Nogales Flood Detention Study

By Laura M. Norman, Lainie Levick, D. Phillip Guertin, James Callegary, Jesús Quintanar 

Guadarrama, Claudia Zulema Gil Anaya, Andrea Prichard, Floyd Gray, Edgar Castellanos, 

Edgar Tepezano, Hans Huth, Prescott Vandervoet, Saul Rodriguez, Jose Nunez, Donald 

Atwood, Gilberto Patricio Olivero Granillo, and Francisco Octavio Gastelum Ceballos

Open-File Report 2010-1262

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia 2010

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Suggested citation:

Norman, L.M., Levick, L., Guertin, D.P., Callegary, J., Quintanar Guadarrama, J., Zulema Gil Anaya, C., 

Prichard, A., Gray, F., Castellanos, E., Tepezano, E., Huth, H., Vandervoet, P., Rodriguez, S., Nunez, J., 

Atwood, D., Patricio Olivero Granillo, G., and Octavio Gastelum Ceballos, F., 2010, Nogales flood 

detention study: U.S. Geological Survey Open-File Report 2010-1262, 112 p. 

[http://pubs.usgs.gov/of/2010/1262/] 

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

endorsement by the U.S. Government.

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

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

Acknowledgements

The authors wish to thank the International Boundary and Water Commission, United States and 

Mexico, U.S. Section for supporting the research (USGS IBM09A0025/IWO IBM10W0014). 

This project was completed as part of a large collaboration of people including Edward Drusina, 

Roberto Fernando Salmón Castelo, John Merino, Luis Antonio Rascón Mendoza, John Light, 

Israel Diaz Arcos, Monica Audelo, Julio Luna Rodríguez, Chris Scott, Emitt Witt, Agustin 

Varela Orozco, and Alejandro Barcenas. We also want to thank Sofia Grigera, Cynthia Wallace, 

Prasad Thenkabail, Edwin Pfeifer, Susan Benjamin, Peter Stauffer, and Tom Owens for their

timely reviews of this manuscript. 
iv

Contents

Acknowledgements....................................................................................................................iii

Acronyms...................................................................................................................................vi

Conversions...............................................................................................................................vi

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

1.0 Introduction .......................................................................................................................... 1

1.1 KINEROS2........................................................................................................................................ 2

2.0 Watershed Delineation......................................................................................................... 3

3.0 Rainfall................................................................................................................................. 3

4.0 Land Use Map...................................................................................................................... 3

5.0 Detention Features............................................................................................................... 6

5.1 Meetings and Field Trips ................................................................................................................ 8

5.2 Modeling............................................................................................................................................ 9

5.3 Assumptions...................................................................................................................................10

6.0 Results................................................................................................................................11

7.0 Caveats...............................................................................................................................13

7.1 Model Calibration and Potential Error.........................................................................................13

7.2 Human Footprint ............................................................................................................................14

7.2.1 Other Detention Features .....................................................................................................14

7.2.2 Maintenance of Detention Features ....................................................................................15

7.2.3 The “Periférico”.......................................................................................................................16

7.2.4 Other Water Conveyances Discovered During the Course of this Project....................19

8.0 Conclusions ........................................................................................................................21

9.0 Future Work ........................................................................................................................22

9.1 LiDAR ..............................................................................................................................................22

9.2 Precipitation....................................................................................................................................22

9.3 Field Measurements of Detention Features ..............................................................................22

9.4 Water Quality..................................................................................................................................23

10.0 References........................................................................................................................23

Appendix A. Detention feature descriptions and field trip notes............................................25

Appendix B. Detailed results from the study; ink to spreadsheet folder ...................................111

Appendix C. Laser mapping quote for Nogales, Mexico ..........................................................112

Figures

Figure 1. Map of international border between the United States and Mexico with derived 

topographic lines, tributaries, and sub-watershed boundary for the Nogales, Sonora, 

sub-watershed based on 10-meter National Elevation Dataset................................................... 4

Figure 2. A 10-meter resolution land-use map, derived from 2008 aerial photos of the 

Nogales, Sonora, sub-watershed...................................................................................................... 5

Figure 3. Location map depicting detention features (circles shown in various colors), in 

relationship to tributaries and roads in the Nogales, Sonora, sub-watershed............................ 7

Figure 4. Photograph of binational collaborators (from left to right), back row: Gilberto 

Patricio Olivero Granillo, Agustin Varela Orozco, Francisco Octavio Gastelum 

Ceballos, Alejandro Barcenas, Donald Atwood, Jesús Quintanar Guadarrama, Hans 

Huth; front row: Lainie Levick, Claudia Zulema Gil Anaya, and Laura Norman. ....................... 8

Figure 5. Photo of field trip group picture (from left to right): Jesus Quintanar, Claudia 

Gil, Floyd Gray, Saul Rodriguez, Andrea Prichard, Edgar Castellanos, Edgar 

Tepezano. (Photograph by A. Prichard.) ......................................................................................... 9
v 

Figure 6. Photo of Represa Cuesta Blanca from upstream (Photograph by A. Prichard). ........... 12

Figure 7. Hydrograph at the Cuesta Blanca detention feature showing results of 

simulating (A) a 10-year, 1-hour event in current land use scenario and (B) a 100-

year, 6-hour event using the most urbanized scenario................................................................ 12

Figure 8. Photo of the Respreso Cinco de Febrero. (Photograph by H.Huth.)............................... 15

Figure 9. Photo of Represa Las Piedras, which is backed up with sediment (left) and 

whose gabion is deteriorating. (Photograph by H. Huth.)............................................................ 16

Figure 10. Photo of field team standing at the base of the Periférico, in front of a culvert. 

(Photograph by J. Callegary.).......................................................................................................... 17

Figure 11. Photo of measurement in culvert (April 13, 2010) at arroyo under the 

Periférico. (Photograph by J. Callegary.)....................................................................................... 18

Figure 12. Photo of Periférico acting as detention feature. (Photograph by H. Huth.).................. 19

Figure 13. Photo of the start of Nogales Wash looking downstream (Photograph by H. 

Huth.)................................................................................................................................................... 20

Figure 14. Photo of culvert at Arroyo Cocodrilo. (Photograph by H. Huth.).................................... 21

Figure 15. Photo of Maquiladora discharge in Cuesta Blanca; pipes lead from industry to 

wash. (Photograph by H. Huth.)...................................................................................................... 23

Tables

Table 1. Embankment dams identified for modeling in this study. ..................................................... 6

Table 2. Summation of all results from the tributaries analyzed for current land use, 

showing the outflow, peak flow, and the sediment yield in a 10-year, 1-hour event, a 

25-year, 6-hour event, and a 100-year, 6-hour event.................................................................. 13
vi

Acronyms

___________________________________________________________________________________

ADEQ-OBEP: Arizona Department of Environmental Protection- Office of Border 

Environmental Protection

ADWR: Arizona Department of Water Resources

AGWA: Automated Geospatial Watershed Assessment

CILA: 

La Sección mexicana de la Comisión Internacional de Límites y 

Aguas

CONAGUA: Comisión Nacional del Agua

DEM Digital Elevation Model

GIS: Geographic Information System

GPS: Global Positioning System 

IBWC: International Boundary and Water Commission

IMIP: Instituto Municipal de Investigación y Planeación

K2: KINEROS2: Kinematic Runoff and Erosion Model

LiDAR: Light Detection And Ranging 

NED: National Elevation Dataset 

NOAA: National Oceanic and Atmospheric Administration

NORCOMM U.S. Department of Defense's Northern Command

OOMAPAS-NS: Water and Wastewater Utility, Nogales, Sonora

TAAP: Transboundary Aquifer Assessment Project, Tucson, Arizona 

UA-SNRE:

University of Arizona-School of Natural Resources and 

Environment

USACE: U.S. Army Corps of Engineers

USDA-ARSSWRC:U.S. Department of Agriculture-Agricultural Research StationSouthwest Watershed Research Center

USGS: U.S. Geological Survey

Conversions 

1 cubic meter (m3) = 35.314 666 721 cubic foot (ft3) 

1 meter (m) = 3.280 839 895 feet (ft)
Nogales Flood Detention Study

By Laura M. Norman1, Lainie Levick2, D. Phillip Guertin2, James Callegary1, Jesús 

Quintanar Guadarrama3, Claudia Zulema Gil Anaya4, Andrea Prichard5, Floyd Gray1, 

Edgar Castellanos4, Edgar Tepezano4, Hans Huth6, Prescott Vandervoet5, Saul 

Rodriguez4, Jose Nunez7, Donald Atwood7, Gilberto Patricio Olivero Granillo8, and 

Francisco Octavio Gastelum Ceballos9

Abstract

Flooding in Ambos Nogales often exceeds the capacity of the channel and adjacent land areas, 

endangering many people. The Nogales Wash is being studied to prevent future flood disasters 

and detention features are being installed in tributaries of the wash. This paper describes the 

application of the KINEROS2 model and efforts to understand the capacity of these detention 

features under various flood and urbanization scenarios. Results depict a reduction in peak flow 

for the 10-year, 1-hour event based on current land use in tributaries with detention features. 

However, model results also demonstrate that larger storm events and increasing urbanization 

will put a strain on the features and limit their effectiveness. 

1.0 Introduction

The cities of Nogales, Sonora, and Nogales, Arizona, are located across from each other 

along the Mexico-United States border in the Ambos Nogales Watershed, a topographically 

irregular bowl-shaped area with a northward gradient. Throughout recent history, residents in 

both cities have been affected by flooding. The primary means of regulating this runoff is a 

series of detention features in Nogales, Sonora. A detention feature is a stormwater management 

facility. Many of these features have proven inadequate in the face of rapidly increased urban 

growth, and land managers on both sides of the border seek information to increase the 

effectiveness of detention features by optimizing future locations. In addition, managers seek to 

understand and characterize the impact of various land cover types on local runoff to mitigate 

flood hazards through informed land-use planning strategies.

 

1

 U.S. Geological Survey (USGS), Tucson, Ariz.

2

University of Arizona, School of Natural Resources and the Environment, Tucson, Ariz.

3 La Sección mexicana de la Comisión Internacional de Límites y Aguas (CILA; Mexican 

Section of the International Boundary and Water Commission), Nogales, Sonora 

4 Instituto Municipal de Investigación y Planeación (IMIP; Municipal Institute for Research and 

Planning), Nogales, Sonora 

5

 University of Arizona, Transboundary Aquifer Assessment Program (TAAP), Udall Center for 

Studies in Public Policy, Tucson, Ariz.

6

 Arizona Department of Environmental Protection- Office of Border Environmental Protection 

(ADEQ-OBEP) , Tucson, Ariz.

7

 U.S. Section of the International Boundary and Water Commission (IBWC), El Paso, Tex.

8

 Comisión Nacional del Agua (CONAGUA; National Water Commission), Hermosillo, Sonora 

9 Organismo Operador de Agua Potable Alcantarillado y Saneamiento (OOMAPAS; Water and 

Wastewater Utility), Nogales, Sonora
2 

One way to capture and visualize the impacts of detention features and land use in a 

watershed is through hydrologic modeling. The KINEROS2 (K2), with the Automated 

Geospatial Watershed Assessment (AGWA) 2.0 geographic information system (GIS) interface, 

is one such model that can be used to identify flood-prone areas, simulate the impact of land-use 

change, and evaluate the impact of potential flood-control interventions (Woolhiser and others, 

1990). Using relatively coarse-scale input data, Norman and others (2010a) employed the K2 

model to evaluate the Ambos Nogales watershed's vulnerability to flooding. 

The demonstration of this model’s utility to simultate potential flooding impacts 

prompted the International Boundary and Water Commission (IBWC) to implement a higher 

resolution study on the impacts of the detention features that have been constructed in Nogales, 

Sonora. The refined modeling provides a more accurate understanding of the volume of water 

being detained by these features under various scenarios and the magnitude of discharge for the 

return periods studied—10, 25, and 100 years. The modeling also provides a way to capture the 

impact of rapid land-use changes in Nogales, Sonora. The city is growing rapidly without much 

regard to slope, location of washes, or infrastructure capacity. Within Nogales, Sonora, the 2000 

census recorded a population of 159,787, with an annual growth rate of 4.9 percent. In 2009, 

unofficial estimates suggest the population is closer to 300,000. On the basis of urban growth 

scenarios predicted by Norman and others (2009), the SLEUTH model predicted that the 

Nogales, Sonora, urban area would grow to almost 3.5 times its 2002 size by 2030. 

This study reports the results of K2 modeling in Ambos Nogales using higher resolution 

data on land cover, land use, and detention-feature geometry. The resulting information can be 

used in planning flood management for the twin-cities area of Ambos Nogales.

1.1 KINEROS2 

Although several models exist for watershed modeling, the KINEmatic Runoff and 

EROSion model (KINEROS2; K2) has advantages because it can be adapted to visualize impacts 

of urban development or detention features on a watershed. K2 is a physically based hydrologic 

model that represents watersheds by a cascade of overland-flow planes and channels. 

Representing spatial variation of rainfall, infiltration, runoff, and erosion parameters can all be 

accommodated. We chose K2 for this study because it can simulate increasing impervious 

surfaces or land-use changes that influence the volume of water that runs off and the amount of 

sediment that can be moved in a watershed while precipitation remained constant and spatially 

uniform (Woolhiser and others, 1990; Smith and others, 1995). K2 has also been extensively 

tested in southern Arizona and should be suitable for the Nogales watershed. Data required to run 

K2 are as follows: 

1. Watershed delineation: Watershed boundaries and topography control the direction of 

water flow across the landscape. 

2. Rainfall: The amount, distribution, intensity, and duration of rainfall determines the total 

amount of water redistributed and processed by the watershed for a given event. 

3. Land use: The type of land cover affects the flow of water locally because of friction and 

infiltration. Impermeable surfaces, such as rooftops and pavement, increase runoff 

amounts in urban areas. 

4. Detention features: The location and geometry of detention features modify flow within 

the stream channel.
3 

Given these inputs that describe initial conditions, the K2 model will output a hydrograph that 

predicts flow at any specified stream location. Development of the various input layers for this 

study is described below. 

2.0 Watershed Delineation

We chose to model the sub-watershed of the Ambos Nogales that has the pedestrian 

border crossing point as its outlet, because this feature has significantly modified the hydrology 

and most of the detention features are located upstream from this crossing. We accessed the 

National Elevation Dataset (NED) elevation data product produced and distributed by the United 

States Geological Survey (USGS) through The National Map Seamless Server 

(http://ned.usgs.gov/) at a resolution of 1/3 arc-second (approx. 10 m.) for the Nogales study 

area. The NED data are considered to be the "best available" data from the USGS. Contours were 

created for 10-meter and 90-meter intervals. Based on hydrological modeling processes within 

the GIS, streams were mapped for the study area as described below. The Nogales Wash 

originates 6.72 miles (10.83 km) south of the border. Using these data and the known border 

crossing point for pedestrians, an outlet was selected and a sub-watershed delineated using the 

AGWA 2.0 platform. The main branch of the Nogales Wash has a contributing area in Nogales, 

Sonora, of 25.79 square miles (66.8 km2

) that discharges into Nogales, Arizona (fig. 1). Actions 

to control and regulate dangerous flows into the urban areas of Ambos Nogales are being carried 

out primarily upstream in Mexico within this sub-watershed. 

3.0 Rainfall 

Rainfall was modeled as spatially uniform across the watershed, so that it is not a 

complicating factor when the objective is assessment of land-use/cover change. Variations of 

homogeneous-design storms were dictated by the National Oceanic and Atmospheric 

Administration (NOAA) Atlas 14 for Arizona (Bonnin and others, 2006). Precipitation depth 

(inches) was extracted at site—Nogales, Arizona (Site no. 02-5921): latitude 31.35°N and 

longitude 110.9167°W (3,907 ft) from Bonnin and others (2006) and used in the model. A 

variety of rainfall events for K2, including a 10-year 1-hour (1.82 in.), a 25-year 6-hour (2.93 

in.), and a 100-year 6-hour (3.76 in.) flood event were used to investigate the relative impacts of 

land cover change on short versus long return period storms. 

4.0 Land Use Map 

A heterogeneous land cover dataset developed by Norman and Wallace (2008) for the 

original K2 modeling of the Ambos Nogales watershed, derived from 60-m resolution Landsat 

imagery aquired on October 7, 1992, was too coarse to support input needed for calculating the 

hydrological parameters of a small watershed and associated detention features. A higher 

resolution land-use map was developed for this project using 1-m. resolution aerial photos of 

Nogales, Sonora, aquired in 2008 (fig. 2). A paper describing the production of this 10-m. landuse map and descriptions of the procedure employed to test its accuracy using recent orthophotos 

of the Nogales, Sonora, watershed was published in July 2010 (Norman and others, 2010b). 
4 

Figure 1. Map of international border between the United States and Mexico with 

derived topographic lines, tributaries, and sub-watershed boundary for the Nogales, 

Sonora, sub-watershed based on 10-m. National Elevation Dataset.
5 

Figure 2. A 10-meter resolution land-use map, derived from 2008 aerial photos of the 

Nogales, Sonora, sub-watershed.
6 

5.0 Detention Features

A detention feature consists of an embankment dam and associated upstream basin

installed in a stream to protect against flooding and downstream erosion. Detention basins are 

designed to store runoff volume and discharge it slowly to reduce the peak discharge 

downstream, reducing associated flash-flood hazards. An embankment dam is an artificial water 

barrier typically created by the compaction of various compositions of soil, sand, clay, and/or 

rock with a semipermanent waterproof natural covering. Water is transmitted through these

features via culverts or tunnels built within the base of the dam. 

Embankment dams typically come in two types: the earthen dam and the rock-filled dam.

Within the Nogales, Sonora, sub-watershed, some new dams are being constructed and some are 

being rehabilitated by Mexico's National Water Commission (CONAGUA). In addition, a rockfilled (gabion-type) flood detention feature, made like caged rip-rap, is being used in the City of 

Nogales. This differs from the other detention features as it is porous and constructed across the 

banks of the streambed and works to attenuate flash floods. Locations for the installation of 

gabion-type flood detention features to reduce flood-stage discharges in washes are based on the 

recommendations of the U.S. Army Corps of Engineers using the HEC-RAS model (U.S. Army 

Corps of Engineers, 2005). 

In this study, we modeled the impacts of the various types of detention features in terms 

of changes in peak flow and discharge in cubic meters per second. Locations and descriptions 

were provided by Gilberto Patricio Olivero Granillo, Claudia Zulema Gil Anaya, Monica 

Audelo, and Julio Luna Rodríguez (table 1; see also fig. 3 and appendix A). For modeling 

purposes, the San Carlos Dique 1 and Dique 2 earthen dams were simulated as one feature 

because they are located close together. The Villa Sonora 1 and 2 earthen dams were also 

combined because they are located close together. With these dams combined for the modeling, 

there were a total of 10 locations simulated.

Table 1. Embankment dams identified for modeling in this study.

_____________________________________________________________________________________

Rock Gabion Dams being constructed by the 

City: 

• Capulines 

• Cuesta Blanca 

• Bellotas Fraccionamiento 

• Bellotas Maquiladoras 

• Chimeneas 

Earthen dams being rehabilitated by 

CONAGUA: 

• Represa Chimeneas 

• Represa Villa Sonora 1 & 2

• Represa Pirinola 

• Represa Unison II 

Earthen dams being constructed by the City: 

• San Carlos Dique 1 & 2

_____________________________________________________________________________________
7 

Figure 3. Location map depicting detention features (circles shown in various colors), in 

relationship to tributaries and roads in the Nogales, Sonora, sub-watershed.
8 

5.1 Meetings and Field Trips 

A series of meetings and field trips began the process for collecting necessary data for the 

modeling of the detention features. A kick-off meeting was held on January 19, 2010, in 

Nogales, Arizona, at which a presentation was delivered with simultaneous translation (Spanish 

and English) describing the modeling effort being funded by the IBWC and the measurements 

that were collected at each site (fig. 4). An agenda was distributed prior to and a worksheet was 

distributed at the meeting for colleagues to fill out and mail back (appendix A). 

Figure 4. Photograph of binational collaborators (from left to right), back row: Gilberto 

Patricio Olivero Granillo, Agustin Varela Orozco, Francisco Octavio Gastelum Ceballos, 

Alejandro Barcenas, Donald Atwood, Jesús Quintanar Guadarrama, Hans Huth; front 

row: Lainie Levick, Claudia Zulema Gil Anaya, and Laura Norman.

Field trips were planned for researchers from the USGS to travel to Nogales, Sonora, to 

acquire measurements and photographs but were postponed several times because of travel 

restrictions and violence in the study area. Three trips were finally taken (summarized below); 

the detention-feature diagrams, measurements taken, and photographs are available in appendix 

A. 

On March 24, 2010, Andrea Harrop Prichard and Prescott Vandervoet from the 

University of Arizona, Udall Center for Studies in Public Policy, and researchers for the 

Transboundary Aquifer Assessment Program (TAAP) surveyed the Chimineas and Represa

Chimineas features with engineers and technicians from IMIP (Claudia Gil, Edgar Castellanos, 

and Edgar Tepezano) and OOMAPAS.

On April 13, 2010, James Callegary and Floyd Gray (USGS), and Hans Huth (Arizona 

Department of Environmental Quality) visited Nogales. Jesus Quintanar facilitated the visit. Ing.

Claudia Gil helped with the visit with Edgar Castellanos and Edgar Tepezano. Of the basins used 

in this model only the Represa Pirinola was surveyed during this trip.

On May 19, 2010, Floyd Gray and Andrea Prichard made a final reconnaissance field trip 

to the detention features in Nogales, Sonora, with Ing. Gil, Quintanar, Rodriguez, Tepezano, and 

Castellanos (fig. 5). The detention features of Maquiladoras (also called Maquillas), Bellotas, 

Capulines, Represa Villa Sonora, Represa Unison II, and Cuesta Blanca were all surveyed during 

this trip.
9 

Figure 5. Photo of field trip group picture (from left to right): Jesus Quintanar, Claudia 

Gil, Floyd Gray, Saul Rodriguez, Andrea Prichard, Edgar Castellanos, Edgar Tepezano. 

(Photograph by A. Prichard.)

5.2 Modeling 

Following on Milczarek and others (2004) and Norman and others (2010a), we used the 

AGWA 2.0 tool to parameterize the K2 model to simulate the impacts of the detention features 

and land use. The internal gages function was used in the AGWA tool to represent the location of 

the detention features. This effectively subdivides the watershed at each detention feature 

location, permitting evaluation of flow at that location. 

The AGWA Land Cover Modification Tool generates a multifractal surface with multiple 

land cover types. The result is a surface consisting of spatially randomly distributed patches 

within any polygon area defined by the user. This was used to convert the watersheds above each 

detention feature to “developed” land for the future land-cover simulations. Two modified land 

covers were created for each watershed: “Urb1,” with open space preserved (33 percent

developed open space, 33 percent developed low intensity, and 34 percent developed medium 

intensity) and “Urb2,” with no open space preserved (33 percent developed low intensity, 34 

percent developed medium intensity, and 33 percent developed high intensity). 

These three land use scenarios were modeled with and without the detention feature for 

all three design storms at each of the 10 embankment dam locations, totaling 174 simulations. 

Each location was simulated for all conditions, except Maquilas, which is already developed and 

was simulated only for current land use and the “Urb2” land use. The Pirinola rock gabion dam 

is located within the watershed (upstream) of the Nogales/San Carlos Dique 1 & 2 earthen dams; 

therefore it is included in the results for Dique 1 & 2. The Chimeneas rock gabion dam is located 

within the watershed (upstream) of the Chimeneas earthen dam and is likewise included in the 

results for the earthen dam. 
10

1) Current Land Use (Norman and others, 2010b) 

i) Without any detention feature 

(a) 10 year 1 hour 

(b) 25 year 6 hour, and 

(c) 100 year 6 hour storms. 

ii) With the dam 

(a) 10 year 1 hour 

(b) 25 year 6 hour, and 

(c) 100 year 6 hour storms. 

2) “Urb1”: 33 percent developed open space, 33 percent developed low intensity, and 

34 percent developed medium intensity

i) Without any detention feature 

(a) 10 year 1 hour 

(b) 25 year 6 hour, and 

(c) 100 year 6 hour storms. 

ii) With the dam 

(a) 10 year 1 hour 

(b) 25 year 6 hour, and 

(c) 100 year 6 hour storms. 

3) “Urb2”: 33 percent developed low intensity, 34 percent developed medium intensity, 

and 33 percent developed high intensity

i) Without any detention feature 

(a) 10 year 1 hour 

(b) 25 year 6 hour, and 

(c) 100 year 6 hour storms. 

ii) With the dam 

(a) 10 year 1 hour 

(b) 25 year 6 hour, and 

(c) 100 year 6 hour storms. 

5.3 Assumptions

• The location of each dam is as close as possible to the actual location based on our 

Digital Elevation Model (DEM; USGS seamless 10-m DEM) but is not always 

modeled at the exact global positioning system (GPS) coordinates. In those cases 

where the GPS locations did not align with the DEM-derived channel locations, the 

points were shifted to fall within the DEM-derivations for predictive modeling. 

• Unless other information was provided, the rock gabion dams and earthen dams were 

modeled as uniform structures with a smooth overflow spillway spanning (1) the 

entire width of the structure for the rock gabion dams or (2) the width of the apparent 

channel for the earthen dams. 

• The banks on each side of the rock gabion dams were assumed to lie at a 45o angle.

This was used in the calculations to determine the width of the channel at the dam 

where the water would flow. 

• The relations between depth of water in the detention ponds behind the dams and the 

discharge out of the dams were input to the model as a stage-discharge rating curve.
11

This information was derived from the 10-m DEM and the total dam height and 

includes total basin volume, total basin depth, and top and bottom surface areas. The 

DEM-derived storage and discharge from the modeling effort matched fairly well 

with what had been provided by IMIP, CONAGUA, and CILA (appendix A). 

• Also, it is important to note that, judging from the photos of the Maquilas detention 

feature, it is filled nearly to the top with sediment and will not perform properly until 

it is cleaned out. We simulated it with its full design height of 4 m. 

6.0 Results 

A hydrograph depicts changes in the discharge of each arroyo/wash measured at the 

embankment dam over time; it is a representation of how a watershed responds to rainfall. The 

final hydrographs depicting each of the 10 locations (12 features) are available in appendix B.

There are nine hydrographs for each location (six for Maquilas) that show the outflow with and 

without the dam and with different design storms so the effect of the dam can be visualized.

These results were also summarized into a table (available in appendix B) describing the outflow 

in cubic meters, the peak flow in cubic meters per hour, and the sediment in kilograms for each 

scenario approximately 150 m downstream of the detention feature, and also describing the 

predicted difference the dam makes.

The hydrographs demonstrate temporal variability of runoff for the selected design 

storms (a 10-year 1-h (1.82 in.), a 25-year 6-h (2.93 in.), and a 100-year 6-h (3.76 in.)), as 

described earlier. The AGWA tool distributes rainfall uniformly over the watershed based on a 

synthetic hydrograph. This is distributed in two-minute time steps for the duration (that is, 6 

hours), and the model is run for 200 minutes after rainfall ends. 

For example, the rock gabion dam being constructed by the City known as Cuesta Blanca 

is pictured below in good maintenance (fig. 6). 

Cuesta Blanca is one of the largest embankment dams in the sub-watershed and has the 

largest total storage of the rock-gabion types there. For a 10-year, 1-hour event, the volume of 

water stored behind the dam was calculated by the model to be approximately 60,000 cubic 

meters (m3

; appendix B); this volume exceeds that of the other rock-gabions in the subwatershed by more than 40,000 m3

. In the 10-year, 1-hour event modeled using the current landuse scenario, the hydrograph shows that there is enough storage behind the dam to reduce peak 

flow by more than 50 percent and to delay the timing slightly (fig. 7A). In the 100-year, 6-hour 

event with the maximum urbanization (Urban 2) scenario, results show that because of the 

increased urbanization and consequent increase in runoff, there is a slight offset or delay in peak 

flow (long enough to fill the dam), but in a flood of this magnitude even the presence of this 

dam, largest of the rock gabions, has little effect on peak discharge (fig. 7B). 
12

Figure 6. Photo of Represa Cuesta Blanca from upstream (Photograph by A. Prichard).

A , B 

Figure 7. Hydrograph at the Cuesta Blanca detention feature showing results of 

simulating (A) a 10-year, 1-hour event in current land use scenario and (B) a 100-year, 

6-hour event using the most urbanized scenario.

In general, the results shown in appendix B demonstrate that the detention features under 

current conditions of urbanization will reduce the peak flow slightly for the 10-year, 1-hour 

event but have less impact during the larger two storm events. When simulated with the 

increased urbanization scenarios, the detention features have little effect and provide only a 

0

20

40

60

80

100

120

140

0 60 120 180 240

outflow (m3/s)

time (min)

Cuesta Blanca 10yr 1hr event

Current Land Use

no dam

with dam

0

20

40

60

80

100

120

140

0 60 120 180 240 300 360 420 480 540

outflow (m3/s)

time (min)

Cuesta Blanca 100y 6h event

Urb2 Land Use

no dam

with dam
13

slight delay in peak flow (minutes) while storage behind the detention features is filled. 

Unsurprisingly, the most effective features are those that are larger in size. 

The research identifies some potential impacts that could be felt at the border fence 

(watershed outlet). Without consideration of the interaction with other tributaries or land barriers, 

the maximum impacts of the features for tributaries analyzed in this study were summed based 

on current land use (table 2). These figures show: 

i) The total potential impact from installing the detention features of concern could 

reduce the total outflow from these locations by 19 percent in a 10-year, 1-hour event, 

by 15 percent in a 25-year, 6-hour event, and by 13 percent in a 100-year, 6-hour 

event, 

ii) the peak flow from these locations would be reduced by 46 percent in a 10-year, 1-

hour event, by 44 percent in a 25-year, 6-hour event, and by 41 percent in a 100-year, 

6-hour event, and 

iii) the sediment yield from these locations would be reduced by 61 percent in a 10-year, 

1-hour event, by 61 percent in a 25-year, 6-hour event, and by 60 percent in a 100-

year, 6-hour event. 

Table 2. Summation of all results from the tributaries analyzed for current land use, 

showing the outflow, peak flow, and the sediment yield in a 10-year, 1-hour event, a 25-

year, 6-hour event, and a 100-year, 6-hour event. 

Channel 

below dam

2utflow 

(m3) 

Peak flow 

(mm/KU) 

 Sediment 

yield (kg)

10 year- w/out dam 

477,136.59 549.71 44,064,895.50 

1 hour w/ dam 

386,575.13 294.78 17,021,843.53

difference 

90,561.46 254.93 27,043,051.97

25 year- w/out dam 

554,098.93 607.33 52,360,957.90

6 hour w/ dam 

471,640.89 337.97 20,173,279.62

difference 

82,458.04 269.36 32,187,678.28

100 year- w/out dam

938,204.12 926.64 106,436,249.70

6 hour w/ dam

817,198.78 543.88 42,613,551.00

difference

121,005.33 382.76 63,822,698.70

7.0 Caveats 

7.1 Model Calibration and Potential Error 

Accurately measured stream-flow data are essential for establishing whether a hydrologic 

model is providing reasonably accurate runoff estimates (Miller and others, 2002). In Ambos 
14

Nogales, there are no flow gages for calibration and validation. Therefore, AGWA 2.0 results are 

best suited for relative change analysis or watershed-to-watershed comparisons (Goodrich and 

others, 2006). Like most models, AGWA 2.0 is also subject to the assumptions and limitations of 

its components, input data, and of course, its users. For example, soil saturation and geology are 

not included in this model, and soil type (clay, sand, or other) and precipitation (distribution of 

rainfall rates and locations) inputs are very low resolution. These are all factors that affect stream

flow and would vary real-time measurements. In addition, the stage-discharge curves for the 

detention features were estimated on the basis of the 10-m DEM. Therefore the model-calculated

storage volume and discharge may not reflect actual conditions. Because of this, the data shown 

above in table 2, and in appendix B, should be used as relative change estimates and not as 

absolute values. 

7.2 Human Footprint 

People living within Nogales, Sonora, have affected the landscape as part of their

everyday life. These anthropogenic manipulations are not included in the modeling effort, but 

they have significant effects on actual runoff. 

7.2.1 Other Detention Features 

Many more detention features, or represas, were identified in the sub-watershed than 

were modeled in this study. Their absence from the model has consequences on the flood 

detention being estimated. For example, Cinco de Febrero is rumored to experience major 

flooding during monsoon but this detention feature was not included in this study (fig. 8). 
15

Figure 8. Photo of the Respreso Cinco de Febrero. (Photograph by H.Huth.)

7.2.2 Maintenance of Detention Features

Detention features require regular maintenance to detain water in flood events. 

Maintenance includes clearing debris, sediment buildup, and dead vegetation, structural 

maintenance of stone rip-rap, and vegetation regeneration on adjacent hillslopes. Detention 

features cannot operate at full capacity if their maintenance is compromised (fig. 9). 
16

Figure 9. Photo of Represa Las Piedras, which is backed up with sediment (left) and 

whose gabion is deteriorating. (Photograph by H. Huth.)

7.2.3 The “Periférico” 

There are a number of features that have significant potential to alter flood peaks and 

flow routing that were only discovered by chance while traveling to survey known detention 

features. For example, there is a major highway being developed, the Periférico (a bypass around 

the city), which is not considered in this model. Large piles of dirt deposited in the canyons to 

accommodate the foundation for this road will act like earthen dams in the arroyo when it rains. 

Erosion and gully formation at the platform might deteriorate the structure and contribute to reshaping the arroyo (fig. 10). 
17

Figure 10. Photo of field team standing at the base of the Periférico, in front of a culvert. 

(Photograph by J. Callegary.)

Although planners have accommodated some potential flow at this location by 

developing the feature with a culvert (approximately 3 feet in diameter), it was observed to be 

half filled with sediment—before the monsoons had even arrived (fig. 11). 

The potential effects of the earthen dams along the Periférico on flash flooding in the 

arroyos could be detention upstream and/or overflow that would affect the road, the arroyo, and 

the people downstream (fig. 12). These structures were not included in the modeling exercise 

described and therefore would need further study. 
18

Figure 11. Photo of measurement in culvert (April 13, 2010) at arroyo under the 

Periférico. (Photograph by J. Callegary.)

 
19

Figure 12. Photo of Periférico acting as detention feature. (Photograph by H. Huth.)

7.2.4 Other Water Conveyances Discovered During the Course of this Project 

The city, state, and country planning organizations have transportations networks historically 

routed in floodplains of the Nogales Wash (fig. 13). Some tunnels have been developed to route 

water under streets, and these features were not included in the model. One example is the 

culvert at Arroyo Cocodrilo (fig. 14), which splits downstream, sending some flow to the main 

branch of Nogales Wash (west branch) and some to the Grand Avenue tunnel (east branch). This 

information implies that the west branch drains a greater area than that delineated from the 

elevation data we used to derive our watershed, and this was not considered in this study. Other 

backyard fencing, buildings, stone walls, and ditch digging are also not included in this study but 

would have impacts on flow. 
20

Figure 13. Photo of the start of Nogales Wash looking downstream (Photograph by H. 

Huth.)
21

Figure 14. Photo of culvert at Arroyo Cocodrilo. (Photograph by H. Huth.)

8.0 Conclusions 

Floods resulting from convective precipitation (intense thunderstorms) are common in 

Ambos Nogales. The flooding exceeds the capacity of the river channel and endangers land areas 

used by many people. Although flood damage could be eliminated by moving buildings away 

from the Nogales Wash and its tributaries, the fact that people continue to inhabit areas 

threatened by flood damage is evidence that the perceived value of living downtown exceeds the 

cost of repeated periodic flooding. Effects of flooding include (a) physical damage (to, for 

example, bridges, houses, cars, buildings, sewer systems, roadways), (b) mortalities (for 

example, through drowning, epidemics, and waterborne disease), (c) contamination of water 

(limiting drinking water), (d) diseases (resulting from unhygienic conditions), (e) damage to 

vegetation (including crops), and (f) economic hardship (such as temporary decline in tourism 

and rebuilding costs). 

The Nogales Wash is being studied to prevent flood disaster. The detention features being 

installed around the perimeter are a good starting defense but often are overwhelmed by flood 

water and require emergency measures such as pumping the detention ponds. The results of this 

modeling exercise will help land managers understand the impact of the detention features under 

various flood and urbanization scenarios. We demonstrate that detention features at current

levels of urbanization will reduce the peak flow for the 10-year, 1-hour event but will have less
22

effect during the larger storm events or when under increased urbanization scenarios. More 

research to address some of the caveats associated with this study is described in the next section 

(Future Work). 

In the summer of 2010, the 10-year events have caused emergency evacuation notices in 

Nogales, Arizona, and the state of Arizona declared a ‘state of emergency.’ Urbanization in 

Nogales is inevitable. It seems that a greater effort could be made to thwart danger associated 

with larger precipitation events in the future, especially for those people who do not have flood 

insurance. This may include investing in the construction of a more robust system of diversions, 

dikes, and floodways in Ambos Nogales, before the predicted population growth occurs. 

9.0 Future Work

9.1 LiDAR

The application of high-spatial-resolution elevation data derived from light detection and 

ranging technologies (LiDAR) to surface hydrologic modeling could improve results. In recent 

years, airborne LiDAR technology has been employed to develop high accuracy digital elevation 

models (DEMs) with horizontal resolution on the order of a few meters. A LiDAR-derived DEM 

might better characterize flow direction, identify sub-basins, and calculate upstream contributing 

areas. Furthermore, a current LiDAR-derived DEM might help to map out detention features, 

tunnel entrances, bridges, walls, culverts, and other obstacles not included in a field survey. A 

LiDAR bid was acquired for the study area (appendix C).

9.2 Precipitation 

This modeling framework is being adapted to a larger “Early Warning Hazard System,” 

in which real-time precipitation data will be streamed into the existing model to estimate 

associated runoff (Project Chief, Floyd Gray). The Department of Defense's Northern Command 

(NORCOMM) is funding the system to develop the most reliable alert system available. A rain 

gage network is being adapted in Nogales, Sonora, to measure precipitation and provide 

electronically recorded precipitation measurements straight to an online rainfall monitoring 

network initially developed for Nogales, Arizona (Rainlog.org). Gages will be well distributed 

throughout the upper watershed at Nogales, Sonora, to citizens of the community, drawing on 

collective local knowledge and support to determine the best locations. Members of the research 

team are recruiting residents who have Internet access and safe locations for the rain gages and 

electronic equipment to begin the process of receiving precipitation data and conveying it to the 

Rainlog Web site. Currently, one rain gage has been installed at the Nogales, Sonora, Water and 

Wastewater Utility. Information from this new station has been displayed online since April 5, 

2010, and will be used to locate the most advantageous sites for larger, more extensive weather 

equipment (Norman, 2010; Norman and others, in press).

9.3 Field Measurements of Detention Features 

Field measurements to generate real-time hydrographs of discharge at the detention 

basins would better calibrate the model and improve results for this study area. This would 

require direct measurements of the stage for the duration of the flow, the storage of the basin, 

and periodic measurements of velocity to rate the stream and determine the relation of stage to 

discharge. Furthermore, the estimated infiltration of water at the detention basins would be 

valuable for calibrating the model and to facilitate groundwater recharge planning. 
23

9.4 Water Quality

Finally, the issue of water quality or potential transfer of contaminants is not considered 

in this model. It was noted that industrial facilities in Nogales, Sonora, often discharge to the 

arroyos (fig. 15). Future research to investigate if contaminants in the channels are infiltrating 

and reaching the potable water supply is warranted.

Figure 15. Photo of Maquiladora discharge in Cuesta Blanca; pipes lead from industry 

to wash. (Photograph by H. Huth.) 

10.0 References 

Bonnin, G.M., Martin, D., Lin, B., Parzybok, T., Yekta, M., and Riley D., 2006, ‘PrecipitationFrequency Atlas of the United States: Silver Spring, Md., National Oceanic and 

Atmospheric Administration, National Weather Service, NOAA Atlas 14, v. 1, version 4, 

accessed online October 15, 2010 at 

http://www.nws.noaa.gov/oh/hdsc/PF_documents/Atlas14_Volume1.pdf. 

Goodrich, D.C., Scott, S., Hernandez, M., Burns, I.S., Levick, L., Cate, A., Kepner, W., 

Semmens, D., Miller, S., and Guertin, P., 2006, Automated Geospatial Watershed 

Assessment (AGWA); a GIS-based hydrologic modeling tool for watershed management 

and landscape assessment, in Proceedings, Third Federal Interagency Hydrologic 

Modeling Conference, Reno, Nev., April 2-6, 2006. 
24

Milczarek, Mike, Yao, Tzung-mow, Goodrich, David, and Levick, Lainie, 2004, Predicting 

groundwater recharge rates in small urbanized watersheds: Southwest Hydrology, 

July/August, 2004, p. 6-9. (Also available at 

http://swhydro.arizona.edu/archive/V3_N4/dept-ontheground.pdf.) 

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. 

Norman, Laura M., 2010, Flash-flood forecasting at Ambos Nogales, in The border climate 

summary: University of Arizona, Tucson, Ariz., Climate Assessment for the Southwest 

(CLIMAS) program, accessed online October 15, 2010 at 

http://www.climas.arizona.edu/files/climas/pdfs/periodicals/BorderClimateSummary_Jun

10.pdf. 

Norman, L.M., and Wallace, C.S.A., 2008, Mapping land use/land cover in the Ambos Nogales 

study area: U.S. Geological Survey Open-File Report 2008-1378, 42 p., accessed online 

October 15, 2010 at http://pubs.usgs.gov/of/2008/1378/. 

Norman, Laura M., Feller, Mark, and Guertin, D.P., 2009, Forecasts of cross-border urban 

growth using the SLEUTH model; Ambos Nogales watershed, United States-Mexican 

border: Computers, Environment, and Urban Systems, v. 33, p. 150-159. 

Norman, Laura M., Huth, Hans, Levick, Lainie, Burns, I. Shea, Guertin, D.P., Lara-Valencia, 

Francisco, and Semmens, Darius, 2010a, Flood hazard awareness and hydrologic 

modeling at Ambos Nogales, US-Mexico Border: Journal of Flood Risk Management, v. 

3, no. 2, 15 p. 

Norman, L.M., Villarreal, M.L., Wallace, C.S.A., Gil Anaya, C.Z., Diaz Arcos, Israel, and Gray, 

Floyd, 2010b, A high-resolution land-use map; Nogales, Sonora, Mexico: U.S. 

Geological Survey Open-File Report 2010-1156, 21 p., accessed online October 15, 2010 

at http://pubs.usgs.gov/of/2010/1156/. 

Norman, Laura M., Gray, Floyd, Callegary, James, Huth, Hans, Gastelum Ceballos, Francisco 

Octavio, Gil Anaya, Claudia Zulema, Goodrich, David, Woodard, Gary, Quintinar, Jesus, 

Nunez, Jose, Oliveros, Gilberto, Molina, Roberto, Guertin, D.P., and Canizales, Eduardo, 

in press, Collaborative work for flash-flood forecasting at Ambos Nogales: International 

Conference on Urban and Global Environmental Change, Arizona State University, 

Tempe, Ariz., October 15-17, 2010. 

Smith R.E., Goodrich D.C., and Quinton J.N., 1995, Dynamic, distributed simulation of 

watershed erosion; the KINEROS2 and EUROSEM models: Journal of Soil Water 

Conservation, v. 50, no. 5, p. 517–520. 

U.S. Army Corps of Engineers, 2005, Ambos Nogales special flood damage reduction study: Los 

Angeles, Calif., U.S. Army Corps of Engineers. 

Woolhiser, D.A., Smith, R.E., Goodrich, D.C., 1990, KINEROS, a kinematic runoff and erosion 

model; documentation and user manual: U.S. Department of Agriculture, Agricultural 

Research Service, ARS-77, 130 p. 
25

Appendix A. Detention Feature Descriptions and Field Trip 

Notes 

Contents of Appendix A

Kick-Off Meeting.......................................................................................................................... 25

Detention Feature Descriptions..................................................................................................... 28

Trip # 1 ...................................................................................................................................... 30

Chimeneas ............................................................................................................................. 30

Represo Chimineas ................................................................................................................ 42

Trip #2 ....................................................................................................................................... 47

Represo Pirinola (a.k.a. Centauro Dam) ................................................................................ 48

Trip #3 ....................................................................................................................................... 54

Maquiladoras (a.k.a. Maquillas) ............................................................................................ 56

Bellotas .................................................................................................................................. 69

Capulines ............................................................................................................................... 77

Represo Villa Sonora ............................................................................................................. 86

Represo Unison II .................................................................................................................. 92

Cuesta Blanca ........................................................................................................................ 99

Kick-Off Meeting

The agenda (fig. 1) for the kick-off meeting included a presentation and the delivery of a 

worksheet (fig. 2) to all parties in attendance. 
26

Figure 16. Agenda for Kick-Off meeting

USGS Update on Watershed Modeling Efforts

Meeting Location

Santa Cruz Active Management Area 

Arizona Department of Water Resources Conference Room

857 W. Bell Road, Suite 3, Nogales, Arizona 85621 

Phone: (520) 761-1814 

January 19, 2010

1 PM - 2 PM 

Goal: Develop a stage-discharge curve for detention features

Background: The USGS, in cooperation with the University of Arizona, and Arizona 

Department of Environmental Quality are conducting a study for the IBWC/CILA on the 

impacts of the detention basins that have been constructed in Nogales, Sonora to help 

provide an understanding of the amount of water being detained by these features. We 

hope to provide information that can be used in planning flood management for the twin 

city area of Ambos Nogales. 

In order to conduct this research within the model identified, we need to get 

measurements taken at each of the detention features that have been constructed. We 

have received a lot of the intended dimensions, but some of the basins have been 

constructed with changes based on their location and site conditions and so we need exact 

measurements to be taken of the features now. Even small variations in elevation and/or 

location can hurt the calculation tremendously. 

Specifically we need GPS locations (Easting, Northing) as well as basin total 

volume, the total basin depth, top and bottom surface areas, and a description of any 

pipes (drainage) to be used to calculate the stage-discharge curve for input to model. 

Tentative Agenda

1:00 PM: Welcome and introductions (IBWC/CILA)

1:05 PM: Background on USGS Proposal and Modeling Efforts (Laura M. Norman, 

USGS). 

1:20 PM: Summary of needs for "as-built" specifications for the detention features since 

they appear to differ from the plans shared with ADEQ and the USGS (Hans Huth, 

ADEQ and Lainie Levick, University of Arizona/U.S. Department of Agriculture).

1:40 PM: Questions from the audience and discussion as needed.

2:00 PM: Adjourn meeting.
27

Nogales Detention Structures

Required Information GPS Coordinates in UTM Zone 12, NAD 83

BASIN NAME

Easting or xcoordNorthing or ycoord

Outflow 

structure 

description

Spillway 

Dimensions

Dam 

Dimensions 

Overall 

Height

Dam 

Overall 

Width

Dam 

Overall 

Thickness

Dam 

Number 

of tiers

Width of 

tier 1

Height 

of tier 1

Width of 

tier 2

Height 

of tier 2

Width of 

tier 3

Height 

of tier 3

Width of 

tier 4

Height 

of tier 4

Width of 

tier 5

Height 

of tier 5

Example 505282.37 3457724.19

3-18"dia tubes 

at 2 ft above 

ground surface 10m x 1m 15 ft 25 ft 10 ft 5 1.5 ft. 1.5 ft 1.5 ft. 1.5 ft 1.5 ft. 1.5 ft 1.5 ft. 1.5 ft 1.5 ft. 1.5 ft

Villa Sonora

Capulines

Cuesta Blanca

San Carlos Dique No. 1

San Carlos Dique No. 2

Bellotas Fraccionamiento

Bellotas Maquiladoras

Chimeneas

Represo Pirinola

Represo Unisom II

Represo Villa Sonora

Represo Chimineas

Location of Dam Description of Dam

Figure 17. Worksheet for calculating needed measurements of the detention basins.
28

Detention Feature Descriptions 

Detention basins being constructed by the city include Chimeneas, Maquiladoras, Bellotas, 

Capulines, Cuesta Blanca [and San Carlos Dique No. 1 and No. 2, and Villa Sonora?] 

Table 3: Coordinates of detention features (UTM, Zone 12, NAD83), provided by Claudia Gil 

and Monica Audelo. 

Name North East Elevation

BELLOTAS 3,459,900.26 504,653.926 1,294.904

MAQUILAS 3,460,203.452 505,261.884 1,270.754

CHIMENEAS 3,460,271.651 501,269.507 1,307.005

CAPULINES 3,457,709.952 505,925.154 1,297.844

CUESTA 

BLANCA 3,459,199.64 506,864.899 1,277.619 

Figure 18. Map of detention features provided by Claudia Gil.
29

Table 4: Coordinates of Detention Features being considered (provided by Julio Luna Rodríguez 

and Claudia Gil).

San Carlos Dique No. 1 506825.37 3460198.55

San Carlos Dique No. 2 506984.06 3460126.51

Bellotas Fraccionamiento 504657.47 3459893.94

Stock Tanks being rehabilitated by CONAGUA, including: Represo Chimineas, Represo 

Pirinola, Represo Villa Sonora, and Represo Unison II.

Table 5: Measurements of rehabilitated detention features provided by Ing Gilberto Patricio 

Olivero Granillo (Coordinador del FONDEN and contracted by CONAGUA)

Represos Latitude Longitude

Available 

Capacity 

(cubic meters)

Current 

Volume 

(cubic 

meters)

Altitude 

(m)

Monthly 

precip 

(mm)

Annual 

precip 

(mm)

CSA (sq. 

kilometers)

Watershed 

#

Pirinola 31.274444 

-

110.911111 748,475.00 9,708.75 1,316 200 700 6.11 16 

Chimineas 31.276667

-

110.974167 797,343.75 32,157.17 1,284 175 625 7.29 17

Villa 

Sonora 31.253611

-

110.944444 99,750.00 1,275.60 1,315 100 500 1.33 7

Unison II 31.235278

-

110.926667 345,870.00 4,114.25 1,427 120 540 4.27 14
30

Trip # 1 

Andrea Harrop Prichard and Prescott Vandervoet from the University of Arizona, Udall Center 

for Studies in Public Policy are researchers for the Transboundary Aquifer Assessment Program 

(TAAP) who helped acquire data for this project. 

On March 24, 2010 they met with Ing. Claudia Gil. Claudia reports that 5 detention features have 

been constructed, although the smallest one is not very useful because new development has 

rerouted the water so it no longer passes through. When University researchers arrived to 

OOMAPAS, they were greeted by a large group of engineers and technicians (about 9) who 

provided tremendous guidance and assistance to our team. 

Chimeneas

Chimeneas is the largest represo, but it is unfinished. Claudia reports that it has been in operation 

since April of 2009, so it has undergone a monsoon season, albeit a relatively weak one. She also 

told researchers that the designer of these structures, Ing. Julio Luna Rodriguez, is a civil 

engineer from the University of Sonora. Once drafted the plans were sent through CONAGUA 

and modified before implementation. Claudia also reports that plans for the Chimeneas to 

contain a vertedor, or notch in the top of the feature (to channel floodwater to prevent bank 

erosion) were scratched by CONAGUA. She also reports that a cama de amortihuamiento (a 

gabion structure on the ground level on the downstream side), used to prevent undercutting in a 

sediment-filled channel, was planned but not completed for the Chimeneas represo. Staff from 

IMIP showed the TAAP researchers that the cortina (gabion blocks) were unfinished on the 

downstream side. It is designed to be kind of a pyramid/step-ladder shape, but estimated 3 (out 

of 5) of those layers are not present on the downstream side. IMIP is waiting for funding for the 

completion of the design, but it does seem to be up and working nonetheless. 
31

Figure 19: Diagram of Represo Chimineas provided by Claudia Gil.

Measurements: 

Length of bottom of detention Feature: 56 feet 

Length of top of detention Feature: 82 feet 6 inches 
32

Figure 20. Photo of Chimeneas Entrance Gate and Well (A. Prichard)

Figure 21. Photo of Chimeneas View from Upstream (A. Prichard)
33

Figure 22. Photo of Chimeneas Upstream North Bank (A. Prichard)

Figure 23. Photo of Chimeneas Organic Soil Upstream (A. Prichard)
34

Figure 24. Photo of Chimeneas Organic Buildup Upstream (A. Prichard)

Figure 25. Photo of Chimeneas View Upstream of Feature (A. Prichard)
35

Figure 26. Photo of Chimeneas (A. Prichard)
36

Figure 27. Photo of Chimeneas Upstream South Bank (A. Prichard)

Figure 28. Photo of Chimeneas Length To Bank at 3m height(South) (A. Prichard)
37

Figure 29. Photo of Chimeneas View from top of Gabion pyramid (A. Prichard)

Figure 30. Photo of Chimeneas (A. Prichard)
38

Figure 31. Photo of Chimeneas (A. Prichard)

Figure 32. Photo of Chimeneas Length To Bank at 3m height (North) (A. Prichard)
39

Figure 33. Photo of Chimeneas View from Downstream (A. Prichard)

Figure 34. Photo of Chimeneas View from Downstream-SouthSide (A. Prichard)
40

Figure 35. Photo of Chimeneas View from Downstream - NorthSide (A. Prichard)

Figure 36. Photo of Chimeneas DirtBank (A. Prichard)
41

Figure 37. Photo of Chimeneas Downstream View from Feature - SouthBank (A. Prichard)

Figure 38. Photo of Chimeneas Downstream view From Feature – NorthBank (A. Prichard)
42

Represo Chimineas

Figure 39. Information describing Represo Chimineas provided by Ing. Gilberto Patricio Olivero 

Granillo.
43

Figure 40. Photo of Represo Chimineas view of the dam from upstream with the hillside on both 

ends (A. Prichard).

Figure 41. Photo of Represo Chimineas view of the dam from upstream with the hillside on both 

ends (A. Prichard).
44

Figure 42. Photo of Represo Chimineas view of the dam from upstream with the hillside on both 

ends (A. Prichard).

Figure 43. Photo of Represo Chimineas view upstream from the dam including the right side of 

the channel (A. Prichard).
45

Figure 44. Photo of Represo Chimineas view upstream from the dam including the right side of 

the channel (A. Prichard).

Figure 45. Photo of Represo Chimineas view upstream from the dam including the left side of 

the channel (A. Prichard).
46

Figure 46. Photo of Represo Chimineas view upstream from the dam including the left side of 

the channel (A. Prichard).
47

Figure 47. Stock Tank TRACK, 2010-04-20, map by Andrea Prichard.

Trip #2 

James Callegary and Floyd Gray (USGS), and Hans Huth (Arizona Department of 

Environmental Quality) went to Nogales on Tuesday, April 13, 2010. 

Jesus Quintanar facilitated the visit. Ing. Claudia Gil helped with the visit with Edgar 

Castellanos and Edgar Tepezano. The tour took place on April 13 and included a review of 

stormwater conveyance infrastructure; installation of internet accessible raingages purchased by 

the USGS under a Department of Defense Northern Command grant; review of potential sites for 

installation of stream gages in Nogales, Sonora; visits to several detention features facilitated in 

part with monies from the EPA Border 2012 Program; and review of potential sites for 

installation of two weather monitoring stations for capture of incoming weather. 

 
48

Represo Pirinola (a.k.a. Centauro Dam)

Figure 48. Information describing Represo Pirinola provided by Ing Gilberto Patricio Olivero 

Granillo.
49

Figure 49. Photo of Represo Pirinola panoramic looking upstream from left to right (H. Huth).

Figure 50. Photo of Represo Pirinola panoramic looking upstream from left to right (H. Huth).
50

Figure 51. Photo of Represo Pirinola panoramic looking upstream from left to right (H. Huth).

Figure 52. Photo of Represo Pirinola panoramic looking upstream from right to left (H. Huth).
51

Figure 53. Photo of Represo Pirinola looking from left bank to right bank along feature (H. 

Huth).

Figure 54. Photo of Represo Pirinola looking downstream (H. Huth).
52

Figure 55. Photo of Represo Pirinola on left bank looking upstream (H. Huth).

Figure 56. Photo of Represo Pirinola on right bank looking towards left bank. Hans Huth.
53

Figure 57. Photo of Represo Pirinola on feature looking upstream and to the right (H. Huth).

Figure 58. Photo of Represo Pirinola on middle of feature looking towards the left (H. Huth).
54

Figure 59. Photo of Represo Pirinola on middle of feature looking down (H. Huth).

Trip #3 

Floyd Gray and Andrea Prichard made a field trip to Nogales, Sonora on Wednesday, May 19th 

with Ing. Gil, Quintanar, Rodriguez, Tepezano, and Castellanos. 

Figure 60. Photo of field trip; group picture (from left to right): Jesus Quintanar, Claudia Gil, 

Floyd Gray, Saul Rodriguez, Andrea Prichard, Edgar Castellanos, Edgar Tepezano (A. Prichard).
55

Figure 61. Engineers from IMIP: Edgar Castellanos and Edgar Tepezano (A. Prichard).
56

Maquiladoras (a.k.a. Maquillas) 

Figure 62. Diagram of Represo Maquilas provided by Claudia Gil.
57

Figure 63. Photo of Represo Maquilas From Upstream (A. Prichard).

Figure 64. Photo of Represo Maquilas Sidewall (A. Prichard).
58

Figure 65. Photo of Represo Maquilas Manhole (A. Prichard).
59

Figure 66. Photo of Represo Maquilas (A. Prichard).

Figure 67. Photo of Represo Maquilas looking upstream, southside (A. Prichard).
60

Figure 68. Photo of Represo Maquilas looking upstream, northside (A. Prichard).

Figure 69. Photo of Represo Maquilaslooking downstream, northside (A. Prichard). 
61

Figure 70. Photo of Represo Maquilas looking downstream, southside (A. Prichard).

Figure 71. Photo of Represo Maquilas From Downstream (A. Prichard).
62

Figure 72. Photo of Represo Maquilas from Downstream, South Side (A. Prichard).

Figure 73. Photo of Represo Maquilas from the East (A. Prichard).
63

Figure 74. Photo of Represo Maquilas Looking Downstream, Southside (A. Prichard). 

Figure 75. Photo of Represo Maquilas (A. Prichard).
64

Figure 76. Photo of Represo Maquilas Looking Downstream, NorthSide (A. Prichard). 

Figure 77. Photo of Represo Maquilas Parking (A. Prichard).
65

Figure 78. Photo of Represo Maquilas Damaged Gabion (A. Prichard). 
66

Figure 79. Photo of Represo Maquilas entrance to Structure (A. Prichard).

Figure 80. Photo of Represo Maquilas damaged gabion Wall (A. Prichard). 
67

Figure 81. Photo of Represo Maquilas damaged gabion East of tunnel (A. Prichard). 

Figure 82. Photo of Represo Maquilas tunnel, approximately 200m West of dam (A. Prichard). 
68

Figure 83. Photo of Represo Maquilas Looking East from Tunnel (A. Prichard).

Figure 84. Photo of Represo Maquilas looking East from top (A. Prichard). 
69

Bellotas 

Figure 85. Diagram of Represo Bellotas provided by Claudia Gil

The represo is a small structure (2 m high, 10-11m across). Due to recent development, water 

flows have been diverted to a nearby road parallel to the stream causing the represo to be less 

effective. Water flows from the NW to SE direction while the represo structure is situated NE to 

SW.
70

Figure 86. Photo from Represo Bellotas from Downstream (SE) (A. Prichard).

Figure 87. Photo from Represo Bellotas from Downstream, SW side (A. Prichard).
71

Figure 88. Photo from Represo Bellotas From Downstream, NE side (A. Prichard).

Figure 89. Photo from Represo Bellotas Looking Downstream, NEside (A. Prichard).
72

Figure 90. Photo from Represo Bellotas Looking Downstream, SWside (A. Prichard).

Figure 91. Photo from Represo Bellotas Looking Upstream, SW side (A. Prichard).
73

Figure 92. Photo from Represo Bellotas Looking Upstream, NE side (A. Prichard).

Figure 93. Photo from Represo Bellotasfrom Upstream (A. Prichard).
74

Figure 94. Photo from Represo Bellotas from Upstream, SW side (A. Prichard).

Figure 95. Photo from Represo Bellotas from Upstream, NEside (A. Prichard).
75

Figure 96. Photo from Represo Bellotas Parallel Street, new Developments (A. Prichard).

Figure 97. Photo from Represo Bellotas from Street, looking at Trucks and dam (A. Prichard).
76

Figure 98. Photo from Represo Bellotas Street, looking upstream ; water flows here instead (A. 

Prichard).
77

Capulines

Figure 99: Diagram of Represo Capulines provided by Claudia Gil.
78

Figure 100. Photo of Represo Capulines from North (A. Prichard). 

Figure 101. Photo of Represo Capulines from Downstream, EastSide (A. Prichard).
79

Figure 102. Photo of Represo Capulines from Downstream, WestSide (A. Prichard).

Figure 103. Photo of Represo Capulines Looking Downstream, EastSide (A. Prichard). 
80

Figure 104. Photo of Represo Capulines LookingDownstream, WestSide (A. Prichard). 

Figure 105. Photo of Represo Capulines looking Upstream, EastSide (A. Prichard). 
81

Figure 106. Photo of Represo Capulines Looking Upstream, WestSide (A. Prichard). 

Figure 107. Photo from Represo Capulines looking South from top (A. Prichard). 
82

Figure 108. Photo of Represo Capulines Looking Upstream (A. Prichard). 
83

Figure 109. Photo of Represo Capulines Looking Downstream, Capulines (A. Prichard).
84

Figure 110. Photo of Represo Capulines From Upstream, WestSide (A. Prichard). 

Figure 111. Photo of Represo Capulines FromUpstream, EastSide (A. Prichard).
85

Figure 112. Photo of Represo Capulines From Upstream (A. Prichard).

Figure 113. Photo approx. 75 m. south of Represo Capulines of Canyon and Waterfall (A. 

Prichard).
86

Represo Villa Sonora

Figure 114. Information describing Represo Villa Sonora provided by Ing Gilberto Patricio 

Olivero Granillo.

Represo Villa Sonora looks like a dry, mudcracked pond that is emptied through a notch in the 

earthen dam into a narrow, steep rocky stream. It was constructed a long time ago to form a 

create water storage for livestock. There are plans to both raise the height to approximately 8m, 

and to rehabilitate the dam with a new concrete barrier. 
87

Figure 115. Photo of Represo Villa Sonora hole Looking Downstream (A. Prichard).

Figure 116. Photo of Represo Villa Sonora Looking Upstream (A. Prichard).
88

Figure 117. Photo of Represo Villa Sonora looking West(downhill) (A. Prichard).

Figure 118. Photo of water behind Represo Villa Sonora (A. Prichard).
89

Figure 119. Photo of Represo Villa Sonora (A. Prichard).

Figure 120. Photo of Represo Villa Sonora from Below Hole (A. Prichard).
90

Figure 121. Photo of Represo Villa Sonora Creek Downstream (A. Prichard).

Figure 122. Photo of Represo Villa Sonora (A. Prichard).
91

Figure 123. Photo of Represo Villa Sonora volcanic rock (A. Prichard).
92

Represo Unison II 

Figure 124. Information describing Represo Unison II provided by Ing Gilberto Patricio Olivero 

Granillo.

This is a large earthen dam, also slated to be raised to about 8 m. 
93

Figure 125. Photo of Represo Unison II from NW (A. Prichard). 

Figure 126. Photo of Represo Unison II creek entering dam from West (A. Prichard).
94

Figure 127. Photo of Represo Unison II on SW (A. Prichard).

Figure 128. Photo of Represo Unison II Looking Downstream(S) (A. Prichard).
95

Figure 129. Photo of Represo Unison II Looking North (A. Prichard). 

Figure 130. Photo of Represo Unison II Looking NE (A. Prichard). 
96

Figure 131. Photo of Represo Unison II Looking NW (upstream) (A. Prichard). 

Figure 132. Photo of Represo Unison II (A. Prichard).
97

Figure 133. Photo of Represo Unison II Rock Outcrop (A. Prichard). 

Figure 134. Photo of Represo Unison II from Downstream (A. Prichard).
98

Figure 135. Photo of Represo Unison II Creek Downstream (A. Prichard).
99

Cuesta Blanca 

Figure 136. Diagram of Represo Cuesta Blanca provided by Claudia Gil. 
100

Figure 137. Photo of Represo Cuesta Blanca bank downstream (A. Prichard). 
101

Figure 138. Photo of Represo Cuesta Blanca Rocks (A. Prichard).
102

Figure 139. Photo of Represo Cuesta Blanca from Downstream (A. Prichard).

Figure 140. Photo of Represo Cuesta Blanca from Downstream, South Side (A. Prichard). 
103

Figure 141. Photo of Represo Cuesta Blanca from Downstream, NorthSide (A. Prichard).

Figure 142. Photo of Represo Cuesta Blanca Looking Downstream, SouthSide (A. Prichard).
104

Figure 143. Photo of Represo Cuesta Blanca Looking Downstream, NorthSide (A. Prichard). 
105

Figure 144. Photo of Represo Cuesta Blanca Looking Upstream, South Side (A. Prichard). 
106

Figure 145. Photo of Represo Cuesta Blanca Looking Upstream, NorthSide (A. Prichard). 
107

Figure 146. Photo of Represo Cuesta Blanca from Upstream,SouthSide (A. Prichard). 
108

Figure 147. Photo of Represo Cuesta Blanca from Upstream, NorthSide (A. Prichard). 

Figure 148. Photo of Represo Cuesta Blanca from Upstream (A. Prichard).
109

Figure 149. Photo of Represo Cuesta Blanca Gabions (A. Prichard). 

Figure 150. Photo of Represo Cuesta Blanca Gabions (A. Prichard).
110

Figure 151. Photo of Represo Cuesta Blanca community, San Carlos (A. Prichard).
111

Appendix B. Detailed Results from the Study 

This Appendix consists of a set of spreadsheet files. They are in this linked spreadsheet folder: 

http://pubs.usgs.gov/of/2010/1262/of2010-1262_appendix_b/
112

APPENDIX C. Laser Mapping quote for Nogales, Mexico

(Matthew Coleman, Airborne 1 Corporation, phone (310) 414-7400 x261, 

coleman@airborne1.com)