Prepared in cooperation with the National Park Service and the Yellowstone Park 

Foundation

Hydrogeology of the Old Faithful Area, Yellowstone 

National Park, Wyoming, and its Relevance to Natural 

Resources and Infrastructure

 

Open-File Report 2014–1058

U.S. Department of the Interior

U.S. Geological Survey
COVER: Aerial overview of the Old Faithful area from the northeast. (Yellowstone National Park photograph by 

Cheryl Jaworowski, October 12, 2010.)
Hydrogeology of the Old Faithful Area, Yellowstone 

National Park, Wyoming, and its Relevance to Natural 

Resources and Infrastructure

By Old Faithful Science Review Panel

Composed of Duncan Foley, Robert O. Fournier, Henry P. Heasler, Bern Hinckley, Steven E. Ingebritsen, Jacob B. 

Lowenstern, and David D. Susong

Prepared in cooperation with the National Park Service and the Yellowstone Park Foundation

Open-File Report 2014–1058

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014

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Suggested citation:

Old Faithful Science Review Panel, 2014, Hydrogeology of the Old Faithful Area, Yellowstone National Park, 

Wyoming, and its Relevance to Natural Resources and Infrastructure: U.S. Geological Survey Open-File Report 

2014-1058, 28 p., http://dx.doi.org/10.3133/ofr20141058..

ISSN 2331-1258 (online)

Any use of trade, firm, or product names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this information product is in the public domain, permission must be secured from the individual copyright 

owners to reproduce any copyrighted material contained within this report.
iii

Contents

Executive Summary....................................................................................................................................................... 1

Introduction and Background......................................................................................................................................... 2

1.0 Geology and Hydrology of Old Faithful and the Upper Geyser Basin ..................................................................... 3

1.1 Geologic and Hydrologic Setting......................................................................................................................... 3

1.2 Geysers............................................................................................................................................................... 4

1.3 Steam-Heated Ground ........................................................................................................................................ 4

1.4 Lessons from Drilling........................................................................................................................................... 5

1.5 Thermal Areas at Yellowstone National Park Are Naturally Dynamic and Unstable............................................ 5

1.6 Eruption Behavior of Old Faithful Has Been Changing ....................................................................................... 6

1.7 Infrastructure and Thermal Areas Inevitably Affect Each Other .......................................................................... 7

2.0 Knowledge Gaps and Suggested Topics for Future Study ..................................................................................... 8

2.1 Background......................................................................................................................................................... 8

2.2 Conceptual Understanding of the System and Its Long-Term Trends................................................................. 8

2.2.1 Chloride-Flux Measurements........................................................................................................................ 8

2.2.2 Airborne Resistivity Measurements ............................................................................................................... 9

2.2.3 Environmental Tracer Data........................................................................................................................... 9

2.2.4 Geyser Frequency and Fluid Discharge Data............................................................................................... 9

2.2.5 Numerical Modeling..................................................................................................................................... 10

2.3 Understanding the Effects of Infrastructure on Thermal Areas.......................................................................... 10

2.3.1 Thermal Measurements.............................................................................................................................. 10

2.3.2 Groundwater-Level Monitoring ................................................................................................................... 10

2.3.3 Shallow Stratigraphy and Structure ............................................................................................................ 11

2.4 Prioritization ...................................................................................................................................................... 11

3.0 Guidelines for Infrastructure Management in the Old Faithful Hydrothermal Area................................................ 12

3.1 Introduction ....................................................................................................................................................... 12

3.2 Long-Term View................................................................................................................................................ 12

3.3 An Approach to Infrastructure Maintenance and Development......................................................................... 13

3.3.1 Red Zone.................................................................................................................................................... 13

3.3.1a Delineation............................................................................................................................................ 14

3.3.1b Management Guidelines ....................................................................................................................... 14

3.3.2 Green Zone ................................................................................................................................................ 14

3.3.2a Delineation............................................................................................................................................ 15

3.3.2b Management Guidelines ....................................................................................................................... 15

3.3.3 Yellow Zone................................................................................................................................................ 15

3.3.3a Delineation............................................................................................................................................ 15

3.3.3b Management Guidelines ....................................................................................................................... 16

Final Thoughts............................................................................................................................................................. 16

Acknowledgments........................................................................................................................................................ 16

References Cited......................................................................................................................................................... 17

Appendix 1. Legal Mandates, Authorities, and Policies Governing the Protection of Geothermal Resources in 

Yellowstone National Park........................................................................................................................................... 26

Appendix 2. Presentations to the Old Faithful Science Review Panel, June 3–4, 2013.............................................. 28
iv

Figures

Figure 1. Geologic map of Old Faithful area. The Mallard Lake, Summit Lake, and Scaup Lake lava flows 

surround the Upper Geyser Basin ........................................................................................................................... 20

Figure 2. Schematic cross section along a 5-kilometer profile from southwest to northeast through the Upper 

Geyser Basin ........................................................................................................................................................... 21

Figure 3. Photograph montage of various types of sediments and hydrothermal deposits 

in the Old Faithful area ............................................................................................................................................ 22

Figure 4. Boxplot showing increase in the eruption interval of Old Faithful from 1960 to the present ..................... 23

Figure 5. Map of the Old Faithful area delineating zones for the protection of the hydrothermal resource and 

infrastructure............................................................................................................................................................ 24

Table 

Table 1. Proposed Zone System for Old Faithful Area ............................................................................................ 25
v

Conversion Factors and Datum

Conversion Factors

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square meter (m2) 0.0002471 acre 

square meter (m2) 10.76 square foot (ft2) 

Volume

liter (L) 0.2642 gallon (gal)

Flow rate

liter per minute (L/m) 0.26 gallon per minute (gal/min) 

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32.

Datum

Horizontal coordinate information is referenced to North American Datum of 1983 (NAD 83).
vi

Members of the Old Faithful Science Review Panel

Duncan Foley

Professor

Department of Geosciences

Pacific Lutheran University

Tacoma, Washington, 98447

Robert O. Fournier

Research Geologist, Retired

U.S. Geological Survey

345 Middlefield Rd.

Menlo Park, California 94025

Henry Heasler

Park Geologist

Yellowstone National Park

P.O. Box 168

Mammoth, WY, 82190

Bern Hinckley

Hinckley Consulting

419 South 5th Street

Laramie, WY 82070

Steven E. Ingebritsen

Research Hydrologist

U.S. Geological Survey

345 Middlefield Rd.

Menlo Park, California 94025

Jacob B. Lowenstern

Research Geologist

U.S. Geological Survey

345 Middlefield Rd.

Menlo Park, California 94025

David D. Susong

Supervisory Hydrologist

U.S. Geological Survey

Utah Water Science Center

2329 Orton Circle

Salt Lake City, UT 84119
1

Hydrogeology of the Old Faithful Area, Yellowstone 

National Park, Wyoming, and its Relevance to Natural 

Resources and Infrastructure

By Old Faithful Science Review Panel

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.
2

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 

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.

Introduction and Background

The Old Faithful area is the pre-eminent location in the world’s first National Park and is a

unique and globally treasured geological area. Since 1872, park administrators have grappled with the 

delicate balance of preserving natural features while maximizing the ability of the public to enjoy and 

explore this natural wonderland. Globally recognized cultural resources also are part of the Old Faithful 

landscape, including Robert Reamer’s 1904 rustic architectural masterpiece, the Old Faithful Inn.

Over the past 50 years, visitation to YNP and Old Faithful has almost doubled, resulting in 

growing needs for parking, lodging, food service, and other essentials in or near the Upper Geyser 

Basin. Park administration must frequently consider the tradeoffs involved with simultaneously 

providing for public enjoyment of the area, maintaining cultural resources, and minimizing impacts to 

hydrothermal resources (natural hot waters and related thermal features). Similarly, it has been 

challenging to maintain park infrastructure, especially underground utilities, in areas with abundant 

natural heat and reactive fluids.

Specific legal mandates address the protection of geothermal and hydrothermal resources in 

YNP and are reviewed in appendix 1. The legislation creating YNP in 1872 states that the park

“...shall provide for the preservation, from injury or spoliation, of all timber, mineral deposits, 

natural curiosities, or wonders within said park, and their retention in their natural condition [17 

Stat. 32].”

For areas outside the park, directives seek to preclude even the threat of adverse effects on the park’s 

hydrothermal resources. An example is the 1994 establishment of the Yellowstone Controlled 

Groundwater Area (YCGA) in an area of Montana outside of the park’s boundary to “allow no impact 

to the hydrothermal system within the reserved lands of YNP.”
3

A panel of leading experts (The Old Faithful Science Review Panel) was convened by YNP to 

provide a summary of current knowledge of the hydrothermal system and its potential vulnerability to 

current and future human activities. The panel consists of seven experts on hydrology, geology, and 

geothermal resources, and met on June 3–5, 2013, at Snow Lodge, near Old Faithful. The panel listened 

to presentations by a variety of park employees, including managers, law enforcement personnel, and 

historians, as well as science briefings by panelists and other invited researchers (appendix 2). The panel 

subsequently communicated through face-to-face meetings, e-mail, and teleconferences to create this 

report.

In this report, we give an overview of present geological and hydrological knowledge of the Old 

Faithful hydrothermal area and Upper Geyser Basin. We also prioritize avenues for improving our 

understanding of key knowledge gaps that limit informed decision-making regarding human use in this 

fragile natural landscape. Finally, we offer suggestions that may assist with present and future 

management of hydrothermal resources in the Old Faithful area.

1.0 Geology and Hydrology of Old Faithful and the Upper Geyser Basin

1.1 Geologic and Hydrologic Setting

Old Faithful and the rest of the Upper Geyser Basin are located in the Firehole River valley. The 

valley is bordered by young rhyolitic lava flows that erupted 100,000–170,000 years ago and formed the 

valley margins (fig. 1; Christiansen, 2001). During the last glacial maximum, the area was covered by 

glacial ice. The glaciers and their meltwater systems deposited up to about 60 m (200 ft) of sediments 

on the valley floor (figs. 2 and 3a). These sediments, which were deposited by ice-contact and icemarginal streams, are largely composed of obsidian sand and gravel derived from the local rhyolites

(Muffler and others, 1982). The sediments have a wide range of vertical and horizontal permeability in 

part due to local hydrothermal alteration and cementation by hydrothermal minerals.

The dominant hydrothermal water of Old Faithful and Geyser Hill is neutral to alkaline in pH 

and rich in dissolved chloride, silica (SiO2), and other elements. Upon cooling at the surface, the water 

precipitates silica sinter that often forms “aprons” around thermal features (figs. 1 and 3b). Studies of 

the chemistry and isotopic composition of the thermal waters indicate that the waters ultimately 

originate as precipitation (rain and snow) but interact with deep rock to gain heat, chloride, and other 

solutes. The thermal waters contain very little tritium (3

H), a hydrogen isotope created in the 

atmosphere, which implies very little contribution from waters less than 60 years old (Pearson and 

Truesdell, 1978; Rye and Truesdell, 2007; Gardner and others, 2011; Hurwitz and others, 2012).

Chemical thermometry of thermal waters discharging in the Upper Geyser Basin indicates that 

most have resided in the subsurface long enough to attain chemical equilibrium with the surrounding 

rock in a zone of porous and permeable rock (an underground reservoir) between 170 and 210 m (560 

and 690 ft) deep at temperatures around 210 °C (400 °F), as discussed in Dr. Robert Fournier’s1

presentation to the panel on June 3, 2013, and detailed in Fournier (1989). These thermal waters 

previously resided in deeper, hotter reservoirs up to 5 km (3 mi) beneath the surface and at temperatures 

estimated at 350°C (660°F). Steep faults and fractures guide the thermal water upward toward the 

 1 The talks were recorded and saved as digital video available from YNP.
4

surface—thermal water is discharged in the topographically low region of the Upper Geyser Basin (fig.

2) at a significant time and distance from its area of infiltration as dilute rain. A National Park Service 

(NPS) chloride-flux monitoring program permits quantification of the combined mass of thermal water 

discharged into the Firehole River from the Upper and Lower Geyser Basins. This program provides a 

means of evaluating changes in the total output of thermal fluids and heat by the hydrothermal system 

that might result from large earthquakes, climate change or human activity (Friedman and Norton, 2007; 

Hurwitz and others, 2007).

1.2 Geysers

Geysers intermittently erupt jets of water. At YNP, geyser eruptions are initiated when water in a 

geyser conduit starts to boil vigorously. The expansion of steam powers the discharge. The geysering 

requires temporary over-pressures created during repeated cycles of reheating by superheated waters. A 

critical requirement for long-lasting activity of a geyser is the maintenance of appropriate permeability 

within the geyser conduits relative to the surrounding rocks. Permeability is decreased by precipitation 

of amorphous silica and other mineral deposits during cooling of thermal water. Permeability increases 

through the action of earthquakes or powerful geyser eruptions that can break the rocks. Limited 

exploration with video cameras, thermometers, and geophysical techniques indicates that the uppermost

part of Old Faithful Geyser’s feeder tube is an irregular fissure with open cavities separated by narrow 

slots or throttles that limit the ease of fluid flow (Hutchinson and others, 1997). The volume of water in 

a newly discovered elongated cavity at the side of Old Faithful (Vandemeulebrouck and others, 2013) 

has been estimated at 62,000 L (16,500 gal), equivalent to the volume of a sphere about 5 m (16 ft) in 

diameter. This does not include the considerable amount of water in the actual geyser tube. A tracer test 

conducted in the Daisy Group of geysers in the 1960s indicated that the reservoir supplying water to 

Splendid Geyser holds more than 270,000 L (71,000 gal) of thermal water (Rowe and others, 1965).

Little other work has been done to explore the subsurface “plumbing” of YNP geysers.

1.3 Steam-Heated Ground

Subsurface boiling inevitably causes migration of steam. When the steam reaches the periphery 

of a thermal area and cools, it will condense beneath the ground surface to create steaming ground as 

found at the margins of the Myriad Group near the Laurel Dorm (fig. 3c). Alteration of near-surface 

sediment in steam-heated zones can create oxidized zones of low-permeability red clays (fig. 3d). These 

clay zones often overlie zones of steam condensation and play an important role in minimizing the 

migration of thermal waters and gases. The exact margins of steam-heated areas may be difficult to 

delineate by eye, particularly where sinter has been deposited on the ground or the ground has been 

disturbed by human activities. Regions affected by hydrothermal alteration have been mapped with 

hyperspectral airborne techniques (Livo and others, 2007), as well as field mapping (Muffler and others, 

1982).
5

1.4 Lessons from Drilling

Much of our understanding of the subsurface beneath the Upper Geyser Basin comes from 

scientific drilling discussed in Dr. Jacob Lowenstern’s presentation on June 3, 2013. One hole was 

drilled by the Carnegie Institute in 1929 (C-1 in the Myriad Group; Fenner, 1936), and three by the U.S. 

Geological Survey (USGS) in 1967 (Y-1 in Black Sand Basin; Y-7 and Y-8 in Biscuit Basin; fig. 1). A 

total of 13 wells were drilled in YNP by the USGS in 1967–68 (White and others, 1975). Investigations 

of these wells involved downhole temperature and pressure measurements, fluid sampling, and coring of 

subsurface rocks. Lessons from the drilling included:

1. In active thermal areas, subsurface water temperatures increased along the boiling-point curve, 

as pressure increased with depth.

2. Water pressures in the channels of hydrothermal convective up-flow were approximately equal 

to or greater than those in the adjacent cold groundwater that surrounded the geyser basins. This 

prevents surrounding cold waters from entering upflow channels that feed geysers.

3. When a well discharging boiling water and steam was “shut,” steam and non-condensable gas 

immediately started to accumulate beneath the valve, resulting in a rapid and significant increase 

in pressure at the wellhead.

4. In the Upper Geyser Basin, glacial sediments in the wells were less than 60 m (200 ft) thick; at 

greater depths, the wells encountered rhyolite flows. The sediment thickness ranges greatly due 

to the original uneven topography prior to deposition of sediments.

5. Drilling close to Whistle Geyser temporarily affected its output and behavior (White, 1991).

1.5 Thermal Areas at Yellowstone National Park Are Naturally Dynamic and Unstable

Thermal features and their feeders change and shift location through time. Some geysers have 

ceased erupting for unknown reasons. Others have ceased erupting for long periods and then restarted.

For example, intervals between major eruptions of Steamboat Geyser (Norris Geyser Basin) have 

ranged from 4 days to 50 years. The interval preceding the major eruption of Steamboat Geyser on July 

31, 2013, was 8 years. Slight changes in behavior of nearby springs and geysers can have major effects. 

For example, in the early 1960s, Daisy Geyser (Upper Geyser Basin) ceased erupting, while 

simultaneously a previously insignificant nearby spring (Bonita) began to discharge at an increased rate. 

A short-term experiment showed that temporarily increasing the level at which water flowed from 

Bonita by 8–10 cm (3–4 in.) could induce eruptions of Daisy Geyser. This illustrates that thermal 

features can be sensitive to small pressure changes from nearby pools or geysers, and suggests 

sensitivity to small changes in local groundwater levels and recharge.

Hydrothermal explosions (rock-hurling eruptions) have occurred numerous times at YNP, both 

during historic times and in the geological record (Christiansen and others, 2007; Morgan and others,

2009). Some occur when natural throttles (narrow constrictions in the path of fluid flow) rupture, 

resulting in a decrease in pressure and an immediate flashing of some liquid water to steam. The 

hydrothermal explosion in 1989 at Porkchop Geyser in Norris Geyser Basin is particularly well 

documented (Fournier and others, 1991). Throttles may fail for many reasons, including seismic activity 

or a disturbance by drilling or digging. Most deep hot spring pools in YNP likely result from relatively 

small hydrothermal explosions. The most notable examples of large hydrothermal explosions near Old 
6

Faithful are the 1880s explosions at Excelsior Geyser in Midway Geyser Basin and the 1959 activity at 

Sapphire Pool, which continues intermittently in nearby pools at Biscuit Basin. Prehistoric explosions 

near the northern end of Yellowstone Lake created a crater more than 3 km (2 mi) across (Mary Bay). A 

1-km-diameter crater (0.6 mi) was formed about 11,000 years ago in Pocket Basin in the Lower Geyser 

Basin, likely due to depressurization associated with draining of a glacial lake (Muffler and others, 

1971).

The effects of strong earthquakes on hot spring and geyser activity in the Upper Geyser Basin 

have been well documented (Marler, 1964). Six days after the 1959 M7.5 Hebgen Lake earthquake, 

Sapphire Pool in Biscuit Basin erupted with violent force, throwing large blocks of sinter into the air, 

greatly enlarging its pool, and issuing a wave of water over the adjacent boardwalk. If anyone had been 

present, it is likely that they would have been fatally scalded. For about 2 years thereafter, Sapphire Pool 

erupted a few times a day to a height of about 45 m (150 ft), before its throat became enlarged to such 

an extent that it could no longer erupt. In contrast, after the same earthquake, it took 2.5 years for 

Seismic Geyser to evolve from a new crack in sinter to a small geyser, and still more years for that 

geyser to reach heights of 12–15 m (40–50 ft). Its eruptions ceased when a small nearby thermal feature 

became active (Marler and White, 1975).

The ground surface at YNP has many sinter-covered areas formed by earlier stages of 

hydrothermal activity. Many of these areas are now covered with forests or other vegetation (Fournier, 

1989). However, hydrothermal activity can rejuvenate unexpectedly in such places. Current scientific 

knowledge is insufficient to predict when or where shifts in activity may take place. Most recent 

changes have been clearly tied to earthquakes or swarms, as with the 1959 Hebgen Lake earthquake, or 

the earthquake swarm in 1978 that caused changes to Cooking Hillside at Mud Volcano (Evans and 

others, 2010). However, changes may occur simply because of the complexity of the numerous 

subsurface cracks, caverns, and mineralized seals.

1.6 Eruption Behavior of Old Faithful Has Been Changing

The average interval between eruptions of Old Faithful Geyser has been getting longer, with 

noticeable increases in both the average and maximum interval. Intervals have changed from an average 

of about 66 minutes in the 1960s to more than 90 minutes in 2013 (fig. 4).

The average interval between eruptions of Old Faithful is affected by local and distant seismic 

events (Marler, 1964; Husen and others, 2004) and also may be affected by changes in the depth to the 

local water table. Decreased groundwater pressure implies a longer recharge time for a geyser eruption.

In the absence of actual groundwater monitoring wells, the only indicator of groundwater elevation or 

pressure is the flow of the Firehole and Madison Rivers. There is a correlation between Old Faithful’s 

average annual eruption interval and variations in the flow of the Madison River, suggesting that 

variations in the water table may be responsible (Hurwitz and others, 2008). Similar correlations were 

found with the eruption intervals of Daisy, Aurum, and Depressions Geysers in Upper Geyser Basin. 

Long-term precipitation and impacts on the local water table are almost certainly factors in the behavior 

of Old Faithful and other geysers.

It is quite possible that the total mass of water erupted from Old Faithful has decreased as the 

average interval between eruptions has increased. However, there have not been measurements of the 

actual discharge associated with eruptions, and it is difficult to evaluate long-term changes of Old 

Faithful without a complete understanding of the total water and heat budget of the eruptions.
7

Although Old Faithful has been erupting about every 1–2 hours since the founding of the park, 

the progressive increase in the time between eruptions, and the history of other geysers, suggest that it 

will not do so indefinitely. Future projections of the average eruption interval are not reliable. Because 

of the complexity of the natural system, it can be concluded that further changes and even cessation of 

Old Faithful eruptions are possible. Logs and stumps found buried in sinter on the geyser mound 

suggest that Old Faithful was completely inactive a few hundred years ago (Bauer and Marler, 1939).

1.7 Infrastructure and Thermal Areas Inevitably Affect Each Other

There is potential for anthropogenic disruption of existing hydrothermal features, including Old 

Faithful. For example, diversion of river water for consumptive use, paving for roads and parking lots,

and the footprint of new buildings can decrease the amount of recharge into the groundwater system. 

Trenches for sewage, electricity, gas, and other infrastructure can change the pathways for movement of 

heat and groundwater. Such changes are evident in the aerial thermal infrared (TIR) images collected by 

the NPS that were shown to the panel by Dr. Cheryl Jaworowski on June 4, 2013, which demonstrate 

heat anomalies from buried pipelines. There are places in YNP where park infrastructure has impacted 

hydrothermal features, in some cases catastrophically. For example, in the 1960s, the excavation of the 

footing for the main support of the Old Faithful overpass intercepted very hot water that flowed at a rate 

of about 150–190 L/min (40–50 gal/min). Nearby hot springs simultaneously dried up. Stopping this 

discharge of thermal water and gas with a cement plug was considered and rejected because the plug 

might cause H2S-rich gas to accumulate under the plug, and then leak around its sides. The H2S would 

then react with water to form sulfuric acid, which would attack both the bridge support and cement plug 

until the plug failed. This would result in near-boiling water cascading over the road. The approach 

devised to allow construction of the overpass to continue was to divert the flow of this water into a new 

culvert so that it could discharge freely from beneath the road about 300 m (980 ft) to the west.

The Laurel Dorm, located behind the Old Faithful Inn, is at the edge of a zone of hot ground, 

with mitigation required to ensure the health of the building and its inhabitants (Heasler and 

Jaworowski, 2011a). The historic Old Faithful Pub, located nearby, was seriously impacted by 

hydrothermal activity, which ultimately resulted in its demolition (Heasler and others, 2009a, 2009b).

The lifetimes of buildings and pipes in corrosive thermal environments are certainly reduced relative to 

similar structures in non-thermal areas. There probably are places in Upper Geyser Basin where such

impacts are yet to be detected or understood.

The cumulative effect of park infrastructure on the Old Faithful hydrothermal system is difficult 

if not impossible to assess. Airborne TIR imagery clearly shows that trenching has altered the natural 

surface temperature pattern in the Old Faithful developed area (Heasler and Jaworowski, 2011b). Any 

specific connection between such changes and the behavior of thermal features is difficult to quantify. 

At this time, scientific data do not exist that allow us to say with any degree of confidence that existing 

and past roads, parking lots, buildings, and subsurface infrastructure have, or have not, affected Old 

Faithful and other features in the Upper Geyser Basin. Scientific data can assist the park in gaining an 

understanding of the nature of the changes that are occurring, how these changes compare in magnitude 

to previous changes, and how the impacts of future infrastructure development and maintenance might 

be minimized.
8

2.0 Knowledge Gaps and Suggested Topics for Future Study

2.1 Background

Infrastructure within developed areas at Old Faithful may affect the hydrothermal system 

directly (for example, by trenching in sinter aprons) or indirectly by intercepting groundwater recharge, 

redirecting fluids and heat, and otherwise changing the heat and pressure distribution in, around, and 

above the hydrothermal system.

In order to evaluate the impact of the developed areas on hydrothermal systems, it is crucial to 

understand the distribution of fluids and heat in the shallow subsurface (upper 10 m or 33 ft). In order to 

evaluate the causes of long-term trends in the behavior of thermal features, it also is crucial to 

understand the larger system that contributes water and heat, including the relationship between the 

shallow groundwater system and upwelling plumes of hot water. NPS staff and others are already 

collecting relevant monitoring data in the Old Faithful area, and these data provide important 

information for assessment of the hydrothermal system. These efforts include chloride-flux monitoring

on the Firehole River, geyser-eruption monitoring, acquisition and analysis of TIR data, and ground heat 

flux and temperature monitoring in conjunction with various infrastructure projects and issues. Many of 

these ongoing efforts are described in “A Hydrothermal Monitoring Plan for Yellowstone National 

Park” (Heasler and others, 2004). In this section, we suggest additional data that could contribute to the 

understanding of relatively local impacts, the larger flow system, or both. We assess the relevance of 

these data to identifying and/or mitigating impacts, and discuss prioritization of additional data 

collection. The park may choose to foster such research through facilitating externally funded research 

projects, or it could utilize either YNP staff or contracted scientists.

Relevant existing data should be thoroughly exploited. We suggest that a comprehensive 

assessment of available information should accompany acquisition of new data. To cite one example:

continuous geyser-frequency and eruption-duration data for Old Faithful are available for approximately 

the past 10 years. These data may have implications for trends in geyser mass discharge, and the data 

should be examined in this light. We also suggest, for instance, systematic efforts to catalog information 

from excavations and borings, and development of a comprehensive database of information acquired 

from hydrothermal-research and infrastructure maintenance efforts. We realize that this is a difficult 

task and something that will take time and funding.

2.2 Conceptual Understanding of the System and Its Long-Term Trends

2.2.1 Chloride-Flux Measurements

The panel commends the longstanding monitoring of chloride flux in the major rivers of YNP

and recommends that it be continued. Thermal water is the predominant source of chloride in rivers at 

YNP. Thus, the multi-decadal chloride-flux dataset can be used to evaluate trends in discharge from the

hydrothermal system. Moreover, the thermal water discharge is a proxy for total heat flux, and permits 

evaluation of the potential response of the hydrothermal system to tectonic activity, climate change, or 

anthropogenic activities (Fournier and others, 1976; Ingebritsen and others, 2001; Freidman and Norton, 

2007; Hurwitz and others, 2007). Existing data have been interpreted as indicating a long-term decline 

in hydrothermal discharge (Friedman and Norton, 2007), although not all investigators agree 

(Ingebritsen and others, 2001; Hurwitz and others, 2007) and additional years of similar data are needed.
9

At present, the USGS streamgage in the Firehole Canyon monitors the cumulative chloride flux 

from all the geyser basins in the Firehole River drainage basin (McCleskey and others, 2012). More 

intensive chloride-flux monitoring on shorter river reaches in the Upper Geyser Basin could improve 

understanding at the individual geyser-basin scale for possible correlation with site-specific 

management activities. For example, one could quantify the total output of thermal fluid from the Upper 

Geyser Basin rather than the entire Firehole River.

2.2.2 Airborne Resistivity Measurements

Discharge from the hydrothermal system is well monitored by the chloride-flux network and, 

increasingly, by gas-discharge and heat-flow measurements. However, long-term conservation also 

requires knowledge of the origins and flowpaths of upwelling hydrothermal fluids. The presentation to 

the panel by Dr. Rick Allis on June 3, 2013, demonstrated the utility of airborne resistivity 

measurements to image/map upflow plume(s) in the Taupo Volcanic Zone, New Zealand—a 

geologically similar environment. A useful target depth for such measurements, per the New Zealand 

example, would be 200–500 m (650–1640 ft). Understanding the flowpaths of hydrothermal fluids 

could provide critical information for assessing vulnerability of the hydrothermal system to 

anthropogenic impacts.

2.2.3 Environmental Tracer Data

The presentation to the panel by Dr. Payton Gardner on June 3, 2013, illustrated the utility of 

isotopic and chemical tracers for understanding flow, mixing, connectivity, and groundwater dynamics 

adjacent to the Norris Geyser Basin (Gardner and others, 2011). A similar dataset in the Upper Geyser 

Basin area could provide new insights into the sources, flow paths, and residence times of fluids in both 

the hydrothermal system and the cold groundwater system, and about the extent of mixing between 

these systems. Residence-time and flow-path information is important for assessing impacts—

particularly indirect impacts that may not manifest themselves immediately. For example, if 

groundwater recharge were impeded due to surface pavement, how long would it take to impact the 

hydrothermal system?

2.2.4 Geyser Frequency and Fluid Discharge Data

Geyser eruptive behavior and the nuances of particular hydrothermal features are of great 

interest to geyser enthusiasts and members of the public. The current geyser monitoring program by 

NPS (using temperature data loggers in outflow channels) provides a general record of system 

dynamics. In addition to eruption monitoring, periodic measurements of fluid discharge from Old 

Faithful would provide valuable information useful for assessing changes to the geyser, conceptualizing 

the geyser, and constraining numerical models. Despite the iconic status of Old Faithful, there has been 

only a single measurement of fluid discharge (in the 1960s; Kieffer, 1984). Does the lengthening of

eruption intervals correspond to a decrease in the total discharge of water from Old Faithful? In other 

words, is less water available to erupt, or is the same amount of water erupting in larger, less frequent 

bursts? On the basis of existing information, it is impossible to determine whether the total discharge 

from Old Faithful is changing. This makes it difficult to assess whether the long-term changes in 

eruptive behavior are related to local anthropogenic impacts or regional meteorological or hydrologic 

factors.
10

2.2.5 Numerical Modeling

A numerical model of Old Faithful Geyser and its nearby surroundings could be developed and 

updated with new information to serve as both a scientific and educational tool. The existence of such a 

model would promote hypothesis testing and system conceptualization. However, because of the high 

degree of non-uniqueness inherent to such models, it would be unlikely to serve as a predictive tool for 

management in the foreseeable future.

2.3 Understanding the Effects of Infrastructure on Thermal Areas

2.3.1 Thermal Measurements

Heat-flow measurements at hydrothermal areas have been done at many sites worldwide 

(particularly in United States, New Zealand, Italy, and Japan) to enhance understanding of fluid and heat 

flow. Despite the global significance of the Old Faithful area, such comprehensive measurements have 

rarely been made here. Presentations to the panel on June 4, 2013, clearly documented the relevance of 

thermal data to Old Faithful infrastructure-management issues. In the TIR images, underground utilities 

were clearly visible in some areas, and hot ground was shown adjacent to buildings, paths, and 

boardwalks (Heasler and Jaworowski, 2011b). We recommend that efforts to collect thermal data be 

continued and systematically expanded. This category includes satellite and airborne TIR data; very 

shallow (about 15 cm or 6 in) temperature surveys, and deeper (about 1 m or 3 ft) temperature surveys 

that would permit quantification of heat flow. The purpose of such shallow holes is not to define deep 

conductive gradients, but rather to identify hot or gassy areas adjacent to infrastructure. Each of the 

above methods has particular strengths. TIR surveys provide synoptic data over a large area and can be 

systematically repeated to detect changes. Very shallow temperature surveys can cover large areas 

(hundreds of square meters) and can be quantitatively converted to heat flow where heat-flow values are 

sufficiently high and seasonal and diurnal temperature variations are negligible or accounted for. The 

more time-consuming deeper (about 1 m or 3 ft) measurements permit heat-flow to be quantified in 

cooler areas. Lessons learned from geothermal development in New Zealand demonstrates that heatflow data can provide useful quantitative guidelines for infrastructure development and can form the 

basis for delineating management zones (Dickie and Luketina, 2005). This type of data collection in a 

developed area like Old Faithful is complicated by the amount of impervious surface (pavement and 

sinter aprons).

2.3.2 Groundwater-Level Monitoring

The hydrothermal systems in YNP are linked to shallow non-thermal groundwater systems by 

direct fluid flow and mixing and by pressure responses. Pressure response can propagate long distances 

in the subsurface. Such linkages constitute the technical and philosophical basis for groundwater 

protection adjacent to the Park as reflected in the Water Rights Compact between the State of Montana 

and the United States of America, National Park Service, as well as State of Wyoming legislation, and 

the withdrawal of federal lands from geothermal leasing in the Island Park Known Geothermal Resource 

Area. Similar groundwater and geothermal protection protocols do not currently (2014) exist within 

YNP. The only existing groundwater-monitoring wells in the Old Faithful area are those associated with

lagoons at the sewage-treatment plant. The panel recommends that shallow monitoring wells be 
11

installed within the Old Faithful developed area. Such wells would provide baseline data on water-table 

levels, chemistry, and temperature in the shallow subsurface. The resulting data could be combined with 

precipitation data to investigate linkages among rainfall, cold groundwater levels, and hydrothermal 

discharge, thus helping to assess the effects of paved surfaces on the local hydrology.

2.3.3 Shallow Stratigraphy and Structure

There is very limited information on the shallow stratigraphy of glacial and alluvial sediments 

within the Upper and Lower Geyser Basins because of the lack of wells and the scarcity of geophysical 

surveys. Vandemeulebrouck and others (2013) described the conduits feeding Old Faithful Geyser, 

demonstrating the potential utility of geophysics in understanding the shallow subsurface. Several 

noninvasive geophysical methods (from electromagnetic to ground-penetrating radar) are widely used to 

investigate shallow subsurface stratigraphy and structure. Some of these techniques might be used to 

map the type and extent of geologic materials, identify conduits feeding key hydrothermal features, and 

assess the effects of buildings and paved surfaces on groundwater recharge. The panel encourages the 

NPS to seek collaborative opportunities to obtain geophysical surveys to address specific concerns 

about the shallow subsurface in the Old Faithful area. The shallow groundwater monitoring wells 

described in Section, “2.3.2, Groundwater-Level Monitoring,” also would contribute information on the 

location and characteristics of geological materials and fluids in the Old Faithful area.

2.4 Prioritization

The panel discussed prioritization of ongoing and prospective hydrothermal monitoring and 

research. Following this discussion, we can suggest only general guidelines. There are several elements 

to consider: (1) usefulness in terms of immediate infrastructure-planning and infrastructure-management 

needs, (2) usefulness in terms of conceptual understanding of the hydrothermal system (and thus longerterm infrastructure planning), and (3) cost. Development of an Old Faithful-specific hydrothermal 

monitoring plan would be a valuable exercise that could add specificity to monitoring activities, assist in 

prioritization, and address data storage and maintenance issues.

We attach particularly high priority to comprehensive assessment and archiving of existing data,

continued chloride-flux and geyser-frequency monitoring, and systematic thermal measurements 

(including TIR). Valuable and relatively low-cost additions would include installation of a network of 

shallow piezometers (groundwater pressure indicators) in the Old Faithful developed area. The panel 

notes that, at least in the United States, abundant piezometer data are collected in nearly all cases where 

groundwater impacts are at issue. Another low-cost monitoring target is periodic measurement of mass 

discharge from Old Faithful. Surficial and airborne geophysical data could be acquired opportunistically 

as potential collaborators come forward to do the work.
12

3.0 Guidelines for Infrastructure Management in the Old Faithful Hydrothermal 

Area

3.1 Introduction

The objective of this section is to provide suggestions for management of the Old Faithful area 

that incorporate our current understanding of the local geology and hydrology. Recognizing that there 

are a host of related issues regarding cultural resources, facilities maintenance, traffic control, visitor 

services, and law enforcement—all of which require thoughtful balancing and prioritization—our focus 

here is on management of the interactions between infrastructure and the hydrothermal system. With 

respect to infrastructure, the goal is to maximize the long-term integrity, utility, and safety of park 

investments. With respect to the hydrothermal system, the goal is to maximize the protection of natural 

processes and features while also maintaining visitor access.

Prior to delving into details, it is appropriate to highlight pertinent lessons from Section 1.0, 

“Geology and Hydrology of Old Faithful and the Upper Geyser Basin” and 2.0, “Knowledge Gaps and 

Suggested Topics for Future Study.” Old Faithful is in the Upper Geyser Basin, one of three major 

geyser basins along the Firehole River (the others being the Midway and Lower Geyser Basins to the 

north). Even though thermal waters emerge only at discrete locations within these basins, they can be 

found throughout the basins at depth, even beneath nominally cold ground. The pathways of water flow 

and discharge change with time in a complex manner that responds to long-term groundwater recharge, 

earthquakes, buildup of natural mineral deposits in flow channels, and human developments.

Occasionally, the changes may be explosive in nature if a natural throttle fails and hot water is rapidly 

depressurized. Subterranean activity occasionally results in the formation of shallow subsurface cavities 

that can further compromise buildings and infrastructure. Compared with most cold groundwater 

aquifers that are more spatially homogeneous and predictable, hydrothermal systems are highly varied 

in structure and permeability. Old Faithful was previously non-erupting, as indicated by fossil trees that 

have been covered with silica deposits. Over the past 50 years, the eruption interval of Old Faithful has

slowly changed, increasing the mean time interval between eruptions from around 60 to more than 90 

minutes. This change possibly could be related to a gradual decrease in the permeability of the geyser 

conduit, long-term decreases in rainfall and groundwater recharge, earthquakes, an increase in 

impermeable areas associated with buildings, parking areas and roads, or some combination thereof.

3.2 Long-Term View

Current (2014) trends in visitation suggest that increasingly more people will desire to visit Old 

Faithful in future years. If the geyser continues to erupt less frequently, each visitor will need to spend 

additional time waiting and using services. The NPS can choose to slowly increase parking, food 

services, sanitation, and other infrastructure needed to accommodate the increasing number of visitors.

Alternatively, NPS can start to evaluate the potential impacts of existing development and the limits 

beyond which further development would be undesirable.
13

An overall guiding principle for the NPS is clearly expressed in "Revisiting Leopold: Resource 

Stewardship in the National Parks" (National Park System Advisory Board Science Committee, 2012, p. 

14):

"Because ecological and cultural systems are complex, continuously changing and not fully 

understood, NPS managers and decision makers will need to embrace more fully the precautionary 

principle as an operating guide.”

Faced with considerable uncertainty, and given the high value placed on hydrothermal features 

in the Old Faithful area, we encourage application of the precautionary principle and emphasize the 

important role of science in informed stewardship. YNP has entered into compacts with surrounding 

States for management of hydrothermal features, which compel the States, even in cases where impacts 

on YNP hydrothermal features may be unknown, to do no harm to the features. A similar standard could 

logically be applied to areas within the YNP. Both the natural and institutional contexts exist in a world 

that is undergoing, “...continuous change that is not yet understood.” (National Park System Advisory 

Board Science Committee, 2012, p. 11.)

We suggest that the NPS consider mechanisms to mitigate the impacts of current (2014) and 

continuously increasing visitation on this fragile natural area. Many parks have successfully used shuttle 

services that reduce congestion and the need for increased parking and infrastructure. The lava plateaus

just outside the thermal basins are geologically stable, lack hydrothermal features, and provide few 

hindrances to infrastructure development. Such areas could serve as staging grounds for visitors, thereby 

avoiding the need for additional visitor services or allowing for the reduction of services in the Old 

Faithful area.

3.3 An Approach to Infrastructure Maintenance and Development

We propose an approach to balancing protection of the hydrothermal system with infrastructure 

needs in the Old Faithful area. Our example uses a “zone” system designed to reduce the impacts to the 

hydrothermal system by infrastructure and conversely reduce the impacts to infrastructure by the 

hydrothermal system.

Delineation criteria and recommended management guidelines for each zone are shown in table 

1. We emphasize that as additional information is developed (see Section 2.0 Knowledge Gaps and 

Suggested Topics for Future Study), both the delineations and suggested guidelines should be reviewed 

and adjusted as appropriate. The zone concept is offered as one potential method to reduce the risk of 

permanently impairing the Old Faithful hydrothermal system and of increasing the longevity, integrity, 

and long-term utility of developed infrastructure. The zone definitions and suggested guidelines are 

preliminary in nature. Details for specific implementation of this strategy could be provided as needed 

by a working group specifically tasked with such a purpose.

3.3.1 Red Zone

The red zone encompasses areas with active hydrothermal activity or with high potential for 

hydrothermal activity that can negatively impact infrastructure, or vice versa. Although additional 

scientific investigation could add to our understanding of these areas, sufficient information is currently 

available to guide general management decisions.
14

3.3.1a Delineation 

Active hydrothermal areas as defined by:

• Active thermal features (hot springs, geysers, mudpots, steam vents).

• Thermal water greater than 30 °C (86°F).

• Hydrothermal gases (H2S, CO2) above Occupational Safety and Health Administration

(OSHA) limits measured either above or below ground.

• High ground-surface temperatures as evidenced by the absence of deep-rooted vegetation 

or presence of recent sinter deposits.

• High subsurface ground temperatures as defined by a temperature at 75-cm depth 10°C

(18°F) greater than a reference temperature at the same depth at a background site.

3.3.1b Management Guidelines 

• Where hydrothermal activity is clearly evident, further development (addition or 

expansion) of infrastructure would be prohibited.

• Existing infrastructure should be retired or reduced as practical. Removal of wellfunctioning existing infrastructure is not indicated unless it can be demonstrated that 

negative interactions with the hydrothermal system are continuing or increasing.

However, as opportunities for relocation/removal present themselves, they should be 

pursued. For example, rather than replacing old or degraded infrastructure in the red 

zone, it could be migrated to less sensitive areas.

• Protocols for maintenance of existing infrastructure (for example, underground utilities, 

parking lots, foundations) should be developed to minimize potential impacts to 

hydrothermal fluid and heat flows.

• Protocols should be developed to consolidate utility corridors and provide for limited 

above-ground utilities in areas determined to fall within red zones.

• Abandoned infrastructure should be carefully evaluated to determine whether its 

presence is affecting the hydrothermal system. If the abandoned infrastructure is 

determined to impact the hydrothermal system, removal or other methods should be 

implemented to reduce or eliminate its impact.

• Preventive removal of infrastructure abandoned in place is not indicated unless there is 

an identified negative impact on hydrothermal features, fluids, or heat flow.

3.3.2 Green Zone

Areas that show little evidence for active or recent near-surface hydrothermal activity are 

mapped as the green zone. Soils are dominated by glacial sands, often containing black obsidian 

fragments. Evidence for past hydrothermal activity (silica sinter, travertine, varicolored clays) is absent.

High surface heat flow has not been identified. These areas have a low potential for hydrothermal 

activity negatively impacting infrastructure, infrastructure negatively impacting hydrothermal activity, 

or both.
15

3.3.2a Delineation 

An initial green zone can be defined as that area within the Upper Geyser Basin mapped as 

"glacial" by Muffler and others (1971) and located southwest of the Grand Loop Road (fig. 5).

Subsurface ground temperatures at 75-cm depth should be within 5°C (9°F) of temperatures at a

reference background site.

3.3.2b Management Guidelines 

• No hydrothermal-based constraints on development and maintenance of infrastructure. 

However, the following conditions should be reported to the park geology staff and 

prompt additional consideration:

• Groundwater warmer than 40°C (104°F).

• Geothermal gases (for example, smell of H2S).

• Hot spring deposits or clay deposits.

• If any of these conditions are encountered, a rapid reassessment of hydrothermal activity 

should occur. If the conditions for a red zone are documented, then construction should 

be reconsidered.

Development in these areas should be planned with allowance for these reporting requirements, 

including appropriate consideration of construction contingencies resulting from unanticipated 

encounters with hydrothermal conditions.

3.3.3 Yellow Zone

Yellow areas have unknown potential for hydrothermal activity that could negatively impact

infrastructure and/or infrastructure impacts on hydrothermal activity. As site-specific studies and 

general research provide additional information, the yellow zone is expected to shrink in size relative to 

the well-characterized adjacent “red” and “green” zones. The “yellow” zones are an obvious priority for 

the local investigation techniques outlined in Section 2.0, “Knowledge Gaps and Suggested Topics for 

Future Study.”

The eastern rim of Pocket Basin in the Lower Geyser Basin provides an example of a locality 

that previously had appeared to be completely free of hydrothermal activity because of the many 

lodgepole pine trees growing there. However, these trees were growing in a region underlain by old, 

decaying sinter. Very active mud pots subsequently appeared and grew over time (R.O. Fournier, 

written communication, December 2013). If development in this area had been contemplated, the old 

sinter would have been a useful clue of potential hydrothermal activity.

3.3.3a Delineation 

• Generally located between the “red” and “green” zones.

• Inactive hydrothermal features without nearby active features.

• Proximal to red zone.

• An area of unknown potential for hydrothermal activity.
16

3.3.3b Management Guidelines 

• Avoid increasing the area of impermeable ground cover such asphalt, concrete, and 

buildings.

• Seek alternative locations for additional and existing infrastructure.

• Seek additional information on the occurrence and movement of hydrothermal fluids.

• Precede new development or infrastructure expansion with site-specific studies of 

thermal water, gases, temperatures, and heat flow. Investigations would include:

1. TIR imagery,

2. Temperature measurements at 0.75–1 m (30–39 in) depth, with less than 5-m

(16 ft) spacing,

3. Contemporaneous measurement of hydrothermal gases, and 

4. A review of the site history with respect to construction, maintenance, or 

management issues related to hydrothermal activity.

Development could proceed after demonstrating absence of hydrothermal activity as described 

in the definition of red zones.

Final Thoughts

It is useful to consider a hypothetical situation where explorers have just discovered Old Faithful

in 2014. How would it be developed? Where would the hotels, gas stations, and restaurants be located?

How much parking space would be desired? Of course, those questions are moot. Highly valued

buildings are now intimately associated with the conception of the geyser itself. Thousands of visitors 

drive into the area each day expecting to witness an eruption of Old Faithful and gaze upward at the 

balconies and rafters of the Old Faithful Inn. In trying to balance strategies for accommodating 

infrastructure, hydrothermal resources, and current scientific knowledge, we have sought to provide 

both present-day and long-term perspectives. Our goal is to ensure that the visitor experience at Old 

Faithful is just as good 100 years from now as it is today.

Acknowledgments

Authors of this report comprise the Old Faithful Science Panel, who met on June 3–5, 2013, at 

Old Faithful, Yellowstone National Park. The work of the panel benefited from a series of presentations 

by National Park Service personnel and park-associated researchers (listed in appendix 2), whom we 

thank for their important contributions. Joe Gardner of the USGS Utah Water Science Center re-drafted 

Figures 1, 2 and 5. Helpful reviews were provided by L.J.P. Muffler, USGS; Richard Allis, Utah 

Geological Survey; Clay Nichols retired, Idaho National Laboratory; and David Hallac, YNP. The Old 

Faithful Science Review Panel meeting was made possible through a grant from the Yellowstone Park 

Foundation.
17

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Muffler, L.J.P., White, D.E., and Truesdell, A.H., 1971, Hydrothermal explosion craters in Yellowstone 

National Park: Geological Society of America Bulletin, v. 82, p. 723–740.

National Park Service, 2006, Management Policies 2006: 180 p., accessed February 21, 2014, at 

http://www.nps.gov/policy/MP2006.pdf.

National Park System Advisory Board Science Committee, 2012, Revisiting Leopold— Resource 

stewardship in the National parks: National Park Foundation, 24 p., 

http://www.nps.gov/calltoaction/PDF/LeopoldReport_2012.pdf.

Pearson, F.J., Jr., and Truesdell, A.H., 1978, Tritium in the waters of Yellowstone National Park, in

Zartman, R.E., ed., Short papers of the fourth International Conference, Geochronology, 

Cosmochronology, Isotope Geology, 1978: U.S. Geological Survey Open-File Report 78-701, p. 327–

329., http://pubs.er.usgs.gov/publication/ofr78701.

Rowe, J.J., Fournier, R.O., and Morey, G.W., 1965, Use of sodium iodide to trace underwater 

circulation in the hot springs and geysers of the Daisy Group, Yellowstone National Park, in

Geological survey research 1965: U.S. Geological Survey Professional Paper 525-B, p. B184–186., 

http://pubs.er.usgs.gov/publication/pp525B.

Rye, R.O., and Truesdell, A.H., 2007, The question of recharge to the deep thermal reservoir underlying 

the geysers and hot springs of Yellowstone National Park, in Morgan, L.A., ed., Integrated geoscience 

studies in the Greater Yellowstone Area—Volcanic, hydrothermal and tectonic processes in the 

Yellowstone geoecosystem: U.S. Geological Survey Professional Paper 1717, p. 239–270, 

http://pubs.usgs.gov/pp/1717/.

Vandemeulebrouck, J., Roux, P., and Cros, E., 2013, The plumbing of Old Faithful geyser revealed by 

hydrothermal tremor: Geophysical Research Letters, v. 40, p. 1,989–1,993.

White, D.E., 1991, Whistle, a nearly dormant geyser in Upper Geyser Basin, Yellowstone National 

Park, Wyoming—The first geyser to be studied by research drilling: U.S. Geological Survey Bulletin 

1967, 13 p., http://pubs.er.usgs.gov/publication/b1967.

White, D.E., Fournier, R.O., Muffler, L.J.P., and Truesdell, A.H., 1975, Physical results of research 

drilling in thermal areas of Yellowstone National Park, Wyoming: U.S. Geological Survey 

Professional Paper 892, 70 p., http://pubs.er.usgs.gov/publication/pp892.
20

Figure 1. Geologic map of Old Faithful area. The Mallard Lake, Summit Lake, and Scaup Lake lava flows surround 

the Upper Geyser Basin. Glacial and post-glacial sediments (tan and yellow) were deposited in between and on top 

of the lava flows. Older lavas (purple) are mostly buried by the younger sediments. The thick black line is the main 

road, and black lines are other roads in the Old Faithful area. Wells completed for scientific drilling prior to 1970 are 

labeled black circles located at Biscuit and Black Sand Basins and near the Myriad Group. Original bedrock 

mapping by Christiansen and Blank (1974).
21

Figure 2. Schematic cross section along a 5-kilometer (3.1 mi) profile from southwest to northeast through the 

Upper Geyser Basin. Vertical exaggeration is about 4X. Glacial sediments that fill the valley overlie volcanic rocks

of various ages, all greater than 100,000 years old. The C-1 drillhole extended 130 meters (400 feet) through the 

glacial sediments and into the underlying lava. The dashed blue line represents the water table. Blue arrows above 

land surface represent precipitation that becomes groundwater recharge. The black dashed line is the approximate 

depth at which waters reach 150°Celsius (302°F). Red-dashed lines represent hypothetical fractures through which 

hot waters rise from depth. Fluid pressures in these hot-water filled fractures are sufficiently high to limit ingress of 

cold waters. Small horizontal red arrows represent hot water flow into shallow aquifers.
22

Figure 3. Photographs of various types of sediments and hydrothermal deposits in the Old Faithful area. a,

obsidian-rich sands form the basis for soils. b, a sinter apron around the orifice of Anemone Geyser. c, to right 

(west) of road, is a steam-heated area in the Myriad Group with clay alteration. d, red low-permeability clay 

associated with earlier alteration and oxidation.
23

Figure 4. Boxplot showing increase in the eruption interval of Old Faithful from 1960 to the present. Post-1990 data 

points (black squares) are annual median values with their associated standard error. Pre-1990 data (black bands) 

represent averages of multiple years with a 10-percent error (gray boxes). Data compiled by Lynn Stephens from 

National Park Service log books.
24

Figure 5. Map of the Old Faithful area delineating zones for the protection of the hydrothermal resource and 

infrastructure. The red zones are areas with high potential for hydrothermal activity negatively impacting 

infrastructure and/or infrastructure negatively impacting natural hydrothermal activity; the green zones have 

minimal hydrothermal-based constraints on development/maintenance of infrastructure; and the yellow zones are 

areas with unknown potential for hydrothermal activity in which site-specific studies should precede development

(see Section 3.3, “An Approach to Infrastructure Maintenance and Development,” for additional discussion).
25

Table 1. Proposed Zone System for Old Faithful Area.

Red Zone Yellow Zone Green Zone

Definition Hydrothermal activity present Potential hydrothermal activity No current evidence of hydrothermal 

activity 

Criteria Active hot springs, geysers, 

vents or mud pots

High hydrothermal gas 

concentrations

High ground temperatures

High heat flow

Potential subsurface hydrothermal 

activity

Potential high hydrothermal gas 

concentrations

Potential high ground temperatures

Potential high heat flow

Hydrothermal deposits absent

Low hydrothermal gas concentrations

Low ground temperatures

Low heat flow

Management 

Guidelines

New or expanded 

infrastructure prohibited

Where practical remove 

infrastructure

Special protocols for 

infrastructure 

maintenance

Seek alternative locations in Green 

Zone

Site specific investigations of

hydrothermal activity:

 hydrothermal gases

 ground temperatures

 heat flow

Consider special design and 

maintenance protocols

Development can proceed if Green 

Zone Criteria met at specific site

No hydrothermal constraints on 

infrastructure development. (Planning 

should allow for accommodation of 

unanticipated conditions encountered 

during construction.)
26

Appendix 1. Legal Mandates, Authorities, and Policies Governing the Protection 

of Geothermal Resources in Yellowstone National Park

Specific legal mandates, authorities, and policies address geothermal protection in Yellowstone 

National Park (YNP). YNP was created by an Act of Congress in 1872. The law mandated that 

Congress “...shall provide for the preservation, from injury or spoliation, of all timber, mineral deposits, 

natural curiosities, or wonders within said park, and their retention in their natural condition [17 Stat. 

32].” The National Park Service Organic Act of 1916 states that units of the National Park system shall 

be managed “to conserve the scenery and the natural and historic objects and wildlife therein and to 

provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired 

for the enjoyment of future generations.” (16 USC 1)

National Park Service (NPS) policies direct the protection of geothermal resources within a park.

The NPS Management Policies 2006 manual states that “The National Park Service will preserve the 

natural resources, processes, systems, and values of units in the national park system in an unimpaired 

condition, to perpetuate their inherent integrity and to provide present and future generations with the 

opportunity to enjoy them” (National Park Service, 2006, chap. 4). The manual contains specific 

guidelines for the protection of geothermal resources within a National Park. “Superintendents will 

strive to maintain the natural integrity of thermal systems, including the movement of air and/or water 

through heated rock, cold water recharge, the proximity of hot and warm water to the heat source, and 

the hydrostatic pressure and elevated temperature. Superintendents will work to prevent unacceptable 

impacts on thermal resources caused by development” (National Park Service, 2006, chap. 4, section 

4.8.2.3).

The most recent guiding principle for the protection of geothermal resources within YNP is 

stated in a 2012 report titled “Revisiting Leopold: Resource Stewardship in the National Parks—A 

Report of the National Park System Advisory Board Science Committee”: “NPS managers and decision 

makers will need to embrace more fully the precautionary principle as an operating guide... The 

precautionary principle requires that stewardship decisions reflect science-informed prudence and 

restraint. This principle should be integrated into NPS decision making at all levels.” (p. 15.)

A primary focus of past legislation has been the protection of YNP’s geothermal resources from 

threats outside of the park. A discussion of this legislation is valuable to illustrate the importance of 

protecting YNP’s geothermal resources

The Geothermal Steam Act of 1970, as amended in 1988 (102 Stat. 1766), seeks to preserve 

geothermal features in units of the National Park System. Specific lists of parks with geothermal 

features are provided. YNP is discussed separately: “the entire park unit is listed as a significant thermal 

feature...” (Federal Register, v. 52, p. 28795). Specifically, the law directs the Department of Interior to 

monitor significant thermal features (30 USC § 1026 Mineral Lands and Mining).
27

In 1994, the State of Montana and the NPS entered into a Water Rights Compact describing the 

reserved federal water rights for five NPS units within the State (85-20-401 M.C.A.). As part of this 

Compact, Article IV established the Yellowstone Controlled Groundwater Area (YCGA) in an area of 

Montana outside of the park’s boundary where special regulations apply. The stated purpose for 

establishing the YCGA is to “allow no impact to the hydrothermal system within the reserved lands of 

YNP.” Montana State agencies are required to monitor geothermal features outside the park’s 

boundaries within the YCGA for potential impact to the YNP system. Geothermal monitoring within the 

park provides critical information to assess impacts from future development proposals.

The State of Wyoming has created a 24 km (15mi) buffer zone around YNP governing for 

permits to appropriate commercial groundwater use. The application to the Wyoming State Engineer 

Office to appropriate groundwater will contain “information necessary to show that the proposed 

development will not impair or produce an injurious effect on the hydrothermal system or hydrothermal 

features located within the boundaries of Yellowstone National Park.” (W.S. 41-3-930).

A Water Rights Agreement between the State of Idaho and the United States for YNP was signed in 

1992 as Water Rights Agreement between the State of Idaho and the United States for Yellowstone 

National Park, January 16 - May 14, 1992, State of Idaho and the United States In this agreement, the 

NPS received federal reserved water rights for groundwater “as is necessary to maintain the natural 

thermal features such as geysers, mudpots, hot springs, and similar features.” This amount of 

groundwater is unquantified and will be resolved as the need arises.

Federal land in the Island Park Known Geothermal Resource Area (KGRA), located 

immediately west of YNP in Idaho, has been placed off-limits to geothermal leasing due to concerns 

about potential impacts to the YNP geothermal system. “Notwithstanding any other provision of law, 

the Secretary shall not issue any geothermal lease pursuant to the Geothermal Steam Act of 1970 

(Public Law 91-581, as amended) in the Island Park Known as Geothermal Resource Area adjacent to 

Yellowstone National Park.” (Department of the Interior and related agencies Appropriation Act, 1985).
28

Appendix 2. Presentations to the Old Faithful Science Review Panel, June 3–4, 

2013

Introductions – Daniel Wenk, Yellowstone National Park Superintendent

David Hallac, Chief, Yellowstone Center for Resources

History of the Old Faithful Area - Lee Whittlesey, YNP Park Historian

Cultural issues - Tobin Roop, Branch Chief of Cultural Resources, Yellowstone Center for 

Resources.

Infrastructure and maintenance challenges in the OF area –

Nancy Ward, Chief, YNP Maintenance

George Helfrich, Chief, YNP Concessions

Ann Rodman, Branch Chief, Yellowstone Center for Resources

Law Enforcement issues – Colleen Rawlings, District Ranger, Old Faithful

Interpretation issues- Linda Young, Chief, YNP Resource Education and Youth Programs

Lessons learned from geothermal development in New Zealand- Rick Allis, Utah State 

Geologist, Utah State Geological Survey

Geologic overview of the Old Faithful area- Jake Lowenstern, USGS Research Geologist

Age dating and isotopic studies of hydrothermal water in YNP - Payton Gardner, Sandia 

National Laboratories

Thermal waters discharged by the hot springs and geysers of the Old Faithful Area- Bob 

Fournier, USGS, retired

Numerical modeling of hydrothermal systems- Steve Ingebritsen, USGS, Research Hydrologist

Airborne thermal infrared studies of the OF area: visualization of anthropogenic changes to the 

Old Faithful hydrothermal system - Cheryl Jaworowski, Geologist, YNP

Near surface observations of groundwater movement and heat transfer in the Old Faithful areaHenry Heasler, Park Geologist, YNP