September 21, 2016
Chesapeake Bay Water Quality Improving
The amount of nutrient and sediment pollution entering the Chesapeake Bay fell significantly between 2014 and 2015, helping improve water quality in the nation’s largest estuary. Experts attribute this drop in pollution loads to dry weather and below-normal river flow, but note local efforts to reduce pollution also played a role. Indeed, related research shows “best management practices”—including upgrading wastewater treatment plants, lowering vehicle and power plant emissions, and reducing runoff from farmland—have lowered nutrients and sediment in local waterways.
The Chesapeake Bay Program (CBP) tracks pollution loads and trends as it marks progress toward improving the health of the Bay. According to data from the CBP and the U.S. Geological Survey (USGS), nitrogen, phosphorus and sediment loads to the Bay were below the long-term average in 2015. Between 2014 and 2015, nitrogen loads fell 25 percent, from 290 million pounds to 217 million pounds. Phosphorus loads fell 44 percent, from 17.7 million pounds to 9.9 million pounds. Sediment loads fell 59 percent, from 7.2 billion pounds to 2.9 billion pounds. Below-average loads are considered positive because reductions in nitrogen, phosphorus and sediment pollution can improve water quality.
The most recent assessment of water quality—which examines dissolved oxygen, water clarity and chlorophyll a (a measure of algae growth) in the Bay and its tidal waters—makes these improvements clear: an estimated 37 percent of the tidal Chesapeake met water quality standards between 2013 and 2015. While this is far below the 100 percent attainment needed for clean water and a stable aquatic habitat, it marks an almost 10 percent improvement from the previous assessment period.
A large portion of pollution loads enters the Bay from the rivers within its watershed. Accordingly, the USGS tracks annual pollution loads and trends in these loads at monitoring stations along nine of the biggest rivers that feed the Bay. In some cases, long-term pollution trends at these stations—which span from 1985 to 2015—reflect efforts to improve water quality. Long-term trends in nitrogen, for example, are improving at six of the nine monitoring stations, including those on the Susquehanna, Potomac, James and Rappahannock (the four largest rivers in the watershed). Long-term trends in phosphorus and sediment, however, are more variable: phosphorus is improving at three monitoring stations and degrading at five, while sediment is improving at three stations and degrading at four. Short-term pollution trends—which span the last decade—show less improvement.
In June, the U.S Environmental Protection Agency released its two-year milestone evaluations of federal agencies’ and watershed jurisdictions’ work toward the Chesapeake Bay Total Maximum Daily Load (Bay TMDL). This “pollution diet” calls for all needed pollution control measures to be in place by 2025, with measures that would achieve 60 percent of pollution load reductions in place by 2017. Computer simulations show these measures are in place to achieve 31 percent of the nitrogen reductions, 81 percent of the phosphorus reductions and 48 percent of the sediment reductions necessary to reach our clean water goals. Evaluations from EPA indicate it is unlikely jurisdictions will meet the 2017 target for reducing nitrogen.
While continued improvements in water quality will take time—due in large part to the lag between the implementation of a conservation practice and the visible effect of that practice on a particular waterway—the ecosystem is beginning to respond to protection and restoration efforts. Last year, researchers observed more than 91,000 acres of underwater grasses in the Bay, which surpassed the Chesapeake Bay Program’s 2017 restoration target two years ahead of schedule and marked the highest amount ever recorded by the Virginia Institute of Marine Science aerial survey.