Canterbury Regional Council says new controls on nitrate leaching won't have an immediate impact but will improve water quality in rivers over time.
The council has approved a new Land and Water Plan which for the first time will set controls on the amount of nitrogen that can be discharged from farming and other activities.
High nitrate levels have been linked to ground water and river pollution in parts of Canterbury.
Critics say the plan doesn't go far enough because it takes a holding-the-line approach that will allow the already toxic levels of leaching that's occurring in some zones to continue and pollution will get worse.
Council Commissioner for resource management act processes, Professor Peter Skelton, acknowledges it will take time to reverse declining water quality in those zones, but he says that will occur as new limits are set for each catchment.
He says there will have to be reductions in leaching from farms to achieve the new catchment load limits.
Professor Skelton says there are a number of ways to do that and one of the easiest, which some red zoned farmers in Canterbury have already done, is to take cows off the land and farm them on hard stands or in cow houses.
He says other techniques for reducing nitrogen leaching are being developed all the time.