Don and a group of dedicated landowners have been working since 2006 to fence, control weedy willows and replace them with sterile willows and native plants.
As a child, Don remembers the stream being heavily polluted. "Back in the 1850s there was a lot of willow planted ... and they blocked the river. The river stunk — you could smell it a mile away.
"As a boy growing up during the 1950s I remember seeing all the eels congregated as they all competed to get their noses into fresh water flowing into the stream from the drains that were emptying their water into the stream.
"The eels had to compete for the limited fresh water available to be able to get the oxygen they needed to stay alive."
In the 1960s the willows were cleared from the river.
"However, there was no follow-up spraying of remerging shoots springing out of the stumps so it was only a matter of about 30 to 40 years later that the willow had managed to re-establish and started following the same process that had happened 100 years before — the clogging of the stream.
"Now, 50 years later, the project is being properly organised and co-ordinated.
"The aim of the group is to try to get the lower Mangapiko Stream back to a lovely free-flowing, clear, native-planted corridor running from Te Awamutu to Pirongia.
"We need funding to achieve this and are probably half way through our project already."
Million Metres is an online fundraising platform that raises money to restore the banks of New Zealand streams, rivers, lakes and wetlands with native bush.
It hopes to raise funds to plant one million metres of waterways with native plants and trees by 2026.
The initiative is led by the Sustainable Business Network in partnership with the Department of Conservation.
The Lower Mangapiko Stream Care Group is asking for help in the form of donations to their crowdfunding website, with funding closing on Tuesday, April 30.
Funds raised will be used on materials to control erosion as well as Million Metres' 15 per cent administration fee.
Click here to support the group.