Rempe Group member Caroline Hackett investigates the role of alluvium deposits in the process of groundwater recharge from the Nueces River to the underlying Trinity and Edwards Aquifers in south-west Texas. Using stream discharge gain-loss surveys, dye tracer testing, geophysical surveys, and water chemistry measurements, we study the storage capacity and transit times of surface water through alluvial deposits. Caroline is co-advised by Dr. Marcus Gary, and interned with him at the Edwards Aquifer Authority during summer 2017.
![](https://www.jsg.utexas.edu/rempe/files/Nueces-background-300x225.jpg)
The upper Nueces River in Uvalde County, TX, has extensive alluvial deposits of mostly chert cobbles that overlay the limestone units of the Trinity Aquifer.
![](https://www.jsg.utexas.edu/rempe/files/20170331_181234-300x225.jpg)
We use geophysical methods including electrical resistivity, ground penetrating radar, and electromagnetic surveying with the EM31, shown above with Amy, Bianca, and Kindra during the spring 2017 Karst Hydrogeology course.
![](https://www.jsg.utexas.edu/rempe/files/20170814_163001-1-300x225.jpg)
We use non-toxic fluorescent dye to investigate whether the dye travels through subsurface flowpaths through alluvium adjacent to the Nueces River.
![](https://www.jsg.utexas.edu/rempe/files/20170814_131314-300x225.jpg)
During August 2017, we also injected fluorescent dye into groundwater wells with help from Steve and Anastacio at the Edwards Aquifer Authority.
![](https://www.jsg.utexas.edu/rempe/files/20170811_165941-300x225.jpg)
We use ISCO automatic water samplers to continuously monitor for the presence of dye during tracer tests.
![](https://www.jsg.utexas.edu/rempe/files/20170315_174846-300x225.jpg)
Uranine dye turns the Nueces River a fluorescent green while helping us determine whether the river water is the source of nearby springs.
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