Watch NZH Local Focus: Resident blames Waikato River dam fluctuations for wetland destruction

Fluctuating Waikato River levels south of Aratiatia Dam are being compared to a one in 200-hundred-year flood by Broadlands Forest resident Graham Sperry.

Mr Sperry has lived near the edge of the Waikato River for 45 years. Over that time he's seen a lot of change, and in the last 15 years says the change, erosion and loss of the wetland by the river's edge, near his property has been "heart breaking".

"What's happened is as the water level fluctuates up and down and the velocity of the water can come in, it erodes the bank, and undercuts the looser soil underneath. It's over half a metre undercut... and the weight of vegetation above that is enough to make it collapse."

He says the artificial control of water flows is to blame for the four metre variance in water height, sometimes several times a day.

"The ramping here is in the order of three to four metres, 14 feet and that has destroyed what used to be an extremely viable wetland habitat and that was assessed in 1996 as being a very healthy environment."

Over time as the water levels changes he says silt has been deposited over vegetation and trees - leaving a visible trace of how high the water gets.

The silt is suffocating plant life and provides a breeding ground for noxious weeds.

"The river is bringing in silt, a silt load every time it comes in here."

Not only is the river killing vegetation it has also meant wildlife that used to call the wetland area home have left.

On the day Local Focus visited, only one fantail was spotted, which Mr Sperry says was the first fantail he had seen down on the river's edge in three weeks.

Mr Sperry says there was a "community" of invertebrate and native wildlife species that used to live in the wetland alongside the river included ducks, fantails, fowls, marsh crake, banded rail and bittern, but today "most of those are gone".

Mr Sperry and other community members want the Waikato Regional Council to review the consent for river flow levels and ensure that the environmental effects of "ramping the river" are being monitored more efficiently.

Graham says he doesn't want to cut down power generation, all he wants is for the river to be managed with a view to protect the environment and maintaining the natural wildlife.

He says Mercury should not be holding water back in Lake Taupo and "letting very high flows go during peak power period demands."

Mercury Energy say they adhere to consent conditions which allow them to release water at the Aratiatia dam and shoreline changes downstream are a combination of different factors.

Mr Sperry wants Waikato Regional Council to cap the variance to two metres, to curtail the worst environmental impacts.

Waikato Regional Council was unable to answer our questions before publication deadline.

Mr Sperry's call follows a Waitangi Day drowning upstream, after a swimmer was swept away when the Aritiatia Dam floodgates were opened.