“开闸放水”常见的英文表达有 “open the sluice gates to release water” 或 “open the floodgates”（此表达更为简洁、常用，在特定语境下可传达类似含义，不过“open the floodgates”更侧重于比喻意义上放开限制、让大量事物涌出，若单纯指水利工程放水，前一种更贴切 ）。
For irrigation purposes, they decided to open the sluice gates to release water.
为了灌溉，他们决定开闸放水。
Once the restrictions were lifted, it was as if they'd opened the floodgates and a flood of new ideas poured in.
限制一解除，就好像他们开了闸，大量新想法涌了进来。（此句为比喻用法 ）