Wiktionary
acequia madre
n. (context South America English) A canal that supplies water for irrigation.
Usage examples of "acequia madre".
It's fed by a ditch they call Roybal's ditch that comes off the Acequia Madre del Sur that used to have a headgate on Indian Creek.
He had been spotted by some little girls en route to Acequia Madre grade school, who chased the beast into a garage and shut the door behind him.