The West Coast's largest lake has achieved water quality targets five years earlier than planned.
Monitoring of Lake Brunner between 1992 and 2010 indicated deteriorating trends for nutrients, water clarity and high levels of phosphorous running off surrounding farmland.
The West Coast Regional Council said targets were set to improve water quality by 2020 but commitment from the local community meant they had already been met.
The council said farmers had built fences to keep stock away from the lakeside and 20,000 plants had been put in.
