Big Bend National 

Park reflect the long and complex Quaternary geologic and 

climatic history of this border region and provide an important 

part of the geologic framework for land and resource management.

Mapping Surficial Geology in the Border Region of Big Bend 

National Park, Texas

By Margaret E. Berry1

1

U.S. Geological Survey, Box 25046, DFC, MS 980, Denver, CO 80225.
12 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

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13

Introduction

The North American Free Trade Agreement (NAFTA), the 

Border Environmental Cooperation Commission (BECC) and 

the U.S.-Mexico Environmental Protection Agency (USEPA) 

U.S.-México Border XXI through Border XXXII (2012) 

Program have all focused attention on the environmental, 

social-cultural, and economic conditions in the U.S.-Mexico 

frontier and have demonstrated the need for a binational, 

transborder approach to addressing problems. Currently, state 

and national government entities, nongovernment organizations, 

and universities are conducting numerous data-collection and 

research activities in the border region. Much of the work being 

done recognizes that the region’s physiography, ecological 

zones, and human phenomena extend uninterrupted across the 

international boundary and cannot be understood if restricted 

to one side of the border. Researchers and land managers 

from both countries need current, accurate, and binationally 

compatible geospatial information to manage such issues as 

water availability and pollution, land-cover change, naturalresource sustainability, and human health (Dohrenwend and 

others, 2001). Toward these ends, a cross-border, geologic-map 

compilation was cooperatively undertaken by the Servicio 

Geologico Mexicana and the U.S. Geological Survey (USGS). 

The compiled map is designed to be utilized as a fundamental 

part of a geographic information system database to further the 

understanding of natural-resource availability and the processes 

involved in urban development, commerce, ecosystem 

sustainability, protected species, and agriculture (fig. 1). The 

compilation involved the merger of eighteen 1- by 2-degree 

quadrangles along the 1,800-kilometer (1,100 miles) extent of 

the border (fig. 1)

Methodology 

In 2004, the USGS and the Servicio Geologico Mexicana signed 

a Mapping Initiative Memorandum of Understanding (MOU) to 

jointly produce matching geologic maps across the U.S.-Mexico 

border. Highlights of the compilation process that developed as 

a result of the agencies’ efforts include: 

• Transboundary 1:250,000-scale quadrangle maps were 

agreed upon as base.

• Compiled maps from several scales—1:250,000 or larger 

(1:500,000-scale maps used for Texas because of the level 

of detail in the maps).

• Databases were created with updated paleontological-and 

isotopic-age compilations. 

• Quaternary portion of the geologic database was enhanced 

where possible with use of Landsat and Digital Elevation 

Model data in the GIS platform.

• Adjusted line work and age designations within several 

kilometers of the frontier only—a “border zone”.

• Created a parallel but integrated nomenclature in 

designated zone during the process of merging the 

stratigraphic column.

Geologic Setting

In general, the U.S.-Mexico border region can be divided 

into six geologic provinces from east to west (1) the gulf of 

Mexico Coastal Plain, (2) Paleozoic and Mesozoic platform 

rocks, (3) an area of terrestrial volcanism and accompanying 

plutonism, (4) an area of structural extension, (5) a transitional 

area between platform rocks and the area of extension, and (6) 

an accreted terrane (Orris and others, 1993).

Utilization of Maps

Utility of a cohesive transboundary geologic map is 

demonstrated in studies such as the geologic framework and 

three-dimensional characterization of the Mexican headwaters of 

the upper San Pedro River project (fig. 1). In this investigation, 

data on geology and geophysics in the San Pedro River Basin 

in northern Sonora, Mexico, and southeastern Arizona were 

combined to develop a three-dimensional conceptual model of 

the basin-fill aquifer that is being used to construct a regional 

ground-water-flow model. This work will better constrain a 

number of significant geohydrologic parameters critical to the 

modeling calculations and forward simulations of flow regimes 

in the river system. Likewise, in addition to hydrologic systems, 

Geologic-Map Compilation of the U.S.-Mexico Border

By Floyd Gray1, Jaime Castro Escarrega2, and William R. Page3

1

U.S. Geological Survey, 520 North Park Ave., Tucson, AZ 85719.

2

Servicio Geológico Mexicano, López del Castillo No. 14, 83180 Hermosillo, 

Son., Mexico. 3

U.S. Geological Survey, Box 25046, Denver Federal Center, MS 980, 

Denver, CO 80225.
14 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

mineral tracts, and ecological zones are contiguous across 

the border region and are more easily understood by using a 

seamless geologic-map product.

References Cited

Dohrenwend, J.C., Gray, Floyd, and Miller, R.J., 2001, 

Processed Thematic Mapper satellite imagery for selected 

areas within the U.S.-Mexico borderlands: U.S. Geological 

Survey Open-File Report 00-309 (3-CD-ROM set).

Orris, G.J., Page, N.J. Staude, John-Mark G., Bolm, K.S., 

Carbonaro, M., Gray, Floyd, and Long, K.R., 1993, Nonfuel 

mineral resources in the United States-Mexico border 

region—A progress report on information available from the 

Center for Inter-American Mineral Resource Investigations 

(CIMI): U.S. Geological Survey Circular 1098, 19 p.

Figure 1. Index map highlighting transboundary quadrangles used in the U.S.-Mexico border geologic-map compilation in red and green.
15

Figure 2. Schematic diagram showing components of the merged geologic data used in the construction of the transboundary geologic map.

Figure 3. Index map and Landsat Thematic Mapper image of the Upper San Pedro River drainage basin.

U.S.-Mexico Border Map 

Western Region Compilation

Figure 3. Index map and Landsat Thematic Mapper image of the Upper San Pedro River 

drainage basin. 

Geologic-Map Compilation of the U.S.-Mexico Border
16 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

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17

The broad valleys along the lower Colorado River, Ariz., 

contain numerous bodies of still water that provide critical 

habitat for birds, fish, and other wildlife. This chain of floodplain lakes is an important part of the Pacific Flyway—the 

major north-south route of travel for migratory birds in the 

western hemisphere—and is also used by many resident-bird 

species. In addition, isolated floodplain lakes may provide 

the only viable habitat for endangered native fish, such as the 

razorback sucker—a fish that is vulnerable to predation by 

introduced species in the main stem of the Colorado River. 

Floodplain lakes typically occupy former channel courses of 

the river and form by river meandering or avulsion. 

Persistent fluvial-sediment deposition (aggradation) 

creates conditions that favor rapid formation and destruction of floodplain lakes, while long-term river downcutting 

(degradation) inhibits their formation and evolution. New 

radiocarbon dates from wood recovered from drill cores near 

Topock, Ariz., indicate that the river aggraded an average of 

3 mm/yr during the middle and late Holocene. Aggradational 

conditions before Hoover Dam was built were associated with 

rapid channel shifting and frequent lake formation. Lakes had 

short life spans due to rapid infilling with fine-grained sediment during turbid floods on the unregulated Colorado River. 

The building of dams and armored banks has impacted floodplain lakes, not only by drowning large portions of the valley 

beneath reservoirs, but also by preventing new lake formation 

in some areas and accelerating it in others. GIS analyses of 

three sets of historical maps show that both the number and 

total area of isolated (that is, not linked to the main channel 

by a surface-water connection) lakes in the lower Colorado 

River valley increased between 1902 and the 1950s, and then 

decreased through the 1970s. River-bed degradation below 

dams inhibits channel shifting and floodplain-lake formation, and the capture of fines behind the dams has prevented 

sediment infilling of the lakes. Bed lowering below dams 

and in artificially confined reaches could potentially dewater 

floodplain lakes. This process is occurring at Beal Lake, a 

natural lake used for native-fish restoration in the Havasu 

National Wildlife Refuge. Sedimentation near the upstream 

ends of reservoirs has created large areas of still water. One 

of the largest, Topock Marsh, is connected to the main channel, restricting its usefulness as a native-fish nursery; other 

backwater areas are confined by bars that isolate standing 

water at tributaries.

Floodplain Lakes and Their Relation to Alluviation Cycles in the 

Lower Colorado River

By Daniel V. Malmon1 , Tracey J. Felger2 , Keith A. Howard1

1

U.S. Geological Survey, 345 Middlefield Road MS 973, Menlo Park, CA 

94025. 2

U.S. Geological Survey, 2255 N. Gemini Drive, Flagstaff, AZ 86001.
18 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

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19

Geologic maps are a fundamental dataset supporting multidisciplinary studies in the U.S.-Mexico border region. We compiled binational geologic maps in parts of southernmost Texas, 

and in Tamaulipas, for the U.S.-Mexico Border Environmental 

Health Initiative. The mapping is based on the integration of 

geologic, geochemical, and geophysical data, and this synergistic 

approach provides a template for compiling map datasets in other 

parts of the border region.

Our research resulted in new mapping of the Pliocene 

Goliad Formation, Pleistocene Lissie and Beaumont Formations, and Holocene Rio Grande fluvial-deltaic deposits in parts 

of Tamaulipas. We also refined existing mapping of the Beaumont and Lissie Formations in Texas. Ongoing research includes 

characterizing the lithology, geochemistry, and mineralogy of 

these map units to provide baseline data important in assessing 

human and wildlife health. Other research includes soil-moisture 

modeling and mapping parts of the Beaumont Formation and the 

Rio Grande deposits to address issues related to permeability, 

surface-water ponding, and vector-borne disease potential. 

Our binational mapping efforts will provide hydrogeologicframework data to support ground-water modeling related to the 

U.S.-Mexico Transboundary Aquifer Assessment Act. Geologic 

maps show the distribution of hydrostratigraphic units and the 

location and geometry of faults and fractures that control groundwater flow and also are pathways for contaminant transport. The 

Beaumont, Lissie, and Goliad Formations, and the Rio Grande 

deposits are ground-water aquifers in the Lower Rio Grande 

Valley, and alluvial aquifers in the Rio Grande deposits produce 

some of the highest quality ground water (less than 1,000 TDS) 

in the valley. New mapping of these formations in Tamaulipas 

provides a unified hydrogeologic framework spanning the U.S.-

Mexico border.

Binational Geologic Mapping in the Lower Rio Grande of 

Southern Texas, United States, and Northern Tamaulipas, 

Mexico

By William R. Page1 , Helen Folger2 , Bernard Hubbard2, Jim Stefanov3 , and Matthew D. Merrill2

1

Arizona Geological Survey, Box 25046, Denver Federal Center, MS 980, 

Denver, CO 80225. 2

U.S. Geological Survey, 12201 Sunrise Valley Dr., MS 954, Reston, VA 

20192. 3

U.S. Geological Survey, 8027 Exchange Dr., Austin, TX 78754. 
20 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

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21

Air quality continues to be an important public health concern within the Salton Sea Air Basin, with areas in both Riverside 

and Imperial counties having some of the worst air pollution/

PM10 levels in the country during certain times of the year. With 

a recent agreement between the water stakeholders and the urban 

areas in southern California some of the water that drains into the 

Salton Sea will be diverted to the cities. Over time this will cause 

the water level to drop and up to 80,000 acres of the Salton Sea’s 

bottom will be exposed and become potential new dust sources 

(fig. 1). Several Federal, State, and local agencies are involved in 

investigating the possible best methods to restore the Salton Sea 

to protect the wildlife habitats and minimize the impact to human 

health caused by new dust sources. The following major issues 

are being investigated by the United States Geological Survey 

(USGS) under this project in collaboration with the Bureau of 

Reclamation and the California Department of Water Resources:

• Use of dual-frequency acoustics to map Salton Sea bot

Lessons Learned from the Salton Sea—Potential Impact of Dust 

Emission to Both Air Quality and Human Health

tom-sediment characteristics to generate a first-order 

potential wind-erosion vulnerability map.

• Analysis and study of the wind characteristics within the 

Salton Sea Air Basin to help predict the potential impact to 

air quality the lower water levels will have on the area, 

including identifying the areas that may be impacted the 

most. 

• Identification of some of the current on-land large dust 

sources in the Salton Sea Air Basin and investigate their 

current impact on the region’s air quality.

To help understand the current wind-erosion vulnerability in 

the Salton Sea region we used satellite-image data to detect and 

identify existing on-land dust sources. This information will help 

with management decisions that are being made on how to best 

restore the Salton Sea to minimize the impact to both wildlife 

habitats and human health. Restoration costs are estimated to be 

in the hundreds of millions to several billions of dollars.

1

U.S. Geological Survey, 2255 North Gemini Drive, Flagstaff, AZ 86001.

2

U.S. Geological Survey, 520 N. Park Ave., Tucson, CA 85719. 

• Identify some of the current on-land large dust sources in the Salton Sea Air Basin

and investigate their current impact on the region’s air quality.

To help understand the current wind-erosion vulnerability in the Salton Sea region we

used satellite-image data to detect and identify existing on-land dust sources. This information

will help with management decisions that are being made on how to best restore the Salton Se

to minimize the impact to both wildlife habitats and human health. Restoration costs are

estimated to be in the hundreds of millions to several billions of dollars.

Figure 1. Photo showing an existing exposed playa surface at the edge of the Salton Sea. A

concern is the potential dust emission from very large areas that could look like this in the futu

due to the lowering of the lake’s water level.

Figure 1. Photo showing an existing exposed playa surface at the edge of the 

Salton Sea. A concern is the potential dust emission from very large areas that 

could look like this in the future due to the lowering of the lake’s water level.

By Pat Chavez1 , Jana Ruhlman1, Miguel Velasco1, Rian Bogle1, John Vogel2 , and JoAnn Isbrecht1
22 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

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23

In many landscapes the potential vulnerability to erosion is 

important, and vegetation sheltering the soils is a critical component that influences the level of vulnerability. In the Mojave 

Desert in the southwestern United States, wind erosion and dust 

emission are concerns with respect to soil loss and its effects on 

air quality and on human health and safety. In Hawai’i, water 

erosion and sediment runoff onto coral reefs are major concerns. Methods to detect, map, and monitor both temporal- and 

spatial-vegetation dynamics within a landscape are critical for 

mapping and monitoring the degree of vulnerability to erosion. 

Changes that occur from season to season in annual vegetation 

and perennial grasses, because of differences in climate/rainfall 

conditions and the spatial distribution of perennial nongrass 

vegetation, are critical parameters that influence potential erosion of landscapes.

Change-detection algorithms and procedures were developed to detect and map differences between wet and dry conditions by identifying areas of annual and perennial grasses, and 

algorithms and procedures for spatial-variability analyses were 

used to detect and map differences in the spatial coverage and 

distribution of nongrass perennial vegetation. These types of 

spatial analyses have been applied in the Mojave Desert and the 

island of Moloka’i, Hawai’i, for studies of wind erosion and 

water erosion, respectively. Multitemporal satellite (Landsat 

TM, IKONOS, and Quickbird) and airborne images (figs. 1 

and 2) collected under conditions of high and low antecedent 

Use of Remote Sensing To Detect and Map Temporal and Spatial 

Vegetation Dynamics to Help Map Landscape Erosion 

Vulnerability—Mojave Desert and Moloka’i, Hawai’i

By Pat Chavez1 , JoAnn Isbrecht1, Miguel Velasco1, and Rian Bogle1

Figure 1. Image map generated by using Landsat TM images to show annual-vegetation dynamics 

in the Mojave Desert, southwestern United States.

1

U.S. Geological Survey, 2255 N. Gemini Drive, Flagstaff, AZ 86001.
24 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

Figure 2. Image map generated by using high-resolution (six-inch pixels) airborneimage data showing percentage of perennial-vegetation cover at a ten-meter field plot 

size, in the Mojave Desert.

rainfall for both locations show that (1) dust emission from 

vegetated landscapes in the Mojave Desert is greatly enhanced 

following drought and almost completely shut down after only 

a few months of heavy winter rainfall, and (2) sediment runoff 

on Moloka’i appears to be effected by the amount of vegetation cover within the watersheds, with the highest amount of 

vegetation dynamics (greening up and (or) having new growth) 

occurring within the lower half of the watersheds being studied. 

From a management perspective, areas identified as having 

the greatest level of vegetation dynamics (the lower half of the 

watersheds) might be some of the more promising sites to consider for management efforts.
25

The Handbook of Texas Online defines colonias as 

unincorporated and unregulated settlements that emerged 

during the 1960s along the U.S.-Mexico border (Texas State 

Historical Association, 2003). The majority of colonias are 

found in Texas (more than 1,400 as of 2001), but they also 

exist in Arizona (80) and New Mexico (120; Ward, 1999; 

Norman and others, 2006). The emergence of colonias within 

the U.S.-Mexico border region can be traced back to the rapid 

growth associated with the Mexican Border Industrial Program during the 1960s. Increased economic growth on the 

Mexican side of the border fueled population expansion in 

sister cities (Parcher, 2002), which are communities where a 

city in one country borders a city in another country, creating 

a large urban area separated by administrative boundaries. 

This rapid population growth in the border region triggered a 

lack of affordable housing, causing new migrants in the U.S. 

to purchase rural homestead lots through a contract-for-deed 

program from land developers. Due to the need to keep prices 

affordable and the absence of effective land-use controls, these 

rural subdivisions were built without proper infrastructure 

(Davies and Holz, 1992). Since the region is binationally interconnected economically, politically, and socially, the phenomenon of colonias is a transborder issue.

With the passing of Senate Bill 827 (SB 827) by the 79th 

Texas Legislature in 2005, the State was mandated to create 

a colonia-identification system and to track the progress of 

State-funded colonia-improvement projects. These efforts 

were spearheaded by the Office of the Texas Secretary of State 

(SOS), and the SB 827 workgroup was formed (Office of the 

Texas Secretary of State, 2006). In order to track the progress 

of State-funded projects, the SB 827 workgroup created a set 

of infrastructure, demography, and health-related criteria for 

ombudsmen in the field to collect. The ombudsmen collected 

data from a variety of sources, including utility companies, 

county-appraisal districts, site visits, and the Office of the 

Attorney General of Texas. Once these data were collected, 

colonias were assigned a color classification of red, yellow, or 

green (fig. 1). 

Since colonias are not uniquely represented within the 

census geography, an explicit long-term working database is 

needed to monitor progress, set infrastructure priorities, and 

measure quality of life indicators within the colonias. Based on 

requirements outlined in SB 827, and in cooperation with the 

SOS, the U.S. Geological Survey (USGS) developed the Colonia Health, Infrastructure, and Platting Status tool (CHIPS). 

CHIPS is a relational database that uses the criteria created by 

the SB 827 workgroup as a template for the database schema. 

This database structure uses a unique key field to link data 

tables, which results in an open-ended design that can integrate 

data from new sources. Relational databases also allow the use 

of Structured Query Language (SQL), which allows users to 

manipulate how data are displayed without altering the original 

data tables. 

Since SB 827 requires a biennial report to be submitted 

by December 1 on even years, it is imperative that the data be 

stored in a format that can be updated easily and used to generate custom reports rapidly. Thus, a graphical user-interface 

(GUI) was designed to allow rapid and consistent data entry 

regardless of the user’s level of familiarity with the database 

structure. As colonia data are revised, the GUI within CHIPS 

provides the capability of updating the color classification of 

every colonia with a click of a single button. The color classification of a colonia can be red, yellow, or green. Red denotes a 

colonia that is either unplatted, has an inadequate potable-water 

supply, or has inadequate wastewater disposal. Yellow denotes a 

colonia that does not meet the red criteria, but still has inadequate trash collection, unpaved roads, or inadequate drainage. 

Green denotes a colonia that does not meet red or yellow criteria. The classification procedure is designed to be easily altered 

if the classification criteria change. Another function of the 

database is a custom-report generator that is integrated into the 

GUI, which allows users with little or no knowledge of database 

queries to extract information with ease. The report generator 

is flexible, and its output can be tailored to be either broad or 

specific. For example, a congressperson could use CHIPS to 

list colonias with wastewater issues in a specific county, while 

a health researcher could list all colonias without access to 

healthcare clinics.

The results of the colonia color classifications are shown in 

figure 1. The ombudsmen populated CHIPs for six counties in 

Texas (Cameron, El Paso, Hidalgo, Maverick, Starr, and Webb) 

from July to December 2006. Of the 1,786 colonias identified 

CHIPS—A New Way to Monitor Colonias Along the U.S.-Mexico 

Border

By Delbert G. Humberson1 and Jean W. Parcher1

1

U.S. Geological Survey, 8027 Exchange Dr. MS 518, Austin, TX 78754.
26 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

in CHIPS, 36 percent are identified as green. The percentage 

of colonias identified as green is higher than the percentage 

of colonias identified as red (24.2 percent) or yellow (22.5 

percent), but still less than the combined percentage of red and 

yellow colonias (46.7 percent). By using CHIPS we can quickly 

compare the distribution of colonias among counties (fig. 1). 

For example, we can see that 10 percent of the total number 

of colonias are in Cameron County, but Cameron County has 

14.5 percent of the total number of green colonias. On the other 

hand, Maverick County has 4.1 percent of the total number 

of colonias, but only 2.3 percent of the total number of green 

colonias. 

With CHIPS it is possible to highlight where funds for 

colonia projects are needed. Hidalgo County accounts for 

84.5 percent of the number of unknown colonias in the six 

counties (fig. 1). This percentage represents 261 colonias 

Figure 1. Distribution of green, yellow, and red colonias within the six Texas counties contained in CHIPS, U.S.-Mexico border region.

Figure 1. Distribution of green, yellow, and red colonias within the six Texas counties contained

in CHIPS, U.S.-Mexico border region.
27

where funding should be directed in order to obtain a color classification. Once the colonias are classified, a more meaningful 

distribution can be created and used to direct future funding.

CHIPS is part of a larger project involving scientists 

from the U.S. and Mexico who are merging landscape 

and demographic data from both countries into integrated 

datasets. These datasets are used to assess environmental 

health issues along the U.S.-Mexico border. To view the 

interactive Web maps, documentation, and links, visit http://

borderhealth.cr.usgs.gov. For more information, contact 

Delbert Geronimo Humberson at (512) 927-3567 or dghumber@usgs.gov, or Jean W. Parcher at (512) 927-3523 or 

jwparcher@usgs.gov.

References Cited

Davies, C.S., and Holz, R.K., 1992, Settlement evolution of 

“colonias” along the US-Mexico border, the case of the 

Lower Rio Grande Valley of Texas: Habitat International, 

v. 16, no. 4, p. 119–142.

Norman, L.M., Donelson, A.J., Pfeifer, E.L., and Lam, A.H., 

2006, Colonia development and land use change in Ambos 

Nogales, United States – Mexican Border: U.S. Geological 

Survey Open-File Report 2006–1112, 121 p.

Office of the Texas Secretary of State, 2006, Tracking the 

progress of state-funded projects that benefit colonias, 

[http://www.sos.state.tx.us/border/colonias/reports.shtml, 

last accessed February 13, 2007].

Parcher, J.W., 2002, Remote sensing method for estimating 

impervious cover for hydrologic modeling applications—A 

case study of the Brownsville, Matamoros area: Austin, 

University of Texas, master’s thesis, 158 p.

Texas State Historical Association, 2003, The handbook of 

Texas online, [http://www. tsha.utexas.edu/handbook/

online/, last accessed February 13, 2006].

Ward, P.M., 1999, Colonias and public policy in Texas and 

Mexico—Urbanization by stealth: Austin, University of 

Texas Press, 298 p.

CHIPS—A New Way to Monitor Colonias Along the U.S.-Mexico Border
28 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

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29

The twin cities of Nogales, Ariz., and Nogales, Sonora, 

Mexico, known collectively as Ambos Nogales (“ambos” is 

the Spanish word for “both”), spanning the Arizona-Sonora 

section of the border in a shared watershed. Ambos Nogales 

is the site of one of the larger maquiladora (twin-plant) programs along the U.S.-Mexico border. The improvement in 

quality of life and environment, along with the promise of 

better jobs and incomes, has generated a considerable flow of 

migrants to Ambos Nogales from the south, particularly since 

the 1970s. Approximately 80 percent of Nogales, Sonora’s 

residents are recent immigrants who find work in the lowwage maquiladoras crowded along the border. This migration to the border and rapid population growth has placed 

enormaous pressure on the land and produced widespread, 

unplanned urban development. 

Development in this region, with its arid-land sensitivity and rugged terrain, is inevitable. However, the area has 

limited land available for development, and the mountainous 

topography makes the cost of site preparation expensive. The 

population of the Arizona-Sonora border area is predicted to 

continue growing—potentially doubling by 2030. Although 

population has been increasing in both cities, growth is most 

dramatic in Nogales, Sonora, beginning with a trend in the 

1940s and leaping again in the 1980s to higher and higher 

rates. In contrast, rates rose slightly in Nogales, Ariz., in the 

1970s, but seem to have plateaued in the 1990s.

Environmental problems in Ambos Nogales are attributable to rapid economic and population growth. Surface activities and discharges to the Nogales Wash are shown to result 

in the deterioration of water quality. Flooding also affects 

low-lying areas throughout Ambos Nogales, where many 

unpaved streets follow the course of natural river washes. 

Erosion susceptibility increases with soil compaction, devegetation, and land-use changes associated with development. 

Pollution generated in border colonias (neighborhoods) may 

impact residents on both sides of the border who share the 

transboundary watershed and airshed. U.S.-Mexico border 

residents are affected disproportionately by many environmental health problems, including waterborne and respiratory diseases. 

In a study done in cooperation with U.S. Department of 

Housing and Urban Development (HUD) and the Instituto 

Nacional de Estadística Geografía e Informática (INEGI), 

urban changes in Ambos Nogales were documented for 1975, 

1983, 1995, and 2002, by using remote-sensing analyses 

(fig.1). These analyses were used to identify colonia development and settlement patterns along the U.S.-Mexico border. 

The urban footprints derived from these data for four 

time periods were input to the SLEUTH urban-growth model 

and coupled with erosion and sedimentation models in a geographic information system (GIS) to estimate future nonpoint 

source (NPS) pollution in this binational watershed (Norman, 

2005; 2007). The modeling approach is designed to predict 

the impacts of increasing urban development on surface erosion and sediment yield. To accomplish this, the model links 

a hillslope-scale erosion-prediction model, the Universal Soil 

Loss Equation (USLE), and a spatially derived sedimentdelivery model (SEDMOD) within a GIS to estimate erosion, 

sediment yield, and sediment deposition across the watershed 

(Norman and others, 2006). The modeling approach will be 

used to support watershed planning. Potential erosion “hot 

spots” related to future development and the effect of different management scenarios used to reduce sediment loads in 

the future will be evaluated (fig. 2). 

 

References Cited

Norman, L.M., 2007, United States-Mexican border watershed 

assessment—modeling nonpoint source pollution in Ambos 

Nogales: Journal of Borderland Studies v. 22, no. 1, 20 p.

Norman, L.M., Donelson, Angela, Pfeifer, Edwin, and Lam, 

A.H., 2006, Colonia development and land use change 

in Ambos Nogales, United States-Mexican border: U.S. 

An Approach to Prevent Nonpoint-Source Pollutants and Support 

Sustainable Development in the Ambos Nogales Transboundary 

Watershed

By Laura M. Norman1 , D. Phillip Guertin2 , and Mark Feller3

1

U.S. Geological Survey, Southwest Geographic Science Team, 520 North 

Park Ave., Str.355, Tucson, AZ 85719. 2

The University of Arizona, School of Natural Resources, 325 Biosciences 

East, Tucson, AZ 85719. 3

U.S. Geological Survey, Rocky Mountain Geographic Science Center, Box 

25046, Denver, CO 80225.
30 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

Geological Survey Open-File Report 2006–1112, [http://

pubs.usgs.gov/of/2006/1112].

Norman, L.M., 2005, Modeling land use change and associate 

water quality impacts in the Ambos Nogales watershed, 

U.S.-Mexico border: Tucson, University of Arizona, Ph.D. 

dissertation, 216 p.

Figure 1. Urban extents of the twin city area of Ambos Nogales in 1975, 1983, 1995, and 2002.
31

Figure 2. Sustainable development plans for Ambos Nogales Watershed based on curbed urban growth and revegetation.
32 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

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33

Land-cover change datasets provide an important contextual tool for understanding changes in water quality, hydrology, and water use over time (Lillesand and Kiefer, 2000). As 

important as land-cover change detection might be, the cost of 

producing these datasets for a large area often is prohibitive. 

A process developed by Michael Coan and Joyce Fry of the 

U.S. Geological Survey (USGS) Center for Earth Resources 

Observation and Science (EROS) has made the production 

of land-cover change datasets less costly by using aggregated 

land-cover data from the National Land Cover Dataset (NLCD) 

1992 (USGS, 2000) and NLCD 2001 (Homer and others, 2004) 

as training data. The land-cover change process uses Landsat 

imagery from 1992 and 2001 classified at Anderson Level I, 

a generalized land-cover classification scheme, to produce a 

land-cover change dataset (Anderson and others, 1976). This 

process eliminates the need to collect training data in the field. 

The USGS U.S.-Mexico Border Environmental Health Initiative (Buckler and Strom, 2004; Buckler and Stefanov, 2004; 

Papoulias and others, 2006) is testing this method on one Landsat scene in the lower part of the Rio Grande/Rio Bravo (fig. 1).

Both the United States and Mexico have programs to produce land-use/land-cover (LULC) datasets by using a nationally 

consistent classification scheme, which can be used to create 

training data for use in the change-detection process. The USGS 

NLCD 1992 and the NLCD 2001 are based on the LULC classification system for remotely sensed data described by Anderson 

and others (1976). Both of these datasets are available in raster 

format at 30-meter resolution. In Mexico, the Instituto Nacional 

The Potential of Binational Land-Cover-Change Detection 

Procedures for use Along the U.S.-Mexico Border

By Zachary D. Wilson1 and Jean W. Parcher1

U.S. Geological Survey, 2000, National Land Cover Dataset: U.S. Geological Survey Fact Sheet

108–00, [http://erg.usgs.gov/isb/pubs/factsheets/fs10800.html, last accessed April 10, 2007].

Woodward, D.G., and Durall, R.A., 1996, United States-Mexico border area, as delineated by a

shared-water resources perspective: U.S. Department of the Interior Field Coordinating

Committee Fact Sheet 1, [http://www.cerc.usgs.gov/FCC/pubs/Fact_sheets/Fact_1/DOI_USMX_Border_FCC_Fact_sheet_1.html, last accessed April 10, 2007].

Figure 1. LULC map of the lower Rio Grande/Rio Bravo and USGS U.S.-Mexico Border

Environmental Health Initiative Subarea 8.

Figure 1. LULC map of the lower Rio Grande/Rio Bravo and USGS U.S.-Mexico Border Environmental Health 

Initiative Subarea 8.

1

U.S. Geological Survey, 8027 Exchange Dr. MS 518, Austin, TX 78754.
34 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

Figure 3. Binational land-cover change detection method modified from Coan and Fry (U.S.

Geological Survey, written commun., 2006).

Figure 2. USGS U.S.-Mexico Border Environmental Health Initiative study area boundary with 

subareas (Woodward and Durall, 1996) and the binationally integrated LULC dataset used for 

creating training points. 

57

Figure 2. U.S. Geological Survey U.S.-Mexico Border Environmental Health Initiative study area boundary with subareas 

(Woodward and Durall, 1996) and the binationally integrated LULC dataset used for creating training points.

Figure 3. Binational land-cover change detection method modified from Coan and Fry (U.S. Geological Survey, written 

commun., 2006).
35

de Geografía, Estadística, e Informática (INEGI), the National 

Geography, Statistics, and Information Technology Institute, is responsible for mapping LULC. INEGI produces the 

1:250,000-scale Mapa de Uso de Suelo y Vegetación (Land Use 

and Vegetation Map) based on visual interpretation of remotely 

sensed imagery by using unified regional-vegetation classification systems developed during the last 70 years by many 

scientists, including Leopold, Muller, and Rzedowski (Instituto 

Nacional de Estadística, Geografía, e Informática, 1993). The 

Mexican LULC data are available in digital vector format. 

Though each country’s classification system is consistent 

within the country’s own borders, the classes defined by the 

respective classification systems do not represent a one-to-one 

relation across the border. Integration of the U.S. and Mexican 

data required the creation of a generalized (modified Anderson 

Level I) binational classification system to which both countries’ LULC data could be reclassified (fig. 2). The integrated 

and reclassified LULC data can then be used to create training 

data for the change-detection process (fig. 3) developed by Coan 

and Fry (U.S. Geological Survey, written commun., 2006). Preliminary results indicate that these procedures could be effective 

in developing binational land-cover change datasets along the 

entire U.S.-Mexico Border.

References

Anderson, J.R., Hardy, E.E., Roach, J.T., and Witmer, R.E., 

1976, A land use and land cover classification system for use 

with remote sensor data: U.S. Geological Survey Professional 

Paper 964, [http://landcover.usgs.gov/pdf/anderson.pdf, last 

accessed April 10, 2007].

Buckler, D., and Stefanov, J., 2004, Internet map service for 

environmental health in the U.S.-Mexico border region: U.S. 

Geological Survey Fact Sheet 2004–3140, [http://pubs.usgs.

gov/fs/2004/3140, last accessed April 10, 2007].

Buckler, D., and Strom, E., 2004, Science data in support of 

environmental health studies in the U.S.-Mexico border 

region: U.S. Geological Survey Fact Sheet 2004–3013, 

[http://pubs.usgs.gov/fs/2004/3013/, accessed April 10, 

2007].

Homer, C., Huang, C., Yang, L., Wylie, B., and Coan, M., 2004, 

Development of a 2001 National Land-Cover Database for 

the United States: Photogrammetric Engineering and Remote 

Sensing v. 70, no. 7, p. 829–840, [http://www.mrlc.gov/pdfs/

July_PERS.pdf, last accessed June 2, 2006].

Instituto Nacional de Estadística, Informática, e Geografía 

(INEGI), 1993, Guía para la interpretación de información 

cartográfica impresa y digital de uso de suelo: Aguascalientes, 

99 p. 

Lillesand, T.M, and Kiefer, R.W., 2000, Remote sensing and 

image interpretation (4th ed.): New York, Wiley and Sons, 

724 p.

Papoulias, D., Parcher, J., Stefanov, J., and Page, W., 2006, 

Interdisciplinary science in support of environmental health 

along the United States-Mexico border: U.S. Geological 

Survey Fact Sheet 2006–3054, [http://pubs.usgs.gov/preview/

fs/2006/3054/, last accessed April 10, 2007].

U.S. Geological Survey, 2000, National Land Cover Dataset: 

U.S. Geological Survey Fact Sheet 108–00, [http://erg.usgs.

gov/isb/pubs/factsheets/fs10800.html, last accessed April 10, 

2007].

Woodward, D.G., and Durall, R.A., 1996, United StatesMexico border area, as delineated by a shared-water 

resources perspective: U.S. Department of the Interior Field 

Coordinating Committee Fact Sheet 1, [http://www.cerc.usgs.

gov/FCC/pubs/Fact_sheets/Fact_1/DOI_US-MX_Border_

FCC_Fact_sheet_1.html, last accessed April 10, 2007].

The Potential of Binational Land-Cover-Change Detection Procedures for use Along the U.S.-Mexico Border
36 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

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37

The Land Cover Trends project, a joint effort between the 

U.S. Geological Survey and the U.S. Environmental Protection Agency (USEPA), uses satellite imagery to classify land 

cover and estimate contemporary (1973-2000) changes in land 

use and land cover in the United States. By using ecoregions 

defined by Omernik and the USEPA, estimates of land-cover 

and land-use change are derived from interpretations of a 

statistical sampling of image blocks from five dates of Landsat imagery. The statistical results, in conjunction with site 

visits, geographical research, and socioeconomic data, are 

used to assess regional driving forces of land-use change. The 

focus of this research examines and compares three adjacent 

southwestern ecoregions—the Sonoran Basin and Range, the 

Madrean Archipelago, and the Chihuahuan Deserts. Combined, these ecoregions stretch along the U.S.-Mexico border 

from south-central California to western Texas. The ecoregions each have their own distinct landscapes, contain high 

amounts of biological diversity, and share common issues that 

affect land use. Increased oil and gas extraction, availability 

of ground-water resources, and reduction of natural grasslands 

because of overgrazing and other desertification processes are 

some of the factors affecting contemporary land use in these 

ecoregions. By using the Land Cover Trends research and 

interpretation results, the rates and types of land-cover change 

are being compared to find similarities and contrasts among 

these three contiguous areas. Initial findings indicate that 

change is infrequent and occurs mostly within the grass/shrub, 

agriculture, and mining classes. A closer examination and 

comparison will provide a look at regional land-cover trends 

for the border areas of the southwest.

Comparison of Contemporary Land-Cover Trends Among the 

Sonoran Basin and Range, Madrean Archipelago, and 

Chihuahuan Deserts Ecoregions

By Jana Ruhlman1 , Leila Gass2 , Barry Middleton1

1

U.S. Geological Survey, 2255 N. Gemini Drive, Flagstaff, AZ 86001.

2

U.S. Geological Survey, 520 N. Park Ave., Tucson, AZ 85719.
38 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

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39

Key Words: landscape characterization, remote sensing, 

geographic information systems, change detection, hydrological process models, habitat models, alternative futures, watershed assessment, San Pedro River (Arizona/Sonora).

It is currently possible to measure landscape change over 

large areas and determine trends in environmental condition 

by using advanced space-based technologies accompanied 

by geospatial data. During the past two decades, important 

The San Pedro River—A Case Study for Examining Past Landscape 

Change and Forecasting Hydrological and Biological Response to 

Urban Growth and Land-Use Change

William G. Kepner1 , Kenneth G. Boykin2 , Darius J. Semmens1, David C. Goodrich3 , Christopher J. 

Watts4 , and D. Phillip Guertin5

1

U.S. Environmental Protection Agency, Office of Research and Development, P.O. Box 93478, Las Vegas, NV 89193.

2

New Mexico State University, Cooperative Fish and Wildlife Research Unit, P.O. Box 30003, MSC 4901, Las Cruces, NM 88003.

3

U.S. Department of Agriculture, Agricultural Research Service, Southwest Watershed Research Center, 2000 E. Allen Road, Tucson, AZ 85719.

4

University of Sonora, Physics Department, Blvd., Encinas y Rosales, Hermosillo, Sonora, Mexico 83000.

5

University of Arizona, School of Natural Resources, 325 Biological Sciences East, Tucson, AZ 85721.

Figure 1. Upper San Pedro Watershed (U.S.-Mexico).
40 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

advances in the integration of remote imagery, computer processing, and spatial analysis technologies have been used to 

develop landscape information that can be integrated within 

hydrologic and habitat models to determine long-term change 

and make predictive inferences about the future. These technologies provide the basis for developing landscape composition and pattern indicators as sensitive measures of large-scale 

environmental change and, thus, may provide an effective 

and economical method for evaluating watershed conditions 

related to disturbance from human and natural stresses. This 

case study for the upper San Pedro River (fig. 1) employs 

a system of land-cover maps generated from a multidate 

satellite-imagery database, which incorporates Landsat MultiSpectral Scanner (MSS) imagery from the early 1970s, mid 

1980s, and early 1990s and Landsat Thematic Mapper (TM) 

imagery from 1997 to examine change during approximately 

a 25-year period. Future environments were examined relative 

to their impact on wildlife habitat and surface-water conditions, for example, sediment yield and surface runoff. Both 

habitat and hydrological outputs were estimated for a baseline 

year (2000) and predicted twenty years into the future by 

using hydrological- and habitat-process models and spatially 

oriented land-use models based on stakeholder preferences 

and historical growth.
41

Key Words: digital land cover, remote sensing, Geographic 

Information Systems, CART analysis, Gap Analysis, National 

Vegetation Classification System, Arizona, Colorado, Nevada, 

New Mexico, and Utah. 

 The Gap Analysis Program (GAP) is a national interagency program that maps the distribution of plant communities 

and selected animal species and compares these distributions 

with land stewardship to identify “gaps” in biodiversity protecContemporary Digital Land-Cover Mapping for the American 

Southwest—The Southwest Regional Gap Analysis Project

By John Lowry1 , William G. Kepner2 , Kenneth G. Boykin3 , Kathryn A. Thomas4 , Donald L. Schrupp5 , 

and Pat Comer6

 

1

Utah State University, College of Natural Resources, Remote Sensing/GIS Laboratory, UMC 5275, Logan, UT 84322.

2

U.S. Environmental Protection Agency, Office of Research and Development, P.O. Box 93478, Las Vegas, NV 89193.

3

New Mexico State University, Cooperative Fish and Wildlife Research Unit, P.O. Box 30003, MSC 4901, Las Cruces, NM 88003.

4

U.S. Geological Survey, Sonoran Desert Research Station, 125 Biological Sciences East, Bldg. 43, University of Arizona, Tucson, AZ 85721.

5

Colorado Division of Wildlife, 6060 Broadway, Denver, CO 80216.

6

NatureServe, 2060 Broadway, Ste. 230, Boulder, CO 80320.

Figure 1. Southwest Regional Gap Analysis Project five-state digital land-cover map. The final

map product contains 125 land-cover classes with a minimum mapping unit of 0.40 ha; only the

15 most abundant land-cover classes are depicted in the map legend.

Figure 1. Southwest Regional Gap Analysis Project five-state digital land-cover map. The final map product contains 125 land-cover 

classes with a minimum mapping unit of 0.40 ha; only the 15 most abundant land-cover classes are depicted in the map legend.
42 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

tion. GAP uses remote satellite imagery (Landsat 7) and Geographic Information System (GIS) technology to assemble and 

view large amounts of biological and land-management data 

to identify areas where conservation efforts may not be sufficient to maintain diversity of living natural resources. Historically, GAP has been conducted by individual states. However, 

this has resulted in inconsistencies in mapped distributions of 

vegetation types and animal habitat across state lines because 

of differences in mapping and modeling protocols. This was 

further compounded from the lack of a national vegetation classification nomenclature. In response to these limitations, GAP 

embarked on a second-generation effort to conduct the program at a regional scale by using (1) a vegetation-classification 

scheme applicable across the U.S., (2) ecoregional units as the 

basis for segmenting the landscape into manageable units, and 

(3) inter-agency investigator teams with land-cover analysis 

and environmental-protection expertise. The program’s first 

formalized multistate effort includes five Southwestern states 

(Arizona, Colorado, Nevada, New Mexico, and Utah), which 

comprise 535,175 square miles, or nearly one-fifth of the conterminous United States. 

Multiseason satellite imagery (Landsat ETM+) from 1999 

to 2001 were used in conjunction with digital elevation model 

(DEM) derived datasets (for example, elevation, landform, and 

aspect) to model natural and seminatural vegetation. Land-cover 

classes are drawn from NatureServe’s Ecological System concept, with 109 of the 125 total classes mapped at the ecological 

systems level. For the majority of classes, a decision tree classifier was used to discriminate land cover types, while a minority 

of classes (for example, urban classes, sand dunes, and burn 

scars) were mapped by using other techniques. Twenty mapping areas, each characterized by similar ecological and spectral 

characteristics, were modeled independently of one another. 

These mapping areas, which included a 4-km overlap, were subsequently mosaicked to create the regional dataset (fig. 1). 

This map was generated by using data from the landcover mapping portion of the Southwest Regional Gap Analysis Project (SWReGAP). These data and related datasets are 

made available to the public by the SWReGAP consortium of 

institutions responsible for their development, and they can be 

obtained via download at http://earth.gis.usu.edu/swgap/landcover.html.
43

In western North America, migration patterns of neotropical land birds evolved within a landscape of a heterogeneous and patchy environments with no political boundaries. 

Western migrant land birds appear to assess migrant routes 

and stopover habitats at four major scales (1) genetically influenced corridor selection, (2) large-scale landscape features, (3) 

vegetation patches, and (4) microhabitat selection within the 

vegetation patch. Along the lower Colorado River in Mexico, 

Calif., and Ariz., these four scales are variously influenced 

by weather, vegetative species, structure, plant-phenology 

patterns, and insect-prey base. In migrating, neotropical 

migrant warblers that we have examined in Sonora, Mexico 

and Ariz., species arrival dates and numbers were variable 

and largely influenced by large-scale weather patterns and 

plant-phenology cycles. Once a microhabitat was selected, 

there was little movement by individual birds over the landscape during the stopover period. Therefore, stopover and bird 

foraging patterns were greatly influenced by plant species and 

phenological patterns of the selected microhabitat. Warbler 

species partitioned foraging habitat relative to foraging height, 

and they preferred native to introduced vegetation. Influences 

on location of warbler foraging within vegetative strata were 

related to abundances of foliage invertebrates that were significantly different among tree species and between native and 

introduced plants. Thus, it appears that large-scale landscape 

features, along with vegetation species, structure, phenology, 

abundance, and insect prey base, all play a role in structuring spring warbler migration patterns in northwest Sonora, 

Mexico and the southwestern U.S. along the lower Colorado 

River corridor.

Stopover Ecology and Habitat Utilization of Migrating Land 

Birds in Colorado River Riparian Forests of Mexico and the 

Southwestern United States 

By Charles van Riper III1

1

U.S. Geological Survey, SBSC Sonoron Desert Research Station, University 

of Arizona, Tucson, AZ 85721.
44 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

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45

Water transfers from Imperial Valley, Calif., agricultural 

users to urban Southern California users, and changes in flows 

from the Mexicali Valley, Mexico, are expected to decrease 

inflows to the Salton Sea. These water transfers and changes in 

flow will result in increased salinity and a lower lake level for 

the Salton Sea. The increased salinity will soon be greater than 

the biological tolerance of most fish and some invertebrate species and, therefore, will effect the food base for many species 

of migratory birds. A lowering of the lake level will also expose 

up to 81,000 acres of lake-bed sediments creating a potential for 

air-quality impacts. The State of California has prepared a draft 

Programmatic Environmental Report assessing eight alternative and two no-action scenarios for restoration of the Salton 

Sea Ecosystem ranging in cost from about $0.8 to $5.8 billion. 

A preferred alternative is expected to be recommended to the 

Legislature in 2007, and major construction is anticipated to 

be initiated by 2014. The Salton Sea Authority has developed a 

5-year Work Plan proposing pilot projects addressing early start 

habitat, controlled eutrophication, preparation of a site-specific 

environmental impact statement, development of preliminary 

designs, and implementation of environmental monitoring. The 

U.S. Geological Survey has begun development of an integrated 

monitoring and assessment plan that includes objectives and 

metrics; retrospective analysis; data collection; data management; data analysis and assessment; reporting; and quality 

assurance.

Salton Sea Ecosystem—Issues and Status of Restoration 

Planning

By Harvey L. Case, III1 and Douglas A. Barnum1

1

U.S. Geological Survey, 78401 Highway 111, Suite R, La Quinta, CA 92253.
46 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

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47

The combined Willcox and Douglas Basins of southeastern 

Arizona along the border with Mexico are being studied as part 

of the Arizona Rural Watershed Initiative Program funded by 

the State of Arizona and managed by the Arizona Department 

of Water Resources. The fundamental goal of this program is 

to improve our understanding of the available water supply in 

Geologic Framework, Hydrologic Monitoring, and Land-Use 

Change in the Willcox and Douglas Basins, Southeastern Arizona

By James Callegary1 , Kurt Schonauer1, and Alice Konieczki1

1

U.S. Geological Survey, Arizona Water Science Center, 520 N. Park Ave., 

Ste. 221, Tucson, AZ 85719.

Figure 1. Map showing physiography and location of water-level monitoring 

sites in the Willcox and Douglas Basins, Southeastern Arizona.

The Willcox (4,947 km2) and Douglas (1,942 km2) Basins (fig.1) are northwest-tosoutheast trending basins in southeastern Arizona, stretching from southern Graham County to 

the U.S.-Mexico border in southern Cochise County. These basins lie within the southeastern 

portion of the Basin and Range geologic province. 

Figure 1. Physiography and location of water-level monitoring sites in the Willcox and Douglas 

Basins, Southeastern Arizona. 

Elevations range from about 3,300 m in the Pinaleño Mountains to about 1,190 m at the 

international boundary with MexicoThe basins consist of alluvial fill underlain by sedimentary 
48 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

rural Arizona. The Rural Watershed Initiative was passed by the 

Arizona legislature in response to increasing pressure on rural 

water managers to provide sustainable supplies of water despite 

rapid population growth and demands for environmental protection. 

There are four specific objectives for the Willcox-Douglas 

portion of the initiative. The first objective is to assess the state 

of knowledge of the ground-water conditions in this region; 

this includes an evaluation of the existing water-level monitoring network and recommendations for improvement. The 

second objective is to improve knowledge of the hydrogeologic 

framework of the basins, including an assessment of depth to 

crystalline basement and an estimation of the distribution and 

permeability of hydrostratigraphic units. The third objective is 

to establish networks for monitoring subsidence and changes 

in ground-water storage. The fourth objective of the project is 

to estimate changes in the amount and distribution of water use 

through time. 

The Willcox (4,947 km2) and Douglas (1,942 km2) Basins 

(fig. 1) are northwest-to-southeast trending basins in southeastern Arizona, stretching from southern Graham County to the 

U.S.-Mexico border in southern Cochise County. These basins 

lie within the southeastern portion of the Basin and Range geologic province. 

Elevations range from about 3,300 m in the Pinaleño 

Mountains to about 1,190 m at the international boundary with 

Mexico. The basins consist of alluvial fill underlain by sedimentary and crystalline bedrock bounded by fault-block mountains. The primary aquifers are in the recent stream alluvium 

and basin-fill deposits. The Willcox Basin is closed, with no 

interbasin inflow or outflow. Historically, ground-water flow in 

the Willcox Basin was toward the Willcox Playa; in the Douglas 

Basin ground-water flow was from north to south toward the 

international boundary. However, ground-water flow directions 

have been altered by pumping, which was greater than 12 million acre-feet between 1915 and 2000 in the two basins. 

The water-level monitoring network consists of 46 wells 

in the Willcox Basin and 27 wells in the Douglas Basin. The 

hydrogeologic framework of the basins is being investigated 

by using borehole data, gravity measurements, and ground- and 

air-based electromagnetic surveys. The electromagnetic surveys 

were done during the summer of 2006 and indicate higher 

electrical conductivities centering on the Willcox Playa with 

the subsurface becoming more electrically resistive north and 

south of this area. Modeling and calibration of the airborne data 

by using the ground-based surveys is currently being carried 

out. At present, gravity monuments are being installed, and a 

survey to study basin structure will probably be done during 

summer 2007. The initial gravity survey will serve as a baseline 

for subsequent measurements used to monitor ground-waterstorage change. Earth fissures are being mapped by using both 

ground reconnaissance and aerial photos. Subsidence is being 

monitored with INSAR images. Land use and water use in the 

study area are primarily for agricultural purposes. Irrigated 

acreage has decreased by about 40 percent since 1960 (from 

about 28,000 to 17,400 hectares in 2006). Irrigated acreage was at a minimum during the 1980s, but increased by 25 

percent between 1992 and 2002. Pumpage peaked in 1974 in 

both basins and then declined through the late 1980s, however, 

pumpage has risen since then, particularly in the Willcox Basin, 

from a low of 82,000 acre-ft in 1987 to 193,000 acre-ft in 

2003. Pumping in the Douglas Basin has remained more stable 

because legislation in 1980 created the Douglas Irrigation NonExpansion Area.
49

The Automated Geospatial Watershed Assessment tool 

(AGWA) is a GIS interface jointly developed by the U.S. 

Department of Agriculture’s Agricultural Research Service, the 

U.S. Environmental Protection Agency, the University of Arizona, and the University of Wyoming to automate the parameterization and execution of the Soil Water Assessment Tool 

(SWAT) and KINEmatic Runoff and EROSion (KINEROS2) 

hydrologic models. The application of these two models allows 

AGWA to conduct hydrologic modeling and watershed assessments at multiple temporal and spatial scales. AGWA’s current 

outputs are runoff (volumes and peaks) and sediment yield 

from KINEROS2, and from SWAT, these runoff and sediment 

yield outputs and several water-quality measurements. AGWA 

uses commonly available GIS data layers to fully parameterize, execute, and visualize results from both SWAT and KINEROS2. Through an intuitive interface, the user selects an outlet 

from which AGWA delineates and discretizes the watershed by 

using a digital elevation model (DEM) based on the individual 

model requirements. The watershed model elements are then 

intersected with soils and land-cover data layers to derive the 

requisite model input parameters (fig. 1). AGWA can currently use STATSGO, SURRGO, and FAO soils and nationally 

available NLCD, NALC and GAP land-cover/land-use data. 

Users also are provided the capability to use their own landcover/land-use data (Miller et al., 2007). The chosen model is 

then executed, and the results are imported back into AGWA 

for visualization. This allows managers to identify potential 

problem areas where additional monitoring can be undertaken, 

mitigation activities can be focused, or alternative management 

can be recommended. AGWA can difference results from multiple simulations to examine relative change from alternative 

of input scenarios (for example, climate/storm change, landcover change, present conditions and alternative futures). The 

AGWA tool, originally constructed in ArcView 3.X, is being 

migrated to ArcGIS 9.X and an Internet-based service (Cate 

and others, 2006) to provide environmental decision-makers, 

resource managers, researchers, and user groups ready access 

to the applications. A variety of new capabilities have recently 

been incorporated into AGWA. They include handling FAO 

soils for international application; pre- and post-fire watershed 

assessments (Goodrich and others, 2005); options for userdefined land-cover change; implementation of stream-buffer 

zones, simulation of nitrogen and phosphorus movement; and 

installation of retention and detention structures. AGWA is 

currently being used for watershed assessment and to support 

watershed planning. Applications include watershed-based 

planning for the Arizona Department of Environmental Quality; assessing the impact of energy development in Wyoming; 

assessing the impacts of landscape change in New York, 

Arizona, Oregon and Virginia (Miller and others, 2004); and 

analysis of alternative futures in the San Pedro River, Arizona 

(Kepner and others, 2005). For more information on AGWA 

visit the AGWA Web site at: http://www.tucson.ars.ag.gov/

agwa/. 

References

Cate, A., Jr., Goodrich, D.C., and Guertin, D.P., 2006, 

Integrating hydrologic models and spatial data in a 

distributed Internet application, in proceedings of the 3rd 

Federal Interagency Hydrologic Modeling Conference, 

Reno, NV, April 2-6, 2006, 6 p. CD ROM

Goodrich, D.C., Canfield, H.E., Burns, I.S., Semmens, D.J., 

Miller, S.N., Hernandez, M.,

Levick, L.R., Guertin, D.P., and Kepner, W.G., 2005, Rapid 

post-fire hydrologic watershed assessment using the AGWA 

GIS-based hydrologic modeling tool, in Moglen, G.E., ed., 

Proceedings of the 2005 ASCE Watershed Management 

Conference, July 19-22, Williamsburg, VA., 12 p., 

CD-ROM.

Kepner, W.G., Semmens, D.J., Bassett, S.D., Mouat, D.A., and 

Goodrich, D.C., 2004, Scenario analysis for the San Pedro 

Automated Geospatial Watershed Assessment (AGWA)—

A GIS-Based Hydrologic Modeling Tool for Watershed 

Assessment and Analysis

By D. Phillip Guertin1 , David C. Goodrich2 , William G. Kepner3 , Darius J. Semmens3, 

Mariano Hernandez2, Shea Burns2, Averill Cate2, Lainie Levick2, and Scott N. Miller2

1

University of Arizona, School of Natural Resources, 325 Biological Sciences 

East, Tucson, AZ 85721. 2

 U.S. Department of Agricultural Research Service, Southwest Watershed 

Research Center, 2000 E. Allen Road, Tucson, AZ 85719. 3

 U.S. Environmental Protection Agency, Office of Research and Development, P.O. Box 93478, Las Vegas, NV 89193.
50 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

River, analyzing hydrological consequences of a future 

environment: Journal of Environmental Monitoring and 

Assessment v. 94, p. 115-127. 

Miller, S.N., Kepner, W.G., Mehaffey, M.H., Hernandez, M., 

Miller, R.C., Goodrich, D.C., Devonald, F.K., Heggem, 

D.T., and Miller, W.P., 2002, Integrating landscape 

assessment and hydrologic modeling for land cover 

change analysis, Journal of the American Water Resources 

Association, v. 38, no. 4, p. 915-929.

Miller, S.N., Semmens, D.J., Goodrich, D.C., Hernandez, 

M., Miller, R.C., Kepner, W.G., and Guertin, D.P., 2007, 

The automated geospatial watershed assessment tool: 

Environmental Modeling and Software, v. 22, no. 3, p. 

365-377. 

Figure 1. The transformation of topography, soils, and land-cover GIS data into KINEROS2 input parameters. A DEM is used to subdivide 

the watershed into upland and channel model elements, each of which are parameterized according to their soil, topographic, and 

land-cover characteristics.

Figure 1. The transformation of topography, soils, and land-cover GIS data into

KINEROS2 input parameters. A DEM is used to subdivide the watershed into upland and

channel model elements, each of which are parameterized according to their soil,

topographic, and land-cover characteristics.
51

Abstract

The effects of flooding cause premature physical deterioration to border infrastructure projects in Ambos [both] Nogales. 

The U.S. and Mexican communities, which make up Ambos 

Nogales, are in the Upper Santa Cruz River Watershed approximately 65 miles south of Tucson. Within Nogales, Sonora, the 

2000 census recorded a population of 159,787 with an annual 

growth rate of 4.9 percent. In 2007, unofficial estimates suggest 

the population is closer to 300,000. The rapid growth of industry and population in Mexico’s northern-border region has put 

increased pressures on State and municipal governments to provide effective and efficient public services, particularly in the 

area of potable water and wastewater infrastructure. Capacity 

issues are further compounded by encroachment of population 

and transportation routes on the floodplains and drainages of 

Nogales Wash and its tributaries. The resulting channelization 

concentrates flows during periods of heavy monsoonal precipitation. These flows erode loose alluvial sediments and disturbed 

soils along the banks of washes. Entrainment of alluvial sediments impacts wastewater infrastructure buried within washes 

with excessive infiltration. Impacted infrastructure generates 

sanitary-sewer overflows and potential disease vectors for the 

populations of Ambos Nogales. The U.S. Environmental Protection Agency (USEPA) has awarded Border Environment (BEIF) 

grants to Ambos Nogales for projects that include the rehabilitation, upgrade, and construction of wastewater-infrastructure 

facilities in these communities. For the projects to be successful 

and sustainable, Nogales, Sonora, needs to consider appropriate 

watershed management and land-use practices. The EPA Border 

2012 Program is one venue that may provide funding to assist 

with this recommendation.

Hydrologic Setting

Nogales Wash is the main drainage conveyance for Ambos 

Nogales watershed. Based on data collected from the Mexican 

Federal Department of Geography and Statistics (INEGI), the 

Sonoran half of the Nogales Wash watershed encompasses an 

area of 68 km2

; an average slope of 13 percent; and a min/max 

elevation of 3,800 and 5,400 ft. The upper end of Nogales Wash 

is in Mexico and is fed by lateral tributaries, with the most significant being El Tecnologico on the west. Nogales Wash runs 

perennially from Sonora to Arizona with a baseflow of 2-3 cfs, 

much of which is supplemented by potable- and wastewaterinfrastructure leaks in Sonora.

Consequences of Monsoonal Flooding

The main wastewater interceptor serving Nogales, Sonora, 

is constructed in the Nogales Wash streambed without anchoring structures. Large runoff events caused by monsoonal 

precipitation dislodge pipe joints, and the pipes fill with sand. 

Most of the broken pipelines are in the main interceptor within 

Nogales Wash; discharges are caused by breaks in the interceptor and subsequent downstream sand obstructions. Finer 

sediments impact the operation and maintenance of the Nogales 

International Wastewater Treatment Plant in Rio Rico, Ariz.

Wastewater infrastructure follows a pattern of unplanned 

development in the upper watershed. During periods of heavy 

precipitation, sand and other obstructions may be introduced 

into subcollectors, which run along streets and lateral washes. 

Heavier sediments settle out in the conveyance where slopes 

flatten usually near or within the main interceptor. Obstructions 

manifest as sanitary-sewer overflows (SSOs) which introduce 

raw sewage into washes and streets. The Nogales, Sonora 

Wastewater Utility (OOMAPAS-NS) works throughout the city 

to implement repairs to impacted infrastructure (fig. 1). 

OOMAPAS-NS also disinfects SSOs that enter the wash 

with chlorine provided by the U.S. International Boundary and 

Water Commission (US-IBWC). The US-IBWC claims to have 

spent more than $90,000 during FY05-06 for disinfection of the 

wash by OOMAPAS-NS staff. Records collected by the Arizona 

Department of Environmental Quality (ADEQ) Border Team 

Hydrologist suggest that Nogales Wash was dosed with 29 tons 

of chlorine in 2005.

During September 2006, Nogales Wash experienced 

extreme runoff contaminated with raw wastewater. There were 

many small breaks in the collection system, but the most significant concern is the Ruiz Cortinez subcollector that conveys 

wastewater for the entire east side of the city. During a visit by 

Causes and Consequences of Monsoonal Flooding in Nogales, 

Sonora

By Hans Huth1 and Dr. Craig Tinney1

1

Arizona Department of Environmental Quality, 400 W. Congress, Ste. 433, 

Tucson, AZ 85701.
52 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

ADEQ on September 11, 2006, the ADEQ Border Team Engineer witnessed more than 1,000 ft of this collector impacted by 

sediment (fig. 2). The specific site was 5 km south of the border 

within Nogales Wash. Although this site does not sustain flow to 

the border, it does add to the contaminate loading of the wash. 

In September 2006, the US-IBWC reported flow rates within 

the wash ranging from 9 to 11 ft3/s, or 5.8 to 7.1 million gal/d. 

Fecal coliform contamination ranged from nondetect to a high 

of more than 2.2 million cfu. The most frequent fecal coliform 

contamination level is in the 200–2000 cfu range. In ADEQ’s 

draft 2006 section 303-d report, Nogales Wash, just north of the 

border, is listed as impaired for fecal coliform and copper.

Mitigation of Monsoonal Flooding

Binational plans made in the late 1990s relied on Nogales, 

Sonora, wastewater projects to alleviate the large uncontrolled, 

raw-wastewater flows that cross the border into Arizona via 

Nogales Wash. The projects are funded through BEIF grants on 

a 50-50 percent match of U.S. and Mexican funds. Although 

the U.S.-funded projects do remove some of the wastewater 

lines from precarious areas, the Mexican-funded portions of 

the rehabilitation may not in many cases. Consequently, the 

integrity of the BEIF projects as a solution to the long-term contamination of transboundary water flows may be compromised 

through weak-link areas in the wash that are impacted by high 

stream-flow events. For this reason, development of appropriate 

land-use, watershed-management, and flood-attenuation plans 

are critical.

In September 2006, the USEPA suggested that the Border 

2012 Water Task Force solicit proposals for physical projects 

that might assist Nogales, Sonora, in mitigating monsoonal 

flooding. One proposal involves healing the slopes of washes 

through engineered sediment-check dams or Rosgen waterretention features. In order to better understand where projects 

might be realized, ADEQ initiated a photographic survey of 

Nogales Wash and its tributaries. Site selection for the survey 

was based on the extraction of stream-order vectors and subwatershed polygons by using INEGI elevation data (fig. 3). These 

data were converted to a Google Earth KMZ file so that hydrography might be superimposed on aerial photographs. Sites were 

then selected for photo documentation based on the locations 

of major tributaries, disturbed soils, and the ranking of subwatershed areas. Respective locations were exported to a global 

positioning system (GPS) for navigation in the field. 

Between September 23, 2006 and March 21, 2007, the 

Border Team Hydrologist collected more than 200 photographs 

tied to more than 50 locations throughout the watershed. Photograph attributes were then exported to a geodatabase for analysis. The survey documented significant encroachment of populations on the floodplain of Nogales Wash and its major tributaries 

at lower elevations (fig. 4), and the conversion of tributaries 

to paved and unpaved roads. This has encouraged downcutting and channelization of drainage features. During periods 

of heavy rainfall, channelization results in concentrated flows 

which erode loose sediments along the banks of washes (fig. 5). 

Given the political challenges posed by established populations 

and transportation vectors within these areas, stabilization of 

loose alluvial materials appears to be the best alternative along 

Nogales Wash and the lower elevations of its tributaries.

Floodplain encroachment is not as significant at higher 

elevations. One example is the large subwatershed on the western side of the basin (fig. 3, subwatershed 17). This subwatershed has an average slope of 15 percent and drains an area of 

7.29 km2

 into a large stock tank known as “La Represa”. The 

stock tank frequently overflows into El Tecnologico Wash, an 

important tributary to Nogales Wash. Similar to Nogales Wash, 

El Tecnologico suffers from sediment deposition in wastewater 

infrastructure (fig. 5). Given the lack of development within this 

subwatershed, this area offers unique opportunities to pursue 

flow-attenuation projects (for example, check dams and/or 

Rosgen features) to help offset flooding and increase infiltration. 

The EPA Border 2012 Water Task Force has identified 

Nogales Wash as a priority and is seeking proposals for physical projects that can help offset impacts of monsoonal flooding 

and sediment deposition within the infrastructure. If you’d like 

more information, please contact the USEPA liaison for the 

Water Task Force, Doug Liden (Liden.Douglas@epamail.epa.

gov), or the ADEQ liaison, Hans Huth (huth.hans@azdeq.gov). 

Additional information on the EPA Border 2012 Program can be 

found at http://www.epa.gov/usmexicoborder/.

Wastewater infrastructure follows a pattern of unplanned development in the upper

watershed. During periods of heavy precipitation, sand and other obstructions may be

introduced into subcollectors, which run along streets and lateral washes. Heavier

sediments settle out in the conveyance where slopes flatten usually near or within the

main interceptor. Obstructions manifest as sanitary-sewer overflows (SSOs) which

introduce raw sewage into washes and streets. The Nogales, Sonora Wastewater Utility

(OOMAPAS-NS) works throughout the city to implement repairs to impacted

infrastructure (fig. 1).

OOMAPAS-NS also disinfects SSOs that enter the wash with chlorine provided

by the U.S. International Boundary and Water Commission (US-IBWC). The US-IBWC

claims to have spent more than $90,000 during FY05-06 for disinfection of the wash by

OOMAPAS-NS staff. Records collected by the Arizona Department of Environmental

Quality (ADEQ) Border Team Hydrologist suggest that Nogales Wash was dosed with 29

tons of chlorine in 2005.

Figure 1. OOMAPAS-NS maintenance

crew addressing impacted infrastructure in

Nogales Wash.

Figure 2. Nogales Wash showing sediment

source on right bank and manholes in the

channel bottom.

Figure 1. OOMAPAS-NS maintenance crew addressing 

impacted infrastructure in Nogales Wash.

Figure 2. Nogales Wash showing sediment source on 

right bank and manholes in the channel bottom.
53

Figure 3. Subwatershed delineations extracted from Mexican Federal Department of 

Geography and Statistics (INEGI) elevation data. Numbers represent drainage area 

rankings. Red and blue indicate east and west subwatersheds, respectively.

Figure 4. Floodplain encroachment and channelization (Colonia 

Virreyes).

Figure 5. Overflow from La Represa erodes soft sediments which impact 

El Tecnologico wash.

Causes and Consequences of Monsoonal Flooding in Nogales, Sonora
54 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

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55

 The Upper San Pedro Basin (USPB) is a ground-water 

system that extends approximately from the Sierra Mariquita 

and Sierra Los Ajos mountains in Mexico through the U.S.-

Mexico international boundary to a bedrock constriction called 

“the Narrows” about 11 miles north of Benson, Ariz. The Sierra 

Vista subwatershed is a surface-water unit within the USPB 

that is bounded on the west by the Huachuca Mountains and 

on the east by the Mule Mountains and Tombstone Hills. The 

southern boundary of the Sierra Vista subwatershed is the 

international boundary with Mexico, and the northern boundary is a watershed divide across the USPB which intersects 

the river at the gaging station near Tombstone, about 1.5 miles 

downstream from the town of Fairbank. The area within these 

bounds includes an alluvium-filled valley with primarily erosional surfaces that slope from the base of the mountains to the 

San Pedro River, which flows north out of Mexico through the 

center of the valley. The basin’s alluvial sediments constitute 

the Sierra Vista subwatershed’s regional aquifer. 

Ground water is the primary source of water for the 

residents of the Sierra Vista subwatershed, which includes Fort 

Huachuca, Bisbee, Sierra Vista, Huachuca City, and Tombstone, Ariz., and for the rural residents of the subwatershed. 

Ground water also sustains the base flow of the San Pedro 

River and supplies an important component of use by the 

associated riparian ecosystem, formally protected through an 

act of Congress as the San Pedro Riparian National Conservation Area (SPRNCA). Water outflow from the Sierra Vista 

subwatershed, including water withdrawn by pumping, exceeds 

natural inflow to the regional aquifer within the Sierra Vista 

subwatershed (U.S. Department of Interior, 2005). As a result, 

ground-water levels in parts of the Sierra Vista subwatershed 

are declining, and ground-water storage is being depleted. In 

the absence of effective management measures, the continued 

decline of water levels and associated depletion of storage will 

eventually diminish ground-water flow to the San Pedro River 

and to riparian vegetation. 

Historically, the USPB has been treated as though a 

hydrologic boundary existed at the U.S.-Mexico boundary; 

ground-water models and management plans generally have a 

boundary near the border. The portion of the basin in Mexico 

was treated as a “black box”, about which little was known, 

and from which an estimated and invariant volume of water 

crossed into the U.S. Recent efforts, including a recently completed USGS flow model, have extended the upstream boundary to hydrologically significant locations in Mexico. 

Inclusion of the Mexican portion of the system into 

hydrologic analysis has resulted in an improved understanding 

of the available data and of what information is lacking. Most 

of the information used to construct the extent and distribution of hydrologic units in the Mexican portion of the system 

came from three sources (1) a hydrologic report (Consultores 

en Agua Subterranea S.A. por Mexicana de Cananea, S.A. de 

C.V., 2000) that provided ground-water hydrographs, well logs, 

and general hydrogeologic information, (2) a model published 

as a thesis (Esparza, 2002) that provided the best information available regarding ground-water withdrawals, and (3) a 

variety of geological and geophysical investigations by USGS 

scientists that provided information to better delineate the 

hydrogeologic framework. These documents allowed delineation of the aquifer and hydraulic properties; however, the part 

of the aquifer on the Mexican side of the USPB is less well 

defined than in the U.S. For example, well logs helped define 

the subsurface lithology, but were insufficient for subdividing 

the aquifer into the multiple units that are defined in the U.S. 

As a result of these and other uncertainties, the new groundwater model included 5 layers on the U.S. side, but only two 

layers on the Mexico side. Additional data in the form of well 

logs and further geophysical analysis would help to better 

describe the hydrogeology of the portion of the basin on the 

Mexican side. Even certain basic issues, such as where mine 

water is pumped and released in Mexico, are not fully understood. In addition, little information is available regarding the 

status of the San Pedro River and riparian system in Mexico. 

The analysis of the USPB as a continuous hydrologic 

system has had the effect of increasing the awareness of decision makers in the Sierra Vista subwatershed about the interconnectedness of the hydrologic system and how upstream 

changes in Mexico might affect management decisions in the 

U.S. Key to that appreciation was the realization of the significant magnitude of pumping that is occurring in the Mexican portion of the basin, owing in large part to mining near 

Cananea. Net ground-water withdrawal in 2002 was 37,400 

acre-feet, of which 21,800 acre-feet was in Mexico and 15,500 

acre-feet was in the United States. 

Sustainability of Water Resources in the Sierra Vista Subwatershed, 

Arizona—Implications of a Cross-Boundary Aquifer

By James M. Leenhouts1 and Bruce Gungle1

1

U.S. Geological Survey, Arizona Water Science Center, 520 N. Park Ave., 

Ste. 221, Tucson, AZ 85719.
56 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

References Cited

Consultores en Agua Subterranea S.A. por Mexicana de 

Cananea, S.A. de C.V., 2000, Actualizacion del estudio 

geohidrologico de las cuencas del Rio San Pedro y norte del 

Rio Sonora en Cananea, Son., 136 p., 5 appendixes.

Esparza, Jose Guillermo De Aguinaga Ruiz, 2002, Modelacion 

geohydrologica del aquifero del Rio San Pedro: Sonora, 

Mexico, Universidad De Sonora, Hermisillo, Professional 

thesis in Geology. 

U.S. Department of Interior, 2005, Water management of 

the regional aquifer in the Sierra Vista Subwatershed, 

Arizona—2004 Report to Congress, 41 p. 
57

Otto von Bismarck reportedly once said, “Laws are 

like sausages, it is better not to see them being made.” I am 

not sure what to make of this remark since law making, not 

sausage making, is my interest. It is an interest that recently 

broadened when I had the privilege of testifying before the 

Water and Power Subcommittee of the House Resources 

Committee on the United States-Mexico Transboundary Aquifer Assessment Act. This bill, numbered S 214 in the Senate 

and HR 469 in the House, gained final approval in the wee 

hours of the 109th Congress and was signed by the President 

on December 22, 2006. My previous involvement in law 

making had been at the state level. 

The program’s purpose is to provide State, National and 

local officials with information to address pressing waterresource challenges in the U.S.-Mexico border region. As 

finalized, the act authorizes the Secretary of the Interior, 

through the U.S. Geologic Survey (USGS), to collaborate 

with the states of Arizona, New Mexico, and Texas, the country of Mexico, and others to conduct hydrologic characterization, mapping, and assessments of priority transboundary 

aquifers. For Arizona, the two priority transboundary aquifers 

established in the legislation are the Santa Cruz River Valley 

and San Pedro aquifers. The program is authorized for ten 

years. 

Working on obtaining Congressional approval of this bill 

was a learning experience. I had once provided written testimony to a Congressional subcommittee, but I had not previously had the opportunity to provide oral testimony. 

Acting USGS director Patrick Lahey and I were the only 

witnesses. Some unexpected, tough questions came up at the 

hearing regarding the bill’s connection to the Colorado River 

and the treaty with Mexico. The Subcommittee chairman held 

the bill to allow additional comments. Through the assistance 

of staff to Senators Kyl and Bingaman amendments to address 

multiple concerns with the bill’s language were developed. 

In contrast to sausage making, which must be a very 

messy business, I was participating in a carefully crafted 

lawmaking process involving compromise and clarification to 

achieve agreement and support. 

As a witness on the bill, I first provided written testimony and then was given a few minutes to present oral 

remarks at the hearing. The oral remarks were not expected to 

be the same as the written testimony. I emphasized the importance of the bill by making the following points.

I testified that the transboundary aquifer assessment 

program will assist Federal, State, and local officials address 

critical water-resource challenges in the U.S.-Mexico border 

region. The act will build the scientific foundation for 

addressing daunting and acute water-resource issues. The 

program also will serve as a catalyst, bringing together the 

human capital and financial resources necessary to characterize transboundary aquifers. The resulting increased understanding should help resolve many of the currently unquantified and, therefore, unresolved water-resource issues.

I emphasized the importance of water to the growing, 

arid Southwest, especially along the border where population continues to grow rapidly on both sides. Water-resource 

issues become more complex and acute along the shared 

border where understanding aquifer characteristics is critical to the human health and economic vitality of this region. 

Along the border many and varied interests need to cooperate 

and participate to address water issues. 

I told how the modeling and data base developed as part 

of the program will address important water-quantity questions including those associated with salinity and toxins. 

Further complicating border water issues are the different 

water-quality standards and the physical relationship between 

surface water and subsurface flows associated with transboundary aquifers that raise special challenges. 

I informed the committee that the need for additional scientific information on water resources is well recognized. For 

example, in fall 2004, the 85th Arizona Town Hall concluded 

that “[to] avoid crisis management, Arizona must engage in 

long-term planning based on good science and data collection 

that should be made widely available throughout the state.” 

Town Hall participants called for sound science and data, as 

well as the dissemination of the information to avoid crisis. 

The program authorized by the bill envisions the partnerships 

necessary to accomplish these tasks.

Front-Row View of Federal Water Lawmaking Shows Process 

Works—U.S.-Mexico Transboundary Aquifer Assessment Act 

Pondered, Passed, and Signed

By Sharon B. Megdal1

1

The Water Resources Research Center, The University of Arizona, 350 North 

Campbell Ave., Tucson, AZ 85719.
58 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

I noted the widespread support for the bill from governmental and non-governmental entities. In addition, a 2005 

U.S.-Mexico Border Governors Conference declaration 

emphasized the importance of the program by calling for a 

collaborative work program that includes “the permanent 

exchange of data and information regarding surface and 

ground water along the border...”.

Passage of the act demonstrated once again that waterpolicy making is a bi-partisan exercise. All recognize the 

need for sound information to develop good water policies 

to ensure needed water supplies to accommodate the rapid 

growth of the border regions. Funding for this newly authorized 

program is needed, and the hard work of obtaining Federal 

appropriations now begins.

The University of Arizona’s Water Resources Research 

Center and its sister centers in New Mexico and Texas are 

expected to work closely with the USGS and collaborators on 

developing this program. I thank those who helped us get this 

far and look forward to working on implementing this legislation . 

More information on the history of the act and its final 

language can be found at the Library of Congress Web site, 

http://www.thomas.loc.gov.

The above is based on Sharon Megdal’s column that 

appeared in the Water Resource Research Center’s bimonthly newsletter, Arizona Water Resource, JanuaryFebruary 2007. 
59

Appendixes
60 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

• Aggers, Lee, U.S. Geological Survey, Denver, Colo.

• Allison, Lee, Director, Arizona Geological Survey, 

Tucson, Ariz.

• Austin, Diane, University of Arizona, Bureau of Applied 

Research in Anthropology, Tucson, Ariz.

• Benjamin, Susan, Chief, U.S. Geological Survey, Western 

Geographic Science Center, Menlo Park, Calif. 

• Berry, Margaret E., Geologist, U.S. Geological Survey, 

Lakewood, Colo. 

• Betancourt, Julio, U.S. Geological Survey, Tucson, Ariz.

• Browning, Dawn, University of Arizona, School of Natu

ral Resources, Tucson, Ariz.

• Callegary, James B., Hydrologist, U.S. Geological Survey, 

Arizona Water Science Center, Tucson, Ariz.

• Case, Harvey Lee, Biologist, U.S. Geological Survey, La 

Quinta, Calif. 

• Chavez, Pat, Physical Scientist, U.S. Geological Survey, 

Southwest Geographic Science Team, Flagstaff, Ariz. 

• Chesley, John, University of Arizona, Department of Geosciences, Tucson, Ariz.

• Crow, Michelle, Representative, Office of Congressman 

Grijalva, Tucson, Ariz.

• Donelson, Angela, University of Arizona, Department of 

Geography, Tucson, Ariz.

• Dos Santos, Plácido, Arizona Water Institute–Arizona 

Department of Water Resources (ADWR), Phoenix, Ariz.

• Eastoe, Chris, University of Arizona, Department Geosciences, Tucson, Ariz.

• Felger, Tracey J., U.S. Geological Survey, Flagstaff, Ariz. 

• Folger, Helen W., Geologist, U.S. Geological Survey, 

Reston, Va. 

• Garate, Don, Tumacacori National Historical Park, Tubac, 

Ariz.

• Gass, Leila, Physical Scientist, U.S. Geological Survey, 

Southwest Geographic Science Team, Tucson, Ariz. 

• Gordon, Leslie C., Geologist/Public Affairs Specialist, 

U.S. Geological Survey, Menlo Park, Calif. 

• Gray, Floyd, Geologist, U.S. Geological Survey, Tucson, 

Ariz. 

• Guertin, D. Phillip, University of Arizona, School of 

Natural Resources, Tucson, Ariz. 

• Gungle, Bruce, Hydrologist, U.S. Geological Survey, Arizona Water Science Center, Tucson, Ariz. 

• Heist, Bruce, National Park Service, Colo.

• Hirsch, Derrick D., Staff Scientist, U.S. Geological 

Survey, Office of the Western Regional Geologist, 

Flagstaff, Ariz. 

• Hoffmann, John P., Assistant Director, U.S. Geological 

Survey, Arizona Water Science Center, Tucson, Ariz. 

• Huth, Hans, Border Programs Coordinator, Arizona 

Department of Environmental Quality (ADEQ), Tucson, 

Ariz.

• Joseph, Bob, Director, U.S. Geological Survey, Texas 

Water Science Center, Austin, Tex. 

• Kepner, William G., U.S. Environmental Protection 

Agency, Las Vegas, Nev.

• Leenhouts, James M., Hydrologist, U.S. Geological 

Survey, Arizona Water Science Center, Tucson, Ariz.

• Light, John, U.S. International Boundary Water Commission Nogales Project, Rio Rico, Ariz.

• Little, Tamarack, Representative, Congresswoman Gabrielle Giffords, Tucson, Ariz. 

• Malmon, Daniel V., Geologist, U.S. Geological Survey, 

Menlo Park, Calif.

• Megdal, Sharon, Director, University of Arizona, Water 

Resources Research Center, Tucson, Ariz. 

• Melchler, Nick, Director, U.S. Geological Survey, Arizona 

Water Science Center, Tucson, Ariz.

• Menges, Chris, Geologist, U.S. Geological Survey, 

Tucson, Ariz. 

• Moring, J. Bruce, Biologist, U.S. Geological Survey, 

Austin, Tex. 

• Norman, Laura M., Physical Scientist, U.S. Geological 

Survey, Southwest Geographic Science Team, Tucson, 

Ariz.

• Page, Ric, Geologist, U.S. Geological Survey, Denver, 

Colo. 

• Papoulias, Diana, Biologist, U.S. Geological Survey, 

Columbia, Mo. 

• Parcher, Jean, Geographer, U.S. Geological Survey, USMexico Border Research, Austin, Tex. 

• Pfeifer, Edwin, Chief, U.S. Geological Survey, Southwest 

Geographic Science Team, Tucson, Ariz. 

• Ruhlman, Jana, Geographer, U.S. Geological Survey, 

Southwest Geographic Science Team, Flagstaff, Ariz. 

• Sass, Sherry, Friends of the Santa Cruz River, Tubac, Ariz. 

• Schwalbe, Cecil, Biologist, U.S. Geological Survey, 

Tucson, Ariz. 

• Stefanov, Jim, Deputy Director, U.S. Geological Survey, 

Texas Water Science Center, Austin, Tex. 

• Updike, Randy, Central Regional Geologist, U.S. Geologi-

- cal Survey, Denver, Colo. 

• van Riper, Charles, Biologist, U.S. Geological Survey, 

Tucson, Ariz. 

• Varady, Bob, University of Arizona, Udall Center, Tucson, 

Ariz. 

• Ward, A. Wesley, Western Regional Geologist, U.S. Geological Survey, Tucson, Ariz. 

• Woosley, Lloyd, Chief Supv. Hydrologist, U.S. Geological 

Survey, Reston, Va.

Appendix 1—List of Participants
61

Facing Tomorrow’s Challenges Along the U.S.-

Mexico Border:

Monitoring, Modeling, and Forecasting Change within the Arizona-Sonora Transboundary Watersheds

A Workshop to Develop a Research Pilot Project in Earth and 

Life Science

March 20-22, 2007

JW Marriott Starr Pass Resort & Spa, 3800 W Starr Pass 

Blvd, Tucson, Arizona

Tuesday, March 20, 2007

08:00 a.m. Registration/Poster Session Set up

09:00 – 09:45 a.m. Introductions, Overview, and Objectives: 

Accomplishments, Desires, Internal/External perspectives

• “Welcome”—Wes Ward, Western Regional Geologist, US 

Geological Survey

• “Overview of the DOI US-Mexico Field Coordinating 

Committee” –Diana Papoulias, FCC Chairperson, Fish 

Biologist, Research, US Geological Survey

• “Status of the U.S.-Mexico Border Health Initiative” –Jim 

Stefanov, Deputy Director, Investigations and Research, 

 USGS Texas Water Science Center

09:45 – 10:30 a.m. Theme Session I: Surficial and Bedrock 

Materials, Resources, and Hazards

1. “Geologic Framework, Hydrologic Monitoring and LandUse Change in the Willcox and Douglas Basins, Southeast 

Arizona”—James B Callegary, US Geological Survey

2. “Sources of groundwater in the Hueco Bolson, Texas and 

Chihuahua: implications of an isotope (O, H, tritium, 

C-14) study in El Paso and the Valle de Juarez”—C.J. 

Eastoe, University of Arizona; B.J.Hibbs, A. Granados O.

3. “Biogeochemical Monitoring of Heavy Metals in SE 

Arizona Food Webs: Sources, Pathways, Deposition, and 

Bioaccumulation” –John T. Chesley, Floyd Gray, Peter 

Reinthal, Joaquin Ruiz, Ailiang Gu, and Chris Eastoe

10:30 – 10:45 a.m. Break

10:45 – 12:00 p.m. Theme Session I continued

4. “Transboundary Cooperative digital geologic map compilation project along the US-Mexico border” by Floyd 

Gray, U.S. Geological Survey and Jesus Jaime Castro 

Escarrega 

5. “Binational geologic map datasets in the Lower Rio 

 Grande area, Texas, Tamaulipas, and Nuevo Leon”—Ric 

Page, Geologist, U.S. Geological Survey

6. “ Techniques of regional-scale mapping of surficial deposits in the border region of southeastern Arizona and southwestern New Mexico, with applications to fluvial interconnectivity and Quaternary drainage history of crossborder hydrologic basins”—Chris Menges, U.S. Geologi-

 cal Survey

7. “The National Park Service Geologic Resource Evaluation 

- Opportunities for mapping in park units along the U.S./

Mexico Border”—Bruce Heise, Geologist, National Park 

 Service

8. “How An Integrated State-Federal Geoscience Information 

Network Can be Applied in the Borderlands.”—Lee Allison, State Geologist, Arizona Geological Survey

9. “Floodplain lakes and their relation to alluvial cycles in 

the lower Colorado River”—Daniel Malmon, Geologist, 

U.S. Geological Survey

12:00 p.m. Lunch Break

1:00 p.m. – 3:00 p.m. Theme Session II: Populations, Urban 

Growth, Infrastructure Health, and Land Use Change

1. “An Approach to Prevent Nonpoint-Source Pollutants and 

Support Sustainable Development in the Ambos Nogales 

Transboundary Watershed”—Laura M. Norman, South

west Geographic Science Center, U.S. Geological Survey 

2. “CHIPS - A New Way to Monitor Colonias along the 

Texas-Mexico Border” –Jean Parcher, Geographer, U.S.-

Mexico Border Research, U.S. Geological Survey

3. “Transboundary Land Cover Change Detection Methods 

- A Consistent Approach” –Jean Parcher, Geographer, 

U.S.-Mexico Border Research, U.S. Geological Survey

4. “Constructing and Maintaining Social Infrastructure for 

the Development of Environmental Projects and Programs 

in Border Urban Communities: The Case of Ambos 

Nogales” –Diane Austin, Bureau of Applied Research 

Anthropology, University of Arizona

5. “Immigration Reform and Quality of Life in Arizona 

and New Mexico Colonias” —Angela Donelson and 

Adrian Esparza, University of Arizona

6. “Comparison of contemporary land-cover trends among 

the Sonoran Basin and Range, Madrean Archipelago, and 

Chihuahuan Deserts Ecoregions.” –Jana Ruhlman, U.S. 

Geological Survey

7. “The detection and mapping of the spatial and temporal 

dynamics of vegetation in arid lands (Mojave and the 

southwest examples)” —Pat Chavez, Southwest 

Geographic Science Center, U.S. Geological Survey

8. “US Mexico Border”—Joaquin Ruiz, Dean, college of 

Science, University of Arizona

3:00 – 3:15 p.m. Afternoon Break

3:15 – 5:00 p.m. Theme Session III: The Role of Environmental Indicators in Determining Impacts, Ecosystem 

Preservation, andClimate Change

1. “Stopover ecology and habitat utilization of migrating land 

 birds in Colorado River riparian forests of Mexico and the 

southwestern United States.”—Charles van Riper III, 

Appendix 2—Workshop Agenda
62 Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border

USGS/SBSC Sonoran Desert Research Station

2. “Lessons learned from the Salton Sea: potential impact 

of dust emission to both air quality and human health” —

Pat Chavez, Southwest Geographic Science Center, U.S. 

Geological Survey

3. “Buffelgrass invasion in the Sonoran Desert with and with

out climate change”—Julio L. Betancourt, Desert Labora

tory, U.S. Geological Survey

4. “Status and issues associated with the restoration of the 

Salton Sea Ecosystem”— Harvey Lee Case, U.S. Geologi-

 cal Survey

5. “Mapping vegetation and endangered species habitat 

across national borders: Insights and perspectives.” Dawn 

M. Browning, Kendal Young, Julie Lanser, and Bruce 

Thompson, University of Arizona

6. “The San Pedro River, a Case Study for Examining Past 

Landscape Change and Forecasting Hydrological and 

Biological Response to Urban Growth and Land Use 

Change”—William G. Kepner; U.S. Environmental 

Protection Agency, Ken Boykin, Darius J. Semmens, 

David C. Goodrich, Christopher J. Watts, and D. Phillip 

 Guertin

7. William G. Kepner, continued

Wednesday, March 21, 2007

0830 – 1030 a.m. Theme Session IV: The Quality and Quantity of Water Resources

1. “Causes and Consequences of Monsoonal Flooding in 

Nogales, Sonora”—Hans Huth, Arizona Department of 

Environmental Quality (ADEQ) Border Programs 

Hydrologist

2. “Defining A Range of Ecologically Relevant Flows for the 

Rio Grande in Big Bend Natl. Park and the Rio Grande 

Wild and Scenic River” –J. Bruce Moring, Biology 

Specialist, Texas Water Science Center, U.S. Geological 

 Survey

3. “Application of the Automated Geospatial Watershed 

Assessment tool (AGWA) on the San Pedro River 

Watershed” –D. Phillip Guertin, Professor, Watershed 

Management, School of Natural Resources, University of 

Arizona

4. “Sustainability of Water Resources in the Sierra Vista 

Subwatershed, Arizona - Implications of a Cross-Boundary 

Aquifer”, James Leenhouts, U.S. Geological Survey 

5. “Navigating Institutional Challenges to Cross-border 

Environmental Policy Research.”—Robert G. Varady, 

Udall Center for Studies in Public Policy, University of 

Arizona

6. “US NORTHERN COMMAND efforts along the Border 

and with Mexican counterparts”—Lee Aggers, U.S. 

Geological Survey

7. “USGS Hydrologic Investigations along the ArizonaSonora Border” –Nick Melcher, Director, USGS Arizona 

 Water Science Center

8. “United States-Mexico Transboundary Aquifer Assessment 

Act” –Sharon B. Megdal, Director,Water Resources 

Research Center, The University of Arizona and Jim 

Stefanov, Deputy Director, Investigations and 

 Research, USGS Texas Water Science Center

10:30 – 10:45 a.m. Break

10:45 – 12:00 p.m. Internal USGS Workshop: Develop an 

“Action Plan”

12:00 p.m. Lunch Break

1:00 – 3:00 p.m. Workshop continues – identify smaller steps 

we need to take in order to accomplish goals (Specific, Performance-related (reflect actions that need to be taken), Involving 

(involve many people’s actions), Realistic, and Observable 

(how will we know when we’ve reached it?)

Action plans should answer the questions: 

1. What needs to be done? 

2. How should it be done? 

3. Who will do it? 

4. By when? 

5. What are the desired results? 

6. How will you know when you’ve succeeded?

3:00 – 3::30 p.m. Afternoon Break

3:30 – 5:00 p.m. Presentations on proposal ideas and commitment

5:00 p.m. End

Thursday, March 22, 2007

Field Trip to Nogales, Arizona

8:00 a.m. Meet at USGS facility on University of Arizona 

Campus and leave Tucson

8:45 a.m. Stop #1—Nogales International Wastewater Treatment Plant, (NIWTP)

Introduction by John M. Light, USIBWC Nogales Project, 

Nogales Project Manager, Rio Rico, Ariz.

9:45 a.m. Stop #2—The Southeast Arizona Area Health Education Center (SEAHEC)

A. Keynote Speaker: Alberto Suàrez Barnett -- City Historian for the Municipal de Nogales (Sonora) “A Brief 

History of Nogales, Sonora and its environmental 

 issues”

B. Estela-Maria Diaz of SEAHEC and students from the 

Nogales High talk about an air quality biodiesel project 

they are involved in.

C. Mexican students working with Diane Austin at the 

Bureau of Applied Research in Anthropology from 

University of Arizona will present following on a water 

harvesting project they are working on with the Asociación de Reforestación en Ambos Nogales (ARAN:

Ambos Nogales Revegetation Partnership).

11:30 a.m. Stop #3—“The Wall”

Floyd Gray identifies surface water crossing point, rail
63

road, and automotive crossings

12:00 p.m. Stop #4—Papachoris’ Zulas Restaurant 

Lunch

1:30 p.m. Stop #5—United Musical Instruments Factory

Floyd Gray presents work done with students from Desert 

View High School to collect water samples around this 

facility in remediation of hazardous substances

2:30 p.m. Stop #6—Tumacácori National Historical Park 

A. “Tour and Orientation”—Don Garate, Interpretative Ranger

B. “Life Along the Santa Cruz River”—Sherry Sass, Treasurer 

 and co-founder of Friends of the Santa Cruz River (FOSCR)

4:00 p.m. Head back to Tucson. (1/2 hour-45 minute drive)
Norman, Hirsch, and Ward—Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border—U.S. Geological Survey Circular 1322