Whangarei river patrol man Milan Ruka says a decision on water takes from Poroti Springs raises doubts about methods used to measure water volumes.
Northland Regional Council has refused an Auckland company consent to take more water from the springs for an export business.
The commissioner ruled that Zodiac Holdings had no reliable way of measuring the impact on Maori or other water users.
Mr Ruka, who challenged the measurement methods at the hearing, says the same can be said of the present take by Whangarei District Council and local irrigators.
He says the systems used are based on old reports and data and cannot give an accurate measurement of water volumes.
Mr Ruka would like the regional council to explain why it believes it has reliable ways of assessing the health of the springs.