Hydrologic Research

Stephanie McPherson for TEI

David Boutt, Assistant Professor of Hydrogeology in the Deparment of Geosciences knows a thing or two about subsurface liquids. “All my work involves fluids of some sort, whether in the shallow or the deeper crusts,” says Boutt. His extensive research in subterranean fluids allows him to assess a situation and determine the best course of action, whatever the scenario. Boutt has been working on a number of water related projects, and is also studying the effects of carbon sequestration on the natural rocky make-up of aquifers.

One research project places Boutt on the Deerfield River Watershed. The Fife Brook hydroelectric dam is a potential cause for concern, as the timed release of water from the dam is altering natural patterns of stream water mixing with ground water, which could eventually affect aquifers. “We’re trying to understand implications of managed surface water,” Boutt says, referring to the dam. To determine just how much water is being transferred from stream to ground, Boutt is using small disks the size of three or four pennies, called the iButton. These mini sensors are self-contained temperature loggers. While the average temperature of ground water is 5 degrees Farenheit, the temperature of surface water changes with the seasons. The underground iButtons detect and record the temperature changes when surface water is pushed into the ground. “We can back calculate how much water must be moving through the ground,” Boutt says. From this, Boutt can determine how the dam-released pulses of water disperse contaminants as compared to natural conditions. “This fluctuation has a significant effect on how much contaminant in the stream gets into the aquifer,” Boutt says. “Temperature data helps tell us how much interaction there is.”

Boutt also examines the geology of the watershed area, analyzing how the changes in the nature of sediments influence the amount of interaction of stream and ground water. This information can be used to improve stream management and protection. For example, raising the level of a stream may in some ways be beneficial, but can also force more contaminants into the ground, having detrimental effects in the long run.
Boutt is also looking at the types of rock that make up Massachusetts aquifers, subsurface reservoirs of water. The more porous the rock, the more potential water an aquifer can hold. Most rocks in Massachusetts are made of less porous but fractured rock, and can hold less water than aquifers elsewhere around the country. Boutt uses a process called borehole geophysics to figure out how much water is actually being stored, and how much contaminant is making its way through. By mapping the fracture network in detail, Boutt measures the hydraulic properties of the well. This analysis will show just how sustainable fractured bedrock wells in Massachusetts are. “So far, it shows a pretty alarming trend,” Boutt says. “Almost all the flow into the well is in the upper hundred meters.” His research on a number of wells throughout the state show that the deeper the hole, the less fractures in the rock, which means there is less water available. Of the 4000 fractures measured in various wells throughout the state, only 4 percent are actively insvolved in contributing water to the well. Also, subsurface temperature measurements of ground water below 100 meters remains generally unchanged, suggesting that there is less movement in these deeper regions. All these factors combine to paint a scary picture of water scarcity, even in seemly water-rich states like Massachusetts. “I’m not necessarily trying to scare people,” Boutt said. “But at the same time … it’s only going to get worse with global environmental change and population growth. At some point, sacrifices have to be made to be able to accommodate those changes.” Boutt is currently working with Office of the Massachusetts State Geologist, and the U.S. Geological Survey in attempts to continue studying aquifer systems in fractured bedrock around the state.

Boutt’s research is not focused solely on water, however. He is working with the Department of Energy on carbon sequestration, which is the process of pulling carbon dioxide from the atmosphere and storing it in subsurface aquifers. Boutt is investigating the implications of carbon dioxide (CO2) injections into deep aquifers and spent oil/gas reservoirs. CO2 can react with certain types of rocks, so the effects of sequestration could be dangerous. “How would a reaction change both mechanical properties and hydraulic properties of the material?” Boutt asks. So far, Boutt has determined that the hydraulic dangers outweigh the mechanical concerns, and has directed his focus there. The CO2 could change the permeability of the rocks and precipitate different cements and new minerals into the aquifer. It could also change the pathways for various liquids or displace other subsurface fluids. Another danger of carbon sequestration is the possibility of fracturing rocks. Since carbon dioxide wants to rise, the rocks that are a natural barrier to flow could crack under the upwards pressure. “We’re trying to understand the physics, and at what pressure the fractures will propagate.”

Besides his research work, Boutt is helping to plan for the Deep Underground Science and Engineering Laboratory, also known as Homestake DUSEL. This National Science Foundation South Dakota mine-turned-lab has been in the works for five years and would comply with the underground needs of a range of sciences, from physics to biology to the geosciences. Boutt is representing the interests of the geoscientists during these planning stages, and he hopes, when the lab is up and running, to study the relationship between deep subsurface fluid movement and the subsurface biosphere. It is known that two thirds of all the biomass on Earth is found deep underground. “One of the things we don’t know is where does that extend? Where does it end?” Boutt asks. This is an interdisciplinary question, as the answer, whatever it may be, has implications for possible life on other planets. “What is the relationship between fluid movement, Earth’s ambient stress state, and life?” Boutt asks. “What controls the distribution of subsurface life?” More information on Homestake DUSEL can be found at http://www.lbl.gov/nsd/homestake/