Watersheds and streams face an increasing barrage of man-made pollutants, whether they run through rural landscapes or filter around the streets of a city. Removing these contaminants (if the process happens at all) can be expensive and chemically intensive. M. Todd Walter, Biological and Environmental Engineering, wants to take a different approach to keeping our waterways clean. “The unique part to my work is, rather than addressing water pollution issues by treating the water, I’m trying to manage the landscape to avoid polluting the water in the first place,” he says.
From Fly-fishing to Studying Water Pollution
Walter has had a personal affinity for promoting water quality and stream ecology ever since his early days as an undergraduate majoring in Agricultural and Biological Engineering at Cornell. “The turning point for me was a fluid mechanics course taught by (now) Emeritus Professor Wilfried H. Brutsaert, who inspired my interest in studying water,” says Walter. “At the same time, I was introduced to fly-fishing, which got me interested in stream ecology.” Walter was soon fly-fishing the waters all around Ithaca, and eventually around the country, traveling to the rivers of Montana and the Adirondacks to pursue his passion.
Phosphorus and Waterways
At Cornell, Walter has focused his research primarily on two major agricultural pollutants—phosphorus and nitrogen. Phosphorus is a major component in dairy farm runoff and poses a serious threat to the local waterways that surround Ithaca and the Finger Lakes region. When phosphorus levels are too high in aquatic environments, algae growth gets out of control, and the algae decomposition then causes a plummet in oxygen levels. Another unpleasant effect—humans treat phosphorus-laden water with chlorine, which creates carcinogenic byproducts.
Thus, Walter wants to prevent the chemical getting into the waterways altogether. “We’ve realized that you can actually predict where in a landscape storm runoff is going to occur,” says Walter. “Thus, for example, we’re able to advise a dairy farmer not to dispose of manure in a field where it’s likely to end up as runoff.” Currently, they’ve translated this knowledge into a web-based, interactive map of the Owasco Lake watershed region, accessible as a resource for anyone interested in knowing where runoff risk areas are located. This resource has opened up a line of direct communication between regional dairy farmers and Walter’s team. “We’ve had farmers call us up to get advice on water management,” says Walter. “One farmer wanted to protect a stream on his land from his dairy cows and asked if we’d come down to test the water to see if his efforts made any difference to the water quality.”
Nitrogen and Ecosystems
Nitrogen, another agricultural pollutant, can lead to similar negative effects in coastal ecosystems, causing the infamous “dead zones” in the Gulf of Mexico and the Chesapeake Bay. Walter wants to exploit the fact that this chemical can naturally leave the liquid environment as a gas in a process known as denitrification. “There are certain parts of the landscape where this process is particularly aggressive,” Walter explains. “We want to exploit this so that nitrogen is kept out of the aquatic system, and look for ways to promote that process.” He and his team have devised a pragmatic application of this idea—large, room-sized chambers full of wood chips, buried in farm fields where nitrogen runoff is severe. The contaminated water filters through the wood chips, which promote and enhance the denitrification process. “It’s been working remarkably well,” says Walter. “Better than we thought it would.”
Others are taking notice of this unusual solution; the Upper Susquehanna Coalition, a network of Conservation Districts that manage the river basin, have begun burying these wood-chip chambers on farms in their region, with help from funding by the U. S. Department of Agriculture Natural Resources Conservation Service. “People are interested in this solution—they want to see us get through the analysis, see how it’s working and how it’s not working,” says Walter, “but people are definitely watching and interested in it—I think it holds a lot of promise.”
Currently, they’ve translated this knowledge into a web-based, interactive map of the Owasco Lake watershed region, accessible as a resource for anyone interested in knowing where runoff risk areas are located.
Beyond solutions that avoid putting pollutants in the water, Walter, along with Natural Resources colleague Laurie Drinkwater, is researching the idea of balancing the ecosystem so that excess nitrogen and phosphorus are not a concern; after all, these elements are naturally occurring and necessary to life. “We’re looking at cropping systems that would restore this balance with plants that actually harvest nitrogen, such as alfalfa or legumes,” says Walter.
Another new area of interest for the Walter group involves tracing the source of pollutants in water bodies through a novel tagging method. By using harmless synthetic “designer” DNA with a certain set of base pairs, his team is able to determine where pollutants end up when they get flushed into the system. This method is the first of its kind to effectively identify and characterize water flowpaths in the field by labeling with these unique DNA barcodes, which offer limitless combinations and enable the ability to identify countless sources of potential contamination.
These areas of research span the breadth of applications, from interactive web maps, to underground wood-chip chambers, to nanotechnology barcodes, yet, “all of my research areas ultimately come back to protecting the quality of the water,” says Walter. “It’s something that’s not only important for us humans, but these aquatic ecosystems as well.”