"It's then the responsibility of the DHB and the district councils to take action," he said.
Action could include further site investigations to establish the source of any contamination, public warnings not to swim or gather shellfish; and putting up permanent warning signs at the worst sites.
Mr Ballinger said there were four simple strategies for anyone trying to judge water quality:
don't swim for two or three days after heavy rain
don't swim if water looks dirty/murky, smells or has scum on its surface
be aware of potential sources of contamination, both nearby and upstream
don't swim if there are warning signs indicating unsafe water
