New data could tell us how much of Utah’s water is simply disappearing into the air

For all the talk about how much water leaves Utah through the Colorado River, that is not the primary way water leaves the state. A lot of it just blows up.

Currently, there is not much detailed data on water loss through evapotranspiration in Utah. This is a measure of how much water evaporates from bodies of water and soil and how much water is released into the air by plants.

“This component has generally been very poorly understood,” said Kathryn Ladig, project geologist with the U.S. Groundwater and Wetlands Program Utah Geological Survey.

That’s why she and other scientists are putting together a new nationwide array of sensors to track it.

“Water use is under a lot of scrutiny at the moment and there is all this legislation. That’s why we’re trying to provide the best possible data to understand how much water could theoretically be saved.”

The collection of monitoring stations is referred to as Utah Flux Network.

It began in 2021 with a location in the city of Wellington in Carbon County and another in the Matheson Wetlands near Moab. Ladig’s team has since expanded it into a series of nine stations, from Bluff and Escalante in southern Utah to salt flats and wetlands in northern Utah. They plan to build another location in Green River next spring.

Each Utah Flux Network station is equipped with scientific instruments that track evapotranspiration in real time by measuring multiple things at once, including wind speed and direction, humidity, soil moisture and solar radiation.

The resulting data could have a major impact on Utah meeting its future water goals. Without clear information about how much water is leaving the Great Salt Lake through evapotranspiration, for example, it would be difficult to know how much water the state needs to release into the lake to achieve desired results.

“In my opinion (evapotranspiration) is the most important thing we can measure at the lake,” said Jake Serago, an engineer at the Utah Division of Water Resources. “That’s probably because it’s the phenomenon we perhaps know the least about.”

His team plans to use data from the Utah Flux Network to improve modeling of water movement through the lake system. The evapotranspiration estimates that Utah has relied on in the past are subject to a high degree of uncertainty, Serago said, especially for a vast, complex body of water like the Great Salt Lake.

“Because the lake is so large, even if the uncertainty is 10%, that is a huge amount of water,” he said.

One of the stations is set up in between Phragmitesan invasive plant, on the shores of the Great Salt Lake. In this particular area, the plants will soon be cleared, said Ladig. Therefore, before and after evapotranspiration data can be helpful in answering questions about the influence of phragmites on water loss.

“Sure, the invasive plant is bad for all ecological reasons, but also how much water does this invasive plant use?”

She hopes another station at Cedar Mesa in southern Utah could provide information about how pinyon-juniper forests encroaching sagebrush landscapes might affect evapotranspiration in this natural habitat. In both cases, Ladig said, the new information could help lawmakers understand where the greatest urgency lies and how to prioritize funding projects.

But the biggest impact of this data could be on farmers.

“Most agricultural users have a very good idea of ​​how much water they are diverting from a stream or well, for example, but they have very little idea of ​​how much water they are actually using,” said Marc Stilson, an engineer at Die Colorado River Authority of Utah.

Some of the water diverted to irrigate crops returns to the local water system, he said, such as water that seeps into the ground and travels to an aquifer or flows from a field into a nearby stream. However, water that evaporates is essentially lost in that area—it is depleted—as it typically rains on another watershed.

Offering farmers and ranchers more detailed data about water evaporation in their fields could help them become more water efficient, Stilson said. For example, it might cause them to try different cultures that could have less perspiration or test alternative Irrigation practices which lose less water through evaporation.

More detailed statewide data could also improve Utah’s position in ongoing developments Conversations about the Colorado River before the current catchment-wide use agreement expires in 2026.

“As we are involved in negotiating the bigger picture of the Colorado River, we want to ensure that the data we have is accurate and trustworthy,” Stilson said.

The data collected so far by the Utah Flux Network has mostly shed light on how to better set up the next monitoring site, rather than on setting policy, Ladig said. There is only so much comprehensive insight you can gain from one or two seasons of information.

Your team plans to analyze the existing data make it available to be announced to decision-makers and the general public within the next one to two years.

“Everyone has an interest in the water being there,” she said. “As we see declines in groundwater and surface water across the state, this will help ensure individual farmers can make decisions or lawmakers can make informed decisions about how water is used.”