Ngāi Tahu, the Government, Canterbury regional council and dairy cooperative Fonterra have contributed funds to the clean-up Lake Te Waihora.
Run-off from surrounding dairy farms and clearance of wetlands has left Lake Te Waihora in Canterbury with the worst water quality of any New Zealand lake.
The Government has contributed $6 million towards the project, while Canterbury Regional Council has put in $3.5 million and Fonterra $1.3 million.
Some of the funds will be put towards compensating farmers for land around the lake that will be converted into wetlands. There will also be changes to farming practices.
It is expected to take as long as 20 years for Lake Te Waihora to be clean again.