Ambient Groundwater Quality of the San Rafael Basin: A 2002 Baseline Study By Douglas C. Towne Maps by Larry W. Stephenson Arizona Department of Environmental Quality (ADEQ) Open File Report 2003-01 ADEQ Water Quality Division Hydrologic Support & Assessment Section Groundwater Monitoring Unit 1110 West Washington St. Phoenix, Arizona 85007-2935 Thanks: Report Preparation: Lorraine Akey, Danese Cameron, Nancy Caroli, Warren Elting, Maureen Freark, Douglas McCarty, Larry Stevenson, and Wang Yu Field Assistance: Elizabeth Boettcher, Joe Harmon, and Jean Ann Rodine. Special acknowledgment goes to Lee Eseman and Carol Bercich of the San Rafael Ranch State Park for facilitating contact with many well owners in the basin who were kind enough to allow ADEQ to collect groundwater data on their property. A nod also goes to Peter Robbins for a memorable well sample. Report Printing: Mario Ballesteros and Crew Photo Credits: Douglas Towne Report Cover: The abundant charm of the San Rafael Valley is aided by the many stunning rural landscapes relatively untouched by modern development. This photo shows the windmill, barn, and pristine rolling grasslands of one of Arizona’s newest state parks, the San Rafael Ranch, located on a terrace overlooking the Santa Cruz River a few miles north of the border with Mexico. In 1998, the Arizona State Parks Board purchased this property and is refurbishing the ranch house in preparation to open the park to the public. The historic three-story, brick French Colonial style structure is considered the best preserved territorial brick ranch in Arizona.”.7 Other Publications of the ADEQ Ambient Groundwater Monitoring Program ADEQ Ambient Groundwater Quality Open-File Reports (OFR) : Lower San Pedro Basin OFR 02-01, July 2002, 74 p. Willcox Basin OFR 01-09, November 2001, 55 p. Sacramento Valley Basin OFR 01-04, June 2001, 77 p. Upper Santa Cruz Basin OFR 00-06, September 2000, 55 p. (With the U.S. Geological Survey) Prescott Active Management Area OFR 00-01, May 2000, 77 p. Upper San Pedro Basin OFR 99-12, July 1999, 50 p. (With the U.S. Geological Survey) Douglas Basin OFR 99-11, June 1999, 155 p. Virgin River Basin OFR 99-04, March 1999, 98 p. Yuma Basin OFR 98-07, September, 1997, 121 p. ADEQ Ambient Groundwater Quality Factsheets (FS): San Rafael Basin FS 03-03, February 2003, 4 p. Lower San Pedro Basin FS 02-09, August 2002, 4 p. Willcox Basin FS 01-13, October 2001, 4 p. Sacramento Valley Basin FS 01-10, June 2001, 4 p. Yuma Basin FS 01-03, April 2001, 4 p. Virgin River Basin FS 01-02, March 2001 4 p. Prescott Active Management Area FS 00-13,December 2000, 4 p. Douglas Basin FS 00-08, September 2000, 4 p. Upper San Pedro Basin FS 97-08, August 1997, 2 p. (With the U.S. Geological Survey) ADEQ Targeted Groundwater Quality Open-File Reports (OFR) : The Impacts of Septic Systems on Water Quality of Shallow Perched Aquifers: A Case Study of Fort Valley, Arizona. ADEQ Open File Report 97-7, February 1997, 70 p. Most of these publications are available on-line. Visit the ADEQ Ambient Groundwater Monitoring Program at: http://www.adeq.state.az.us/environ/water/assess/ambient.html#studies http://www.adeq.state.az.us/environ/water/assess/target.html#studies Contents II Contents III CONTENTS Abstract ............................................................................................. 1 Introduction .......................................................................................... 2 Purpose and Scope ................................................................................ 3 Physical Setting ................................................................................... 3 Cultural Setting .................................................................................... 6 Geohydrology............................................................................................. 9 Groundwater Use ................................................................................... 9 Groundwater Movement, Depth, and Recharge ......................................................... 9 Groundwater Sampling Results ......................................................................... 10 Water Quality Standards/Guidelines ..................................................................10 Water Quality Standard/Guideline Exceedances ........................................................12 Suitability for Irrigation .............................................................................12 Analytical Results ..................................................................................12 Groundwater Composition ............................................................................. 17 Groundwater Quality Patterns .......................................................................... 21 Conclusions ......................................................................................... 22 Suitability of Groundwater for Domestic Use ...........................................................22 Groundwater Basin Overview ........................................................................23 Study Design and Data Evaluation ...................................................................23 Recommendations .................................................................................... 24 References .......................................................................................... 25 APPENDICES Basic Data ........................................................................................... 27 Data on Sample Sites ...............................................................................27 Groundwater Quality Data ...........................................................................28 Volatile Organic Compound Analyte List ............................................................. 34 Investigation Methods .................................................................................35 Sampling Strategy ..................................................................................35 Sample Collection ................................................................................. 35 Laboratory Methods ............................................................................... 36 Sample Numbers .................................................................................. 36 Data Evaluation ...................................................................................... 39 Quality Assurance .................................................................................39 Data Validation ................................................................................... 40 Statistical Considerations .......................................................................... 42 Contents IV FIGURES Figure 1. San Rafael Valley photo. .......................................................................2 Figure 2. Captain Spring sample photo. ..................................................................2 Figure 3. SRF Satellite image. ...........................................................................4 Figure 4. Santa Cruz River corridor photo. ................................................................5 Figure 5. Santa Cruz River near USGS gaging station photo. ................................................5 Figure 6. Abandoned homestead and windmill photo. ......................................................6 Figure 7. Former Lochiel customs house photo. ...........................................................6 Figure 8. Oklahoma! movie advertisement. ...............................................................7 Figure 9. SRF land ownership and rock types map. ........................................................8 Figure 10. SRF water quality exceedances and sampling sites map. ..........................................11 Figure 11. Captain Spring overflow photo. ................................................................10 Figure 12. Wildfire photo. ..............................................................................10 Figure 13. Mine adit in Patagonia Mountains photo .......................................................12 Figure 14. Irrigated pasture in Santa Cruz River floodplain photo ............................................12 Figure 15. TDS and sulfate levels in the SRF map. .........................................................18 Figure 16. Hardness and nitrate levels in the SRF map. .....................................................19 Figure 17. Piper trilinear diagram. ........................................................................17 Figure 18. Calcium and bicarbonate graph. ...............................................................20 Figure 19. TDS and hardness graph. .....................................................................20 Figure 20. Sodium watershed boxplot. ...................................................................21 Figure 21. Stable isotope graph. .........................................................................22 TABLES Table 1. SRF sites exceeding health-based water quality standards (Primary MCLs) .......................... 13 Table 2. SRF sites exceeding aesthetics-based water quality guidelines (Secondary MCLs) ................... 14 Table 3. Summary statistics for SRF groundwater quality data. ............................................ 15 Table 4. ADHS/Del Mar laboratory methods used in the SRF study ........................................ 37 Table 5. Summary results of SRF split samples