Harvested stormwater counters climate change, Rainwater Catchment Bay Area, East Bay, Danville, Oakland, Walnut Creek, San Ramon, BlackHawk
Very Interesting stuff on Rainwater Catchment systems, which we install, and Water Conservation for all of California but especially for Bay Area, East Bay, Contra Costa, Walnut Creek, Danville, Palo Alto, Peninsula, and Oakland Residents.
By Suzanne Bohan
Contra Costa Times
Posted: 08/16/2009 12:00:00 AM PDT
Stormwater flowing off rain gutters, sidewalks and roadways may be the state’s new liquid gold as Californians face shrinking water supplies due to rising temperatures, a new report asserts.
“In Western states, there’s been an increasing push to see this as a water supply resource,” said Noah Garrison, an attorney with the Natural Resources Defense Council who co-authored the report, “A Clear Blue Future,” released last week.
Garrison teamed with UC Santa Barbara and University of Washington researchers to release this analysis of how rainwater capture or infiltration projects could make up for water shortages attributed to altered weather.
By 2050, winters cut short by climate change are expected to reduce by one-quarter the snowpack in the Sierra, according to the state Department of Water Resources, with greater depletion projected in the decades beyond. As these vast fields of high-mountain snow melt during the spring, summer and fall, they provide a steady source of pristine water to rivers heading to the lowlands, which replenish reservoirs supplying tap water used by millions.
Stormwater that’s usually dumped into the nearest waterway could fill a critical gap in this predicted shortfall, the new report states.
For the areas studied — urbanized regions of Southern California and portions of the Bay Area — capturing more of this rainwater at residential and commercial sites could net
more than 400,000 acre-feet of water a year, enough to supply two-thirds of the water used annually by the city of Los Angeles. If government and industrial sites were added to the equation, the water savings projection for those regions alone would increase by another 75,000 acre-feet annually. Hundreds of thousands more acre-feet of water are likely available if the rest of the state is factored in, Garrison said.
And capturing rainwater in cisterns or barrels, or diverting it into open fields, rain gardens or ponds, keeps it from entering the stormwater runoff system, which now contributes the majority of the pollutants fouling natural bodies of water.
It’s not news that rainwater runoff entering stormwater systems, and then creeks, rivers, bays and ultimately the Pacific, arrives laden with the detritus of city and suburban life — particles of heavy metals such as copper and mercury, PCBs, excess pesticides and fertilizers from gardeners and farmers, pathogens in pet waste, and plastic-laden trash.
In late July, the Natural Resources Defense Council released its 19th annual report on beach water contamination, which reported that polluted water from dirty stormwater and sewage overflows led to 20,000 beach closures or posted health advisories nationwide in 2008, a figure unchanged for four years.
Pollutants in the water
In California, 8 percent of the beaches tested for pollutants — primarily high bacterial levels — exceeded national standards, with a handful of the worst offenders closed or posted with advisories more than half the time. Most were at the numerous swimming beaches in Southern California, although in the Bay Area a few areas, such as Candlestick Point in San Francisco and Campbell Cove State Beach in Sonoma County, exceeded standards a third of the time. On the Peninsula, volunteers with the San Mateo chapter of a coastal advocacy group, Surfrider Foundation, conduct weekly water tests to protect surfers and other coastal water users from illnesses triggered by pathogens swept into the ocean by runoff.
“There are chronically polluted places,” said Edmundo Larenas, head of the San Mateo chapter.
Within the past decade or so, however, a new way of addressing stormwater pollution emerged using a technique called “low impact development,” or LID. The generic-sounding term refers to strategies for restoring native hydrology to a developed site, in that no more water runs off it during a storm than would if the site were undeveloped.
Under that scenario, rainfall hitting a developed area may be directed so that it sinks into the ground. In addition, the microbes in the soil and plants serve as “biofilters,” trapping such pollutants as heavy metals and chemicals, and converting them to less harmful substances or absorbing them.
“The ability of soil and vegetation to really filter out pollutants is absolutely amazing,” Garrison said.
Bay Area at forefront
The Bay Area now has scores of small and large biofiltration projects for capturing stormwater. For example, in San Mateo County, a $4 increase in registration fees for vehicles in the county, passed in 2005, is funding six pilot “green stormwater” projects. These include rain gardens and swales — long, narrow, vegetated depressions designed to hold and filter water — at Brisbane’s City Hall and next to the parking lot at the Fitzgerald Marine Reserve in Moss Beach.
In Walnut Creek, North Creek Church added a rain garden when it built a new church in 2008. At Mission Bay in San Francisco, swales create a small wetland that filters stormwater before it enters the Bay. And a parking lot overlooking Lake Merced in San Francisco features permeable pavement that lets rainwater sink into the ground, recharging the lake and an aquifer.
Other cities are pushing even harder to divert rainwater from the stormwater system. In Portland, Ore., the city’s Clean River Rewards program gives residents a discount on their utility bills for managing stormwater on their property. And in 2004, 76 percent of Los Angeles voters approved a $500 million bond measure to fund low impact development projects for capturing polluted stormwater before it fouls the region’s famed beaches.
A representative with the California Building Industry Association said no one was available to comment on the effect of low impact development requirements, which in the Bay Area and other regions apply to large development projects.
The use of rain barrels or cisterns to capture precipitation is another key technique in low impact development. Last year, the San Francisco Public Utilities Commission set aside $10,000 to subsidize the cost of 55-gallon rain barrels, so city residents paid $69 instead of $129. The funds were quickly depleted, and the agency plans to expand the program this year, commission spokesman Tyrone Jue said.
Juan Fuentes, an artist who lives with his family in San Francisco’s Bayview-Hunters Point neighborhood, said he’s delighted with the rain barrel he got from the program. It sits below a downspout next to his studio.
“I’m really excited about getting four or five next year,” Fuentes said. With that many, he expects to water his garden and a neighbor’s for the season.
“We won’t have to rely on faucet water,” he said. A sequence of rain barrels is also easy to set up and maintain, Fuentes added.
Conservation in action
At Mills College in Oakland, a 2,000-gallon container stores rainwater for the Natural Sciences Building, which opened in 2007. The water is used for the building’s toilets, and harvests as much as 60,000 gallons a year, as the water is used and then replenished by rainstorms. The new Graduate School of Business, opening this fall, has a 4,000-gallon cistern for holding runoff that will also supply the building’s toilets.
The growing numbers of low impact development projects were often designed with stormwater pollution-prevention in mind, but they have the added advantage of providing a critical new source of water as California’s population increases, but water supplies from the Sierra are expected to decrease, said Garrison, with the Natural Resources Defense Council. They can also provide an emergency supply of water in the event of a natural disaster, such as an earthquake, or a fire.
“LID was first simply developed as a way to eliminate pollution,” he said. “The second benefit that’s equal, if not more important, is it provides a safe, reliable water supply.”
In addition to easing pressure on the state’s overtaxed water system, rain that is harvested or directed to replenish underground water saves a substantial amount of energy, Garrison said.
The Department of Water Resources is the largest single user of electricity in the state, as it uses power to distribute water statewide, pumping it over such mountain ranges as the Tehachapi to reach Los Angeles. The Natural Resources Defense Council and others are pointing to low impact development, since it captures water locally, as a way to help reach greenhouse gas reductions called for by Assembly Bill 32, the 2006 state law that mandates greenhouse emissions by 2020 drop to 1990 levels. It’s also a cost-effective alternative to building ocean desalination plants, Garrison said, with none of the concerns about the plants’ effects on marine life, or their massive energy requirements.
Tom Mumley, assistant executive officer for the San Francisco Bay Regional Water Quality Control Board, which regulates water quality in the region, also noted the water-saving benefit of capturing rainwater, in addition to its critical role in pollution prevention.
“It all adds up,” he said. “It’s so logical.”
Rain barrels — These containers, usually 55-gallon drums made of durable plastic, are directly fed by downspouts. A spigot at the bottom fits a garden hose, and gravity forces out the water. The barrels include a mesh covering to prevent insects, such as mosquitoes, from entering.
Diverting runoff — A simple method for reducing stormwater runoff is attaching a large tube to a downspout, and directing the water to a wide, unpaved area where it can spread out and infiltrate the soil.
rain gardenS — These gardens are planted in depressed areas near buildings’ downspouts, which allows them to capture rainwater and let it slowly soak into the ground. They’re designed to withstand extremes in moisture. Riparian plants, adapted to grow along streams, are well suited for rain gardens.
For details, go to the Low Impact Development Center’s Web site, www.lowimpactdevelopment.org.
To view the report, “A Clear Blue Future: How Greening California Cities Can Address Water Resources and Climate Challenges in the 21st Century,” go to www.nrdc.org.