The Potomac Conservancy has released an analysis of the “new climate reality” that is already dawning on the Potomac River watershed, hoping to raise awareness and spur action.

The Potomac’s watershed is home to more than 6 million people in parts of Pennsylvania, Maryland, Virginia and the District of Columbia. Here, torrential downpours interspersed with longer dry periods will make it harder to keep sediment out of waters that are already warming over time. Rising sea levels will worsen underlying conditions. And, by midcentury, summers in the DC metro area could be excruciatingly hot, the report states.

Hedrick Belin, Potomac Conservancy

Hedrick Belin, president of the Potomac Conservancy, says his organization’s latest report focuses on how climate change will impact the Potomac’s watershed. “I think there’s a real opportunity to prepare people,” he said.

The impacts detailed in the report reflect many of the changes occurring at a global scale. But climate change is hitting each region differently, and the Potomac Conservancy wants watershed residents to understand the nuances close to home, where policies and preparations take place.

“I think it’s easier to get people to care about what’s happening with the climate when they know about what’s happening in their neighborhood,” said Audrey Ramming, the climate science journalist who penned the report for the Potomac Conservancy.

Many solutions to pollution and flooding concerns can also pull double duty to reduce the full blow of predicted changes. To that end, engineers, water quality experts and residents are grappling with challenges of current and future impacts.

“We certainly want to use [the report] to help guide decisionmakers in policies going forward,” conservancy President Hedrick Belin said. “I think there’s a real opportunity to prepare people.”

The conservancy is releasing the 111-page report to the public in bite-size pieces, with one of its six chapters emailed out every few weeks through the summer and into the fall. The full report is available on the group’s website.

The first chapters cover how climate change hits the Potomac region differently from others and how the changes are fueling extreme weather and rising waters. Other chapters touch on public health impacts, environmental justice, agriculture, fisheries and different scenarios for the future, depending on the region’s adaptations and actions.

Demand is growing for locally focused reports like these, said atmospheric scientist Anne Stoner. Stoner specializes in localized climate studies as a senior scientist at ATMOS Research & Consulting and was a key source for the Potomac project. She also co-authored a 2015 paper that made climate projections specific to the DC area based on two scenarios.

Sailboat on the Potomac River

A sailboat travels the Potomac River near Alexandria, VA. A water thermometer at one location on the river reached 94 degrees after a heat wave in July 2019.

“This is a trend in the field, because it’s not always just an overview that’s needed,” Stoner said. “A lot of times, [these reports are] being used in engineering to figure out how they need to plan for the future with water rising and conservation needs, for example.”

The Potomac study used readings from three weather stations in the region to map trends and projections. Climate, the report explains, is like the baseline of a song and weather is the melody, getting all the attention with colorful ups and downs.

“Because weather, and therefore climate, are not uniform across the globe, each region’s ‘song’ is a little different,” the report states.

Though it can be hard to say for certain whether a particular storm was caused by climate change, one local scientist said that climate change is like “loading the dice” in favor of extreme weather events. In the Potomac watershed, a warming atmosphere is able to build up more moisture before it gushes out as rain, leading to more intense storms with more dry days in between. This phenomenon also makes blizzards more likely, even if the winters are milder. Hurricanes and nor’easters are also becoming more frequent and more intense, impacting local infrastructure.

Take, for example, a year like 2020, when the District of Columbia experienced seven rains that dumped at least 2 inches in one day — a record for a calendar year. This was just two years after the National Weather Service named 2018 the region’s wettest year on record. Overall, the report finds that heavy precipitation in the region has increased by 71% from 1958 to 2012.

Even when it’s not raining, parts of the Potomac watershed now experience “sunny day flooding” from high tides. Sea level is rising faster in the mid-Atlantic than elsewhere — by 1.5 feet since 1900 compared with a global average of 8 inches — and the land is sinking. Changes in the Atlantic Gulf Stream are also reducing how water is wicked away from the coast.

“DC is right on a tidal river, so you get a lot of twice-a-day flooding,” Ramming said. In some places, especially around DC’s popular Tidal Basin, “people will park their cars and the water will be past their tires when they come back.”

The DC region is also coming off of its hottest decade on record. And the number of days when the heat index tops 95 degrees may double by midcentury and triple by 2080, according to the analysis. That affects people, wildlife and water quality. After a heat wave in July 2019, for example, water thermometers near Little Falls along the Potomac River reached 94 degrees.

“The number of heat waves [is] increasing … It’s going to be something that the area will have to figure out how to deal with,” Stoner said.

Belin said this summer is as good a time as any to have conversations about what a warmer future could look like and how the region can plan for it. Those concerned about the health of the Potomac River and the Chesapeake Bay will have to tweak their restoration plans to allow for such drastically different weather patterns.

He said programs like Maryland’s recent commitment to plant 5 million trees over the next decade will both improve water quality and reduce urban heat islands, which are exacerbated by climate change. The same is true for Virginia’s commitment to better fund pollution reduction measures on agricultural lands. Government incentives for green infrastructure will also reduce flash flooding in the region and pollution in its rivers.

“People are seeing this individually — the flooding that is happening in wet weather events. There are people who, in the past their basement never flooded, and now it is,” Belin said. “So what are we going to do?”

Read the full climate report or sign up for email installments at PotomacClimateReport.org.

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