Discovery that could kill disease and locals have known about it for hundreds of years. This is nbc nightly news with kate snow. Good evening. In nebraska tonight they are bracing for more historic high water with record snowfall in february and then rainfall this past week and now temperatures in the 50s melting off that snow. Rivers are cresting. 11 million americans tonight face the threat of flooding from nebraska through other parts of the midwest down the Mississippi Valley and all of the way to the south. And landed. Really cold, and many now in shelters indefinitely. It looks like an ocean everywhere. Nebraskas governor declared states of emergency and dozens of counties and tribal lands describing the damage as unbelievable devastation. In nebraska, the 90yearold spencer dam was destroyed sending floodwaters into nearby towns with bridges washed away, Emergency Responders went in on both to help. There is an entrance, Paradise Lakes insane. The rising waters are blamed for at