INVESTIGATING VADOSE-ZONE HYDROLOGY AND AQUEOUS GEOCHEMISTRY IN ALPINE KARST AQUIFERS AT TIMPANOGOS CAVE NATIONAL MONUMENT, UTAH

Water-tracing and groundwater investigations were conducted during 2012, at Timpanogos Cave National Monument (TICA) in Utah, to help National Park Service (NPS) Resource Managers understand the scope and characteristics of the contributing watershed, which may extend outside the NPS boundaries and into the adjacent U.S. Forest Service. Water in TICA is seasonally restricted to five primary sites (Hansen Lake, Middle Lake, Cavern of Sleep, Hidden Lake and Soda Pop Pit) and the sheet-flow and drip waters that contribute to these pools. Water levels in Hansen and Middle Cave Lakes are strongly tied to the spring snowmelt and precipitation. In contrast, water levels in Cavern of Sleep and Hidden Lake remain relatively constant.

One aspect of this study was qualitative dye tracing. On April 13, 2012, frozen ‘bombs’ of concentrated Eosine, Fluorescein, and Rhodamine WT were dropped at selected sites from a helicopter flown over the boundary between TICA and the National Forest. Activated charcoal receptors placed in the five principle cave pools and the American Fork River downstream of TICA were replaced each week and analyzed for the dyes. As of this abstract, dye has not been recovered from the sites, although this is an ongoing investigation and further traces are planned.

Concurrent with dye tracing, ten weeks of geochemistry data suggest differences among cave pools and the American Fork River. The pH values for all sites display a downward trend over the course of the study. The American Fork River maintains the lowest SpC. Values of SpC at Hansen Lake are consistently lower than the other pools. Temperature data from Hansen Lake are stable and 0.5 C° lower than data from Cavern of Sleep and Hidden Lake, potentially illustrating a difference in source waters. Interestingly, Middle Lake warms 0.5 C° during this study from that of Hansen Lake to that of Cavern of Sleep, which perhaps indicates a shift in recharge from melt water to that of phreatic groundwater.