WASHINGTON – The Chesapeake Bay has absorbed excessive amounts of freshwater over the past four months, when streamflow broke a September record and ran 60 percent higher than normal in October.
The U.S. Geological Survey said it expects November to be a more normal month, although streamflows are still expected to be above average. The increased flow, mostly attributed to this year’s tropical storms, delivers more nutrients and sediment — the bay’s primary pollutants.
But experts say the timing of the streamflow could have been worse.
“It doesn’t look like it’s going to have a dramatic effect this year because it’s late in the season,” said Scott Phillips, Chesapeake Bay coordinator at the Geological Survey. “You might see an effect this spring when the water starts to warm up.”
Biological activity is slowing as winter approaches, experts say, but if the coming months are full of rain and snow, the heavy flows will continue to pick up runoff from farms, urban areas — even air pollution. That can result in cloudy water blocking sunlight to underwater plants and algae blooms taking away oxygen that is needed by fish, crabs and oysters.
In such a scenario, said Bill Street, director of watershed restoration at the Chesapeake Bay Foundation, “Underwater grasses die off. Fish don’t have as much healthy habitat.” He said about 80 percent of bay pollution comes from runoff.
In September, streams and rivers dumped 116 billion gallons of water a day into the bay, the most since record-keeping began in 1937 and 72 percent higher than the record set in 1975. In October, about 45 billion gallons entered the bay every day, the USGS said.
Bay watchers said there were some plumes of clouded water in the bay in September, and that bay users may still see a few turbid areas now.
While the Susquehanna River normally accounts for about 50 percent of the freshwater flow into the bay, that percentage was even higher in September as the river carried hurricane waters down from Pennsylvania, said Wendy McPherson, a USGS hydrologist.
“A lot of the hurricanes pretty much missed us,” McPherson said. “But they did hit Pennsylvania and that’s part of the Chesapeake Bay watershed.”
Bay experts said that wet years like this one and 2003, have been hard on the bay. During the late 1990s and in 2000 through 2002, by comparison, rainfall was minimal and the bay started to recover, Street said.
“The drought does that just by not having the rainfall deliver the pollution,” Street said. “But of course we can’t count on that to save the bay.”
This year’s sediment pollution was also unusual because some of it came from reservoirs.
“This was the first time we had large amounts of sediment scoured out of the reservoirs and into the bay,” Phillips said.
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