Drained Lake Perez gives students a chance to study water chemistry

BARREE TOWNSHIP, Huntingdon County -- With an eye to understanding groundwater flow, students in Pamela Sullivan’s geochemistry class took a field trip to Lake Perez this fall to collect samples that would be the basis of their semester’s work.

“I was focused on what contributed to surface water in the Shale Hills,” said Helen Gall, one of the graduate students in the class.

As it happens, the lake Gall and other students were collecting samples from is empty. But, that wasn’t a problem. A team of researchers in Penn State’s College of Earth and Mineral Sciences are interested in what’s going on beneath the ground and around it, not just above it. To find out, faculty, researchers and students installed wells to monitor that underground activity in the bed of Lake Perez, which has been drained for dam repairs since 2008.

This semester, students in that Department of Geosciences course, along with researchers in the college’s Earth and Environmental Systems Institute (EESI), have been using data from those wells to gain insight on the impact of dam removal on the connection between surrounding streams and the underground water.

The timing of the project is critical, as researchers have the unique opportunity to study the sediments and groundwater while the lake is empty, and after the dam has been repaired and the water restored.

“That’s one of the coolest things about this,” said Sullivan, a postdoctoral scholar. “Not often do you get to collect data before and after a dam is installed.”

Sullivan, who is teaching “Techniques in Environmental Geochemistry” this semester, said when the lake is refilled researchers will be able to get a better understanding of the lake’s “legacy sediments” — the dirt and debris at the bottom of the lake bed — and how those sediments interact with the water in the ground and streams. By extension, researchers can look at what influence the dam has on two unnamed creeks, which flow into Shaver’s Creek, then into the Juniata, which eventually makes its way to the Chesapeake Bay.

“What is the influence of dams on downstream water quality?” Sullivan said is one of the questions being asked.
The research on the lake bed is also part of a larger project that Susan Brantley, distinguished professor of geosciences, is leading. The Susquehanna Shale Hills Critical Zone Observatory (CZO) is a National Science Foundation-funded initiative focused on understanding the impact of water that moves from the canopy of trees through the top layer of the earth into the bedrock below, including the chemistry of those interactions.

Brantley noted that this type of research into better understanding water chemistry and how it interacts with its surrounding environments is particularly relevant given the growth of the natural gas industry in the Marcellus Shale region, which crosses through Pennsylvania.

“By collecting this type of water quality data at multiple points across Pennsylvania we’ll be in a better position to understand what, if any, impact deep horizontal drilling, including the use of water for hydraulic fracturing, has on the surrounding environment,” Brantley said. “At the same time, students are learning about the water quality testing and modeling processes first-hand.”

Students in the “Techniques in Environmental Geochemistry” class Sullivan is teaching worked in small groups at the beginning of the semester on water sample collection. Those samples are processed and analyzed for a number of constituents, including at a laser isotope machine on campus. The students have been using data on water chemistry (pH, conductivity and elemental concentrations) to study the interaction between surface and groundwater.

Molly Cain, a junior in geosciences, is looking at variations that may occur at three different sites within the CZO.

“The CZO is an interesting watershed,” she said. “Although it’s small, each site is diverse in terms of vegetation, soil type and underlying rock.”

The CZO is a multi-year project focused on understanding how water moves through rocks in the Shale Hills region of Pennsylvania and the chemistry of sedimentary rocks.

“Everyone had something different to contribute to it and a different way of looking at it,” Cain said of the class, which is a mix of upper-level undergraduates and graduate students. “It was very hands-on.”

Lake Perez is part of the 7,000-acre Stone Valley Recreational Area, which Penn State owns and operates. The Office of Physical Plant is in the process of repairing the dam, with work on it expected to be completed in early 2014.

According to the Office of Physical Plant, the refill will be slow and carefully monitored. The lake is expected to be returned to normal levels by mid-2014.

While students in the Geochemistry class took water samples early in the fall semester, research that’s part of the Critical Zone initiative is ongoing. To enable that groundwater monitoring to take place even after the lake is restored, Sullivan and EESI research associate Andrew Neal have been extending the height of the wells that were installed in the lake bed.

To predict groundwater flow in the lake bed, Sullivan and Neal drop pressure sensors attached to cords into the well tubes. When the sensors are removed, they can be attached to a computer to produce a data reading.

“We’ll be able to see if damming influences or changes the hydrodynamics of the Shaver’s Creek watershed,” Sullivan said.

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Last Updated December 16, 2013