The San Pedro River Case Study:
Using Science to Influence Integrated
Decision-making for Watershed Management
Key words: San Pedro River; watershed assessment; geospatial data; geographic
information systems; landscape characterization; landscape ecology; remote sensing.
Background
Vegetation change in the American West has been a subject of concern throughout
the past century. Major regional shifts in dominant land cover have been reported
in the literature and have largely been attributed to land-use impacts following
human settlement in the 1870s. Other authors have hypothesized historical change
in climate have accounted for vegetation change. Although several studies have
addressed specific aspects of vegetation change in the Southwest, few have attempt-
ed to synthesize the cumulative impacts over a large regional or watershed area.
Human land-use management practices are the most important factor influencing
ecosystem structure and functioning at local, regional, and global scales. Hie type,
magnitude, and distribution of land use is a major factor affecting contemporary
ecological and hydrological condition and directly relates to the ability of the envi-
ronment to provide ecosystem goods and services, e.g. water supply, wildlife habi-
tat, and sustainable forage.
No where have the issues of landscape change and subsequent environmental
impairment been of most concern than in the international watershed of the San
Pedro River. The San Pedro River in northeast Sonora and southeast Arizona has
been simultaneously called one the "Last Great Places" (The Nature Conservancy)
and the "Fourth Most Endangered River System" (American Rivers) in the United
States. For five years, 1995 through 2000, a broad partnership of community and
business leaders, university faculty, and international government researchers and
land managers have worked together to evaluate the consequences of natural and
human-induced environmental change on the Upper San Pedro Watershed. Initially
the San Pedro stakeholders were concerned whether landscape change had
occurred within their community and whether that could be concretely measured
and documented. In particular they were concerned about the stability of ecosys-
tems and their vulnerability to change. As time evolved, community stakeholders
became particularly concerned regarding sustainable endpoints such as water
availability, wildlife habitat, water quality (erosion), and livestock forage
(native grassland).
In response to the community concern, scientists and managers from about 20 U.S.,
4 French, and 3 Mexican agencies and universities created an interdisciplinary,
multi-national, and multi-agency consortium to harness their limited and unique
resources within this geographical initiative. The Semi-Arid Land-Surface-
Atmosphere (SALSA) Program was created and operated on the principle of volun-
tary collaboration whereby researchers and community stakeholders interact with
one another across disciplinary, institutional, and political boundaries to address
environmental problems. The purpose of the SALSA program was to facilitate sci-
entific and decision management interactions and to serve as a platform for research
coordination, data assimilation and synthesis, and information exchange. The ulti-
mate product of the SALSA effort was to develop a comprehensive "knowledge-
base" of data, interpretive information, and tools that will aid environmental deci-
sion-making within the San Pedro community.
The SALSA program sought to accomplish the community objective using both
existing and innovative technologies coupled with sustained cooperation among
scientists and community stakeholder groups. The work was pursued through two
separate but highly interrelated ecosystem components, i.e. water balance and
Office of Research and
Development
National Exposure
Research Laboratory
Environmental Sciences
Division
Landscape Ecology
Branch
For More Information
Contact:
William Kepner
kepner.william@epa.gov
Website:
http://www.epa.gov/
nerlesd1/land-sci/
san-pedro. htm

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The San Pedro River Case Study: Using Science to Influence
Integrated Decision-making for Watershed Management
ecological complexity. Terrestrial water balance deter-
mines water availability, the primary factor limiting
human and wildlife populations in semi-arid regions.
Ecological complexity, e.g. species, habitat, and land-
scape diversity, is a key indicator of environmental
quality and stability. Watersheds comprise well-
bounded hydrological systems, and encompass many
biological and cultural systems of interest. By examin-
ing the water balance and ecological complexity at
the watershed scale, the SALSA results have direct
applicability to environmental management activi-
ties based on community watershed units.
Assessment Methodology and Tools
Traditionally, information for vegetation change has
largely been derived from the technique of repeat
photography or via historic land survey descriptions.
This approach has been primarily qualitative in
nature and focused on small areas or sites of concern.
It is currently possible to measure change over large
areas, such as watersheds or regions, and determine
trends in ecological and hydrological condition using
advanced space-based technologies, e.g. Landsat
earth observing satellites. The San Pedro River com-
munity was interested in examining change through-
out the entire watershed and thus remote imagery
was acquired for four dates (1973,1986,1992, and
1997) over an approximately 25-year period. The
watershed was characterized into a 10-vegetation
class system selected by the stakeholder community
and the derived digital land cover maps were ana-
lyzed in a geographical information system using
ARC/INFO software. Change was analyzed using
landscape statistical software to produce landscape
statistics, including actual total extent throughout
the watershed.
Acquisition of primary data and database develop-
ment are initial features of any landscape indicator
and assessment project. It also became necessary to
develop a geospatial database browser for this proj-
ect. Spatial coverages and the supporting information
(metadata) were organized relative to their geograph-
ical availability and theme and made available for
download in ARC/INFO export format. The informa-
tion was acquired from a number of sources and
includes data generated within the EPA. The metada-
ta include important information relative to acquisi-
tion, location, processing level, file size, formal and
comply with Federal Geospatial Data Committee
standards. The San Pedro Browser (EPA/600/C-
00/002) is currently accessible on-line at the
EPA website (http://www.epa.gov/nerlesdl/
land-sci/san-pedro.htm). Additionally, CD-ROM
copies were produced and distributed to the stake-
holder community.
Study Results and the Role of Science
The experience in the San Pedro watershed demon-
strated the value and the role of using science in the
community decision-making process. The landscape
characterization and change detection work were
published and identified the significant changes that
have taken place in the last quarter century (Kepner
et al. 2000). The information was further used as
input variables for hydrologic response models
which demonstrated the affect landscape change has
on stream runoff (erosion) and loss of ground water
infiltration. Additionally, the information has been
used to model for potential wildlife habitat and has
been preliminary tested for development into a
watershed assessment alias. The Data Browser is cur-
renlly being used by the interagency San Pedro
Partnership Committee as the data source for com-
munity planning and development decisions relative
to watershed protection and wildlife corridors and
thus provides a focus for exchanging ideas and build-
ing consensus on significant environmental issues.
For further information contact:
William G. Kepner
U.S. Environmental Protection Agency
National Exposure Research Laboratory
Environ menial Sciences Division
Landscape Ecology Branch
P.O. Box 93478, Las Vegas, NV 89193-3478
Phone: (702) 798-2193
Fax: (702) 798-2692
E-mail: kepner.williarii@epa.gov
http://www.epa.gov/nerlesdl/land-sci/home2.htm
http ://www. tucson.ars.ag.gov/salsa/salsahome.html
Reference
Kepner, William G., C.J. Watts, C.M. Edmonds,
J.K. Maingi, S.E. Marsh, and G. Luna. 2000. A
Landscape Approach for Detecting and Evaluating
Change in a Semi-arid Environment. Environmental
Monitoring and Assessment 64:179-195.
WEBSITE ANNOUNCEMENT
336I eb 01
SEPTEMBER 2001

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