https://www.openstreetmap.org/way/88373103 if it really is still there, should be visible in imagery.  Canals are meant to be large so they conduct enough water for irrigation.  The tagging is suspicious as "derelict" as this should still be visible unless it's underground then it needs layer=-1/tunnel.

also is https://www.openstreetmap.org/way/595198480 truly on surface or underground?