Research Team to Take Inventory of Cache Valley Groundwater

A team of researchers from Utah State University, the University of Utah and the U.S. Geological Survey is looking at the journey of groundwater — from rain or snow to well and all the rock in between.

Surface water is something we can see and measure. We watch it melt from snow in the mountains and course its way through Cache Valley via rivers and streams.

But there’s another source of water beyond what the eye can see. It settles down deep between the rocks, bubbling up from springs and pumping up from wells, and it provides much of our drinking and irrigation water.

“When people in the valley turn on the tap, it’s nearly always groundwater,” said Bethany Neilson, a USU professor with the Utah Water Research Laboratory.

But without significant data on Cache Valley aquifers, it becomes difficult to know how much is available for new groundwater rights applications.

“Each new application can result in a new straw in the same bowl, so to speak,” Neilson said.

The research team aims to measure how large that bowl is and how fast it fills back up.

“We need to address key data gaps in understanding of our groundwater systems,” said Dennis Newell, a USU professor in geochemistry collaborating on the project. The last groundwater budget for Cache Valley was compiled in 1990. Now with access to more accurate and precise techniques, the researchers can build on these important prior studies to produce more reliable estimates.

The project’s focus is to study how much and how old the water is in the aquifers, and then estimate how fast those aquifers recharge, or fill up with new groundwater.

By taking samples of environmental tracers from wells, the researchers can study how fast new water reaches the aquifers and where it comes from, including whether it began as snow or rain.

“Basically, a sample of water collected from a well or spring can have fingerprints based on its natural chemistry that we can use to identify generally where the water in the sample has been,” said USGS hydrologist Eric Humphrey.

The tracers sampled for include tritium, noble gases, isotopes and ions that indicate water sources and transit time of water. No contaminants will be sampled for.

All of this information will feed a new USGS model that includes details of Cache Valley’s groundwater system. It will be used to make forecasts for various climate and pumping scenarios and consider municipal and agricultural needs to assess availability for future population and industry growth.

Those results can help immediately with additional water allocation decisions and source protection, but they will also provide a tool in the long run for managers to make decisions.

“Water managers often ask, ‘how reliable is my well?’” Humphrey said. “We hope this study will help answer those kinds of questions.”

The state-funded study brings collaborators from several entities and expertise areas. The different departments at USU have knowledge of the local users and geology of the region, while colleagues from the University of Utah have completed similar studies in the past and experts at USGS bring their vital modeling work to build on.

“It’s kind of a unique study where we can bring in all these different partners to try to work on this problem,” Newell said.

Ultimately, the research will guide water management and ensure existing water rights holders get the water they’re allocated.

“We will have a much better handle on whether we have extra water available to allocate to new users,” Neilson said.