The Chesapeake Bay Program announced this week that water quality in the Chesapeake Bay met its highest standard for water quality since monitoring began in 1985, besting its previous record reported in 2017.
According to preliminary data, an estimated 42 percent of the Chesapeake Bay and its tidal tributaries met clean water standards for clarity (measured by observing underwater grass abundance), dissolved oxygen, and chlorophyll-a between 2015 and 2017. This five percent increase from the previous assessment period is due in large part to reductions in chlorophyll-a (a measure of algae growth) and increases in underwater grass abundance and dissolved oxygen in the open waters of the Bay.
New research conducted by Chesapeake Bay Program experts, and published in Science of the Total Environment, described the “positive and statistically significant trends” observed in the water quality of the Bay – an important indicator of environmental health. This suggests that the water quality of the Bay is improving due to the decades-long effort to reduce nutrient pollution and is more resilient to the impacts of extreme weather (such as Hurricane Irene and Tropical Storm Lee). However, water quality remains far below 100 percent attainment, with 58 percent of tidal waters still considered impaired.
Water quality is influenced by nutrient and sediment loads from the watershed and vary each year due to land use andriver flow. Between October 2016 and September 2017, river flow to the Bay measured a below-average of 47.7 billion gallons per day. During this same period, approximately 240 million pounds of nitrogen, 12.7 million pounds of phosphorus and 4.3 billion pounds of sediment reached the Bay: a 0.4 percent, seven percent and 14 percent decrease from the previous assessment period, respectively.
While the amount of nitrogen, phosphorus and sediment entering the Bay from the watershed can change dramatically from year to year, the fact that nutrient and sediment loads decreased between 2016 and 2017 even as river flow increased could be a positive sign toward controlling pollution. However, the impacts from the record amounts of rainfall across the entire watershed in 2018 are still being realized and will be reflected in the data being collected now. These weather patterns not only contributed to high river flows and heavy flooding, but also brought a larger amount of fresh water into the Bay, leading to fewer jellyfish, a lingering “dead zone” and finfish moving to new areas. It remains to be seen how this will impact the water quality of the Bay in the future.
Monitoring data collected from River Input Monitoring stations on the nine major rivers in the Chesapeake Bay watershed provide long-term trends for nitrogen, phosphorus and sediment entering the Bay and its tidal tributaries. A recent U.S. Geological Survey (USGS) analysis of long-term trends (1985-2017) in pollution loads found that nitrogen loads improved at the majority of the stations. However, long-term trends in phosphorus loads indicate improving conditions at only three stations and degrading conditions at another five, while long-term trends in sediment loads show improving conditions at three stations and degrading conditions at two.
In early April, the Chesapeake Bay Program will release the 2017-18 Bay Barometer: Health and Restoration in the Chesapeake Bay Watershed, which will further explain how the entire Chesapeake Bay ecosystem and its watershed are responding to the partnership’s collective protection and restoration efforts.
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