Most streams in the Chesapeake watershed are in poor condition, according to data released Monday by the Chesapeake Bay Program.
The federal and state partnership that coordinates restoration efforts, also released data showing reductions in key pollutants over the past 25 years at monitoring sites along tributaries that feed the Chesapeake, but noted levels were still below restoration goals.
The stream survey involved sampling of nearly 8,000 streams sites between 2000 and 2008 and found 54 percent were in poor or very poor condition while 27 percent were in excellent or good condition.
Peter Tango, Chesapeake Watershed Coordinator for the U.S. Geological Survey, said the monitoring shows a clear link between land use and stream quality with those in urban, farming and mining areas faring the worst.
Chesapeake Bay Foundation scientist Beth McGee said the findings show the fragile nature of streams, and how small amounts of development can affect them.
Paved surfaces covering as little as 5 percent to 10 percent of an area can affect nearby streams, and urban areas such as Baltimore and Washington can often have 30 percent to 50 percent, McGee said.
Streams are affected because paved surfaces do not allow rainwater to seep into the ground where it is filtered, but instead runs off the hardened surfaces into waterways, carrying pollutants.
“When you keep that in context it’s not surprising a majority of our streams are not in good health,” said McGee, a water quality scientist for the foundation, a nonprofit bay advocacy group that was not involved in the research.
Nitrogen and phosphorus monitoring, meanwhile, found reductions at 70 percent of monitoring sites throughout the bay watershed while cuts in sediment, which can cloud water and bury bay grasses, were noted at 40 percent of the 32 monitoring sites. The readings were adjusted to account for differences between rainier and drier years, the researchers said.
Scott Phillips, the U.S. Geological Survey’s Chesapeake Bay Coordinator, said much of the improvement can be attributed to upgrades to wastewater treatment plants, which often yield the most immediate gains because they affect a single source. Changes in farming practices and other changes that are spread over wider areas take longer to detect, but are having an impact, he said.
The program also released its estimates for the amount of each of the three pollutants that entered the bay in the 12 months ending in September.
Flows into the bay were about average, but heavy winter snows led to higher flows at times that washed pollutants into the Chesapeake.
About 9 million tons of sediment, for example, entered the bay in that period, an increase of seven million tons over the prior year and one of the highest loads in the past 20 years, more than double the long-term average of four million tons.
Meanwhile, about 278 million pounds of nitrogen reached the bay, 43 million pounds more than 2009, and about 16 million pounds of phosphorus, seven million pounds more than in 2009. The bay program’s goal is about 202 million pounds of nitrogen and 13 million pounds of phosphorus. Nitrogen and phosphorus, which come from sewage, fertilizer and automobile and power plant emissions, are so-called nutrients that can cause algae blooms that rob bay water of oxygen.
Will Baker, the president of the Chesapeake Bay Foundation, which sued the federal Environmental Protection Agency over the slow pace of bay restoration, said the reductions were good news but incremental steps in the restoration process.
“If we let down our guard now, there’s no doubt in my mind the bay will revert to being even worse than it is today,” Baker said.