UM studies accuracy of measuring instruments
If snow falls on the mountain and no one is around to measure it, how much does it snow? That’s the question UM hydrology Assistant Professor Marco Maneta seeks to answer.
“We’ve been working in hydrology for a long, long time,” Maneta says, “but we still do not have an accurate way of measuring the total volume of precipitation in our mountains.”
That might sound surprising. In Montana, eager skiers look up the daily snowfall report. In summer, irrigators and river rafters check river flows. Each day, the weather report tells us how much rain or snow to expect. Our lives are saturated with precipitation reports in this mountainous country, where so much of livelihoods and recreation depend on water. In an era of climate change, drought and warming winters, Westerners are paying close attention to this finite resource.
Accuracy and representativeness of these measurements matter. That’s why Maneta has come up with a model to characterize spatial uncertainty and to estimate the effect of using inaccurate precipitation levels on our hydrologic predictions. His research centers on the Bitterroot Mountains, ideal for proximity to UM and for the north-south direction of the range. Storms from the west strike the peaks perpendicularly for a classic look at mountain snowfall accumulation.
Maneta knows people who study those readings religiously won’t appreciate learning they are suspect. But to demonstrate the problem, he picks up a marker and sketches a mountain on his office whiteboard. Then, he inserts a small square part way down from the summit to represent a SNOTEL sensor.
SNOTEL is short for Snow Telemetry, a system run by the Natural Resources Conservation Service across the western U.S., designed to collect snowpack and other meteorological data that, in turn, produces water supply forecasts. A SNOTEL station measures snowpack water content at a location using a pressure-sensing snow pillow and also collects snow depth information, precipitation and air temperatures.
Next, Maneta draws the cloud laden with moisture approaching the mountain, ascending, and then releasing moisture at greater amounts above the SNOTEL sensor. The problem with SNOTEL, Maneta says with an emphatic tap on the little square, is that the sensors tend to be too low to measure the high-elevation, high-snowfall zones. The reason? People periodically have to check the sensors, and the sites have to be accessible so the sampled locations may not be representative of what is happening on average on the mountain.
Climate change makes it more important than ever to have a better read on total precipitation. As the climate warms, scientists are predicting increases and decreases in snow and rain, and in the timing of flooding. Where warmer temperatures connect with rain clouds, that warmth increases the ability of the air to carry more moisture.
“Our question is, if there is to be an increase in precipitation over western Montana, as climate scientists are predicting, could we detect it?” Maneta asks.
He strives to measure the correct volume of water that drives the ecology of plants, as well as the flows of streams and rivers that support fisheries. To do that, he and his graduate students have developed models that combine physics with field observation.
Maneta’s work connects directly with the key principle of the Montana Institute on Ecosystems. Weaving the various science fields together contributes to a holistic picture of the world we live in.
Andrew Wilcox, a UM geomorphology professor, says he depends on Maneta’s findings to study the way water carries sediments and, in turn, shapes stream channels and habitats for fish and other aquatic organisms. Ultimately, he evaluates which types of streams across river networks are likely to be more vulnerable or resilient to climate change, an effort that Wilcox hopes will help guide river restoration and management.
“Marco’s models are allowing us to understand the hydrology of a Bitterroot basin at a detailed scale,” Wilcox says. “Even where there are no water gauges, his models are giving us estimates of stream flow throughout a river network.”
To provide a more precise model of precipitation, Maneta’s graduate students climb high into the mountains to conduct field checks on the equipment that helps to refine the model. Eventually, field observations will be contrasted with Maneta’s hypothesis to confirm if SNOTEL sites underestimate precipitation in mountainous country.
“You might think that more precipitation would be detectable in the stream flow record, but if we are also seeing a lot more greening of plants and evapotranspiration, that can make up the difference,” he says.
Maneta, however, focuses on the hydrology and relies on geomorphologists, ecologists and social scientists to fill in the story. He credits support from the IoE for the Bitterroot watershed project, with additional grants from US-EPA, the NASA EPSCoR/Montana Space Grant Consortium program and the Montana Water Resources Association.
More than a professor who builds models on computers, Maneta freely admits to a lifelong passion for freshwater as a life source. From his childhood growing up in Spain near one of its major rivers, the Guadiana, he learned early on about the importance of water and the rules people make to govern its use to assure a future for the fertile farms of his homeland.
He pursued hydrology and eventually moved to the U.S. After completing his postdoctoral work at the University of California, Davis, he moved to UM in 2009 as an assistant professor in the geosciences department.
If we are to understand the trees, plants, wildlife and how we as people live within our watershed, Maneta believes we first must know the hydrology, a field that may sound technical but at its heart lies the beauty of the water itself.
“There’s something primal about flowing water,” Maneta says. “It’s like watching a fire burn. What you’re seeing appears on one hand predictable and on the other random.”
— By Deborah Richie