Photo by Kevin Harber.

In its annual State of the Nation’s River report, the Potomac Conservancy gave its namesake body of water a “C” for overall health. So its parents are only mildly disappointed.

“After suffering the effects of historical overfishing, pollution and habitat destruction for decades, it is no wonder that the Potomac River’s recovery is a slow one,” the Conservancy says in the report. “Fortunately, there has been a renewed commitment at the start of the 21st century to return the Potomac to full ecological health. And we’re starting to see some signs of progress as evidenced in this report.”

The report card targets five areas — fish, habitat, pollution, land and people — to rate. It shows improvement in the area of pollution and fish recovery. The lowest grades, “D”s in this case, were received for underwater grasses and stream water quality in habitat, and phosphorus in pollution. The lowest overall rating came from habitat. Here’s why, for example, the stream water rating is so low.

Impaired water quality is a common challenge for our nation’s rivers and streams, and the Potomac River is no different. To assess the health of non-tidal streams and wadeable rivers, the Chesapeake Bay Benthic Monitoring Program developed a special health index in 2012 that combines data from a variety of monitoring programs. Based on this index, the average, area-weighted score for Potomac River stream health is 35.91, or “Fair” (bordering on “Poor”).

Read the whole report here.