Climate & Sustainability
Innovative and artful rainwater harvesting nourishes gardens and hope
UC Santa Cruz cosmologist leads widely interdisciplinary project funded by the Center for Coastal Climate Resilience to turn urban runoff into low-cost irrigation
This 500-gallon tank will irrigate the UC Santa Cruz Village garden with rainwater during the region's dry season. It was designed, built, and adorned with a painted mural by students as part of an interdisciplinary pilot project funded by the university's Center for Coastal Climate Resilience. (Photos by Carolyn Lagatutta)
A team of scientists, artists, engineers, and students have joined forces at UC Santa Cruz to help promote the use of stored rainwater as a resource for growing food close to home.
Backed by a $100,000 grant from the university’s Center for Coastal Climate Resilience (CCCR), and with support from OpenLab, UC Santa Cruz cosmologist Alexie Leauthaud-Harnett is leading a multi-year project to study the agricultural potential of rainwater harvesting. Additionally, Leauthaud and her team are developing educational resources to help guide anyone through the process of building their own sustainable garden irrigation systems.
Rainwater harvesting involves collecting rainwater for use in everything from flushing toilets to irrigating gardens. In natural landscapes, rainwater soaks into the porous ground, gradually making its way into aquifers and water sources. But in built environments, rainwater streams off hard rooftops into impermeable, paved streets and washes pollutants and trash into sewers and waterways. When the water has nowhere else to flow, it pools and causes flooding. Harvesting rainwater can help divert some of that wasted resource into sustainable systems.
Community roots
Leauthaud worked with engineers and UC Santa Cruz undergraduate students to design a water-harvesting system that can collect 500 gallons of water from rooftops and keep a garden watered throughout Santa Cruz’s dry season, which runs from March to October. The system relies on gravity rather than electric pumps, requiring no power to operate.
The idea for the water-harvesting project stems from an experience Leauthaud had while working on another program she is nurturing, Seed Spoon Science. This program connects Latinx STEM students on campus with local families to build home gardens that double as a food source and natural laboratory for children to learn about climate science.
One day, when Leauthaud was building these garden beds, she recalled a participant asking her, “Well, have you thought about water? Because asking me to grow food is great, but the city of Santa Cruz has increased water prices.”
That got Leauthaud, an associate professor of astronomy and astrophysics, thinking about how she could help lower the cost for families wanting to grow their own produce. When she noticed in 2023 that CCCR was seeking proposals for pilot projects aimed at addressing climate change in coastal communities, she saw it as an opportunity for seed funding.
From galaxies to gardens
Leauthaud reached out to UC Santa Cruz’s Impact Designs: Engineering and Sustainability through Student Services (IDEASS) program, which uses hands-on projects to teach students how to engineer solutions to environmental problems. At the time, IDEASS students were learning about rain tanks that could be filled from the gutters that line roofs. Layla Scott, an IDEASS alumnus who was advising students at the time, became the project manager and lead rain engineer on Leauthaud’s CCCR-funded project.
Designing rain harvesting systems teaches students how to think like a rain engineer, Scott said, “to take the nuisance of flooding or too much water in one space and turn that into a solution, using that water for irrigation or toilet flushing or fire prevention.”
The online gardening world contains plenty of websites explaining how to build DIY rainwater-harvesting systems or extolling their virtues. But Leauthaud, an avid gardener, was frustrated with the lack of a single resource that provided accurate and accessible information on the subject. “It’s actually quite hard to find answers to pretty simple questions sometimes, like how does compost work, and how much water should I put down?”
Leauthaud wanted to develop a resource that could teach people how to build their rainwater-harvesting systems while also providing information on how much water they could save and how much produce they could grow. She approached this task with the same rigor she brings to her research on the cosmos.
Scott worked with students in the IDEASS program to design and build the project’s first tank, which was installed at the UC Santa Cruz Village garden last June. The green, 500-gallon plastic tank is fed by a PVC pipe hooked into a rooftop gutter. The harvested rainwater first passes through a mesh filter to remove larger debris, such as leaves. After that, the water flows into a dead-end pipe called a “first flush diverter,” where finer waste, such as bird droppings, sinks to the diverter’s base. The water that reaches the top of the diverter then flows into the tank, which feeds into the drip irrigation system snaking through an 8-foot by 4-foot garden bed.
Everything from the piping to the gravel-filled platform supporting the tank to the wood-framed garden bed was built by IDEASS students who documented the process to produce educational videos and instructions.
A living laboratory
This garden isn’t just for growing food, it’s also a laboratory. For the past year, students have been planting crops of Newham lettuce to study how much food the garden can produce using harvested rainwater. James Curtiss, an undergraduate in UC Santa Cruz’s Environmental Science program, is interning with Leathaud as the garden’s lead data gatherer.
On April 21, Curtiss presented their results at a celebration of the project’s progress, dubbed the “Water Fair,” held at the Seymour Marine Discovery Center. During a six-month period, the garden produced 336 heads of lettuce and used only 261 gallons of water, Curtiss told attendees.
“And we have a 500-gallon rain tank up there, so that means we could have grown potentially double that throughout the entire summer with just rainwater harvested off the roof,” said Curtiss, a farm field and irrigation staff member at the UC Santa Cruz Center for Agroecology.
Leauthaud is working with a UC Santa Cruz graduate student using publicly accessible satellite imagery to estimate the amount of yard space in Santa Cruz that could be converted into rainwater-fed gardens. Combining data from both the garden and the mapping study, Leauthaud hopes to calculate the total quantity of produce that could be cultivated by home gardens relying on harvested rainwater.
As part of the project’s education and public outreach efforts, Scott and the IDEASS students installed a second tank next to the entrance of the Seymour Center, where visitors can stop to learn about rainwater harvesting.
“It’s a seamless system, one of our best designs that we’ve installed so far,” Scott told attendees at the Water Fair. “The design and installation are almost identical, a sign of a well-planned engineering system.”
The tank at Seymour will soon be adorned with a mural designed by Alberto Miguel Vazquez, a master’s student in UC Santa Cruz’s Environmental Art & Social Practice master of fine arts program.
“They had heard about my interest in thinking about water, water scarcity, and food sovereignty,” Vazquez said, “and this project just seemed to really align with those.”
For Leauthaud, bringing together diverse disciplines such as art, science, and engineering is necessary for addressing Earth’s climate crisis. “It’s going to require highly interdisciplinary work across all the different sectors. It’s also a challenge that faces everybody,” she said. “Whether you’re in the humanities or in astrophysics, like myself, or you work at Safeway, everyone’s going to face these challenges.”
“It’s going to require highly interdisciplinary work across all the different sectors. … Whether you’re in the humanities or in astrophysics, like myself, or you work at Safeway, everyone’s going to face these challenges.”
Alexie Leauthaud-harnett
The project website currently includes instructions for building a water-harvesting system along with preliminary results from the team’s gardening research. The next step, Leauthaud said, is to expand the website to include instructions for how much water to use for gardening, informed by the team’s ongoing research.
The act of building rainwater-harvesting systems, Scott said, is also a way to empower people who don’t know where to start when confronting the climate crisis. Scott planned this year’s Water Fair around the theme of “hope.”
“The work that we completed together was insightful,” Scott told attendees, “and I can confidently say UCSC is working towards environmental advocacy and creating systems to save our planet Earth.”
The project’s co-investigators are environmental studies professor Elliott Campbell, who holds the Gliessman Presidential Chair in Water Resources and Food Sustainability, and physics professor Sue Carter. Other collaborators include Tamara Ball, lecturer and director of experiential learning at the Baskin School of Engineering, residential-education coordinator Maya Hernandez, and retired mechanical engineer Kenneth Minardi, a mentor and technical advisor with the IDEASS program since 2011.