WASHINGTON, D.C. – (Press Release) The amounts of nitrogen and phosphorus—which in excess can degrade water quality—have declined dramatically in the Potomac River since the 1980s, and are on track for further reductions, says a new COG report.

The findings of the report, Potomac River Water Quality in Metropolitan Washington, were presented today to the COG Board of Directors. The report analyzes long-term data from 1985 to 2016, rather than relying on a single year or point in time, which can be impacted by weather conditions.

Investments in and actions by the region’s wastewater treatment plants largely account for this significant progress, supporting increases in jobs and population while improving Potomac water quality.

For example, discharges of nitrogen from the region’s wastewater treatment plants have decreased by about 75 percent from their peak in the early 1990s, and phosphorous by about 94 percent from levels in the late 1970s.