The Government has injected a further $3 million into the Lake Taupo protection project to help meet the target of reducing nitrogen entering the lake, mainly from livestock farming.
The project aims to protect water quality by reducing nitrogen flowing into the lake by 20%, or 170 tonnes a year, by 2020.
It is funded by the Government, Waikato Regional Council and Taupo District Council.
The programme has already significantly reduced the amount of nitrogen by helping landowners change their farming practices, including replacing pasture with plantations.
The chief executive of the trust running the project, Graeme Fleming, says the size of the task increased after it found that initial calculations underestimated the amount of nitrogen entering the lake from the surrounding catchment.
Initially the trust was working towards reducing nitrogen by 153 tonnes but that was increased to 170 tonnes once it was realised that the total amount of nitrogen in the catchment was higher than first estimated.
Mr Fleming says planned measures to reduce nitrogen inflows include converting some land to forestry, changing farming systems and reducing the number of stock.
He says most of about 100 larger-scale farms and a large number of smaller landholdings that are in the Taupo catchment have the resource consents they need to continue farming within the nitrogen reduction limits.