Authorities have privately discussed the possibility that aquifers supplying Christchurch's pure drinking water may become contaminated with nitrates from intensive agriculture.
The concerns have emerged from recent scientific work by Environment Canterbury (ECan), which shows deep groundwater from the Waimakariri district could be flowing towards Christchurch.
It is the first time ECan's modelling has showed that is a possibility.
It is understood the information has not been publicised due to ongoing scientific uncertainty, along with the the risk of it becoming politicised due to the upcoming election, said one source familiar with the situation. See more