For the first time, researchers have produced a well-documented, methodologically sound estimate of how much water erupts from Yellowstone National Park‘s Old Faithful Geyser during each cycle.
A team of scientists from the USGS, the University of California Davis, UC Berkeley, and the National Park Service studied 45 eruptions and found the average volume of water discharged was 27.9 cubic meters, or about 7,370 gallons. Individual eruptions ranged widely, from 12.2 to 44.3 cubic meters (3,223 to 11,703 gallons), depending largely on eruption duration.
To get the numbers, researchers installed a portable flume in one of the geyser’s outflow channels and continuously monitored specific conductance in the adjacent Firehole River. They supplemented those measurements with calculations accounting for steam and heat output. The study was published in the Journal of Volcanology and Geothermal Research.
The findings are notable partly because prior estimates were poorly documented. The National Park Service’s longstanding figure of 14 to 32 cubic meters had no clear methodology behind it.
To put the new average in perspective, a single Old Faithful eruption is equivalent to filling roughly 140 standard bathtubs or loading four to five concrete mixer trucks. It would take approximately 90 eruptions to fill an Olympic-size swimming pool.
Researchers also confirmed that shorter eruptions, those under 2.5 minutes, produced less water than longer ones, which typically run three to five minutes. Interestingly, no link was found between erupted volume and the length of time between eruptions.
The data will serve as a baseline for detecting future changes tied to seismic activity, climate variability, and shifts in subsurface heat. Old Faithful draws enormous crowds to Yellowstone each year, and understanding its behavior more precisely helps inform how the park manages one of its most visited natural features.
