Harnessing rainwater for later use: Ancient solution to modern extremes

In one Texas suburb, a battle of rainwater harvesting tanks is on. During a neighborhood garden tour in May, Kyle Peavy spotted Richard Townsend’s 260-gallon tank and decided to go even bigger. Just two months later, Mr. Peavy installed his own rainwater harvesting system – four times the size. 

“I’m both proud and slightly envious,” says Mr. Townsend of Mr. Peavy’s system.

The two neighbors use the tanks to water their backyard gardens. And while plants like rainwater better than sink water, the men installed these water systems for another reason besides gardening. Both see rainwater harvesting as a practical way to respond to water scarcity. They’re not alone.  

Rainwater harvesting dates back more than 4,000 years to early Roman and Mayan civilizations. In its simplest form, it involves collecting water as it falls from the sky into barrels, so the water can be saved for later use. Today, this ancient solution is seeing a resurgence among homeowners, businesses, school districts, and at least one church. 

Among green solutions to climate change, rainwater harvesting stands out in its potential to address two sides of a water paradox – flooding that destroys critical infrastructure, as well as drought conditions that threaten freshwater supplies. 

“We know that some areas are going to become drier. We know that storms are going to become bigger. And thinking about any practice that can help us address multiple of these issues is really important,” says Sarah Sojka, associate professor of physics and environmental studies at Randolph College in Lynchburg, Virginia. 

As Americans across the United States turn back to one of the oldest methods in the book, there’s a sense of empowerment that comes from knowing one small action can have a ripple effect. One small tank might just inspire something bigger. 

Tuning in to natural cycles

Typically, when rainwater falls on a roof, it is routed through a gutter system out into the yard or driveway and eventually into the road. Along the way, the water picks up pesticides and road contaminants, before flowing into curbside cuts that direct it into a nearby stream or lake. 

As the urban landscape has become more and more built up, the number of impermeable surfaces, such as paved roads, has increased, forcing larger quantities of water – and pollutants – into local waterways. When storms become more intense, the problem compounds, and these waterways overflow. 

Rainwater harvesting tanks divert that flow path, reducing the amount of water that hits local systems all at once. As stored tank water replaces tap water for outdoor use, the draw on the municipal supply is reduced, and water that soaks in through the ground eventually helps to replenish baseline flow.

But it’s not just an old-new way to water. It’s also a new way to think about water as more than an unending supply that spews from the tap. In drier climates especially, rainwater harvesting can provide a visual reminder of natural cycles, which can precipitate the ultimate goal: an actual reduction in water use.

“What does it mean when an area has a drought?” asks Mr. Townsend. “If you live in an urban area and you can water your grass with sprinklers, then it’s not so obvious that maybe your area hasn’t had rain in two months.” 

And although Mr. Townsend doesn’t consider himself a “green warrior,” he wants his children to understand these cycles. The rainwater tank, which shows natural ebbs and flows, helps him share greater water consciousness with his children. 

Scaling up

In a 2014 survey conducted by the Government Accountability Office, 80% of water managers anticipated freshwater shortages within the decade in at least some part of their state. Although one rainwater harvesting tank is unlikely to change local water quality and supply, when implemented at scale, the tanks can aid in overall water conservation – and local governments are taking notice. 

To encourage widespread adoption, cities across the U.S. are subsidizing the costs of tank installation, which can range from a few hundred to several thousand dollars.

Tucson, Arizona, started its rainwater harvesting rebate program in 2012, after residents had been living under drought conditions for over a decade. In Arizona, water is sourced from groundwater and the Colorado River, which was put under a drought contingency plan in 2019. 

Since it was implemented, the rebate program has resulted in more than 80 million gallons of rainwater being collected, giving Tucson a small way to diversify its water source. “Water supplies are limited, and the more we can utilize the water that comes to us directly and naturally, the more we can begin to build … a more resilient urban landscape for our whole community,” says Tucson Water’s conservation program manager, Candice Rupprecht. 

“Americans just really like being self-sufficient, and ... at its core, this is self-sufficiency,” says Jaimie Galayda, a rebate participant who now works for Tucson Water.  

Fouad Jaber, a professor and water resources extension specialist at Texas A&M University, adds that the uptick in rainwater harvesting is being driven by a growing, collective, environmental consciousness. But not everyone is sold on the system’s benefits. Skeptics worry that rainwater collection will speed depletion of already-threatened bodies of water. 

But when rainwater is collected, says Dr. Jaber, it reduces the amount of water used from the municipal supply, which comes from local waterways. And if used for outdoor purposes, the water will soak into the ground, eventually feeding back into local bodies of water.

Thinking bigger than one

During the 2002 drought in Santa Fe, New Mexico, water was in such short supply that the city shut off irrigation to community parks, and Santa Fe High School let its baseball fields die. That’s when the school’s baseball coach put in a request for the school district’s first rainwater harvesting cistern. Since then, the district has installed tanks at five other schools that together can capture over 500,000 gallons.  

School districts are big resource consumers, says Lisa Randall, the sustainability program coordinator for Santa Fe Public Schools. “That, to me, means we have a big responsibility to our students and our community and the planet.”  

It could take decades before the project pays for itself, depending on water prices, but the return goes beyond finances. 

“With storms predicted to be less frequent but more intense when we have them, any effort that we can make to reduce our demand on the potable municipal system and capture and use rain and storm water when it falls is extremely beneficial,” says Ms. Randall. “It expands the city’s ability to deliver water to other customers in a time of drought.” 

St. Louis has a different problem, but rainwater harvesting is helping just the same. Like many older cities, St. Louis has a combined sewer system, meaning storm pipes connect with wastewater pipes. Normally, all the water is treated before entering the Mississippi River, but large storms overwhelm the system, creating direct overflow into the river. And when large quantities of water enter all at once, the water quickly swells out into the surrounding communities.  

Large rainwater cisterns like the one at Jubilee Community Church help to divert the water before it overflows. In 2018 the church installed a 150,000-gallon cistern with funding and other support from St. Louis’ municipal sewer district and The Nature Conservancy. Rain flows off the church’s roof to the underground catchment, then irrigates a large garden and orchard, which includes tomatoes, cucumbers, beets, figs, and even juju berries.  

Building the rainwater tank with the garden on top is a way of reinvesting in the community, says Andy Krumsieg, the church’s pastor. “This is a very sustainable project because it will keep water out of the sewer system forever … and it created a tool for urban agriculture.”

“It’s mutually beneficial,” he says.  

Ms. Randall sees it that way too – and points out that the benefits go beyond the local community: “[Rainwater harvesting] contributes to a broader climate solution because when anybody does this work, we all win, no matter where it’s done or who does it.”