Monday, June 6, 2022

All Models are Wrong, But Some are Useful

 is the old saying. Bay Journal, States challenge findings of Chesapeake computer modeling, "Figures show little progress in reducing nutrient pollution from farms"

State officials have voiced strong concerns about updated Chesapeake Bay computer modeling that shows little overall progress in controlling nutrient runoff from farmland.

The updated modeling suggests that meeting the Bay’s 2025 cleanup goals — already highly unlikely — will be even more difficult than regional leaders believed just a few months ago.

If correct, the figures indicate that work over the past decade by farmers to plant cover crops, install stream buffers, construct manure storage facilities and undertake other conservation practices were largely offset by increased crop production, more fertilizer use and more livestock.

The model revisions also show greater increases in nutrient pollution from urban stormwater than previously estimated, but those were small compared to the farm changes.

The U.S. Environmental Protection Agency recently signed off on the model changes, saying the updates followed normal procedures approved by the state-federal Bay Program.

But state officials questioned the new results at recent meetings and in written comments, citing uncertainties with the underlying data. They also worry about creating the perception within the farm community, where distrust of Bay computer modeling is already high, that efforts to reduce runoff have produced few results.

The EPA uses the computer model to track progress toward meeting nutrient reduction goals under the Bay’s total maximum daily load, or “pollution diet,” established in 2010.

The TMDL set the maximum amount of nitrogen, phosphorus and sediment that can reach the Bay each year from states in the watershed. States are to implement all actions needed to achieve those goals by 2025.

The updated calculations show estimated annual nitrogen reductions from 2009 to 2020 being 6.25 million pounds less than what was calculated just a few months earlier, largely because of new data showing the intensification of farm operations, including a sharp increase in fertilizer use.

That means the region has achieved only about a third of the 71 million pounds of nitrogen reductions needed to meet the 2025 goal. And most of those reductions came from upgrading wastewater treatment plants, a job that is mostly completed. The vast majority of future nitrogen reductions must now come from farms and, to a lesser extent, urban stormwater.

The story was better for phosphorus as the figures showed 533,000 more pounds of reductions than previously estimated.

But the region was already on track to meet phosphorus goals, while significantly off track for nitrogen, which tends to have a worse impact on Bay water quality.

State officials have questioned the underlying data, and many contend that the model results sometimes show worsening nutrient trends in places where water quality monitoring shows improvements.

“We don’t think that the data sources are the right data sources … or even the best,” said Pat McDonnell, secretary of the Pennsylvania Department of Environmental Protection, at a May 17 meeting of senior state and federal environmental officials. “It just puts us, and I’m sure other jurisdictions, in a challenging position.”

Scott Mandirola, deputy secretary of environmental affairs with the West Virginia Department of Environmental Protection, said the results showed a tenfold increase in fertilizer use in urban areas in his state’s portion of the watershed, “which I don’t believe anybody accepts as being factual.”

Andrew Wheeler, a senior adviser to Virginia Gov. Glenn Youngkin, said officials in his state have “seen inconsistencies in the [nutrient] loading data” produced by the model when compared with water quality monitoring. He called for “transitioning to more monitoring, instead of modeling, [for] assessments of progress going forward.”

Ann Swanson, executive director of the Chesapeake Bay Commission, which includes representatives from state legislatures, said the updated findings should be used, but that states should be allowed to achieve the additional 6.25 million pounds of nitrogen reductions after 2025.

“Right now, it’s very clear that we will not reach the TMDL, [that] we will not make that pollution diet,” Swanson said. “We will hold our heads very, very high. And we will get as close as we can. And we remain with our foot on that pedal.”

As the aphorism suggests, no model can completely capture the absolute truth, but with the right data and the right coding, a model can be used to get good insights into how the system will respond to changes in inputs. But the Chesapeake Bay is pretty damn big, and I don't think the sources (and sinks) are that well known. I suspect the Bay model, by comparison, is pretty crude. Agriculture is the chosen scapegoat of the managers, all those individual decisions made by farmers for their own benefit has the regulators lusting for control.

And, I don't think they're serious about achieving a clean Bay by 2025. Then what, fire the EPA Bay Program staffers, and put them on welfare? Will the Chesapeake Bay Foundation declare victory and disband?  Nope. They need a certain amount of Bay pollution to continue.

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