Suburban Streams Important for Restoration of Bay

By ALEX DOMINGUEZ
Associated Press Writer

BALTIMORE (AP) - Restoration efforts on streams in low density residential areas should yield the most nitrogen-reducing benefit for the Chesapeake Bay, a University of North Carolina researcher said Tuesday.

Removing nitrogen is a key to bay restoration efforts because the so-called nutrient, from sources including lawn and farm fertilizers, fuels algae blooms that rob bay water of oxygen and keep light from reaching underwater grasses.

Lawrence Band, the University of North Carolina researcher, presented an analysis of nitrogen flows in streams in the bay watershed at an American Geophysical Union conference.

The researcher said streams in low density residential areas have the combination of factors that lend themselves to restoration efforts.

Breaking down nitrogen compounds into gaseous nitrogen that can return to the atmosphere requires bacteria that live in low-oxygen or oxygen-free environments, such as the aquifers that run below many streams. The bacteria in those aquifers get the oxygen they need by stripping it from the compounds, freeing the nitrogen to return to the atmosphere.

However, development in many cases has created environments where rainwater runs quickly off paved parking lots, driveways and lawns, filling nearby streams and flowing to the bay before it has a chance to seep into the aquifer.

To help the process, ecological stream restoration efforts often redirect the flow to slow the stream and spread it over a wider area, allowing the water to sink into the aquifer.

While streams in urban areas often produce high amounts of nitrogen, surrounding development tends to make their flow too fast-moving. Forest streams on the other hand tend to flow slowly, but with little nitrogen content.

"Low density suburban (streams) yield both a large amount of nitrogen through septic systems, lawn fertilization and so forth, and most of that load comes at fairly low discharges," Band said.

Getting the most nitrogen reduction from stream restoration also has large financial implications, Band said, noting Chesapeake Bay restoration is estimated to cost $18 billion and stream restoration in itself has become a multibillion dollar effort.

Peter Groffman of the Institute for Ecosystem Studies said he was awaiting data from studies on stream restoration efforts in the Baltimore area to see whether they document reductions that could be used by local governments as proof of nutrient reduction.

Sharon Hall, an Arizona State researcher who also appeared at the conference, said urban planning should take into account natural nitrogen removal methods.

"We're not thinking ahead, per se, about nitrogen removal," Hall said. "We're thinking about removing water from the street."

Retention ponds in some developments, for example, often collect rainwater and help slowly recharge underground aquifers, but fertilization of lawns overwhelms them with nitrogen, she said.

Band said stream restoration is not merely a suburban effort. Planners in urban areas, for example, can take advantage of open land in abandoned industrial or residential areas near streams to create the conditions for nitrogen removal.

"It's a trade-off," Band said, noting streams were often altered to help flood control.

"You have the opportunity to redesign those areas to be more natural and probably a much more pleasant area for people to live in."

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