Properly designed “rain gardens” can effectively trap and retain up to 99 percent of common pollutants in urban storm runoff, potentially improving water quality and promoting the conversion of some pollutants into less harmful compounds, according to new research scheduled for publication in the Feb. 15 issue of the American Chemical Society journal, Environmental Science and Technology.
The affordable, easy-to-design gardens could help solve one of the nation’s most pressing pollution problems, according to the study’s authors, Michael Dietz and John Clausen of the University of Connecticut.
More than half of the rainwater that falls on a typical city block, one with 75 percent or more impervious cover — such as roads or parking lots — will leave as runoff, according to the Environmental Protection Agency.
This runoff includes metals, oils, fertilizers and other particulate matter, the Connecticut researchers note. Easy-to-construct rain gardens — shallow depressions in the earth landscaped with hardy shrubs and plants such as chokeberry or winterberry surrounded by bark mulch — offer a simple remedy to this problem, they say.
In their two-year study of roof-water runoff, the researchers found that rain gardens significantly reduced concentrations of nitrates, ammonias, phosphorous and other pollutants reaching storm drains. In addition, design tweaks that allowed polluted rainwater to pool at the bottom of the gardens permitted bacteria in the soil to convert harmful nitrates into nitrogen gas, preventing them from entering the groundwater.
Living in high desert country, you would think retaining rainwater runoff would have been a priority for decades. Not in a state [New Mexico] where politicians actively battle to retain last place status for education, income and common sense. So, the number of projects like this are negligible.
Meanwhile, countries with budgets in the pick-and-shovel class work hard at achieving what we throw studies at. A notable example being the Chennai Metro Water District in India. I ain’t kidding about the pick-and-shovel part; but, they go out and do something instead of talking about it.
I’m all for these urban rain gardens. What’s with all the lawns? Most people have them and would think their lawn is as unique as they are, if they could.
Great, now the vegitation and soil are even more contaminated…I guess you can’t win either way.
Like the highway in front of our house they rebuilt in 2002. When they built the adjoining ditch, they filled it with large rocks so any run off will soak right into the ground. Of course this brings with it all the oils, salt, rubber, and other contaminants with no chance to degrade. Of course some soil would help separate the solid particles and hold the dissolved material a little longer.
Given the choice, I would rather have a grass filled ditch which could strain the runoff before it soaks into the ground water. It is hard on the mower to cut the noxious weeds sprouting from between the rocks anyways.
Actually Pat, hydrocarbons like oil and gasoline do biodegrade. Salt of course doesn’t biodegrade, but it does get dissolved and swept away by water.
Eideard–do you have a link to a practical website explaining how to build a rain garden on a small scale, that works in arid climates like NM, AZ or NV, and doesn’t wind up as a semi-permanent puddle in your yard? I’m not referring to rain barrels as in your link , but groundwater recharge.
Floyd — I’ll try to find you one in the morning. Just finished up tomorrow morning’s posts and I’m about to watch the tape delay telecast of Bolton Wanderers kicking Arsenal out of the FA Cup.
Google your way around Austin, TX. There have been several biz started there since the city council 1st supported rainwater runoff retention.