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The Complete GAP Manual
Water Quality
Water Quality Testing Labs
Water Quality Control Boards

Safe Water Practices for Growers

Water used in the production of almonds can be a source of microbiological contaminants. Water used in irrigation and especially in any foliar applications to almonds may introduce and widely disseminate pathogens to the orchard and the crop.

It’s important to become familiar with the sources and quality of the farm’s water supply. Identify all potential sources of contamination, such as unsafe water routes, shared water conveyance conduits and seasonal influences upon the water supply. Identify any potential or likely nearby sources for septic or effluent discharge into the water conveyance system and intake. Take proactive measures to protect the quality of water used on the farm whenever possible. Coordinate interactions with regional Water Quality Control Boards and Irrigation Districts to ensure a continued safe water supply and timely communication of any testing results.

The Almond Board of California recommends that all water used for foliar applications comes from a pathogen-free source. Although not a common practice, the use of surface water for a variety of foliar treatments has occurred. Growers should ensure that applicators only recharge spray tanks from well-designed and protected ground water sources or a municipal water supply.

Water Testing Guidelines

Monthly testing is highly recommended until sufficient experience with quality, over the course of at least two harvest seasons, is available.

During future seasons, test annually at the beginning of each season

    • Closed, underground or capped well systems

Test quarterly throughout the season

    • Uncapped wells
    • Open canals
    • Reservoirs
    • Collection ponds/Recycled water

Maintain copies of water quality reports (monthly, quarterly or annually)

    • Municipality or district water systems

Water test for possible microbial contaminants

    • Fecal Coliform/E. coli (Irrigation water standards have no established maximum contaminant level for microbiological contaminants but current research suggest that a single point maximum for E. coli of 126/100ml is a useful threshold that can be easily met in most irrigation sources of California)
 Possible mitigation measures for E. coli detection level of “present” or “positive”
    • Re-test using a quantitative or MPN (most probable number) format rather than presence/absence format 
    • Disinfect water source
    • Re-test and double testing frequency
    • Add filtration system to water source
    • Add chlorination system to water source
    • Check condition and protection of capped well
Note: Maximum Contaminant Level for Fecal Coliform/E. coli is 0.0% for Drinking Water Standards. (Title 22, California Code of Regulations, Section 644463.1). There is no current scientific basis to require Drinking Water Standards for irrigation water.
Additional background information on irrigation water quality standards, GAPs microbial testing and access to Water Quality planning resources are available from the University of California, Davis and the Water Quality and Technical Assistance Program for California Agriculture.
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