A lot of water has flowed under the bridge since

(a lot of (или much) water has flowed (gone, passed или run) under the bridge(s) since) ≈ много воды утекло с тех пор, как Например: ...it's been four - five years since she graduated high school... she won't remember me from a hole in the ground. Lot of water's flowed under the bridge since then. (A. Saxton, The Great Midland, The New Year, 1939) — ...четыре-пять лет тому назад она окончила школу... да она меня нипочем не вспомнит. Много воды утекло с тех пор.

Англо-русский фразеологический словарь