By Sonia Scherr 

What effect do people have on water quality?  

That’s the central question underlying the work of UNH Environmental Science Professor Bill McDowell, who studies suburban watersheds in southern New Hampshire. “We’re trying to understand how characteristics of the landscape affect the water quality in a stream,” says McDowell, whose research also has taken him to Puerto Rico and the Czech Republic. “Much of our work in New Hampshire is focused on the impact of suburbanization and urbanization on water quality.”  

For good reason: The state’s population has grown steadily over the past three decades, especially in the Seacoast region, leading to changes in land use as farms and undisturbed areas have been replaced by buildings and pavement. (In fact, according to recent U.S. Census data, New Hampshire ranks first among all New England states in its development rate.) At the same time, climate change is causing bigger storms and more rain. Regular sampling of streams, rivers and groundwater by McDowell’s lab group has shown significant differences in the levels of contaminants over time, suggesting that the rural-to-suburban shift, along with more extreme weather, is influencing water quality.  

Now, however, McDowell hopes to gain far greater insight into the fundamental processes that drive variations in water quality. He’s a member of a statewide research team led by UNH that has received a five-year, $20 million grant from the National Science Foundation’s EPSCoR Program to study changes in the state’s ecosystems. As part of that project, his lab will conduct stream sampling at nine sites using sensors capable of measuring contaminants every 15 minutes, rather than just weekly or monthly. “With these data, we’ll be able to get a much better understanding of how climate and land use interact to determine water quality,” says McDowell, who directs the New Hampshire Water Resources Research Center at UNH.  

High-frequency sampling will enable researchers to observe changes in stream chemistry over very short time intervals, helping them figure out what, exactly, is controlling that chemistry. Among McDowell’s questions: Are streams in heavily-developed areas worse off than those in areas with moderate or low development? How is this relationship between land use and water quality affected by severe weather? Does water quality improve after big storms because everything has been washed clean? Finding the answers will allow researchers to predict water quality in the future, McDowell says. “If we change the land use, then we’ll be able to understand what water quality might result.” 

Even without high-tech sampling, McDowell’s lab group has found evidence for nitrogen saturation in the state’s coastal watersheds and elevated nitrogen in the Lamprey River, the largest waterway flowing into Great Bay. These findings are concerning because the bay, the state’s most important estuary, is already showing the effects of nitrogen pollution, such as dangerously low dissolved oxygen levels and a reduction in eelgrass that provides vital habitat for fish. Because of the bay’s decline in health, the New Hampshire Department of Environmental Services has listed it as “impaired” by nitrogen, meaning that it is currently in violation of the Federal Clean Water Act.  

Nitrogen occurs in water naturally but also comes from human activities such as fertilizer use and wastewater treatment in private septic systems and public sewage treatment plants. It can stimulate the growth of nuisance algae, depleting the oxygen necessary for aquatic life to flourish. Managing nitrogen effectively is important for the well-being of Great Bay, McDowell says, but that’s difficult when key aspects of the element’s biology remain a mystery. For instance, of the nitrogen that comes into the Lamprey River watershed, only about 20 percent actually enters the river; it’s unknown where the rest of it goes. If it’s being removed by wetlands or by forested zones bordering waterways, then the loss of such areas due to development could cause nitrogen levels to increase in rivers.

 As he seeks a better understanding of the factors affecting water quality, McDowell knows that a lot is at stake. “Water is one of our regional assets. The economic health and the health of the ecosystems is really enhanced by the fact that we have relatively good water quality overall and relatively good supply as well.”

It wasn’t always that way, though. In fact, a century ago the region’s rivers were in terrible shape. Some of the world’s biggest textile and woolen mills operated along them — and untreated waste got dumped directly into the water. “At the same time that our situation is pretty enviable overall in terms of water quality, it’s not bullet proof,” McDowell says. “The past shows we can destroy what we have.”  

McDowell’s own motivation for studying the rivers that flow into Great Bay comes partly from seeing the decimation of Chesapeake Bay. He made frequent trips to the Chesapeake while growing up in Pennsylvania, boating and fishing on waters rich with oysters, crabs and other fish. “I remember how great it was to be on the Chesapeake 45 years ago, and it’s just not that way anymore,” he says. “I don’t want to see Great Bay go through the same decline.”