Bureau scientists aim to increase our understanding of the hydrogeology of Fort Stanton Cave by assessing the local water balance for a flood event in Snowy River Passage. Since the discovery of Snowy River Passage in 2001, Fort Stanton cave, located in southern New Mexico (see figure), has become a world-class cave. There are many exceptional aspects of Snowy River, including the white calcite formation that lines the stream bed along most of the known length of the passage, making it the longest speleothem in the world. Over the last twenty years, cave explorers and researchers have been collecting geologic, hydrologic and geochemical data, with the objective of identifying the water source(s) associated with several ephemeral floods that have been observed in Snowy River Passage. Recently, researchers from NM Tech, UNM, and the USGS have constructed a preliminary hydrogeologic conceptual model of Snowy River based on existing data sets. According to this model, Eagle Creek is the primary source of water that periodically floods Snowy River Passage. During times of high stream discharge in Eagle Creek, enough water infiltrates through the streambed sediments to initiate flooding in the passage. Much of this water ends up discharging at Government Spring and flows into the Rio Bonito. Water in the Snowy River stream is also lost to downward leakage and evaporation.
The main objective of this study is to examine hydrogeologic processes in Snowy River Passage by analysis of individual flood events. For a specific flood event, we will measure:
- The volume of water that infiltrates downward through the Snowy River streambed
- The volume of water that evaporates from the Snowy River stream
- The volume of water that discharges at Government Spring
These measurements will allow the calculation of the volume of water that infiltrated from Eagle Creek to initiate flooding in Snowy River Passage. These water balance calculations will help to test our current conceptual model and constrain a two-dimensional hydrologic flow model that is being developed.
Another objective of this study is to build a pan evaporimeter that records continuous data in the cave to accurately estimate evaporation rates in high-humidity caves. This instrument will be a useful tool to study microclimates in other caves in arid regions, presenting opportunities for future collaborative projects. Monitoring evaporation rates in humid caves in arid areas can provide information about the effects of climate change on cave microclimates.
