Executive Summary
A panel of leading experts (The Old Faithful Science Review Panel) was convened by
Yellowstone National Park (YNP) to review and summarize the geological and hydrological
understanding that can inform National Park Service management of the Upper Geyser Basin area. We
give an overview of present geological and hydrological knowledge of the Old Faithful hydrothermal
(hot water) system and related thermal areas in the Upper Geyser Basin. We prioritize avenues for
improving our understanding of key knowledge gaps that limit informed decision-making regarding
human use in this fragile natural landscape. Lastly, we offer guidelines to minimize impacts to the
hydrothermal system that could be used to aid decisions by park management.
Old Faithful sits within the Upper Geyser Basin, an area of abundant hydrothermal activity
where boiling waters extend from the surface to significant depth within glacial sediments and
underlying volcanic rocks. The geyser systems are directly fed by waters recharged decades to millennia
ago, which are surrounded by colder, younger waters. Activity of the geysers is controlled by complex
subsurface plumbing with fractures and conduits separated by regions of low permeability. Observations
over the past century indicate that the thermal areas and their features are both fragile and highly
dynamic. Although Old Faithful has erupted regularly for the past 150 years, it exhibits changes in
eruptive behavior over time, and the average interval between eruptions has increased by about 50
percent over the past 50 years. It is clear that human activity has modified the hydrothermal system in
the past; conversely, natural features pose ongoing hazards to humans and human infrastructure.
Current (2014) long-term programs to measure heat discharge by chloride-flux monitoring, and
more recently by thermal-infrared imaging, are crucial for assessing the status of the hydrothermal
system. Complementary studies could include airborne resistivity, environmental tracers, numerical
modeling, and greater emphasis on measuring the discharge of water during geyser eruptions. Such data
are needed to better understand the subsurface plumbing systems that feed the geysers. Further
understanding can be gained through installation of shallow groundwater observation wells, surface
geophysical studies, and direct measurement of temperature gradients near the surface. It also is critical
to archive existing data from all studies in a manner that will be readily accessible to scientists and
decision makers. Monitoring and data collection can be achieved through the YNP geology program, by
direct funding to other groups, or by encouraging and facilitating externally funded research.
There are many documented examples at YNP and elsewhere where human infrastructure and
natural thermal features have negatively affected each other. Unless action is taken, human conflicts
with the Old Faithful hydrothermal system are likely to increase over the coming years. This is partly
because of the increase in park visitation over the past decades, but also because the interval between
eruptions of Old Faithful has increased, lengthening the time spent (and services needed) for each visitor
at Old Faithful. To avoid an increase in visitor impacts, the National Park Service should consider
2 alternate strategies to accommodate people, vehicles, and services in the Upper Geyser Basin, such as
shuttle services from staging (parking and dining) areas with little or no recent hydrothermal activity.
We further suggest that YNP consider a zone system to guide maintenance and development of
infrastructure in the immediate Old Faithful area. A “red” zone includes hydrothermally active land
where new development is discouraged and existing infrastructure is modified with great care. An outer
“green” zone represents areas where cooler temperatures and less hydrothermal flow are thought to
exist, and where development and maintenance could proceed as occurs elsewhere in the park. An
intermediate “yellow” zone would require preliminary assessment of subsurface temperatures and gas
concentrations to assess suitability for infrastructure development. The panel recommends that YNP
management follow the lead of the National Park System Advisory Board Science Committee (2012) by
applying the “precautionary principle” when making decisions regarding the interaction of hydrothermal
phenomena and park infrastructure in the Old Faithful area and other thermal areas within YNP.
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First posted April 11, 2014
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