Oregon Trail pioneers came up with the name Thousand Springs. They likely didn’t count them. The springs tumble out of the canyon walls on the (roughly) north side of the Snake River from (again, roughly) Niagara Springs northwest of Buhl to the springs that fill Billingsley Creek at Hagerman. Many of the springs, which run a steady 58 degrees, have been captured for trout production or production of power, so they are less spectacular to view today than they were before the turn to the Twentieth Century.
But where do they come from? That was a puzzlement to the pioneers who named them, but geologists have it figured out. Much of the Snake River Plain consists of fractured basalt. Over theeons,s rain and snowmelt found its way through the cracks, filling them up much the way a sponge absorbs water. Water from as far away as the southern reaches of Yellowstone National Park has been seeping into the aquifer for thousands of years. The Lost River isn’t so much lost as it is hiding. It dives down into those cracks so thoroughly that it disappears.
The Snake River, with a bit of help from the Bonneville Flood, has been carving its canyons into that basalt, eroding away the “foot” of it and giving the water a chance to drain. Those are the springs along the canyon wall. There are also springs beneath the river, such as crystal clear Blue Heart Springs.
There may have been a balance of water going in and water coming out at one time. Now, water pumped for irrigation is depleting the aquifer faster than nature can fill it up. That’s why the springs have measurably diminished over the past few decades.
The picture shows the main Thousand Springs site near Hagerman before 1910, when construction of the concrete capture structure was completed. This is how it would have looked to the pioneers who named it.