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Storage dams detrimental to the environment

Freshwater ecologist Amber McEwan. PHOTO/FILE

Large-scale water storage dams are not the answer to water shortages, nor do they deliver the environmental benefits promised, some industry experts say.

Towns should instead look at better water management to control wastage.

Masterton-based freshwater ecologist Amber McEwan said any ecological benefits of water storage dams were “generally overstated”.

Regulated river flows from water storage dams had a negative impact on native fish species, she said.

“Native fish need floods, but they need periods of big flows and small flows at a certain frequency, they are very complex.”

One of the major effects of a dam was the shift from high and low flows.

“These are part of a healthy flow regime, so flow regulation is never good for fish.”

It was possible to do “flood harvesting” by storing small amounts of water from floods to use in times of stress.

“But that’s never what happens. No matter what anyone else says, [water storage dams] facilitate land use and intensification and there’s no way anyone can argue that.

“That increases the stresses on the fresh water systems,” she said.

Mrs McEwan said the region’s towns can be “extraordinarily wasteful” with water.

“As far as minimising the risk of ecological harm, reducing our water use, rather than creating water storage, is the way to go.”

Forest & Bird lower North Island regional manager Tom Kay said the public’s perception of water storage schemes has been “skewed” by the “talk up of the potential benefits”.

“We almost never see an analysis produced by a developer that presents an estimate of the environmental or public costs of one of these schemes – I’m yet to see the environmental implications of the Water Wairarapa project seriously considered,” he said.

“We can’t afford to keep cutting off habitat with massive concrete structures – we’re already so close to losing our native freshwater species.

“That’s not even considering the impacts of increases in nutrient and sediment loads that result from the land use intensification required to pay for these schemes.”

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