water over the dam
An event or set of events which has already happened and cannot be changed.
I have two other philosophies. One is: Do the best you can with what you have. The other is: Don't worry about water over the dam.
ADJ
hydroelectric
VERB + DAM
build, construct
breach
Heavy rainfall caused the old dam to breach, forcing thousands of people to evacuate.
DAM + VERB
burst
When heavy rains came, engineers worried the old dam might burst.
hold sth back
The concrete dam held back millions of gallons of water during the heavy rainfall.
PREP
~ across/on
The government built a new dam across the valley to control flooding.