Dubious Stream-Fencing Numbers Reveal Limitations of Bay Model

5/24/2014 7:00 AM
By Andrew Jenner Virginia Correspondent

Earlier this year in an article about Virginia’s stream fencing cost-share programs, <@body italic>Lancaster Farming<@$p> reported the state was 85 percent of the way to its goal of fencing streams in nearly every pasture in its portion of the Chesapeake Bay watershed.

It was a number from the Chesapeake Bay Program’s mathematical models, which are used to help assess progress and inform decision-making under the bay Total Maximum Daily Load, or TMDL. It was also a number that far overstates the amount of actual stream fencing in Virginia, according to multiple people who work closely on the issue.

Estimates vary on actual stream bank fencing, but it generally falls at or below — sometimes well below — 20 percent of streams that have been fenced to exclude livestock in bordering pastures.

Acknowledging the problem with the stream-fencing number, state and federal officials say they’re working together to improve this aspect of the bay model. In the meantime, the misleading suggestion that Virginia is nearing its stream-fencing goals hasn’t diminished the state’s emphasis on stream fencing, which remains one of its top conservation priorities for agriculture.

“The model is a management tool,” said James Davis-Martin, the Chesapeake Bay nonpoint source coordinator for the state’s Department of Environmental Quality. “To effectively use the management tool, you have to understand its limitations. This is one of its limitations, which is why Virginia isn’t basing policy on that” stream fencing number.

Policy is being based, though, on the fact that progress on reaching the state’s stream fencing goals has come very slowly. Since 2012, the state has upped its ante by offering a new cost-share program that pays the entire cost of fencing streams with a 35-foot buffer. It’s been a popular program that farmers have used to fence about 150 miles of stream in the Chesapeake Bay watershed, according to the Virginia Department of Conservation and Recreation. Davis-Martin said the state has committed to fencing 4,700 new miles of stream in the bay watershed between 2010 and 2025 as part of its plan to comply with the TMDL.

The Annapolis, Md.-based Chesapeake Bay Program is the agency that collects TMDL-related data from the states in the bay watershed and manages the bay modeling tools. Katherine Antos, the Chesapeake Bay Program’s implementation and evaluation team leader, said in situations such as the confused stream fencing numbers, where model-reported data doesn’t match on-the-ground observations, bay program staff work with the agencies reporting data to identify and fix problems.

“CBP and Virginia are aware the stream fencing data may not be accurate and we are working together to fix it,” Antos said.

Simply adding up the total amount of stream fencing that is now keeping livestock out of streams is no easy matter as multiple exclusion programs have been promoted over the years by various state, federal and private agencies. Because these groups developed different record-keeping methods over time, it has become difficult to assemble a single, comprehensive list of all stream fencing projects.

Adding to the complexity is the fact that individual fencing projects can receive funding from multiple sources, raising the possibility that these may be double-counted when different agencies report data. Other datasets may not distinguish between exclusion fencing and cross-fencing in a pasture when they’ve been installed as part of the same project, making it hard to determine how much of the fence is actually exclusion fencing on those pastures. Finally, any stream fencing funded independently by a landowner may not be counted in any database.

The Smith Creek watershed in the Shenandoah Valley serves as a good example. As a designated USDA “showcase watershed,” it has received extra funding and attention from conservation agency staff since 2010. But solid stream fencing numbers are hard to come by.

According to a 2009 TMDL document for Smith Creek — the most recent one published — just under 10 miles of fencing has been installed in the watershed. That’s less than 6 percent of the 183 total miles of fencing needed to protect streams along nearly all of the pastures in the watershed.

Since the end of 2008, farmers using state cost-share programs have added 10 new miles of stream exclusion fencing along Smith Creek, according to the Virginia Department of Environmental Quality. Since 2009, National Resources Conservation Service programs have been used to install another 12.6 miles of fencing in the watershed, although a significant portion of that total is cross-fencing within pastures not stream-exclusion fencing.

The private, nonprofit Valley Conservation Council has overseen projects totaling another 1.7 miles of upstream fencing.

So it appears that new fencing along Smith Creek totals no more than 20 miles. Even in a watershed that has received extra attention and funding, it is clear the total amount of stream fencing installed to date has come nowhere near the goals of the Smith Creek TMDL, nor the commitments made by Virginia under the entire bay TMDL.

Plugging questionable data like this to the Chesapeake Bay model introduces an additional level of guesswork as the model itself contains assumptions about the very basics such as the total amount of pasture in Virginia that needs stream fencing.

In other words, no one’s exactly sure how many miles of fence exists, nor the exact amount of stream miles in Virginia’s portion of the bay watershed that should be fenced.

While the models are an important aspect of the overall implementation of the bay TMDL, Antos said that success will ultimately be measured against real-world water quality in the Chesapeake Bay, not numbers from the models.

And while clear glitches in the modeling tools have been used in arguments that the entire TMDL is flawed and misguided, Davis-Martin said that focusing on these issues distracts from the simple, basic premise of the process: cleaner water.

“This thing with the model is really not very important at all in the grand scheme,” he said. “What’s important is the Chesapeake Bay’s health and local water quality, which improves greatly when you exclude cattle from streams.”


Would you allow a natural gas pipeline to cross your farm?

  • Yes
  • No
  • Unsure

User Submitted Photos

View photos      Submit your photos

10/25/2014 | Last Updated: 1:15 AM