Determining Flow Systems Using Chemical Data and GIS in Cuatro Cienegas, Coahuila, Mexico Shanna Evans December 2, 2004

Importance ► The basin was set aside as a preserve by the Mexican government in 1994 ► More than 70 endemic and/or endangered species inhabit the basin (DFWC, 2003) ► It has a spring density of pozas (spings) per square kilometer (Winsborough, 1990) ► Water levels have dropped approximately cm in the past five years (Lesser, 2001) ► Where is the water coming from and where is it going?

Location- Chihuahuan Desert Blue points on Cuatro Cienegas Map are springs within the basin

Objectives ► Integrate water chemistry for the Cuatro Cienegas Basin into GIS ► Provide conductivity map to examine chemistry in the basin ► Demonstrate temperature variations in the basin ► View spatial variability of chemistry to examine flow paths

Chemical Data ► Water samples and corresponding GPS locations were collected at 35 sites during April and June, ► Samples were analyzed for major anions and cations ► Conductivity, pH, DO, ORP, Temperature, and alkalinity were measured in the field Poza Juan Santos

Building the Geodatabase ► Base files from Jennifer Howeth and A. Moline were in geographic and projected formats (NAD and UTM) ► 6 Feature Datasets were created for the basin ► CC lies in UTM zone 13 and zone 14 ► All GIS data was finally projected into the UTM Zone 13 format

► Integrate water chemistry for the Cuatro Cienegas Basin into GIS ► Provide conductivity map to examine chemistry in the basin ► Demonstrate temperature variations in the basin ► View spatial variability of chemistry to examine flow paths Objectives

Integrating Chemical Data into GIS ►Problems!!!  GPS positions taken in the field were in UTM Zone 13 and Zone 14  Some sample sites did not have locations associated with them ►Solutions!!!  Data were separated into 4 spreadsheets and saved as dbf4 files: ► Zone 13 ► Zone 14 ► No data with known XY location from other source ► No data without known XY location

Integrating Chemical Data into GIS Each pink point is a sample site containing chemical data, but the data was stored in 4 layers!

Integrating Chemical Data into GIS ► Excel spreadsheets and the Add XY tool saved the day! ► The layers were combined into one for chemical data interpolation

► Integrate water chemistry for the Cuatro Cienegas Basin into GIS ► Provide conductivity map to examine chemistry in the basin ► Demonstrate temperature variations in the basin ► View spatial variability of chemistry to examine flow paths Objectives

Conductivity Map! ► Spline and kriging methods were not accurate in their interpretation. ► Inverse Distance Weighted method was most accurate

► Integrate water chemistry for the Cuatro Cienegas Basin into GIS ► Provide conductivity map to examine chemistry in the basin ► Demonstrate temperature variations in the basin ► View spatial variability of chemistry to examine flow paths Objectives

Temperature Maps! IDW and Spline Temperature Map Kriging Temperature map

► Integrate water chemistry for the Cuatro Cienegas Basin into GIS ► Provide conductivity map to examine chemistry in the basin ► Demonstrate temperature variations in the basin ► View spatial variability of chemistry to examine flow paths Objectives

Chemistry and Flow Systems?? 5 flow systems most likely exist in the basin

Chemistry and Flow Systems?? ► Higher conductivities were at the end of flow paths and toward the center of the basin ► Evaporation controls chemical evolution ► This is consistent with the proposed flow systems Conductivity map of the basin

Chemistry and Flow Systems?? ► Higher temperatures were at the source of the spring and toward the end of the flow paths ► Interesting, but not necessarily helpful Temperature map of the basin

Chemistry and Flow Systems?? ► Alkalinity in the basin may be an indicator of separate flow systems ► The Anteojo and Hundidos systems had the highest alkalinities Alkalinity map of the basin

Conclusions and Recommendations ► GIS is a useful tool in viewing chemical data to analyze flow systems based on spatial variability ► GIS alone cannot interpret the chemical data- one must know the chemical processes involved ► In order to obtain a more accurate chemical data map, more springs in the basin must be analyzed

References ► Desert Fishes Council Web. 2003, Cuatro Cienegas Home Page, maintained by Dean A. Hendrickson. ► Lesser & Associates, and Gerencia de Aquas Subterraneas. 2001, Hydrologic Synopsis en the Hundido, Cuatrocienegas, and Ocampo Valleys, Coahuila, Evaluation Report for the Commission Nacional de Aguas, Mexico City, Mexico. ► Winsborough, Barbara, Some ecological aspects of modern fresh-water stromatolites in lakes and streams of the Cuatro Cienegas Basin, Coahuila, Mexico, The University of Texas- Austin Dissertaion, 341 pp.