Effects of agriculture and urbanization on shallow ground-water quality in the arid to semiarid Western United States

Angela Paul, U.S. Geological Survey; and Michael R. Rosen, U.S. Geological Survey

Urbanization is occurring throughout the United States with exceptionally rapid rates occurring in the west. From 1995 through 2025, Arizona, California, Nevada, and Utah are all projected to be within the top 10 fastest growing states. In the arid to semiarid west, desert and agricultural lands are diminishing as urban centers expand. The western United States heavily utilizes ground-water resources for potable water supplies and irrigation. Urbanization can result in changes in water-management practices as the demand for drinking water increases and demand for irrigation water declines. Assessing shallow ground-water quality can provide insight into the effects of land use on ground water that can potentially reach deeper potable-water supplies.

Ground-water samples were collected as part of the National Water Quality Assessment Program (NAWQA) from 1994 until 2004 in Arizona, California, Nevada, and Utah. The objectives of this study were to determine the presence or absence of man-made organic compounds and if different compounds are present in shallow ground water beneath urban and agricultural land uses. Ground-water samples collected during this study were analyzed for pesticides and volatile organic compounds. In general, triazine herbicides (atrazine, prometon, and simazine) were detected in both agricultural and urban ground-water samples. Similar concentrations of atrazine were detected in both agricultural and urban ground-water samples; however, atrazine was detected more frequently in urban samples. Simazine and prometon were associated predominately with ground-water samples collected from agricultural and urban areas, respectively. Generally, diuron and thiocarbamates were detected more frequently in ground-water samples from agricultural areas than those from urban areas. Trihalogenated methanes (THM’s), methyl tert-butyl ether (MTBE), and tetrachloroethene (PCE) occurred predominately in urban ground water whereas dibromochloropropane was associated with agricultural ground water. Results from this study may contribute to understanding aquifer susceptibility to land-use effects in areas where shallow ground-water quality data is limited.

Biographical Sketches

Angela Paul is currently a hydrologist with the US Geological Survey located in Carson City, Nevada. In 1992 she received a Bachelor of Science in Environmental Toxicology from UC Davis, in 1996 a Masters of Science in Ecotoxicology from Clemson University and, in 2003, a Masters of Science in Environmental Chemistry from the University of Nevada, Reno. Angela began working for the US Geological Survey in 1998 and is currently in charge of coordinating the surface-water sampling efforts for the Nevada Basin and Range (NVBR) Study Unit as part of the National Water Quality Assessment (NAWQA) Program.

Dr. Michael Rosen is currently the Nevada Basin and Range (NVBR) Study Unit Chief for the National Water Quality Assessment (NAWQA) program at the US Geological Survey. Michael joined the USGS in May 2001 and is based in Carson City. Before working with the USGS he was employed for almost 8 years at the Institute of Geological and Nuclear Sciences in Taupo, New Zealand as the Ground Water Program Leader. He has also worked 2 years in the Division of Water Resources (now referred to as Land and Water) CSIRO in Perth, Western Australia; Curtin University of Technology (1 year), Perth, Western Australia; and at the Limnological Research Center at the University of Minnesota (1 year). He is a dual citizen but was born in the US in Philadelphia and received his undergraduate degree in Geology at Haverford College, his master’s degree from the University of Rochester and his PhD from the University of Texas at Austin. Michael’s research in the past has covered the fields of hydrochemistry (water quality), sedimentary geochemistry, paleolimnology (including paleoclimate research), ecology, geothermal research, Antarctic research, and hydrogeology. Much of his work in New Zealand involved the use of chemical and isotopic methods to detect and prevent environmental degradation to ground water resources in New Zealand.