With more than three-quarters of Idaho currently experiencing drought conditions, researchers at Idaho State University are investigating whether underground barriers could help the state hold onto water that would otherwise flow away — a concept already proven in Japan but untested in the United States.

Bruce Savage, professor and chair of Civil and Environmental Engineering at ISU, is leading a team studying what are known as subsurface dams — underground walls that slow or stop groundwater flow while allowing some water to pass through. The stored water can later be pumped out for use or released to recharge rivers and aquifers downstream.

How Subsurface Dams Work

Unlike conventional above-ground reservoirs, subsurface dams hold significantly less total water, but they come with practical advantages. Water stored underground is shielded from evaporation and surface contamination, and construction causes far less environmental disruption than building a traditional dam.

The technology is not entirely novel. Individual barrier wall components have been used in some U.S. states to protect coastal areas from saltwater intrusion and to manage groundwater around construction sites. But the full subsurface dam concept has not been deployed in the United States, making Idaho’s research a potentially groundbreaking application.

“We’re sending a lot of water out to the ocean,” Savage told East Idaho News, summarizing the core problem the research is meant to address.

Mapping the Best Sites

Mel Campbell, an ISU graduate with a master’s degree in geographic information science, is building a statewide model to identify where subsurface dams might work best. Campbell is analyzing every Idaho stream using variables including elevation, slope, stream geometry, nearby water sources, average precipitation, and bedrock geology.

The ideal site has a wide groundwater flow area that narrows into a smaller channel — a configuration that makes it easier for a barrier to capture and hold water. The surface layer must be permeable enough to allow water infiltration, while the bedrock beneath must be impermeable and structurally sound. The model also accounts for major geologic faults, which can compromise bedrock integrity through cracks and fissures.

High-elevation streams fed by snowmelt are particularly attractive candidates because the water is less vulnerable to contamination.

Early analysis has identified three promising regions: southeastern Idaho south of the Eastern Snake River Plain Aquifer, areas north of the aquifer, and portions of Central Idaho.

The Stakes for Idaho Water Supply

The Eastern Snake River Plain Aquifer is central to Idaho’s water security, providing drinking water to nearly 300,000 Idahoans. Water levels in that aquifer have declined steadily over decades, a trend that has intensified pressure on agriculture and municipalities alike as demand continues to outpace natural recharge.

Savage’s team is specifically interested in whether subsurface storage can work in Idaho’s snowmelt-driven hydrology. “The research question is whether they can be successfully combined in Idaho’s high-elevation, snowmelt-driven aquifers,” he told East Idaho News.

What Comes Next

The project remains in an exploratory phase. The next stage will involve field researchers analyzing subsurface geology at the top candidate sites and measuring groundwater volume and flow rates. The team also plans to consult with state water managers and assess potential effects on existing water users and wildlife.

The research is a joint effort between ISU and Boise State University, drawing on engineers, geoscientists, and sociologists. Funding comes through I-CREWS — the Idaho Community-engaged Resilience for Energy-Water Systems grant program.

If the fieldwork and modeling confirm viable locations, the findings could offer state water policymakers a new tool for managing Idaho’s water future — one that works with the existing geology rather than reshaping the landscape above it. That would be welcome news in a state where roughly 77.5 percent of land is currently under drought conditions and pressure on water rights is unlikely to ease.