Why is Thousand Springs no longer made of 1,000 springs and where does the water originate from?
South of Hagerman, Thousand Springs is clearly visible from the Thousand Springs Scenic Byway. Thousand Springs is renowned for its many fresh natural underground springs emerging from the Eastern Snake Plain Aquifer, a Lake Erie-sized underground reservoir. Its water erupts from the nearby steep, rocky canyon walls and cascades into the Snake River below. Other springs bubble up from deep within the riverbed.
“The Thousand Springs region is a major discharge point for water in the Snake River Plain Aquifer,” said Shawn Willsey, College of Southern Idaho professor of geology.
“The aquifer is contained within basalt lava flows that erupted from various volcanic vents over the past 3 million years. The basalt has fractures, pore spaces, rubble zones, and other characteristics that provide conduits for the water to travel through.
“The decrease in spring discharge over the past hundred or so years is undoubtedly the product of using water from the aquifer for aquaculture and power along with irrigational wells which tap the aquifer upgradient from Thousand Springs,” Willsey said.
In the early 1900s, irrigators started diverting water from the Snake River into canals.
“Surface irrigating raises the water table which causes more flow coming out of the spring. We reached the maximum discharge in the 1950s. It has come down since then,” said Sean Vincent, hydrology section manager for the Idaho Department of Water Resources.
He said the decline in aquifer water levels is due to groundwater pumping for agricultural purposes, the conversion from flood irrigation to sprinkler irrigation, and climate.
“The discharge decreased because pump technology increased. Flood to sprinkler irrigating was a big move because although it was more efficient because you don’t use as much water, it’s a double-edged sword because there is less of it,” said Vincent. He said flood irrigation applied more water than crops actually used, but it percolated into the ground and recharged the aquifer — and the springs.
The springs and the quality of their water have drawn attention since the area was first settled. The Valley of the Thousand Springs had many developers and owners, but it wasn’t until 1912 that power was first generated by the Thousand Springs Power Co. Idaho Power took over production in the area starting in 1916.
Mild winters and clean, oxygenated spring water with a consistent temperature also drew fish producers, making the region the current center of trout production in the U.S.
“The water in the aquifer comes from many sources including the mountains around the Lost River Valley and the Lost River itself,” Willsey said. “One reason why there are so many springs in the Thousand Springs region is that the Snake River takes a northward turn and intercepts water in the aquifer which generally travels from northeast to southwest. Groundwater in the aquifer moves fairly slowly at rates ranging from 0.5 to 20 feet a day.”
The Big and Little Lost rivers disappear into sinks, a depression where the water flows into the ground, Vincent said. The lost rivers do not reach any larger river, but vanish into the aquifer, giving the rivers their name. The sinks of both rivers are near the Idaho National Laboratory, northeast of Craters of the Moon. Water from both rivers emerges about 100 miles away at Thousand Springs and Devil’s Washbowl.
The larger canyon springs have gauges, providing good measurements, Vincent said. “We look at the total discharge rate because it’s hard to count the number of springs.” Currently there are 100 springs.
Several processes still recharge the aquifer, Vincent said, including surface irrigation, tributary underflow, precipitation, and losses from streams, rivers and canals that leak to some degree.
But discharge levels at Thousand Springs continue to decline. “We’re approaching the levels of where we were in 1900 but we’re still above it,” Vincent said.