States in the Chesapeake Bay watershed have agreed to write plans later this year that will acknowledge the extent to which climate change will require significantly more work in the future to clean up the Chesapeake Bay.

Stormdrain during rainfall

Climate change has been linked to heavier rain events. The more it rains, the more runoff will carry nutrient pollution into waterways. 

In December, state and federal officials in the Chesapeake Bay Program had agreed that the scheduled updates to state-specific cleanup plans would outline ways to address the impact of climate change. But they stopped short of requiring that the plans acknowledge the magnitude of the impact: The Bay Program’s computer models show that states will need to reduce an additional 9 million pounds of nitrogen and 500,000 pounds of phosphorus to offset the impacts of climate change on Bay water quality.

Environmental groups sharply criticized that omission, saying that the public needs to be alerted to the size of the problem and begin planning now.

In March, the Principals Staff Committee, made up of senior state and federal Bay policy makers, backtracked a bit. When states update their Bay pollution control plans, they will now include the Baywide model projections figures to acknowledge the challenges posed by climate change.

The change “underscores that we are aware of the significant added responsibilities that are presented,” said Maryland Environment Secretary Ben Grumbles, who chairs the committee. “The science is not exact on this, but we also can’t afford to wait for that perfect and mythical moment where all the science is perfect and everything is fully understood. We need to be proactive.”

The significance of the problem was only recognized in the last few months. 

When the U.S. Environmental Protection Agency issued its “pollution diet” for the Bay, formally known as the Total Maximum Daily Load, in 2010, it set limits on the amount of water-fouling nutrients and sediment that could reach the Bay. Each state wrote a watershed implementation plan showing the steps it would take to achieve those goals by 2025. 

At that time, it was recognized that new science, including information about climate change, could change those numbers in the future. To assess and adapt to those changes, a scientific review was planned as part of a Mid-Point Assessment scheduled to take place halfway to the 2025 deadline, after which the new science would be used to update state plans.

The Midpoint Assessment took place in 2017. But when modeling estimates for climate change were released in December, officials were caught off guard by the enormity of the impact. A projected 9 million additional pounds of nutrients are expected to reach the Bay – that’s a significant increase, which must be added to the approximately 40 million pounds of nitrogen reductions still needed to meet the TMDL goals. In addition, states  need to reduce another 6 million pounds of nutrients to make up for what is now spilling past the Conowingo Dam. 

The climate-related impacts stem largely from increased rainfall and greater storm intensity, which drive more nutrients off the land and into streams. The cleanup goals in the 2010 TMDL were based on modeling that assumed steady climate conditions from the early 1990s through 2025. Instead, average precipitation during that period is on track to increase by slightly more than 3 percent, meaning the previous modeling underestimated the amount of nutrients that will wash off the land.

Under the policy approved in March, all states will acknowledge the nitrogen and phosphorus figures as preliminary estimates to convey the size of the problem, but they are not required to set state-specific goals to address it for now. Instead, the updated plans drafted later this year will describe how each state will adapt to changing climate conditions, such as promoting pollution control practices that are better able to handle increased rainfall.

Meanwhile, the Bay Program will refine its climate estimates and present updated figures in March 2021. It will also review its existing suite of nutrient control practices and identify those that are likely to be the most effective under changing climate conditions or which provide multiple benefits, such as flood control and nutrient reduction.

In September 2021, jurisdictions are to adopt state-specific nutrient reduction goals to offset climate impacts and incorporate them into their nutrient control strategies.

At least for now, though, the Bay Program is not saying that those additional actions must be implemented by 2025, and several state officials expressed skepticism that it could happen.

David Flores, a policy analyst with the Center for Progressive Reform, said he was pleased that the committee agreed to incorporate the preliminary figures in cleanup plans because it emphasized the urgency to start addressing climate impacts now.

“That window of time between September 2021 and the end of the year 2025 is going to be quick,” Flores said. “It is a very narrow window for them to potentially address very significant amounts of pollution that are otherwise unaccounted for now.”

But he and others expressed concern that the committee did not explicitly commit to using updated modeling figures presented in March 2021 when revising nutrient goals that September.

“There is a chance they could look at the numbers and say the science still isn’t good enough and kick the can down the road again,” said Beth McGee, director of science and agricultural programs with the Chesapeake Bay Foundation.

Grumbles said he believes the states are fully committed to “account for additional nutrient and sediment pollutant loads” in 2021 to offset impacts of changing climate conditions. He also noted that states have the option of adopting their own numeric goals now, rather than waiting until then, and that Maryland might consider doing so.

Karl Blankenship is the founding editor of the Bay Journal and Bay Journal Media. You can reach him at

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