Scientific Investigations Report 2007–5179
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2007–5179
Effects of Agriculture and Urbanization on Quality of Shallow Ground Water in the Arid to Semiarid Western United States, 1993–2004
National Water-Quality Assessment Program
By Angela P. Paul, Ralph L. Seiler, Timothy G. Rowe, and Michael R. Rosen
Table of Contents
Conversion Factors, Datums, and Abbreviations
Foreword
Abstract
Introduction
Description of Study Areas
Methods
Water-Quality Conditions
Summary and Conclusions
Acknowledgments
References Cited
Appendixes
Figures
Figure 1. Location of regional National Water-Quality Assessment (NAWQA) Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 2. Location of wells sampled in agricultural and urban areas within regional National Water-Quality Assessment (NAWQA) Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 3. Dissolved-oxygen concentration in ground water from agricultural and urban areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 4. Statistical relation of dissolved-oxygen concentration among regional National Water-Quality Assessment Program study units and respective land-use settings, in the arid to semiarid Western United States, 1993–2004.
Figure 5. Nutrient speciation in ground-water samples collected from agricultural and urban areas in regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 6. Percentage of nutrient detections following recensoring of nutrient datasets for entire dataset, and after removing replicate analyses, retaining only the most recent analysis at a given site, within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 7. Effect of land use on the percentage of detections following recensoring of nutrient data sets for entire data set and after removing replicate analyses, retaining only the most recent analysis from a given site, within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 8. Nutrient concentration in filtered ground-water samples collected from agricultural and urban areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 9. Nutrient concentration in filtered ground-water samples collected from agricultural and urban areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 10. Relation between land use and application of nitrogen fertilizer and households served by septic systems within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 11. Nitrate concentration in water samples collected from all agricultural wells, agricultural wells in the San Joaquin-Tulare Basins (SANJ) study unit, and agricultural wells in the Central Arizona Basins (CAZB), Nevada Basin and Range (NVBR), Rio Grande Valley (RIOG), and Sacramento River Basin (SACR), 1993–2004.
Figure 12. Relation between median nitrate concentration with median fertilizer application rate and median dissolved-oxygen concentration in agricultural and urban areas in the Nevada Basin and Range (NVBR), Rio Grande Valley (RIOG), and Sacramento River Basin (SACR), 1993–2004.
Figure 13. Relation between ranked nitrate concentrations and ranked well, aquifer, and land-use characteristics in agricultural areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 14. Relation between ranked nitrate concentrations and ranked well, aquifer, and land-use characteristics in urban areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 15. Relation between ranked nitrate concentrations and ranked nitrogen application rates in agricultural areas within in regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 16. Relation among iron, nitrite, and dissolved-oxygen concentrations in ground-water samples collected from agricultural areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 17. Pesticide detection frequency in ground-water samples collected from agricultural and urban areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 18. Triazine herbicide detection frequency in ground-water samples collected from agricultural and urban areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 19. Relation of atrazine and deethylatrazine (CIAT) detection frequencies in ground-water samples collected from urban and agricultural areas to percentage of agricultural and urban wells within each dissolved-oxygen category within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 20. Carbamate detection frequency in ground-water samples collected from agricultural and urban areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 21. Simazine pesticide use by county and township-and-range-scale coverages, and (graphical comparison of pesticide-use scales in the San Joaquin-Tulare Basins (SANJ) study unit.
Figure 22. Volatile-organic compound class detection frequency in ground-water samples collected from agricultural and urban areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 23. Trihalomethane detection frequency in samples collected from agricultural and urban areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 24. Relation of chloroform detection frequency in ground-water samples collected from urban and agricultural areas to percentage of agricultural and urban wells in each dissolved-oxygen category within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 25. Solvent detection frequency in water from wells sampled from agricultural and urban areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 26. Relation of solvent detection frequencies in ground-water samples collected from urban and agricultural areas to dissolved-oxygen concentration within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Figure 27. Relation of methyl tert-butyl ether (MTBE) detection frequency collected from urban and agricultural areas to dissolved-oxygen concentration within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Tables
Table 1. Average annual temperature, average annual precipitation, and estimated evaporation rates for regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Table 2. General aquifer characteristics, ground-water type, and water-quality data for ground-water samples collected from regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Table 3. Long-term method detection and censoring limits used during data analyses for this regional study.
Table 4. Median values for selected well, aquifer, and land-use characteristics for regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Table 5. Median concentration of nutrient species within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Table 6. Reactions sensitive to oxidation-reduction conditions that may influence nutrient concentrations in ground water.
Table 7. Nitrate occurrence in shallow ground water beneath agricultural and urban areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Table 8. Pesticide occurrence in shallow ground water beneath agricultural and urban areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
Table 9. Volatile-organic compound occurrence in shallow ground water beneath agricultural and urban areas within regional National Water-Quality Assessment Program study units in the arid to semiarid Western United States, 1993–2004.
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Send questions or comments about this report to the author, Angela P. Paul, (775) 887-7697.
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