We all go through growing pains as we get older, and that seems to be the case with the Old Faithful Geyser in Yellowstone National Park, as the geyser isn't as faithful as it once was and could eventually go dormant.
In just the past five decades, the geyser whose reliable gushers earned it its name, has slowed down. While Old Faithful in the 1960s erupted on an average of every 66 minutes, in 2013 the average was more than 90 minutes.
However, whether that decrease in reliability is natural, or has been caused by human development in Yellowstone's Upper Geyser Basin, is hard, if not impossible, to say. But construction projects in the past have directly impacted some thermal features in the basin, in some cases "catastrophically," according to a report on the basin's geothermal plumbing and human infrastructure.
Seeing an Old Faithful eruption is one of the main attractions of a Yellowstone vacation, and so word that those eruptions are becoming less timely can be disconcerting. Exactly why the eruption intervals have gotten longer in recent years is difficult to say, according to members of the Old Faithful Science Review Panel that was organized to look at geothermal issues and infrastructure in the Old Faithful area.
"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," the panel wrote in its report. "There is a correlation between Old Faithful's average annual eruption interval and varitions in the flow of the Madison River, suggesting that variations in the water table may be responsible. Similar correlations were found with the eruption intervals of Daisy Aurum, and Depressions geysers in the 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."
While the scientists surmise that the total mass of water spouted every time Old Faithful erupts could be diminishing over the years, there have been no measurements of that output, "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."
Nevertheless, they say, the bottom line is that Old Faithful will not erupt indefinitely.
"Future projections of the average eruption intervals 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."
Of course, a new factor has been inserted into the landscape around Old Faithful in the past two centuries: humans. And their collective footprint on the park's Upper Geyser Basin could be having an effect on Old Faithful, the scientists say.
"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," they point out. "Trenches for sewage, electricity, gas, and other infrastructure can change the pathways for movement of heat and groundwater."
These impacts are not theoretical, the scientists note.
"There are places in Yellowstone National Park where park infrastructure has impacted hydrothermal features, in some cases catastrophically," they stress. "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 40-50 gallons per minute. 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 gas then might react with water to create sulphuric acid, the story went on, which would eat away at both the bridge support and cement plug, until it failed.
While it's difficult at best to gauge what effects human infrastructure in the Upper Geyser Basin is having on the geothermal plumbing system, thermal imaging done in recent years "clearly shows that trenching has altered the natural surface temperature pattern in the Old Faithful developed area," the report notes.
Still, "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.
Just the same, "Infrastructure and thermal ground don't easily coexist. Hot ground isn't good for buildings, roads and pipelines; conversely, parking lots and sewer lines disrupt the natural hydrology,' says USGS Geologist and Science Review Panel Co-Chair Jacob Lowenstern. 'The popularity of Yellowstone is only increasing with time, so the park needs to consider means to minimize the human impact on both its cultural and natural resources."
To that point, Yellowstone Superintendent Dan Wenk says the report "serves as a starting point for management of the most intensively visited location within Yellowstone National Park."
"There may be no place on Earth that presents the challenges where such iconic natural and cultural features are within such a short distance of each other," the superintendent adds.
You can find the report here.