Pollution levels are not heading in the right direction for the largest river on Maryland’s Eastern Shore.
A new study by the U.S. Geological Survey of nine major Chesapeake Bay tributaries found that the Choptank River was the only of these big waterways to see large increases in nitrogen pollution over the last three decades.
Nitrogen pollution in the Choptank River rose a whopping 53 percent between 1978 and 2008, according to the research by Bob Hirsch, a hydrologist at the U.S. Geological Survey, and colleagues. Too much nitrogen can stimulate the growth of algae that blooms and then dies, causing low-oxygen “dead zones.”
“Given the land use in that area, we have to say that it’s some aspect of agriculture that is doing it,” said Hirsch of the increase in the Choptank. “There is a reservoir of nitrogen that has been building up over the last several decades” in the ground water on the Eastern Shore, he said.
The Choptank was the only Eastern Shore river studied, but Hirsch said that the results in this waterway are likely typical for the agriculture-intensive Delmarva peninsula.
The figures in the study were adjusted for rainfall, so that the nitrogen levels do not spike during wet years (when more nitrogen fertilizer would be washed by rain off the land) and drop during dry years.
In other Chesapeake Bay tributaries, such as the Susquehanna and Potomac Rivers, nitrogen pollution levels dropped since 2000, according to the report. In the Patuxent River, nitrogen levels dropped by 26 percent between 1978 and 2000, and then by another 15 percent from 2000 to 2008.
The Baltimore Sun, in a report published last night (September 15) a few hours after Bay Daily, said that the increase in pollution in the Choptank brings into question whether a landmark Maryland law passed more than a decade ago, called the Water Quality Improvement Act of 1998, is working to reduce pollution. The law requires farmers to self-record fertilizer application and create "nutrient management plans."
The Sun wrote: Russell B. Brinsfield, director of the Maryland agricultural experiment station at Wye, "and others acknowledge that farmers on the Shore and elsewhere in the state have been required for years now to have plans limiting how much fertilizer they put on their fields under a 1998 'nutrient management' law. The USGS data show no sign that such plans have made a difference in the Choptank's water quality."
Part of the problem in the Choptank River, Hirsch told Bay Daily, is the ground around the waterway is sandy and does not contain much natural organic material. This lack of organic material means that nitrogen in the soil does not disappear very fast, because there is very little conversion of the nitrates into harmless nitrogen gas, Hirsch said.
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By Tom Pelton
Chesapeake Bay Foundation
(Photo of the Choptank River by Joseph Hart)
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