Ground Water Protection Program Contracts

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These projects were funded by contracts with the Department of Pesticide Regulation (DPR) of the California Environmental Protection Agency. The statements and conclusions in these reports are those of the contractors and not necessarily those of the California Department of Pesticide Regulation. The mention of commercial products, their source, or their use in connection with material reported herein is not to be construed as actual or implied endorsement of such products.

Contract Number Contract Description
Contract 05-0102 Using Isotopic Ratios and Major Minerals Data to Identify the Sources of Ground Water and Ground Water Nitrate In Relation to Pesticide Residues

Wells contaminated with pesticide residues frequently contain elevated concentrations of nitrate. Analysis of the isotopic ratios of oxygen and nitrogen indicated that agricultural ammonium-based fertilizers contribute significantly to nitrate contamination. This study provides additional evidence that agricultural recharge water is an important source of pesticide residues in ground water. The study was conducted by the California Water Institute at the California State University Fresno Foundation. Contract period: June 13, 2006 through March 31, 2008.

Final Report: Suen, John C. 2008. Using Isotopic Ratios and Major Minerals Data to Identify the Sources of Ground Water and Ground Water Nitrate in Relation to Pesticide Residues, June 2008, PDF (649 kb).

Contract 02-0171 Holding Pond Mitigation Practices to Prevent Ground Water Contamination

Following detection of pesticide residues in a contiguous area of shallow ground water near Tracy, in San Joaquin County, California, DPR conducted a cooperative study with the University of California Cooperative Extension to determine the exact pathway for movement of the residues to ground water in this area. This study provided the basis for a pond water management strategy and provided data to demonstrate the effectiveness of those procedures to decrease ground water contamination by preemergence herbicides. Contract period: January 20, 2003 - January 1, 2004.

Final Report: Prichard, D., L. Schwankl, and M. Canevari. 2004. Develop Holding Pond Mitigation Practices to Prevent Herbicide Movement to the Ground Water, California, September, 2004, PDF (366 kb).

Contract 02-0144 Effectiveness of Pre-emergence Herbicides Applied through Low-Volume Irrigation Systems

This study provided data on the effectiveness of chemigation and was used to demonstrate the application of pre-emergence herbicides through low-volume irrigation systems to Central Valley citrus growers. The study plan was developed in conjunction with the Center for Irrigation Technology (CIT) at the California State University, Fresno. Contract period: July 1, 2002 - June 30, 2004.

Final Report: Basinal, L., T. Jacobsen, A. Da Silva, J. Troiano, P. Reising, D. Laird, D. Stubbs, and A. Barefoot. 2005. Demonstration of Effectiveness of Chemigation of Pre-emergence Herbicides Applied through Low-Volume Irrigation Systems, California, February, 2005, PDF (228 kb).

Contract 01-0153 Simazine Runoff Losses from a Cover-Cropped Citrus Orchard

Preemergent herbicide losses via runoff in California are a potential source for ground water contamination. A study was conducted by the University of California Cooperative Extension to evaluate the effects of cover crop on simazine losses in runoff that resulted from winter rainfall in commercial citrus growing conditions. Contract period: October 1, 2001 - June 30, 2002.

Final report: O'Connell, N. and F. Liu. 2002. Simazine Runoff Losses From a Cover Cropped Citrus Orchard, California, June, 2002, PDF (36 kb).

Contracts 99-0173
and 99-0176
Citrus Herbicide Mitigation Practices: Demonstration and Evaluation

The loss of preemergence soil-applied herbicides to surface water runoff decreases the effectiveness of the application and creates a water quality hazard in the receiving waters. Studies were conducted by the University of California Cooperative Extension to evaluate weed control efficacy under selected weed management practices and to measure selected management practices for mitigating preemergent herbicide movement in rainfall runoff from citrus orchard middles. Contract period: September 1, 1999 to June 30, 2001.

Final Report: O'Connell, N. and F. Liu. 2002. Citrus Herbicide Mitigation Practices Demonstration and Evaluation, California, June, 2002, PDF (125 kb).

Contract 95-0238 Mitigating Ground Water Contamination in Citrus and Grapes

Simazine residues are frequently detected in wells sampled in Fresno and Tulare counties, California. Surface and ground water contamination through runoff and leaching has been attributed to simazine use in citrus and grapes. A study was conducted by the University of California Cooperative Extension to evaluate the mechanisms of off-site movement of herbicides in citrus orchards and a drip-irrigated vineyard. Contract period: July 1, 1995 - June 30, 2006.

Final Report: Prather, T., F. Liu, N. O'Connell, M. Freeman, K. Hembree. 1999. Mitigating Movement of Simazine Into Ground Water in Citrus and Grapes, California, September, 1999, PDF (226 kb).



For content questions, contact:
Sheryl Gill
1001 I Street, P.O. Box 4015
Sacramento, CA 95812-4015
Phone: (916) 324-5144
E-mail: Sheryl.Gill@cdpr.ca.gov