The sinks and the lower courses of both rivers are within the land of the Idaho National Laboratory, northeast of Craters of the Moon. Water from both rivers emerges about away at Thousand Springs near Hagerman and other springs downstream of Twin Falls. Due to irrigation using the aquifer's water, most of the rivers' water is pumped out of the ground, used to irrigate crops, and returned to the ground as irrigation drainage, where it eventually emerges at the springs and joins the Snake River.