Sentence:  The canal employed a series of <WSD>hydrostatic locks</WSD>—also called bear traps—that would create an “artificial flood” that changed water levels, allowing the barges to flow freely in either direction. 
Meaning of the word marked with <WSD> tags:  (countable) A lock for raising and lowering boats on a canal or waterway that operates by using pressurized water to flood or drain the level inside the lock.