Farmers in the Lake Rotorua catchment say they can't believe results showing the worst dairy effluent discharge audit in six seasons.
Half of the 32 sites inspected had serious compliance issues over the disposal of dairy waste.
Farmers say the random audit was done during non-ideal, wet spring conditions.
Bay of Plenty Regional Council says at least 10 notices have already been served to farmers about unacceptable levels of nutrients leaching from farm land into waterways.
The council's Regulation and Monitoring Committee chairman Malcolm Whitaker says there was evidence of faulty irrigation systems and effluent storage ponds overflowing into water courses.
But Federated Farmers says it can't understand how farmers achieved about a 90% compliance rate last season only to fail dismally this year. It wants an urgent meeting with the regional council.