About a third of the Chesapeake Bay and its tributaries recently met water quality standards that monitor restoration progress — a decline since they were last measured, officials said Wednesday.
In its most recent three-year assessment, for 2017 to 2019, the Chesapeake Bay Program found the water quality score slid to 33%, down from 38% in 2016 to 2018. That showed a decline from a high of 42.2% during the 2015 to 2017 period.
The bay program is a massive partnership among nonprofits, academic institutions and local, state and federal governments that have worked to restore the estuary since the 1980s.
Officials periodically measure water quality using three parameters: the abundance of underwater grasses, chlorophyll as a measure of algae growth and dissolved oxygen, which reflects the bay’s ability to support marine life.
The recent decline is linked to unusually wet weather in 2018 and 2019, the bay program said in a statement. Rain can wash pollution into the bay, spurring algae growth and low-oxygen “dead zones” that can suffocate life.
Program scientists specifically noted a decline in oxygen in deeper areas of the water, likely tied to weather-driven river overflows.
Pollution from wastewater and sediment and nutrients commonly used in agriculture, such as nitrogen and phosphorus, affects the water quality. Efforts to stop such materials from entering the bay include changing the way farmers lay out and manage crops, planting greenery buffers along streams and improving wastewater treatment facilities.
Since 2009, these conservation practices have lowered overall nitrogen by 13%, phosphorus by 14% and sediment by 4%, the bay program also said this week.
By 2025, states in the watershed, including Virginia, are supposed to have more of the practices in place to meet pollution reduction goals set by the Chesapeake Clean Water Blueprint.
Katherine Hafner, 757-222-5208, katherine.hafner@pilotonline.com
