2025 ·
Flow and Groundwater Levels, Species and Habitat
Into the Depths: Uncovering Wimberley’s Hidden Waterways Through Dye Tracing
In spring 2018, a group of scientists and agencies worked together to conduct a dye-trace study near Jacob’s Well Spring (JWS) to better understand how water moves through the underground karst system in the Cypress Creek watershed.
The goal was to find out if water from Raccoon Cave—a limestone cave in the Lower Glen Rose formation—flows into Jacob’s Well or nearby wells. This kind of information helps scientists understand how water travels underground and can inform groundwater protection strategies.
On March 27, 2018, five pounds of a fluorescent dye (Rhodamine WT) were poured into Raccoon Cave and flushed with water. Researchers then monitored for traces of the dye at several locations: five area wells, Jacob’s Well, and spots along Cypress Creek downstream of the spring. Jacob’s Well was monitored using an automatic sampler, a sensor in the water, and daily charcoal packets that absorb dye. The other locations were checked weekly with charcoal samplers. Monitoring continued through May.
The results were mixed.
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No dye was detected in the water samples.
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Very small traces of dye were found in charcoal samples from two wells and downstream in Cypress Creek, but these were low concentrations and only appeared in the first week after the test.
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One well already showed some dye before the test, making the result unclear.
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No dye was detected after June 4, 2018.
Even though the dye results were unclear, other data from instruments measuring water quality (like temperature, turbidity, and conductivity) showed changes shortly after rainfall. This suggests that rainwater quickly enters the underground system and reaches Jacob’s Well—possibly through features like Raccoon Cave.
Recommendations:
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Repeat the dye test at Raccoon Cave using a larger amount of dye.
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Leave charcoal samplers in place for at least a week to better capture any dye movement.
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Carefully analyze background dye levels before the next test to ensure accuracy.
This study provides valuable insights into how water moves underground in the Cypress Creek area and offers guidance for improving future dye-trace efforts.