Watershed Hydrology with Sara Mitchell, associate professor of biology and director of environmental studies

By Maura Sullivan Hill

Course Description
Watershed hydrology is the study of how water moves through and is stored in the environment. Students in this course will investigate various hydrologic processes and the land/surface characteristics that control how water moves through a watershed, and how water is stored both on the surface and underground. Topics will include an introduction to the hydrologic cycle, precipitation, interception, evaporation, snow hydrology, infiltration, groundwater hydrology and contamination, runoff, streamflow, hydrographs and flooding. This class is field-based and involves weekly lab classes and field trips to put classroom concepts into action.

Students will learn how to measure and analyze hydrologic data using quantitative, computer, field and laboratory tools. These are the same tools that working hydrologists use to solve real-world problems.

Students complete three exams, weekly laboratory classes/field trips, problem sets and a water use lifestyle project. The water use lifestyle project is an opportunity to reflect on the impact that personal water use has on the environment. During the second half of the semester, Professor Mitchell and the students record their water consumption and attempt to reduce it over several weeks, keeping journals and writing a final reflection about the process.

Required Texts
Introduction to Physical Hydrology by Martin Hendriks (2010); A Civil Action, by Jonathan Harr (1986)

On the Day HCM Visited Class
Have you heard the term “100-year flood?” Most people think it’s a flood that only happens every hundred years, and sometimes the term can be tossed around incorrectly during flooding disasters. That’s because it actually refers to a flood that has a one percent chance of being exceeded in a given year, as Mitchell told her students during the April 19 class on floods that I attended. It was especially relevant given that the class took place just a day after a flood in Houston, Texas, was front and center in the news cycle. That flood incident resulted in casualties, displaced thousands and shut down roads, businesses and schools in the city.

Mitchell and her students discussed why river channels flood (river channels naturally adjust to fit a flood discharge that happens about once every two years, so most rivers overtop their banks, at least a little bit, about once in every three years) and flood recurrence intervals. Together, they tackled the probability of a 100-year flood on the Straight River in Minnesota, using data from the U.S. Geological Survey. Then, they talked about floodplains, low-lying areas adjacent to rivers that are at risk for floods, and calculated the risk of floods in different locations in “Hazard City,” a fictional town on a river.

Part of the Holy Cross campus is in the floodplain of the Middle River here in Worcester, which runs right below campus. Mitchell used this as an example of development planning for a floodplain area: “The football and baseball fields are in the floodplain, but Williams, the dorm, is not. Fields are easier to fix up after a flood, compared to if a dorm or academic building flooded.”

The group also discussed their water use lifestyle project. Mitchell joined them in their efforts to reduce superfluous water consumption. Some of the students employed creative methods, even leaving dirty dishes in the sink instead of washing them, but most were more practical, like not running the sink while brushing teeth, etc. It was the last week of their project, and Mitchell calculated how much they saved, as a class, through their efforts: 1,000 gallons of water.

Professor Bio
Professor Sara Mitchell joined the Holy Cross faculty in 2006, after earningher Ph.D. from the University of Washington. She is an associate professor in the biology department and directs the Environmental Studies program. Mitchell is a geomorphologist, which means she studies landscapes and how they form and change over time. She investigates glacier- and river-carved landscapes, using field and geographical information systems (GIS) methods. In addition to this Watershed Hydrology course, she has taught Introduction to Geology, Environmental Geology, Geomorphology and Paleoclimatology. She has co-authored 13 peer-reviewed publications and is active in her field as a member of the American Geophysical Union (AGU), Geological Society of America (GSA) and the National Association for Geoscience Teachers (NAGT).

Concepts into Action
“This class is all about water. We start in the sky with cloud formation, precipitation and snow, and then we work our way down,” Mitchell says. “From there, we go into how water soaks into the ground and gets into groundwater, and we spend several weeks talking about groundwater, groundwater flow and contamination. At the end of the semester, we talk about surface water, streams and floods, as well as urban
hydrology issues.”

And the students don’t just talk about these concepts—it is important to Mitchell that they get out in the field and apply them. Several of their weekly laboratory classes involve field work, and she often brings in guest speakers. “By having the guest speakers, they are talking with people who are doing this work every day,” she says. “My husband, who is a groundwater geologist for a consulting company in Boston, came to class, and a stormwater engineer from the city of Worcester came to talk about flooding during storms.” The field trips range from a visit to the Wachusett Mountain Ski Area, to learn about how they create snow, to the drinking water treatment facility in Holden that supplies all the drinking water for the city of Worcester. “We got a tour of their process, and then the assignment was to think about parallels between Worcester and Flint, Michigan. They had to understand the process and regulations for drinking water. Could that kind of water crisis happen here?”

Classroom to Career
“Watershed Hydrology was my first exposure to the basic concepts of hydrology, which I now apply every day, at every site that I work to remediate,” says Karlyn Whipple ’14. She works as an environmental scientist at a private environmental consulting firm that specializes in remediation of petroleum-impacted sites in Massachusetts. “Everything we learned in Watershed Hydrology, from monitoring well construction and groundwater contouring, to in-situ (under surface) remediation and Phase I assessment technical reports, has become a concrete and applicable skill that I employ daily.” Whipple says that this course changed the trajectory of her professional life: “Professor Mitchell’s class had an inordinate impact on my career choice. She went above and beyond as an educator to expose her students to tenable and viable career opportunities associated with each concept we covered. Professor Mitchell was approachable, fostered an environment of inquisitive learning and was genuinely interested in our futures as scientists.”  ■