Malad Gorge in Idaho shows especially clear evidence of spring water emerging from the vast Snake River Aquifer through porous pillow basalts. On the opposite side of the canyon, where the river widens, a concentrated spring flow measuring 600 cfs, or cubic feet per second, sends 300,000 gallons of water each minute into the Malad River. From the waterfall upriver to the Snake River below, about 1200 cfs of spring water issues from the base of the canyon, equal to thirty-six million gallons each hour and making the Malad Springs one of the largest in the country. The Snake River Aquifer is a vast underground reservoir flowing beneath the surface and through the Snake River Plain lavas under about 10,000 square miles of south-central Idaho. Experts estimate that it holds enough water to cover the entire state of Idaho in one and a half inches of water. Melting snow and rainwater feed the aquifer from a basin of 35,000 square miles, and the water follows permeable basalt layers southwest until it reaches the Snake River Canyon and emerges as springs. Near Hagerman, Idaho, the Thousand Springs area contains 11 of the 65 largest cold springs in the United States.