Another Government Model Disputes Bay Diet

Study raises doubts about EPA's model

A study released this month by one federal agency may supply critics of another's Chesapeake Bay cleanup plan with more ammunition.

Among the findings of the United States Geological Survey study, "Sediment Sources and Transport in the Chesapeake Bay Watershed," is that forested areas account for 2 percent of sediment entering waterways in the Chesapeake Bay Watershed.

According to the Environmental Protection Agency's latest model, forest accounts for more than 15 percent of the sediment degrading the bay — 7.5 times as much.

The EPA's model is guiding mandated reductions of phosphorous, nitrogen and sediment among bay watershed states, a cleanup strategy that could cost Virginia more than $15 billion dollars to implement, according to a State Senate Finance Committee report released last November.

My sense is that the less important forest sources are to the Bay, the more important other sources, including storm water and agriculture are likely to be relatively more important.  However, agricultural representative have leaped onto the opportunity to attack EPA's model as flawed (again).  And since that model is expected to cost them a great deal of money, they have a point that the EPA owes it to them to do the best possible job of getting it right..

But discrepancies in the model and questions about how the data is collected have undermined support for the plan among some groups and led the American Farm Bureau filing a federal lawsuit to halt implementation of the plan until questions about the model are resolved.

"I'm not convinced that the bay model is accurate or even close to accurate," said Virginia Department of Forestry Assistant Director of Forest Management for Water Quality Matt Poirot. "There's a lot of assuming that's being done, and right or wrong, it's going to take years to get the model close to being right."

Remember the "Laws of Models":  1) All models are wrong, the only question is by how much and in what direction.  2) The direction the model errors is likely determined by the beliefs of the model's authors.  With this simple guidance in mind one can guess that EPA's model errors in a direction designed to get the management action they desired before the model was written.  USGS?  I'm not sure they have management action in mind, and I suspect they have less skin in the game.