Farm pollution still troubles Chesapeake

Grain and poultry farming in Delaware and on Maryland's Eastern Shore still contribute the largest amount of nitrogen and phosphorous to the Chesapeake Bay and tributaries, despite efforts to better manage manure and commercial fertilizer application, according to a new study by the U.S. Geological Survey.

Among the issues: the long term buildup of phosphorous in soils from previous unchecked stockpiling and application of poultry manure — a practice that is now regulated in both states -- the concentration of nitrogen in the groundwater over the last half-century, and the sandy soils that contribute to rapid movement of nitrogen and phosphorous into streams and creeks during heavy rains.

"It's depressing," said John Schneider, the state watershed assessment administrator. Schneider said that even as local farmers and regulators in both states have worked to reduce pollution, it is difficult to find signs that the actions are having an impact.

Schneider said the long term buildup of nitrogen in the groundwater – something that occurred over many decades – "masks any improvement that we are making."

The reason: groundwater slowly makes its way to surface waters like creeks and streams that feed the rivers and ultimately flow into Chesapeake Bay.

As an example, Schneider points to the lowest time for stream flows in Delaware, typically in the late summer and early fall. There isn't much rain and almost all the flow in the streams is coming from groundwater that seeps up from the bottom, he said.

That is when state officials find the highest levels of nitrogen in these small waterways, he said. The numbers for nitrogen are going up instead of down in spite of better farm management, he said.

"When we look at trends over the last 10 years, we see an increasing trend," he said.

High levels of nitrogen and phosphorous in waterways cause excessive algae and other plant growth. The plants make the water cloudy so light doesn't reach the bottom. And as the aquatic plants die and decompose, they use up oxygen in the water which can lead to fish kills.

"On the Eastern Shore, the concentrations of nitrogen in groundwater, and nitrogen and phosphorus in surface waters, are well above natural levels and are among the highest in the nation," said Scott Ator, a USGS hydrologist and co-author of the study. "We are also seeing worsening nitrogen and phosphorus concentrations in the Choptank River, which is the largest river on the Eastern Shore, despite management practices to improve water quality."

The headwaters of the Choptank are in Delaware and the Nanticoke watershed is Delaware's largest drainage basin. The Nanticoke flows into Chesapeake Bay.

The Eastern Shore study area, which includes Delaware, covers about 7 percent of the Chesapeake Bay drainage area but acre for acre application of nitrogen and phosphorous is twice what it is in other parts of the bay, the study found.

"The disproportionately large nitrogen and phosphorus yields from the Eastern Shore to the Chesapeake Bay are attributable primarily to agricultural activities but are also influenced by natural hydrogeologic and soil conditions," said Judith Denver, a USGS hydrologist and co-author of the study. "The findings from the report will help inform more strategic placement of management practices intended to better utilize crop nutrients and reduce the excess available for transport to groundwater and streams."

The findings come as the federal Environmental Protection Agency is working with the Chesapeake Bay states to reduce nutrients and sediments flowing into the bay and tributaries. The plan is designed to speed the cleanup effort which has been underway for decades. Each state has a pollution limit it must meet through watershed implementation plans.

Contact Molly Murray at 463-3334 or mmurray@delawareonline.com. Follow her on Twitter @MollyMurraytnj.