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Below the Surface

Understanding ground water transport to protect water resources
  • Hydrologist David Boutt on site in the Atacama Desert in Chile

The team’s research results are being used by stakeholders in one project to better understand the dynamics of lithium transport and the hydrologic functioning of these unique and economically significant resources.

Nearly 99 percent of the Earth’s liquid freshwater is found in the ground, and underground reservoirs buffer against climate change, droughts, and help moderate the temperatures of lakes, rivers and streams. Understanding the processes of this hidden resource is the work of UMass Amherst hydrologist David Boutt (Geosciences).

Boutt and his team study freshwater systems around the globe. Their research focuses on ground water recharge (where and how water makes it into the ground), ground water discharge (where and how it leaves the ground), and how it is transported between the two.

“Our group does a lot of work trying to understand how the geologic structure of the subsurface influences how much water is in the ground, how long it takes to a get from recharge area to a discharge area and how these transit times influence water quality,” says Boutt.

He and his team also look closely at base-flow, the portion of the water in a river or stream that comes directly from ground water sources. They often start by placing thermistors, highly sensitive temperature-sensing elements, into the water. To locate where the ground water is entering the surface water, the team looks for areas where the temperature is stable.  To obtain data quickly over large distances they use distributed temperature sensing (DTS) to track the ground water’s various temperatures along the relevant underground pathways. The DTS process utilizes a long, thin telecommunications-grade optical fiber cable the thickness of a strand of hair, which is calibrated to known temperatures and placed in surface water or boreholes. When light is shone down the cable, the technology allows the researchers to determine the temperature at one-meter increments along the cable deployment.

In the Tidmarsh Farms-Beaver Dam Brook Restoration project funded by the US Department of Agriculture-Natural Resources Conservation Service, Boutt is helping to restore 400 acres of cold-water stream and wetland surrounding Beaver Dam Brook, which encompasses a large portion of the south coastal watershed in the eastern part of the state. The restoration will provide unobstructed headwater-to-ocean passage for cold-water fish, improve water quality in the watershed, and will nurture biodiversity. Much of the wetland system will be reconstructed and restored to its original function as a flood plain flowing from the brook to the Atlantic Ocean. Boutt’s subsurface measurements are helping planners understand the structure of the subsurface so that they can redirect channels and colder water critical for cold-water fish survival.

Taking advantage of advances in sensing technology, Boutt and his team deploy ground-penetrating radar to obtain images and data on subsurface conditions. Walking along the surface with a transmitter that emits electromagnetic waves into the ground, the team can detect what is below the surface by the way the signal bounces off the underground layers and returns to the transmitter. Peat, an organic-rich, low permeability barrier to ground water flow, is especially challenging to the project as little ground water can get through to cool or warm the surface waters. Boutt and the team have established a hydrological baseline for the disturbed wetland and will continue to take fresh measurements and document change as the restoration progresses.

As part of a major effort to understand ground water recharge into fractured bedrock aquifer systems Boutt and his team are analyzing temperature distributions in the West Brook watershed in Whately, Massachusetts. Because these waters are fed primarily through ground water, they remain cold and well oxygenated throughout the year, making them ideal for the study and cultivation of young Atlantic salmon. This work has been funded over the years by the US Geological Survey, the National Science Foundation, the National Institutes for Water Resources, and the Massachusetts Water Resources Research Center.

Boutt is also conducting research in the Atacama Desert, Chile, where large amounts of lithium are extracted from shallow subsurface brines. Lithium—a rare earth element used in phones, batteries and many electronic devices—is found in the world’s driest habitats. Because lithium extraction operations have become increasingly large and essential to many technologies, some stakeholders have asked Boutt and collaborators at the University of Alaska and Penn State to study the natural process that delivers lithium to the brines. Boutt explains that as ground water flows down from the Andes Mountains and into the desert, it interacts with subsurface brines to form brackish lagoons. These lagoons, comprised of water with a higher salinity than freshwater but lower than brines, are considered environmentally sensitive areas that warrant protection. The team’s research results are being used by stakeholders to better understand the dynamics of lithium transport and the hydrologic functioning of these unique and economically significant resources.

As the lead Principal Investigator of the hydrogeology group in Geosciences, Boutt collaborates with colleagues in UMass Extension, Massachusetts Geological Survey, the Water Resources Research Center, and other water experts across campus.

Boutt became a hydrologist to study the earth’s processes in a way that has a direct impact on societally relevant issues. He finds the work both gratifying and humbling.

“Earth sciences…it’s just bigger than you. It’s got a history that goes way beyond human history,” Boutt says.

Amanda Drane ‘12

Banner image: David Boutt in the Atacama Desert, Chile