F & M Bubble Study
In 2017, Franklin and Marshall College started a hydrologic experiment to study the geologic characteristics, groundwater flow, recharge area to the spring, and identify the source. According to researchers with the college, it is believed that some of the water that flows into the Bubble drains off of South Mountain, while the majority of it comes from the southern side of South Mountain near the Pigeon Hills area in York, PA.
Researchers are currently working on a project to test their theories of where the Bubble gets its water by conducting a dye-tracing test at the source-region they pinpointed through satellite data. Additionally, the Bubble is being used to develop programs to aid in water protection and contaminant mitigation efforts.
Here is the latest updates from Bob Walter, Professor of Geoscience at Franklin and Marshall College:
Over the past 10 years, our research team at Franklin and Marshall College has studied groundwater flow, regional tectonics, bedrock fracture patterns, and water quality associated with the spring seeps at Boiling Springs, PA. The largest of these springs, “The Bubble”, is the seventh largest discharging spring in the State. A USGS study in the 1980s demonstrated that seven-times more water is discharged from The Bubble than can be accounted for by precipitation in its topographic watershed, and that the temperature of its water is roughly six months out of phase with the local climate. These observations piqued our curiosity because it means that at least some of its water comes from outside it’s topographic area and that it must be traveling over a long distance, so we began a study to see if we could find its source. In 2017, we identified a probable source area about 20 miles southeast of Boiling Springs, using a novel computer code termed ECHO-GPM that compares regional precipitation events (from NASA satellite data) with pressure surges in the spring measured by sensors installed in the spring.
Because our research has important implications for watershed protection, it has gained considerable interest among the Boiling Springs community, including the South Middletown Township Board of Supervisors that provided funds to purchase instrumentation to measure water quality data at the Bubble around the clock. We call this the Boiling Springs Groundwater Observatory, which was installed August 6, 2021, and is maintained by our F&M research team.
The immediate goal of this research project is to test the hypothesis that the source of the water discharging at The Bubble is actually 20 miles to the southeast. To help with this test, in late February 2023 we installed three automated fluorometers at the observatory. This marked the beginning of a long-term dye tracing experiment. Working with a colleague from Shippensburg University, this summer we will place three environmentally friendly dyes around the source area, which eventually will be detected by the fluorometers if our hypothesis is correct. The installed sensors will alert us to the presence and concentration of these dyes the moment they appear at the spring. The time delay from placement in the source area to their detection at the Bubble could be months or years, but only a sophisticated system like we have set up at the Bubble can confirm the source of the water flowing from the Bubble.
Expanded notes:
Jake Howey, who graduated last May, completed his Honors Thesis on the geochemical analyses of surface and ground water in and around the Bubble. We concluded that the most likely scenario is that the Bubble is sourced from a mix of groundwater originating from precipitation along both Pigeon Hills (York County) and South Mountain. The evidence is quite compelling. Our three new students, Bryce, Mia, and Ting are continuing Jake's work, in addition to new studies outlined below.
Working with Prof. Todd Hurd at Shippensburg, we began our dye tracing test this summer, inserting dye in promising locations along South Mountain. We are working on identifying locations in Pigeon Hills to do the same this Fall. As you might recall, we have three sensors installed at the Bubble (fluorometers) that will capture the dye signal if and when it arrives at the Bubble, which we anticipate will be at least six months from the time the dye was deployed (that is, not until later this year), most likely later. In the meantime, Todd has placed charcoal bags in the Bubble and at various other spots, which he checks every few weeks as a secondary dye detection system that he studies in his fluorometer at his lab in Ship.
The data collection system at the Bubble has been updated to make it easier for us to view and analyze the massive amounts of archived water quality data we are gathering there. We are working on generating data analyses and data smoothing methods. It is likely that we will need to purchase software specifically designed to analyze continuously collected water quality data (such as the software package from Aquarius). Once we get that system up and running, we can begin to share data publicly. I'm not sure when that would be, but hopefully sometime this academic year, or by next summer at the latest. There is a lot of work involved in that.
It would be useful to add some new sensors to our array, for example to measure nitrate and chlorophyll, and of course the existing sensors wear out and need to be replaced occasionally.