Water in part of Idaho’s Eastern Snake Plain Aquifer travels much faster than previously thought, according to scientists.

State Department of Water Resources hydrogeologist Neal Farmer and Idaho Power hydrologist David Blew have mapped the underground terrain and studied how it impacts springs.

Farmer told Capital Press the work in part helps researchers define, delineate and understand the aquifer instead of relying on hunches.

“Therefore, that helps us understand why springs occur where they do…,” he said.

The aquifer’s level has declined in recent decades because of population growth and a move to more efficient irrigation systems that allow less water to soak into the ground.

The department said lower aquifer storage and spring flows, and erratic surface water flows in the Snake River are among the results.

The state has for years funded a recharge program that returns water to the aquifer.

To track the groundwater flow, two dozen dye-trace trials have been conducted in 13 locations since 2009. Idaho Power and the state Water Resource Board pay for them.

A powder approved by the U.S. Environmental Protection Agency turns the water fluorescent green. Scientists track the dye with fluorometers placed in monitoring wells to measure dye concentrations.

They found that water takes three to five years to travel from aquifer-recharge sites to the Snake River, “the kind of retention the board wants to see with ESPA recharge sites,” a project summary from the board said.

However, studies show groundwater moves much faster than expected in the aquifer’s western portion. It moves especially quickly near the Malad River Gorge and next to springs near the Snake River rim.

A study near the aquifer’s midpoint tracked water flowing more than 30 miles across the Snake River Plain, from the state’s recharge basin north of Eden to points west of Jerome over the last three years. Water there traveled 393-653 feet a day.

To the west, a study at a state recharge site near Shoshone found the dye cloud moved up to 1,500 feet per day.

Farmer said that in addition to tracking aquifer recharge, the work can shed light on modeling efforts, water chemistry and how water-borne contaminants are transported.

“Another interesting outcome has been the spread of the dye laterally” as it moves farther from the release point, he said. “This is the first time it has been documented on these scales in a basalt aquifer.”

Lateral spread can be important for determining contaminant impact or in placing water-quality monitoring wells, Farmer said.

The work also looks at how long water remains in the aquifer before it emerges on its west end at Thousand Springs — its outlet in the basalt cliffs above the Snake River near Hagerman.

The board said the natural-spring discharges near Hagerman comprise most of the river’s flow below Milner Dam and are important to hydropower production. The natural springs also are important habitat, and their discharges help maintain and improve the river’s water quality.

Studies show some of the aquifer-recharge flows are moving into Box Canyon Springs or  Thousand Springs.