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Rainwater Catchment and Water Quality

How do you know your catchment water is safe?

Standards for water quality are generally developed by health organizations at local, state, federal, or world-wide levels.  The County of Hawaii's Water agency applies standards to the water supplied through its water mains.  The World Health Organization produces guidelines for countries around the world.


When water isn't supplied by the county, often the case in rural areas, residents must collect and store water for delivery to their homes for both general household use and for drinking.  The University of Hawaii's CTAHR has developed guidelines, techniques and best practices for catchment-dependent households.  (See our link below to "Guidelines for Rainwater Catchment Systems"). However, residents on catchment aren't required to follow these guidelines and practices. 

Whether water is safe for household use or for drinking can be a complicated subject.  On one side of the issue is the water itself:  "Where did it come from, how was it stored, was it filtered or treated, and how was it delivered to a household?"  On the other side of the issue is the water use: "Is the water for general use (washing, cleaning, bathing) or also for drinking?"  And finally, if the water is being consumed, "Who is drinking the water, what is their life experience with water quality, and how vulnerable is each person in the household?"  In the end, the answer may be, "It depends."

PMKCA's president, Joe Clarkson, recently received an analysis of the water collected in his catchment tank and delivered to his house. The PMKCA Newsletter issue for November 2023 summarized his family's experience with catchment water and the results of the testing performed on his water. To keep that article of a reasonable size and degree of technicality, many interesting details were omitted.

Residents of PMKCA's communities and of other rural communities on the Hamakua Coast will find the details of Joe's results interesting and informative.  Here is a link to the complete article.

"Rainwater Harvesting and Catchment Water Quality" 


Joe Clarkson, PMKCA President

What are Hawaii's guidelines for catchment water quality?

The Big Island has a high percentage of residents who don't have access to county-supplied water and depend on rainwater collected on their property for household use and for drinking.  Recognizing the potential health risks of poorly stored and untreated water destined for households, the University of Hawaii's College of Tropical Agriculture and Human Resources (CTAHR) has published a set of guidelines and best practices for collecting, storing, and maintaining quality water supplies on site.

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Guidelines for Rainwater Catchment Systems for Hawai'i


Patricia S. Macomber

University of Hawaii CTAHR

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