The water quality of the Waikato River is still deteriorating despite many actions to improve it, a new report reveals.
The Waikato River Authority has delivered its five-year report to the Crown and Waikato River iwi on the effectiveness and progress being made to restore the catchment.
NIWA has analysed 650 trends from a combination of indicators and found while 25-percent were improving, 45-percent were not, and for the rest, it was difficult to tell.
Freshwater and estuaries centre manager Neal Hudson said while it is not obvious there is progress being made, improvements take time.
''The way land use and river waters interact there's sometimes quite a delay between an action on land and its impacts on water becoming evident.''
''We are currently seeing the effects of land use activities maybe 10, 20, 50-years back and it will take some time for those impacts to start to lessen and for a reversal to take place."
Hudson said it took a long time for the river to get into the state it is now.
He said it was good to have a long term view.
''They (the Waikato River Authority) are expecting about 80-years before they really achieve what they want and that reflects probably 80 to 100-years of human activities historically that have caused us to be in the situation we are today.''
The Authority said while it has clearly had areas of success, it also acknowledged much more needed to be done to restore and protect the river catchment.
Co-chairs Tipa Mahuta and Paula Southgate said there is continued confidence in the Restoration Strategy for the Waikato River and Waipā River providing guidance and a blueprint for the most effective restoration initiatives.
They said although a lot has been achieved in the past 10 years, there is a need to continue to push harder.
"We have talked about an 80-year time frame to see significant improvements in the rivers and catchment. Even this period is too long to wait for some and so we can't afford to be complacent."
Over the 10-years since the establishment of the Authority, it's overseen the planting of 2-million native trees and shrubs, 64,000 non native plants, and fenced nearly 400-kilometres of waterway.