When it comes to watersheds, identifying the origins of pollution entering a river or stream isn't always a simple task.
Rain falling over the area the watershed drains tends to pick up and carry along with it any particulates it encounters, whether that’s loose dirt, fertilizer-impregnated soil from a farm or motor oil from a road. Because it lacks an obvious origin, scientists call this form of environmental contamination “non-point source pollution.”
Thanks to stricter controls imposed by the Clean Water Act in 1975 over single-source pollution, such as discharge pipes, non-point source pollution is now the leading cause of water pollution, says Tennessee Aquarium Conservation Institute Geographic Information Systems Analyst Sarah Sweat.
“We know where the pollution comes from, but we cannot necessarily control it because you cannot point to who or what is contributing to the pollution,” Sweat says. “Sedimentation from non-point source pollution is one of the greatest threats to aquatic animals in the Southeast.”
Sedimentation is so dangerous, she explains, because many southeastern aquatic species live on the bottom of streams. Over time, as sediment settles, it fills in the crevices in which they live, destroying their habitat. In addition, murkiness caused by floating sediment can drastically affect the survivability of fish species that rely on sight to feed.
Earlier this year, researchers at the Conservation Institute tasked students at the STEM School Chattanooga with designing and building 3-D models of the regional watershed for use in educational demonstrations of how non-point-source pollution can affect local waterways.
Using terrain data provided by Sweat and a suite of high-tech tools in the school’s Fabrication Laboratory (Fab Lab), 12 juniors from the school spent nine weeks building geographically accurate representations of the Chattanooga landscape. The teams, each consisting of three students, were also tasked with using different materials in their model to demonstrate the effects of water traveling over porous and non-porous surfaces, which can dramatically affect non-point source pollution's impact.
“It’s been great working with the Conservation Institute,” says Ken Kranz, the school’s Fab Lab instructor. “This is an awesome project. It exemplifies what the STEM School is all about. It’s a great application of science, technology, engineering and math, all of which came together in this project.”
On March 16, representatives from the Conservation Institute visited the school to see the models and evaluate the students' presentations explaining their design and build process.
The teams' approaches varied widely. Some used low-density foam, while others relied on wood or a repurposed foam bodyboard. Some models were smaller — the size of a pair of text books laid side by side — while others sprawled across two folding tables.
As they explained the work that went into creating each model, the teams described a slew of obstacles they faced. For some, choosing materials was the primary headache, whether because of its expense or a lack of malleability once they began fabricating. Others experienced tool failures or issues with waterproofing (the models were expected to be able to showcase runoff using water applied to their surface).
Ultimately, the project was as much about learning about non-point source pollution and the local watersheds as it was encouraging the students to think creatively and learn from their failures. One of the models will eventually be chosen for use in watershed demonstrations at the Conservation Institute, but all four exceeded expectations, Sweat says.
“I was impressed that they could make a realistic Chattanooga landscape out of a variety of different materials,” she says. “Each group brought something new to the table, and each model was different.
“Anything that they did to model the watershed or to get in there and get hands-on with ways to create models and think about it from a spatial location and non-point source pollution is a win.”