I've been watching the news about the Oroville dam in California, and am praying for some divine intervention. Apparently, the emergency spillway is expected to fail within hours. Mandatory downstream evacuations have been implemented.
If the spillway fails we can only pray that the entire structure somehow does not fail. My research shows that this reservoir holds 3,500,000 acre-feet of water. I can't find reference of any reservoir this large ever failing in the world. The Teton Dam in Idaho was holding 251,000 acre-feet when it failed. There was one in China that failed in 1975 with about 400,000 acre-feet.
Lets hope that the news is over-exaggerating this issue, and if not, lets hope and pray for all of our friends and neighbors downstream.