The Western United States is home to some of the most extensive agriculture and growing communities in the country. One of the key factors that sustain these developments is the meltwater from snow-capped mountains, which spills out every spring. For years, models have been used to predict the amount of streamflow available each year, assuming a small fraction of snowmelt enters shallow soil, with the remainder rapidly exiting in rivers and creeks. However, new research from University of Utah hydrologists suggests that this is not the case.

According to their findings, most spring runoff heading to reservoirs is actually several years old, indicating that most mountain snowfall has a long journey as groundwater before it leaves the mountains. This means that there is an order of magnitude more water stored underground than most Western water managers account for, said research leader Paul Brooks.

The team collected runoff samples at 42 sites and used tritium isotope analysis to determine the age of the water. Their findings were published in the journal Nature Communications Earth & Environment and co-authored by Utah geology professors Sara Warix and Kip Solomon in collaboration with research scientists around the West.

Determining the age of mountain streamflow is crucial for predicting how mountain hydrology will respond to changes in climate and land use, according to the researchers. They noted that there would be a lag between input storage and response, which means that even though models have been good in the past, they may not be reliable in the future.

The research also highlighted the importance of incorporating groundwater storage component into models to make good decisions moving forward. Brooks conducted sampling in 2022 while on sabbatical, visiting 42 sites twice, once in midwinter and again during spring runoff.

The state of Utah’s tracking is particularly robust, providing continuous streamflow data dating back 120 years. It’s an unparalleled dataset that has enabled hydrologists to document historic cycles in climate and streamflow that would otherwise have been missed, Brooks said.

According to Solomon, the vast majority of Earth’s fresh, usable water is underground, but just how much is there remains a puzzle. Dating water offers clues, and for determining the age of water, Solomon turns to tritium, a radioactive isotope of hydrogen with a half-life of 12.3 years.

The average age of the runoff sampled in the study varies among the catchment basins depending on their geology. The more porous the ground, the older its water is, since the subsurface can hold a lot more water. By contrast, glaciated canyons with low permeability and shallow bedrock, such as Utah’s Little Cottonwood Canyon, provide far less subsurface storage and younger waters, according to the study.

For decades, federal and state water managers have relied on a network of snowpack monitoring sites to provide data to guide forecasts of water availability for the upcoming year. It’s now clear that such snowpack data doesn’t provide a complete picture, according to the researchers.

“For much of the West, especially the Interior West where this study is based, our models have been losing skill,” Brooks said.

The growing disconnect between snowfall, snowpack volumes and streamflow is driven by variability in these large, previously unquantified subsurface water stores. As a case in point, Brooks highlighted the 2022 water year, which saw snowpacks in many Western states that were near or just below average. Yet that year experienced record low groundwater storage, resulting in much below average spring streamflow.

This new understanding of mountain streamflow has significant implications for water management and resource planning, particularly as the West continues to experience climate variability and change.

The discovery of a skeleton in a Roman cemetery in York has provided the first archaeological evidence of gladiatorial combat between humans and lions. The bite marks found on the skeleton confirm that it was a gladiator who fought against a lion, providing a rare glimpse into the lives of these ancient fighters.

Malin Holst, a lecturer in Osteoarchaeology at the University of York, led the research team that made this groundbreaking discovery. She explained that the bite marks were likely made by a lion, which confirms that the skeletons buried at the cemetery were gladiators rather than soldiers or slaves.

“This is the final piece of evidence from work that began in 2004,” said Holst. “We have been excavating and analyzing human remains from the Roman cemetery on Driffield Terrace, and this discovery provides a unique insight into the lives of these ancient fighters.”

The skeleton was buried with two others, and overlaid with horse bones. In life, it appears to have had some issues with its spine that may have been caused by overloading to its back, inflammation of its lung and thigh, as well as malnutrition as a child, which he recovered from.

The lion bite wound — confirmed by comparing it to sample bites from a lion at a zoo — was not healed and is therefore likely to have been his cause of death. It is believed that the individual was decapitated after death, which appears to have been a ritual for some individuals in the Roman period, although the reasons for this remain unclear.

Analysis of the skeleton points towards this being a Bestarius, a gladiator role undertaken by volunteers or slaves.

The discovery has significant implications for our understanding of Roman entertainment culture. It was previously thought that gladiatorial combat only took place in major cities like Rome, but this find suggests that it was also practiced in smaller cities and towns throughout the empire.

“We often have a mental image of these combats occurring at the grand surroundings of the Colosseum in Rome,” said Holst, “but these latest findings show that these sporting events had a far reach, well beyond the centre of core Roman territories.”

York appears to have held gladiator arena events until as late as the fourth century AD. The presence of distinguished Roman leaders in York would have meant they required a lavish social life, and it is not surprising to see evidence of gladiator events, as well as such an extensive burial site for them.

The research team’s findings were published in the Journal of Science and Medical Research PLoS One, and are a collaboration between the University of York, Maynooth University, Cranfield University, Durham University, King’s College London, York Archaeology, and York Osteoarchaeology Ltd.

The study reveals that three consecutive years of drought contributed to the ‘Barbarian Conspiracy’, a pivotal moment in the history of Roman Britain. Researchers argue that peripheral tribes took advantage of famine and societal breakdown caused by an extreme period of drought to inflict crushing blows on weakened Roman defences in 367 CE.

The researchers used oak tree-ring records to reconstruct temperature and precipitation levels in southern Britain during and after the ‘Barbarian Conspiracy’. They found that southern Britain experienced an exceptional sequence of remarkably dry summers from 364 to 366 CE, with average monthly reconstructed rainfall in the main growing season (April-July) falling to just 29mm in 364 CE.

The drought-driven grain deficits would have reduced the grain supply to Hadrian’s Wall, providing a plausible motive for the rebellion there which allowed the Picts into northern Britain. The study suggests that given the crucial role of grain in the contract between soldiers and the army, grain deficits may have contributed to other desertions in this period.

The researchers argue that military and societal breakdown in Roman Britain provided an ideal opportunity for peripheral tribes, including the Picts, Scotti, and Saxons, to invade the province en masse with the intention of raiding rather than conquest. Their finding that the most severe conditions were restricted to southern Britain undermines the idea that famines in other provinces might have forced these tribes to invade.

Ultimately, the researchers argue that extreme climate conditions lead to hunger, which can lead to societal challenges, and eventually outright conflict. The relationship between climate and conflict is becoming increasingly clear in our own time, making these findings relevant not only for historians but also for policymakers and researchers today.