On Wednesday, 22 mature plants were discovered growing in a heavily vegetated area near an unnamed stream close to Lake Ohau, while 120 plants were located on public land near Duntroon in February.
Senior Constable Nayland Smith, of Omarama, said in addition to the 22 plants, several pieces of equipment used to help grow and irrigate them were recovered, including 50m of alkathene pipe, garden hoses, several 20kg bags of blood and bone mix, lime, netting, garden stakes, other irrigation materials and two automatic timers.
He believed the yet-to-be located person or persons behind the operation were likely to be experienced growers, Snr Const Smith said.
"I think they've probably done it before and they've spent a few dollars too ... They've put in a lot of work to set it up."
The crop would have a street value of "a few thousand dollars".
While the discovery of cannabis plantations was not common in the area around the Waitaki Valley, it was probably grown regularly, he said.
"I certainly know there is the odd smaller plant that gets grown up there ... but it's not on a huge scale."
Police wanted to speak to a "person of interest" about the matter, he said.
The 120 plants discovered growing on public land near Duntroon resulted in one arrest, Senior Constable Peter Scott, of Kurow, confirmed, as a result of what he described as a "sophisticated" operation.
"It was certainly a big, organised cannabis operation ... Unfortunately, it's getting more and more common and we are paying more attention to it."
In a separate investigation, Snr Const Scott said a search warrant was executed at a Kurow address a fortnight ago which uncovered a "sizeable" hydroponic growing operation and a "significant amount" of cannabis and small amount of methamphetamine.
One person was arrested and was facing several drug-related charges, he said.
