Police seized nearly 150 cannabis plants from eight different plots along creek lines in South West bush yesterday.
Yarloop and Waroona police were helped by the Police Air Wing in finding the $280,000 haul.
Sgt Ross Adam said the location of some of the crops meant PolAir crew had to be winched into the area to pull some of the plants back up to the aircraft.
He said it appeared the plots were spread across about 5km of the creek line at Hoffman, about 25km north-east of Harvey, and they looked to have been set up by at least two separate groups.
Sgt Adam urged members of the public to report suspicious behaviour such as people carting in large amounts of water into bushland.
Anyone with information regarding the Hoffman set up is asked to contact Crime Stoppers on 1800 333 000.