The subsequent investigation found that an effluent irrigation pipe had been disconnected and effluent had then siphoned from the pipe by gravity over a 14-hour period.
The effluent flowed across a short distance of land and into the stream.
Following the conviction Waikato Regional Council urged dairy farmers to seek advice about effluent management from accredited experts.
The council's investigations and incident response manager, Patrick Lynch, said the incident was completely avoidable.
"The farmer had invested heavily in attempts to manage his effluent, however, he did not source good advice.
"The system did not have the usual safeguards and this discharge was the outcome. We strongly urge farmers to work with accredited dairy effluent designers to ensure their systems are fit for purpose," Lynch said.
Bella Ridge Farms Limited did not want to comment on the conviction.