Water Measurements in Durham’s Rain Catchers Project to Begin in June 2015
April 29, 2015
The Durham Public Works Department is set to begin the third phase of its Rain Catchers
stormwater management project by mid-June.
The project, designed to test the effect of stormwater retention on the water quality of Durham’s South Ellerbe Creek, began in 2013 by measuring the quantity and quality of stormwater runoff entering the creek without any retention measures in place.
“We’re looking at all the things that might be effected,” said Michelle Woolfolk, a water quality engineer for Durham Public Works. “Changes in the amount of water, rate of water, quality of water, nutrients or something else.”
glides over roofs, roads and lawns collecting pollution and nutrients before running into a storm drain. The drain shuttles that polluted water into local streams and rivers so quickly that the water can erode away the riverbanks.
In rural areas, rainwater can soak into the ground where plants and soil can clean it and let it leach into local creeks a little at a time, which not only improves water quality but also prevents the storm surge from getting too high and eroding the creeks.
In cities and suburbs, however, rainwater does not have enough time to soak into the ground before finding its way to a storm drain. Rain gardens and cisterns trap water and let it slowly seep into the ground.
Woolfolk says, however, that very few studies have been done to quantify exactly what effect these rain catchers have on urban streams and over what period of time. So she and her colleagues will chart the effect of every major rainstorm at five locations on South Ellerbe Creek — which feeds Falls Lake, a major drinking water source — for a year, then come back and do it again in another three years, to determine the long term effects.
“We’ll probably see the real decrease in pollution in a few years. This summer we may see a very modest change or no change at all,” Woolfolk said. “We have this small area and we’re going to monitor the heck out of it.”
Monitoring the heck out of the creek requires a lot of work. Every time a rain storm is about to hit, they have to set up their equipment anew, hoping the storm will be big because the data is no good without a significant amount of rain. When the rain stops, they have to go back out, tear down their equipment, download any information collected and send their water samples off to a lab to be returned in four weeks.
They are on call 24 hours a day. If it rains, someone has to be there to measure it. Woolfolk says the days can be long, but it is worth it to protect our water.
“It’s a bit of a cliché but we’re all part of the problem and we’re all part of the solution,” she said. “Water is a common resource and we all need it.”
That is the message that Laura Smith, the public education coordinator for Durham Stormwater and GIS Services, has been promoting. Smith recruited participants for the Rain Catchers project and led public educational events to get local residents interested in stormwater.
That interest manifested itself in the form of 256 rain catchers around South Ellerbe Creek, exceeding the goal of 230. Those rain catchers included 41 rain gardens, 108 cisterns and 106 trees.
Even outside the Ellerbe Creek area, the message caught on.
“It was really gratifying when we heard from a group of people who regularly walked through a neighborhood with rain catchers,” Smith said. “They liked what they were seeing and asked us for more information.”
Smith says many families not included in the Ellerbe Creek study have asked for information on building their own rain gardens or cisterns. But she also says the science of reducing storm runoff is constantly improving.
Smith pointed to recent research from NC State University
that shows the effect of disconnecting a gutter’s downspout. While many water quality experts believed runoff does not quickly soak into clay-rich North Carolina soil, graduate student Natalie Carmen showed that letting water from the downspout run over the lawn reduces runoff by 47 to 97% compared to running it into a culvert.
“This is groundbreaking research,” Smith said. “Part of the reason we wanted it is it hasn’t been done before.”
As Woolfolk and the engineers begin to make their first post-intervention measurements, Smith encourages people both in and out of Durham to consider ways to control their stormwater.
“We are seeing improvements with the work we are doing,” she said. “Let’s keep doing it more of the same and keep seeing that improvement.”
— Daniel Lane
Daniel Lane covers science, technology, medicine and the environment in North Carolina.