Buffering Wisconsin’s water quality with science

May 14, 2009 By Jill Sakai

Spring in Wisconsin heralds a new growing season. But the warming temperatures also bring heavier runoff from farm fields, carrying pollution and contaminants into the state’s lakes and streams.

[photo] Elvers Creek

Vegetated strips of land called riparian buffers, such as the one shown here along Elvers Creek in Dane County, help filter runoff from agricultural fields to remove excess nutrients and sediments before the water enters streams and other waterways. Researchers at the Center for Limnology recently described a series of principles and guidelines for identifying the highest priority areas in Wisconsin where such buffers and other conservation efforts are likely to yield the largest improvements in water quality.

Wisconsin’s waters have long been known to be negatively impacted by agricultural runoff, including phosphorus, nitrogen and sediments. To date, however, attempts to mitigate the resulting damage and improve water quality have been hampered by the problem’s complexity — Wisconsin has a lot of water and a lot of farm fields, and not all interactions between the two are equal.

“It’s such a challenging issue because it’s diffuse — little bits here and there, and it all adds up to make a huge problem. Those are the hardest ones to solve,” says UW–Madison limnologist Jake Vander Zanden.

Previous conservation proposals typically have not accounted for differences across the landscape, relying instead on voluntary participation or mandated statewide standards. Many such approaches are too expensive to be feasible or don’t reach the most troubled areas, Vander Zanden says.

“By identifying and targeting the high-priority areas, we expect to have a higher positive impact on water quality and a more efficient program.”

Jeff Maxted

In a recent series of three papers published in the journal Environmental Management, he and other researchers from the Center for Limnology tackled the complexity head on, treating the statewide variability as an advantage rather than a drawback. Their approach: Find the areas with the greatest potential for improvements, and start there.

The research grew out of a larger project called the Wisconsin Buffer Initiative (WBI), an unusual partnership of agricultural and conservation interest groups, state and federal agencies, and university scientists. The WBI was formed in 2002 and charged with the goal of developing a science-based framework to help policymakers address state water quality issues related to agricultural pollution.

Many factors contribute to water quality and equal efforts in different areas will not necessarily lead to equal improvements, says Pete Nowak, a professor in the Nelson Institute for Environmental Studies who led UW–Madison’s role in the WBI.

For example, some waters are already so degraded that restoration will require far more than field-level efforts. Conversely, protecting already healthy waters with few polluting inputs may not represent the best use of limited dollars.

Instead, he says, it makes sense to focus on the regions that lie between these two extremes: those streams and lakes at risk of being irreparably damaged by continued pollution.

The new papers lay out a series of principles and guidelines for identifying the areas where conservation efforts are most likely to yield improvements in water quality, creating a ranking system that identifies the highest priority watersheds in the state.

“By identifying and targeting the high-priority areas, we expect to have a higher positive impact on water quality and a more efficient program,” says Jeff Maxted, a water resources specialist involved with the studies.

While targeting is not a novel idea, the innovation of their new work is in offering a science-based framework to determine how and where to target.

The first step, then, was to identify which parts of the state represent the most promising targets for conservation efforts to prioritize. “[We had] to start to get an understanding of the distribution of pollution, and then to develop a concept and a method for how to allocate resources in order to get the greatest bang for the buck,” Vander Zanden says.

They divided the state into nearly 1,600 independent watersheds, regions where all the water drains to a single outlet, each a manageable size of about 20 square miles. They ranked the watersheds based on several criteria reflecting their current condition, pollution level, physical properties and their potential to respond positively to conservation practices.

“We ranked each watershed based on not just its existing amount of pollution but also how much pollution can be reduced,” says Matt Diebel, a postdoctoral fellow in limnology who conducted the buffer research as a large part of his graduate thesis.

The result is a priority ranking of the state’s watersheds, giving a clear indication of where buffers (vegetated strips of land between fields and streams) or other conservation practices might have the biggest impact on improving water quality.

“Through identification of how those hotspots are distributed across the state, we came to the realization that you really need to build a critical mass of effort in any given area before you’re going to see any results that are identifiable,” Diebel says.

In creating a set of practical guidelines, they also evaluated the most efficient way to allocate limited resources. The papers include a chart that describes the optimal conservation program design, including the best balance of breadth and depth of effort, for a range of budgets, from $2 million to $200 million.

This grounding in reality sets the WBI apart from other approaches, Nowak says, and helps nonscientists use the results. “For the first time [legislators] have a ranked list. If they have $50, they know which watershed in the state they should put that $50 toward. If they have $50 million, they know how far down the list they can go,” he says.

With a prioritization framework in hand, the researchers are now working with landowners to test their ideas on the ground to start to identify possible solutions. Different approaches may work better in different regions, they say, and comparisons between watersheds will be helpful in identifying best practices.

The recommendations based on these studies and others from the WBI are currently under consideration as state agencies are working to draw up a new set of guidelines for implementing conservation practices in the state.

“This was a beautiful example of how the university can use the Wisconsin Idea philosophy of working with the citizens and their interest groups in the state to solve a very complex problem, of finding the appropriate role for science in that process,” Nowak says.