Some articles on zanja, zanjas:

Zanja Madre - Later Improvements
... since 1878 that several improvements would have to be done to the zanjaยน systems ... In 1888 the city planned to put pipe in most of the existing zanjas, but budgetary shortfalls did not allow the work to be finished ... The tunnel at the headwater of the Zanja Madre was reconstructed and much of the conduit was either brick or concrete lined ...