PARA515

1. Controls for water quality of
irrigation source water
Regulations or Best Management Practices?

2. Water Quality Regulations:
Advantage
• Creates arbitrary water quality
standards
• Convenient for govt.
• Politically correct
• Creates data of uses
• Increases awareness of issue
Disadvantage
• Requires government support
• Requires resources to fund,
administer and enforce.
• Difficult to enforce - geographical
challenge of non-point source of
contamination.
• Only as good as resources put into
system.
• Epidemiology of pathogens from
irrigation water not well
understood

3. Best Management Practices
Advantages
• A system that provides guidance
to ensure source water is low
risk of microbial contamination.
• Financial incentives for good
practices.
• Builds on shared learning.
Examples - Commodity Specific
Guidance for Leafy Greens,
Melons and Tomatoes
Disadvantages
• Volunteer compliance
• A farmer needs to determine that it is
in their ‘economic interest’ to
undertake the control measures. The
farmer must clearly see the potential
economic benefits from implementing
management controls: i.e., erosion
control measures to maintain soil
fertility, less water usage (minimum
tillage), drainage development, capital
costs associated with improved
manure handling and distribution,
wetland construction, etc.
(Sagardoy, 1993).

4. Quantitative Microbial Risk Assessment Tool
• A model that establishes a relationship between concentration of
pathogens in irrigation water and the probabilities of human illness.
• Can be used for many variables - specific pathogen, water sources,
and agriculture management methods. Uses complex modeling to
achieve a ratio of annual risk of infection, i.e., 1:10,000
• Adopted by the WHO in developing guidelines for water related
diseases.
• Limitations: currently only at laboratory scale, needs to be scaled up
to field, misses complex microorganisms processes of decay and
persistence.

5. Constructed Wetlands - example
• Constructed wetlands (on-site) can be a low-cost and effective
treatment methods for reducing nutrients and bacteria from irrigation
waste water.
• Factors: Importance of the design is key - to address, hydraulic
retention times, sedimentation and aquatic vegetation types. The
shorter the hydraulic retention times, the better, as long treatment is
achieved. (Sagardoy, 1993).

6. Recommendations:
• Prevention management approach in best.
• Water quality of source water needs to be of a potable standard.
• Ensure no cross-connection within water distribution systems and install
back-flow prevention devices.
• Prevent faecal contamination of produce on site.
• Washing and sanitizing of produce before distribution – irradiation.
• Supply chain management – refrigeration and limit people coming in
contact with produce.
• Develop and implement a Water Safety Plan & Quantitative Microbial Risk
Assessment Tool
Source: Lynch, et al (2009), Gelting, et al (2014)

7. Source:
Pachepky, Y., et al. (2011). Irrigation Water as a source of
pathogenic microorganisms in produce: A review
(Sagardoy, 1993).