Severn River receives mixed results in report

Though the annual survey of the river notes small improvements, they are not related to efforts to control stormwater

A pair of fishermen try their luck on the Severn River in Annapolis. (Joshua McKerrow/Baltimore Sun Media Group)

Tom Guay, left, explains to volunteers how to use equipment to measure underwater grass beds in the Severn River. (Rachael Pacella/Baltimore Sun Media Group)

The water that has swept into local tributaries this year from heavy rains has made the Severn River less salty, hurting oysters but sparking an explosion of dark false mussels that thrive in fresher water. Those mussels, also filter feeders, might have improved water clarity.

Meanwhile, high winds that were also prevalent in 2018 have helped improve the dissolving of oxygen in local waters.

While both those things are good, they don’t signal much progress for researcher Andrew Muller. Each year the Naval Academy associate professor and his wife and research partner Diana Muller, executive director of Maritimas, study water quality issues related to the Severn.

Last week, the Mullers presented this year’s edition on the health of the river to the Severn River Association.

Tom Guay, spokesman for the Severn River Association, noted that a crew of citizen scientists goes out and measures salinity, temperature, pH, clarity and oxygen levels at 16 stations along the Severn to inform the State of the Severn report. Testing is done from July through the end of October.

Andrew Muller said the river is seeing some benefit in its response to the climate system — but not from the hard work of people putting in projects to reduce stormwater runoff and restore the environment.

“We haven’t really seen any measurable significant improvement in the Severn River that can be attributed to any upland restoration,” he said.

The Mullers gave water clarity a B this year — a mark that signals about 80 percent clarity. Bacteria levels also got a B at 83 percent. Dissolved oxygen got a 62, total nitrogen a 17 percent and total phosphorus a 50.

Muller makes the grades, but said they can be misleading. He said he would prefer to measure the health of a system by looking at something his wife and he developed called the “hypoxic squeeze index” — which he said measures the “livable area” in a water column.

The index essentially shows how much of the water is livable for fish, factoring in low dissolved oxygen on the bottom that drives fish up, and heat from the surface that drives fish down.

That index shows there are poorly flushed parts of the Severn.

The river has seen challenges this year — most notably excessive rain and the opening of the Conowingo Dam at the top of the bay, which flushed fresh water downstream and caused salinity in the Severn to drop. That low salinity is bad news for newly planted oyster spat; Muller said a majority of it will likely die.

Muller said he still hasn’t seen evidence that upland restoration projects are having an effect on water quality, despite the efforts of the county, state and environmentalists.

And, as he has in the past, he again warned against the impact of overdevelopment. The amount of impervious surface in the region has increased dramatically since the 1980s, he said. When water hits those surfaces, such as pavement, it picks up whatever is on the surface and then it flows into the watershed.

“It’s in many respects one step forward, five steps back, because we are seeing development continue in the county that’s outpacing our restoration efforts,” he said.

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