Rains clouded bay, but temporarily

Record downpours decreased water clarity

October 07, 2004|By Rona Kobell | Rona Kobell,SUN STAFF

The bad news is that last month's hurricanes dumped record amounts of rain into the Chesapeake Bay, causing a sharp drop in water clarity and an increase in pollution.

The good news is that the murky conditions Ivan, Frances and Charley exacerbated are probably temporary and won't spoil what has been a great year for upper bay grasses and water quality.

"In the short term, the bay got cloudier," said Scott Phillips, the Chesapeake Bay coordinator for the U.S. Geological Survey. But in the long term, he said, water quality should not be affected.

Phillips presented his findings yesterday at the annual Chesapeake Bay Monitoring Data Analysis Workshop in Laurel, where scientists from Maryland and Virginia gathered to discuss the bay's overall health.

The Susquehanna River, which provides the bay with about half its fresh water, was the largest factor in the trends Phillips described. The river's flow into the bay reached 113,000 cubic feet per second, the highest amount for a September in 67 years.

For the first time in eight years, the Susquehanna's current was strong enough to pull up sediment trapped in Conowingo Dam and carry it downstream. The result, Phillips said, was inordinately cloudy water. At times, water clarity measurements in areas north of the Bay Bridge were about a 10th of a meter, a fraction of the clarity usually seen this time of year, which is about a meter.

But the consensus seemed to be that for all the damage the hurricanes caused in the short term, the consequences would have been far worse for the bay had the storm hit in June, as Tropical Storm Agnes did in 1972. Fall's cooler temperatures also bring winds that mix the bay's water, diluting pollution. Also, in September, the bay grasses that provide crucial habitat for crabs and food for waterfowl are virtually finished with their growing season.

Though bay grass growth recently hit a 20-year low, researchers have seen a bumper crop in the upper bay since spring. They attribute that to a decline in phosphorus flowing into the bay from Pennsylvania farms and to a strange kind of macro algae. Most algae block the sun and hinder grass growth, but scientists say they think the blooms in the upper bay, which form a thick carpet over the grasses, might be trapping sediment and helping the grasses grow.

Peter Tango, chief of quantitative ecological assessment with the Maryland Department of Natural Resources, called the upper bay's grass growth "phenomenal" and predicted that it might set a record, even if water clarity does not.

"It's basically chocolate milk down the middle of the bay now," Tango said. "I'm sure those clarity records are going in the other direction."

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