Groundwater Resources in the Cuatrocienegas Basin

Coahuila, Mexico                                   

                                                                                         

Site Background & References
Data Sources
NoriasWater Quality
Georeferencing
Irrigation Canal HydroNetwork

PURPOSE

 

Cuatrocienegas de Carranza is a valley located in the state of Coahuila, Mexico. The site is a hydrologic basin sustaining a groundwater dependent ecosystem, as well as acting as the primary source of irrigation water for farming within the basin and adjacent valleys. The objective of this GIS project will be to use GIS data files, water quality sample results, and conceptual groundwater flow modeling tools to develop the following:

·        Phase I - Develop a water quality presentation for the Ejidos Antiguos Mineros village

·        Phase II -Georeference Geologic Maps to identify locations for geophysical transects & testing

·        Phase III - Create a HydroNetwork for irrigation canals within the valley to be used to identify possible gaging station sites

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Navigating this site (Index):

The site is set up with  6 main pages that can all be reached from this index page.

 

Page 1 - The Site Background & References  presents a general summary about the Cuatrocienegas location without discussion of GIS applications. This information was gathered from a literature search and provided key information for the development of the GIS project objectives.  Without and adequate knowledge of needs at the project site the various Phases for the GIS project could not have been identified.

 

Page 2 - The  Data Sources page presents a listing of data used to develop the main geodatabase for the GIS project and hyperlinks, where appropriate, to access the same data online.

 

Pages 3, 4, &  5 - These pages present the task objectives, results, future work, and a listing of the basic steps taken to complete the phase.  These pages are NoriasWater Quality, Georeferencing, and  Irrigation Canal HydroNetwork.

 

Finally, Page 6 - This page is an Appendix document that shows the steps completed to differentially correct raw data points from GPS coordinates for inclusion in the overall project.

 

Or, you may continue reading a TEXT ONLY version of the report on this page to see a version with figures and diagrams please visit linked pages (Note: due to problems with uploading internet files some graphics are not displaying correctly).

 

 

Introduction / Site Background

 

The Cuatrociénegas basin is encompassed within the broadly defined area that falls within the transboundary jurisdictions between the United States and Mexico established through a 1944 treaty allocating the management of shared waters of these two nations.  Cuatrociénegas may be many miles distant from the actual border, but the site represents an example of the water resource management problems exhibited up and down the U.S.-Mexico border. 

 

Cuatrociénegas is located within the Chihuahuan Desert region of Mexico. Springs and surface water expressions located in the basin create a groundwater dependent ecosystem characterized by a unique level of endemism, with numerous species identified as specific to the area. These species are supported by the more than artesian springs that discharge within the valley.  

 

The valley is believed to be a natural closed system or closed basin (surface water), but due to current irrigation practices transport outside of the valley the system has become an artificially open one.  Recently, decreases in water levels within the valley are disrupting the surface ecosystems and raising doubts about the future viability of continued irrigation within the valley.

 

Currently there is very little information available regarding the hydrogeology within this basin. In order to address issues associated with drawdown in the basin an analysis of current conditions needs to be completed.

 

It is with this basic information that I decided to develop my three GIS project goals.

 

Phase I, the development of a water quality presentation came about due to questions from villagers in Ejido Antiguos Mineros while I collected samples there in August 2002. There was general lack of information regarding the potable water sources used by villagers and I committed at that time to communicate my analysis results to the residents during a subsequent visit. This GIS project offered an opportunity to develop the basic outline for that presentation.

 

Phase II, georeferencing paper copies of geologic maps is an important task because the current hydrologic boundary conditions within the Cuatrocienegas basin are not known. Therefore, geophysical testing may be a valuable means of identifying faults or other geologic features that act as boundaries. In order to develop a reasonable work plan and cost estimate the geologic maps for the basin need to be compared with the locations of irrigation canals, mapped spring discharges, and other surface features in the area.

 

Phase III, creating a hydronetwork is one of the most valuable tools that GIS can offer for the Cuatrocienegas basin. There are no permanent gauging stations located on irrigation canals within the valley. Considering that irrigation is expected to be the largest component of discharge from the basin, it is imperative to quantify use patterns and flows within them. Using the few sporadic measurements available and the gps coordinates for the irrigation canals a hydronetwork can be developed and used to identify likely gauging station locations, as well as help show what available flows may indicate about usage.

 

 Data Sources

 

Initially simple basemaps were created using data downloaded from Mexican government websites, together with data provided by Dr. Dean Hendrickson of the University of Texas Biological Sciences Department. The sites used for these initial basemaps are:

http://www.dot.state.tx.us/insdtdot/orgchart/isd/gps/gps.htm  and  http://www.conabio.gob.mx/sig/cart_linea.html.

 

Additionally, data analysis results and GPS data collected by the author in August 2002 was used to develop both shapefiles and feature datasets. A complete description of this process is presented in Appendix A of this website.

 

Near the completion of my project I met with Carlos Patino, a graduate student with the Dept. of Engineering and Water Resources, University of Texas at Austin working on the development of a Decision Support System for the Transboundary Area. He provided a series of maps showing the state outlines on both the Mexican and U.S. sides of the border, as well as a DEM with better resolution than the one I was previously using. These files helped improve the quality of my project.

 

Other resources for more information may be available from the following websites:

http://www.semarnat.gob.mx,  http://infoteca.semarnat.gob.mx/, and http://www.inegi.gob.mx.

 

Project Development for Phase I - Water Quality Comparison of Community Wells
 

Task Objectives:  The Ejido Antiguos Mineros is a small village located on the southern perimeter of the Cuatrocienegas Basin.  A series of water quality samples were collected from hand dug wells, or "norias", used as the primary potable water sources for the village.

 

This portion of the GIS project will be to analyze water quality samples and compare results to internationally accepted potable water standards and link the data to spatial database for development of maps and diagrams for presentation.

 

Using GIS, Excel and Aguachem programs create graphics and maps that demonstrate trends observed in the water analyses.

 

Steps Taken to Complete this Phase

  • Converted and differentially corrected GPS data collected at the time of sampling.

  • Water Analysis Samples converted to .dbf file that included attributes for over 30 water quality analytes, site sampling ID's, names, and geographic locations.

  • Used X-Y analysis to import sample locations as a layer onto a basemap.

  • Manually corrected sample locations and created final layer with attribute table.

  • Weighted sample sites by conductivity values and changed symbols to graded values (As shown in Map in Results Section above).

  • Began developing maps for additional parameters.

Results:  Maps were created using symbol & labeling options together with the spatial relationships in GIS. These maps provide valuable visual tools for demonstrating observations to stakeholders in the Ejidos Antiguos Mineros Village.

 

Graphic representations of water quality parameters were tied back to the site map and individual parameters were shown with weighted values. The use of weighted values creates an easy to interpret indicator of relative concentrations for each parameter.

 

Future Work:  In December 2002, a suite of maps and graphs for all critical water quality parameters will be developed. Once completed the results will be formated results for presentation to community residents in poster style.

 

Project Development for Phase II - Georeferencing Geologic Maps

 

Task Objectives:  Integrate non-digital data with the GIS digital format to use for the identification of geophysical testing transect locations. Geologic maps are commonly unavailable in digital format so the ability to add these maps to a geodatabase is extremely valuable for a variety of uses.

 

Steps Taken to Complete this Phase:

  • Scanned Geologic Maps into .tif format

  • Identified points on maps with known UTM coordinates

  • Added to scanned images to geodatabase in ArcCatalog

  • Added maps to ArcMap file

  • Opened Georeferencing Tool in ArcMap

  • Manually selected UTM locations and added to layer

  • Updated Maps with georeference tool and saved new layer.

Results:  Over 7 maps have been successfully georeferenced. As shown above, the non-georeferenced map (left) is incorrectly skewed and once georeferenced (right map) the display can be used as an underlying base for layers and shape files within the geodatabase. Transects can now be overlaid and actual distances can be estimated for proposal development purposes.

 

Future Work: Combine all 7 maps into one merged map and present projected geophysical transect lines as part of a research proposal.

 

Project Development for Phase III - Build a HydroNetwork for Irrigation Canals

 

Task Objectives:  Develop a HydroNetwork for irrigation canals within the Cuatrocienegas Basin for use in the identification of permanent gaging station locations and as a step toward building a tool that can be used to evaluate various flow/use scenarios with the La Becerra Irrigation Group.

 

Steps Taken to Complete this Phase:

  • Prepared base data files including adding flow attributes at known measurement locations

  • Identified edges and junctions to create Hydrojunction feature

  • Created set of ArcHydro files (with appropriate names)

  • Built a geometric network

  • Used ArcHydro Tools to evaluate newly built network

Results: Data was successfully prepared for use in a HydroNetwork. A basic flow network was created. A HydroEdge network was created and flow directions were delineated to create the ultimate flow map (shown on linked page).Upon closer evaluation of the flow network gaps within the irrigation canal network basemap were identified. These gaps prevented further use of ArcHydro tools until a more complete data set can be created.

 

Future Work:  Return to field and map actual irrigation channels using GPS. Once a complete feature dataset for the canals can be created a new HydroEdge layer will be added to the HydroNetwork and additional ArcHydro Tools will be applied.

 

Conclusions

The work completed for this GIS project has provided a wide-range of new tools that I can apply to a variety of settings in the Cuatrocienegas basin. Each of the Phases completed for this project will provide practical information of real-world value for 3 very distinct problems within the valley. Completing the project using this 3-pronged approach has actually provided me with the opportunity to explore and apply a variety of tools from the ArcGIS/ArcHydro program. In the future I hope to begin using GIS applications for groundwater and decision support system projects.