Newswise — GAINESVILLE, Fla. --- Federal environmental law can be tricky business. Defining which bodies of water are protected by the federal Clean Water Act can impact the permits required for someone developing their land, especially when wetlands could be affected.
Supreme Court decisions in 2001 and 2006 narrowed legal protections for geographically isolated wetlands, which are those surrounded by higher land. The new legal test created from those decisions protects wetlands and streams only when it can be proven that there is a “significant nexus” to downstream navigable waters. The legal test has created confusion because there is no consensus about what constitutes a significant nexus.
A University of Florida research team, whose study is published online in the journal Water Resources Research, shows that geographically isolated wetlands can be connected in ways that are largely ignored, but that may be critically important for watershed storage and stabilizing downstream flows. The study was funded by the Environmental Protection Agency.
When the Clean Water Act became law in 1972, two-thirds of the country’s lakes, rivers and coastal wars were unsafe for fishing and swimming. The EPA reports that roughly one-third of the nation’s waters remain troubled today.
A new rule that federal officials hope will clarify where the Clean Water Act applies, and where it does not, is under review. If eventually approved, the rule would still require a significant nexus demonstration for most geographically isolated wetlands.
Previous research by the UF team showed that geographically isolated wetlands alternate between being a sink and source of water to the surrounding shallow aquifer. In the latest study, they explored the impacts of that alternating hydrology on regional water flows.
They combined two modeling systems to analyze how landscapes with varying climate, soil type and wetland attributes create stream flow. After hundreds of model runs across all the scenarios, each simulating water behavior over 1,000 years, they were able to demonstrate that isolated wetlands, especially small ones, dramatically impact flows to downstream creeks and streams.
While the flow volumes are not dramatically impacted by the presence of geographically isolated wetlands, those flows are buffered, or significantly less variable, which has important implications for stream biological and chemical health, said Matthew Cohen, a UF associate professor who specializes in ecohydrology.
From a water policy standpoint, this suggests the connection between wetlands and federally protected waters should not be limited to those with direct surface connections, but that the Clean Water Act could also apply where below-ground connections exist, he said.
Daniel McLaughlin, a former UF assistant research scientist who joined the Virginia Tech faculty this month, called the EPA’s proposed rule change a “very hot topic.”
The UF study, on its own, isn’t enough to make a full legal argument that geographically isolated bodies of water deserve federal protection, he said. But it’s a start.
“This is one specific way that these wetland systems can influence the hydrology of downstream water bodies,” he said. “There are other hydrologic functions, as well as biological and chemical ones, to consider. So this is just one part of a growing body of scientific evidence to demonstrate the various ways that geographically isolated wetlands affect downstream waters.”
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