Catching Raindrops

Stormwater catchment systems support water conservation

By: Darlene Dela Cruz

May 1, 2026

A catchment system can store rainwater in barrels for later use in watering plants and outdoor cleaning. Photo by Olivier Koning
A catchment system can store rainwater in barrels for later use in watering plants and outdoor cleaning. Photo by Olivier Koning

Glen Hong of Kaimukī worked with environmental nonprofit Mālama Maunalua to install rain barrels for a rainwater catchment system at his home.

“I’ve wanted to have rain barrels for a while to help conserve water and to help irrigate garden areas and some trees,” Hong says.

Mālama Maunalua, the City and County of Honolulu Department of Facility Maintenance and a hui of private sector companies and nonprofits installed more than 200 rain barrels at properties across O‘ahu through the Rainwater Incentive Program they launched last year. Mālama Maunalua Executive Director Doug Harper says the positive response for this pilot program indicates public interest in the benefits of rainwater catchment systems.

“We estimate the barrels will remove almost 500,000 gallons of runoff annually,” Harper says.

Creating a catchment system to channel water from your roof through your gutters and into rain barrels in your yard can be a DIY project or done by professional contractors. The Honolulu Board of Water Supply (BWS) explains that your optimal catchment system depends on the climate in your area, the space available on your property and your budget for labor and equipment.

Stackable rain barrels work best in apartments and smaller properties in urban Honolulu. Areas like Kāneʻohe with expansive yards can accommodate larger systems. Any catchment system, regardless of size or complexity, can help residents save money and conserve resources.

Catchment systems can range from a singular barrel as seen at Glen Hong’s Kaimukī home (above) to larger cisterns attached directly to rooftop gutters (illustration example below).

“Rainwater is a free source of non-potable water that anyone can collect and use on their ornamental plants and for outdoor cleaning,” says BWS Civil Engineer VI Lorna Heller. “Using rainwater helps you save money on your water bill as well as save on your sewer bill.”

Hawai‘i Department of Health (DOH) officials caution that catchment systems require adequate filtration, water treatment and maintenance to prevent contamination.

“Rain catchment systems can be affected by pests, environmental contaminants, bacteria and parasites, and chemicals from roofing materials,” DOH said in an email statement. “A properly designed rainwater catchment system can address these concerns.”

An app called Follow the Drop, downloadable from Google Play and the Apple App Store, allows local residents to see how their catchment systems impact the environment. Lauren Roth Venu, founder and CEO of 3RWater, explains that her company developed the app with local government groups and neighborhood nonprofits to educate residents on the cumulative effect catchment systems have on communities.

“If we can all do a little bit, it can add up to quite a lot,” Venu says.

Additional Resources:

  • Mālama Maunalua: malamamaunalua.org
  • Hawai‘i Green Growth: hawaiigreengrowth.org
  • Hui o Ko‘olaupoko: huihawaii.org
  • Honolulu Board of Water Supply: boardofwatersupply.com
  • University of Hawai‘i College of Tropical Agriculture and Human Resilience: www.ctahr.hawaii.edu/hawaiirain
  • Purchase rain barrels for catchment systems at Hardware Hawaii, City Mill and other local home improvement stores

This story appears in the May/June 2026 print issue of Ku‘u Home magazine.