Land Use Change Impacts on Acequia Water Resources in Northern New Mexico
UNIVERSITIES COUNCIL ON WATER RESOURCES
JOURNAL OF CONTEMPORARY WATER RESEARCH & EDUCATION
Land Use Change Impacts on Acequia Water Resources in Northern New Mexico
Alexander “Sam” Fernald
Terrell T. “Red” Baker
RStates are undergoing rapid and farural areas throughout the western United reaching land use changes that impact water management, riparian ecosystems, and traditional cultures. Areas that have historically been focused on agricultural activities are being converted to various configurations of residential and urban land use (Anella and Wright 2004). Impacts to water resource use and management include: potential risks of ground water contamination due to increased numbers of single household septic systems, potential overdraft of ground water resources, surface water quality impacts, and changes in the distribution of water supplies from agricultural to municipal and industrial uses.
In northern New Mexico, the acequia1 water
use regime and attendant acequia-related cultural
values are at particular risk due to increasing
urbanization pressures and the potential impacts
on actual water use, water quality, and riparian
vegetation along the Rio Grande and irrigation
(Rivera 1998; New Mexico Acequia
Association 2006 )
. In the research we present in this
paper, we employ Geographic Information Systems
(GIS), remote sensing, and aerial photography
interpretation techniques to create a series of land
use maps to assess the impacts of land use change
on critical water resources and local communities
along the Alcalde Reach of the Upper Rio Grande
Basin. Through discussions with acequia members
and examination of related archived documents,
we also began preliminary exploration into cultural
values associated with the acequia system and the
traditional way of rural life. The land use maps
that we generate depict the intersection of land
use changes and the attendant impacts to water
resource use and management – risks to ground
water, changes in acequia management and water
use, and riparian ecosystem impacts. This project
is well suited to provide local and state planning
programs with constructive methods for further
research, and is also applicable to other western
states with similar challenges.
The objective of this research is to examine
land use change across time to assess the potential
impacts of these land use changes on water
resource use and management, the effects on
riparian vegetation communities, and the attendant
changes to acequia cultural values and ways of life
in the study area. The specific research questions
we explore in this project are:
• What is the allocation of land among agricultural,
riparian, housing, and other uses through time?
• What major changes in land use have occurred
in the study area in the last 40 years?
• What impacts have occurred to acequia water
use and management in the area in light of
potential impacts to ground water from septic
tanks and changes in the use and distribution of
acequias as landscape and water management
• What impacts have occurred to riparian
vegetation in the study area as a result of these
land use and water resource use changes?
Details of the Study Area
As detailed in Figure 1, the Alcalde Reach of
the Rio Grande is located in north central New
Mexico. It is a region that is unique in both its
physical and cultural landscapes. Land use along
this reach includes irrigated cropland, rangeland,
riparian vegetation, and small rural communities.
For centuries the acequia system has traditionally
supported agricultural practices in the region.
The irrigated crops grown include alfalfa, apples,
chile, sweet corn, and other crops of regional
importance. Riparian vegetation grows along both
the Rio Grande and along the acequias that are
situated along this reach. Similar to other regions
in northern New Mexico, this region is undergoing
increasing pressures from rapid population growth
to convert agricultural land and acequia delivered
water to other uses. These qualities of the river
reach and the presence of a New Mexico State
University research station in the region make it a
highly appropriate study area.2
Research Approach and Methods
Land use in the Alcalde region was mapped for
the years 1962, 1997, and 2003. By employing
aerial photography interpretation techniques,
we mapped historical changes of land use and
generated digital data layers for further analysis
in the ArcGIS software package. For the 1962
land use, we obtained and scanned historic black
and white aerial photography, which we then
geo-rectified using the geo-referencing tools in
ArcGIS. We employed a similar technique with
digital orthophoto quadrangles obtained through
cooperation with the United States Army Corps of
Engineers to map the 1997 land use. The 2003 land
use was mapped using QuickBird “pan sharpened”
multi-spectral satellite imagery obtained from
Digital Globe, which also required geo-referencing
In addition to the GIS mapping, we
groundtruthed the 1997 and 2003 land uses for clarification
of mapping uncertainties, though some of the land
use classifications in 1997 remain uncertain to some
degree due to the nature of ground-truthing imagery
that is nearly a decade old. To address this issue, we
consulted with Mr. David Archuleta, a long-term
resident of the valley and employee of the New
Mexico State University Alcalde Research Station,
who has been active in acequia management and
operation of the research station. Mr. Archuleta
provided invaluable local knowledge that aided
us in the ground-truthing process. Using the same
mapping process, we also examined changes to
riparian vegetation cover along the banks of the
Rio Grande and along the acequia, with the goal of
exploring the impacts of land use change over time
on the riparian ecosystems.
Examination of land use change over time also
allowed us to explore the potential impacts of the
increase in the use of on-site wastewater treatment
systems on regional ground water resources. The
entire study region is outside of any centrally
managed wastewater collection and disposal
network; accordingly, all increases in residential
land use relie on these on-site systems for
wastewater disposal. On-site wastewater systems
have been acknowledged as a potential source of
risk to ground water aquifers, especially in areas
with shallow depth to ground water
Geary and Whitehead 2001)
The use of GIS to examine a range of water quality
issues has proven useful in past research
specifically examined health
risks due to the interaction of shallow ground
water and agricultural chemicals using GIS tools
in southeastern Pennsylvania. Through the use
of GIS-based cartographic modeling techniques
(Tomlin 1990, 1991)
, we examined the spatial
cooccurrence of these on-site systems with shallow
ground water areas obtained from the WATERS
database compiled and managed by the New
Mexico Office of the State Engineer (New Mexico
Office of the State Engineer 2005). The output of
this analysis shows areas of the underlying aquifer
that are vulnerable to contamination.
Land Use Change
Land uses were classified into six categories:
residential, riparian, orchard, undistinguished row
crop, pasture, and fallow. The mapping results
showed some key land use conversions in the
region, and these changes are detailed in Table 1
and Figures 2 through 4. The total orchard acreage
has changed considerably since 1962. By 1997,
orchards had decreased to 100 acres from 289
acres in 1962, a decrease of approximately 65
percent. The orchard acreage had further decreased
by 2003, encompassing only 88 acres. Similar to
orchards, row crops have also decreased. In 1962,
row crops consisted of 415 acres. In 1997, row
crops made up half of that figure with only 207
acres and, by 2003 there were only 192 acres.
Another major change in the region was residential
land use, which has increased significantly since
1962. Residential land use consisted of 139 acres
in 1962. By 1997 residential land use increased to
639 acres, and the 2003 figure was 908 acres. The
total riparian acreage doesn’t appear to have been
significantly affected by land use change during
this time period. The total riparian cover in 1962
was 436 acres; in 1997 it was 382 acres; and by
2003 it was 420 acres. It is difficult to identify
whether the riparian increase was a result of actual
growth, or if the spatial resolution of the imagery
used for mapping determined these figures. The
main result we see is that the extent of this land
cover classification has not varied more than 10
percent over the time period being examined.
With increasing development in and around
Alcalde and a lack of a centralized wastewater
treatment and disposal system, the water quality in
the region is at potential risk, particularly from the
increased use of on-site septic tank systems. One
objective of our project was to build a framework
with which to determine potential risks to ground
water quality along the Alcalde Reach, using GIS
tools as detailed above in the discussion of methods.
Septic tank data for 2003 extracted from the 2003
satellite imagery was used, as well as data from the
New Mexico Office of the State Engineer and New
Mexico State University Alcalde Science Center,
Natural Resource Conservation Service soils data,
and the United States Geological Survey Digital
Wells that had a depth to water less than 130
feet were selected and, we assumed that wells
deeper than this would not see notable risk from
seepage from on-site wastewater disposal systems.
From this selection we created a new shapefile of
point features with spatially referenced depth to
water data, and we then used the Ordinary Kriging
method of interpolation (Environmental Science
Research Institute 2006) to generate a continuous
depth to water surface. We then converted this
surface to a fill contours shapefile, which was then
converted to a raster file. Finally, we reclassified
this raster based on depth to water values.
The soils data layer was clipped to the study area
polygon that was digitized around the wells layer
to generate a more accurate depth to water surface.
Based on the infiltration characteristics and insight
gained from the work of
Brito et al. (2005)
classified the clipped soils shapefile and converted
it to a raster dataset. We also confirmed that this
dataset was geo-referenced to the other raster data
layers being examined in the GIS analysis.
Two Digital Elevation Models that covered the
study area were downloaded from the seamless.
usgs.gov website and converted to Environmental
Systems Research Institute-compatible raster
datasets. We then used tools within the
Environmental Systems Research Institute Spatial Analyst
extension to generate a surface of slope for the
two Digital Elevation Models, and these files were
merged into one seamless slope raster data file for
the study area.
To generate a surface of aquifer vulnerability, we
completed weighted raster calculations using Map
Algebra routines, specifically, the raster calculator
in the Spatial Analyst extension of ArcMap. To
generate an infiltration surface, we combined the
slope and soil datasets, weighting the slope layer
by a factor of 0.4 and the soils by a factor of 0.6.
The next calculation included both the infiltration
raster and depth to water raster, with the infiltration
surface being multiplied by 0.4 and the depth to
water surface being multiplied by 0.6. The final
step was to overlay the weighted raster datasets
using the raster calculator in ArcMap, which
provided us with the final aquifer vulnerability
areas, as depicted in Figure 5. Inspection of this
map indicates that the sub-regions of the study
area that are at the highest risk largely coincide
with agricultural land use. Accordingly, efforts
at preserving agricultural areas that are already
underway and supported by the region’s residents
may have an additional benefit in preventing large
scale residential development that present risks
to ground water quality due to the use of on-site
wastewater treatment systems.
In the research described in this paper, we
deployed a series of geo-spatial analysis tools to
examine land use change in the Alcalde region of
the Upper Rio Grande Basin from 1962 to 2003,
specifically exploring the potential impacts on
regional water resources and related agricultural
and economic activities. The GIS tools we used
provided a very useful spatial framework and
analysis capability, allowing the integration of
aerial photography, satellite imagery, readily
available Digital Elevation Models, local well
data, and expert local knowledge. The results that
we uncovered include a documented decrease in
row and orchard crops and an attendant increase in
residential development in the area of investigation.
We also developed a relative risk assessment tool
that yielded a map of aquifer vulnerability due to
on-site wastewater treatment systems and shallow
depth to ground water.
The results of this work provide useful insight
into areas where future land use conservation
efforts may yield the greatest benefit, and the
techniques employed in this work may be useful
to other researchers interested in similar questions
in other mountainous regions in the American
Southwest. In future work, we will examine how
the land uses we have documented are impacting
underlying cultural values in the region, with a
special focus on potential insights that may aid in
future cultural preservation efforts.
Funding for this research was provided by the
Office of the Vice President for Research (VPR)
at New Mexico State University, through the
Water Science and Education Center of the Natural
Resources Cluster. We wish to thank the staff of
the VPR’s office at New Mexico State University
for this important financial support, and we also
wish to thank the leadership of the New Mexico
Water Resources Research Institute for support
extended to us in this work. This research would
not have been possible without the assistance
of staff at the New Mexico State University
Alcalde Sustainable Agriculture Science Center in
Alcalde, New Mexico. We also wish to thank Mr.
Alfredo Montoya, Alcalde Acequia Commission
member, and Mr. David Archuleta, Alcalde
Acequia Association member, for their guidance
and assistance. We also wish to acknowledge the
assistance that Ms. Yeliz Cevic and Mr. Tyler
Hannun provided in the aquifer assessment work
that was conducted as part of this project.
Author Bios and Contact Information
MARQUITA ORTIZ is a Graduate Research Assistant in
the Department of Geography at New Mexico State
CHRISTOPHER BROWN is an Associate Professor in
the Department of Geography at New Mexico State
University. He is the corresponding author for this paper
and can be reached at .
ALEXANDER “SAM” FERNALD is an Assistant Professor
in the Department of Animal and Range Sciences at
New Mexico State University.
TERRELL T. “RED” BAKER is an Associate Professor
and Extension Riparian Specialist at New Mexico
Cooperative Extension Service, New Mexico State
BOBBY CREEL is an Associate Director of the New
Mexico Water Resources Research Institute.
STEVE GULDAN is the Director of the Alcalde
Sustainable Agriculture Science Center, New Mexico
An acequia or community irrigation ditch is an
institution common to the native people of the
American Southwest for irrigation
Acequias are usually historically engineered canals
that carry snow runoff or river water to agricultural
fields. Most acequias were established more than
200 years ago and continue to provide a primary
source of water for farming and ranching ventures
in areas of the United States once occupied by
Spain or Mexico. Known among water users
simply as the acequia, an acequia association is
an institution that governs members’ water usage
that is based on local precedents and history. An
acequia organization is lead by a mayordomo or
ditch rider who administers usage of water from a
ditch and regulates which water-rights holders can
release water to their fields on what days
1988 and Norstrand 1992)
2. The NMSU Sustainable Agriculture Science Center
at Alcalde is located directly in the heart of the
study area, and one of the co-authors of this article,
Dr. Steve Guldan, is the Station Director. The
station and staff are parcientes or members of the
Alcalde Acequia Association, and the station enjoys
a strong connection to the acequia water resource
management regime that is the focus of this study.
Annela , A. and J. Wright . 2004 . Saving the Ranch: Conservation Easement Design in the American West . Island Press,Washington DC.
Brito , M. G. , C. N. Costa , J. A. Almeida , D. Vendas , and P. H. Verdial . 2005 . Characterization of maximum infiltration areas using GIS tools . Engineering Geology 85 : 14 - 18 .
Crawford , S. 1988 . Mayordomo: Chronicle of an Acequia in Northern New Mexico . University of New Mexico Press, Albuquerque, New Mexico.
EnvironmentalScienceResearchInstitute(ESRI) . 2006 . Spatial Analyst and ArcMap documentation describing various interpolation routines . ESRI, Redlands, California.
Geary , P. and J. Whitehead . 2001 . Groundwater contamination from on-site domestic wastewater management systems in a coastal catchment . On-Site Wastewater Treatment, Proceedings of the Ninth National Symposium on Individual and Small Community Sewage Systems , 11 -14 March 2001 , pp. 479 - 487 . Fort Worth, Texas.
Harris , P. 1995 . Water quality impacts from on-site waste disposal systems to coastal areas through groundwater discharge . Environmental Geology 26 ( 4 ): 262 - 268 .
Hess , M. 2001 . Spatial Analysis of Breast Cancer Incidence Rates and Well Depths in the Octoraro Watershed . Unpublished Masters Thesis , Department of Geography and Planning, West Chester University, West Chester, Pennsylvania.
Lovato , P. 1975 . The Community Ditch Systems of Northern New Mexico: A Reprint of Las Acequias Del Norte . Water Resources Research Institute Report Number 060.
New Mexico Acequia Association (NMAA) . 2006 . El Congreso de las Acequias. Annual Meeting of Acequia Association members hosted by the NMAA in Taos , NM, 2 December 2006 .
New Mexico Office of the State Engineer (NMOSE ). 2005 . Water Administration Technical Engineering Resource System (WATERS) Online Database , available at http:// iwaters.ose.state.nm.us:7001/iWATERS/, accessed 27 September 2005 .
Norstrand , R. 1992 . The Hispano Homeland , The University of Oklahoma Press, Norman, Oklahoma.
Rivera , J. A. 1998 . Acequia Culture: Water, Land, and Community in the Southwest . University of New Mexico Press, Albuquerque, New Mexico.
Tomlin , C. D. 1990 . Geographic Information Systems and Cartographic Modeling . Prentice Hall, Englewood Cliffs, New Jersey.
Tomlin , C. D. 1991 . Cartographic modeling . In Goodchild, M., D. Maguire and D. Rhind . (Eds). Geographical Information Systems: Principles and Applications . Longman Group Ltd., Harlow , Essex, United Kingdom.