Research Blog
My research interests include high-resolution monitoring and modeling techniques to better understand groundwater flow in spatially and temporally complex geologic systems. Methods include geochemical sampling of groundwater after recharge events, fracture flow modeling, and the use of thermal imagery from drones. My study sites have included areas in Minnesota, Missouri, Pennsylvania, Florida, and now western Montana. |
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To better understand one of my field sites (consisting of a sinking stream which drains to a spring), I'll be conducting a quantitative dye trace in the upcoming weeks. While dye tracing is fairly common practice to determine connections between sinkholes and springs in karst settings, they tend to be more qualitative in nature, essentially determining whether the connection exists by flushing dye into the sink and capturing it with carbon packets at the spring. While this is a useful way to determine the connections, it doesn't necessarily give quantitative details about that connection (i.e. how much of that sinking water then reaches the spring). To step it up a notch and do a more quantitative dye trace involves a bit more effort and planning. The discharge of the sink and spring needs to be known and monitored, the concentration and rate of dye being steadily injected into the sink needs to be known, and the concentration of the dye at the spring needs to be measured through time. This then involves some extra equipment such as dye injection pumps and dye detection loggers. I performed a trace similar to this for my master's research so I feel fairly confident in what sort of information I'm able to get out of it (https://link.springer.com/article/10.1007/s12665-015-4348-0). First order of business was putting the pump rig together. Below is a small drip-rate peristaltic pump (~50 mL/minute). The initial pump wasn't really designed to run for long periods of time, so I had to modify it with some copper tubing which acts as a cooling system as the liquid is pumped through it. I was quite proud of this modification! (Note: this is just water plus some red food coloring to better see it). Next, we got a pair of Cyclops-7 fluorescein loggers. These loggers emit light at a certain wavelength with one sensor, which excites the fluorescine dye which then emits at a different wavelength. The logger records the intensity of the excited wavelength as concentration. One logger will be installed at the spring to record the concentration of dye reaching the spring, while the other will be used for spot checking all the sites during the day of the trace. They were quite easy to set up and calibrate. Working and mixing with the dyes was the next step to ensure that the loggers were functioning properly (and that I was mixing the dye properly). With a week or so to go before the trace I'll be using this time to get more familiar with the loggers, make sure the pump is pumping consistently, and mostly just hoping that the weather cooperates!
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