New Mexico Geological Society Annual Spring Meeting & Ft. Stanton Cave Conference — Abstracts

Monitoring evaporation rates in humid caves in arid areas may provide information about a variety of cave features and processes, including speleothem formation and growth, cave biota and their habitats, the effects of climate change on cave microclimates, and seasonally changing ventilation patterns within the cave. With funding from the National Cave and Karst Research Institute, a cave evaporimeter was designed and deployed at two different locations within Fort Stanton Cave. The evaporimeter consists of an aluminum container where the water level within the container is monitored by a linear potentiometer that records a water level change of 0.24 mm to a data logger.

The initial deployment of the cave evaporimeter at Inscription Rock within Conrad’s Branch recorded 0.65 mm of evaporation over a period of 124 days, 5/15/2020 through 9/15/2020, with the first 92 days showing no appreciable evaporation. The second deployment of the cave evaporimeter at Turtle Junction recorded 2.60 mm of evaporation over a period of 110 days, 7/12/2021 through 10/29/2021. The results are displayed in the figure below.

The most predominant driving force of evaporation within a cave is the exchange of near-fully saturated air within the cave with minimally saturated air outside the cave. This exchange of air is driven primarily by barometric pressure differences inside and outside the cave, with the current understanding that evaporation near the cave entrance will be greater than farther inside the cave. Although the data collected was not concurrent, it was collected during similar seasons one year apart. Contrary to what was expected, the evaporation rate deeper within Fort Stanton Cave was four times greater than that near the entrance. These results lead to the following question: what’s driving the higher evaporation rate at Snowy River?

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