When it pours

You may be able to harvest more rain than you think


There is often confusion about the extent to which we can collect rainwater under Colorado law.

But those who think rainwater harvesting is prohibited outright are all wet.

Even though it seems logical that we should be able to use water that falls on our own property, state water laws have traditionally limited the collection and storage of precipitation because of those who have rights to that water downstream.

The regulations were loosened a bit under a 2009 law that allows residential properties that use or are entitled to a well — and that are not served by municipal water or a water district — to collect water from their rooftops.

And according to Boulder landscape designer and contractor Alison Peck of Matrix Gardens, even those without a well may have more flexibility than they think under state law.

While one may not be able to direct rain that falls from gutters into a cistern or barrel, Peck says water from downspouts can be diverted to patches of earth to support the growth of gardens, shrubs and trees — instead of flowing down pavement and concrete to the local storm drain.

“I’d been interested in rainwater harvesting for years, but always heard it was illegal,” she says. “Every drop of precipitation that falls is owned by somebody.”

That is changing nationally, especially in arid areas like Tucson, Ariz., and Santa Fe, N.M., which now actively promote rain collection. And nationally, one of the most significant urban water challenges is stormwater management. In big cities on the East Coast, Peck explains, the infrastructure is sometimes so old that the sanitary sewer system is connected to the stormwater system, and both drain into the sewage treatment plant, meaning that the plant gets overloaded during major storms, which can cause polluted sewer water to escape. So there is a big push nationally to reduce the amount of water that goes into those types of stormwater systems.

Even along Colorado’s Front Range there have been commercial precipitation harvesting projects where water coming off of parking lots is directed to landscaped areas, for instance, or special porous concrete is used to allow water to seep into the earth below.

“‘Thou shall not use rainwater’ was this monolithic edifice that was never going to change,” Peck says. “But that is changing.”

One way to look at rainwater harvesting, she explains, is that it is simply a way to restore the environment to its natural state, to the conditions we had before cities and their houses, roofs, parking lots, streets, sidewalks and driveways made water flow instead of get absorbed.

Peck confirmed that homeowners can legally make use of the rain in their gutters in certain ways after she checked with the Colorado Division of Water Resources for a project she is working on. That project is to create a rainwater harvesting system for a new home in the Prospect neighborhood of Longmont. The house is on track to receive a LEED (Leadership in Energy and Environmental Design) platinum rating from the U.S. Green Building Council, and was designed by CU architecture and engineering students on a 2007 Solar Decathlon team. The building will use no fossil fuels and will have 100 percent of its energy produced by solar photovoltaics. Owner Kitty Brigham says the rainwater harvesting system will be a key factor in gaining LEED platinum status.

Peck says she learned that property owners are not just limited to watering their lawns and gardens with redirected downspouts, they can even collect water for a brief period behind earthen berms or in small depressions, as long as the water soaks into the earth within 24 hours.

She explains that one of the main challenges is to divert rainwater before it hits pavement.

“A lot of times driveways are the biggest collectors of rainwater, and it’s hard to catch it because it’s headed down to the street,” Peck says.

Once the water is diverted and reaches its alternate destination, like a bush, she suggests placing a piece of flagstone below the spout to keep the rushing water from eroding the soil into channels. The flagstone helps spread and disperse the water.

One method Peck formerly employed was a system of perforated pipes that would carry water and distribute it through holes. But she found that the pipes often got debris or animal nests in them, so now she recommends keeping water on the surface when possible.

“The simplest strategy is to make downspouts go onto land, not more paving,” Peck says.

One option is to create a “rain garden,” a small depression formed to gather rainwater, planted with vegetation that doesn’t mind getting flooded during storms.

Another consideration is the depth of the root systems being watered. Many plants native to the arid West have evolved deep root systems that allow them to survive drought. Peck says lawns can be good at holding and absorbing water, but most yards in Colorado have bluegrass, which has a shallow root system, so locals may be better off directing rainwater to trees, shrubs and perennials that have deeper root systems and “can pull on that water over a long period.”

Pointing a downspout into a shallow-rooted vegetable garden is probably not a good idea for the same reason, she says, adding that a heavy storm could result in damaging inundation.

There are also safety precautions to consider. Peck advises directing water at least 10 feet away from house foundations.

“You don’t want to flood your basement,” she says, adding that some developments have been constructed in areas with expansive clay soil that can damage foundations when it gets soaked.

Homeowners should also be careful not to direct water over leach fields or to neighboring properties, and Peck notes that creating rain gardens or swales next to established trees and shrubs might upset the below-ground balance to which they have become accustomed.

With a little common sense and some extra downspouts, gutters or pipes, she says, Colorado homeowners can take advantage of their precipitation without running afoul of state law.

To make sure you are following the rules properly, check out the Division of Water Resources website at http://water.state.co.us.

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