KENTUCKY KARST
especially during the smaller dye spikes on June 19th when dye was actively traveling through the system. Note the lack of data on Figure 5 between June 18th and June 19th: this was due to removal of the probe for safety at the park overnight during flood conditions.
Using the dye arrival time for calculating conduit velocity between the Campbell House sinkhole and McConnell Springs yields a time of travel of 2,112 ft/hr (17.88 cm/s). Or in per- haps more familiar terms, 0.4 miles per hour. However, one could use dye peak time to calculate, yielding slightly differ- ent results, but because the probe was removed overnight, we cannot be confident of the maximum peak time. Regardless, these conduit velocities are very fast compared to the hydraulic conductivities reviewed by the author in eastern Kentucky, non-karst aquifers, which range from 10-2 cm/sec to 10-7 cm/ sec (10 ft/day to 10-4 ft/day) (Garrison, 2015; Minns, 1993).
As the average groundwater temperature in Kentucky is 12°C (54° F), the daily surface water temperature measure- ments at each location indicate that the stream water is warmer in high flow conditions at this time of year. Surface water at McConnell Springs measured 18.55°C (65.39°F) when the dye quantity peaked in the first day and fluctuated based upon rainfall and discharge, but gradually decreased to approximately 18°C (64.4°F).
Conclusions
The primary objective of this study was to use the Cyclops 7 infrared probe to more accurately measure dye travel time through the Middle Ordovician karst of Lexington, Kentucky. This was done to refine the numbers found in the Norris et al. study from 2016 and to test efficacy of the probe. Temperature mea- surements were also collected. Below is a summary of rel- evant conclusions:
Dye deployed into the Campbell House sinkhole during high flow appeared at McConnell Springs (which is 1.9 km, or 1.2 mi, down gradi- ent) 3 hours after injection and later peaked at a concentration of approximately 1,200ppm. Using time of first dye arrival, conduit flow velocity between the Campbell House sink- hole and McConnell Springs was calculated 17.88 cm/sec or 2,112 ft/hr (50,688 ft/day). These conduit velocities are fast compared to the non-karst aquifers, which range from 10-2 cm/sec to 10-7 cm/sec (10 ft/day to 10-4 ft/day).
the dye’s travel time, and (3) the water temperatures measured at these karst springs in high-flow conditions was warmer due to excess rainfall from the day before the dye injection being forced through the karst system with little time to cool to ambient temperatures.
In addition, dye concentration fluctuations observed after first arrival exemplify (1) the importance of collecting frequent (in this case, 1-minute) measurements and (2) the complexities of karst systems. Without these frequent measurements, the intricacies of peaks and troughs would not be observed. Lastly, it appears there is a weak but noticeable correlation between discharge and dye concentration on June 19th of this study.
According to the manufacturer, the detection limit of the probe is 0.01ppb, which is the same as the spectrophotometer that used per the traditional method (in water). Therefore, any sensitivity difference has no significant impact on results in this case
If directions are followed and the Cyclops 7 probe is cali- brated accurately, it performs as advertised, with less field work than traditional methods. However, it recommended to collect water and charcoal samples for backup data.
Other notes: On the probe’s chart readout, there are two lines (battery power and gain) that cannot be removed (this had to be done manually using Microsoft Paint, which took 45
Figure 5 - Dye data logger measurements. Blue represents dye concentration while black represents temperature. Note that the lack of data between June 18th and June 19th was due to removal of the probe for safety.
The following observations were corroborated from the previous study: (1) high-flow conditions likely facilitated accelerated dye travel time through conduits due to increased hydraulic head caused by flooding at the Campbell House sink- hole, (2) the regional topographic relief of 21.3 m (70’), stream gradient of 6 m per 1.6 km (20’ per mile), and the structural dip of the bedrock (3°-5°- NE) probably had little influence on
minutes). One also might feel uncomfortable leaving an instru- ment of this value in a stream overnight, which for us led to a data gap. It is suggested that the device be camouflaged and as well-secured as possible. However, with some relatively minor adjustments and with appropriate security procedures for the device, this could be a tool that hydrogeologists utilize on a regular basis.
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