Monday, February 26, 2024

Gabrielle has brought new urgency to HB water planning

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Dam on the Makaroro River would be useful in flood and fire, says Tim Gilbertson.
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By Tim Gilbertson, chair of and a shareholder in Water Holdings HB. His views are not necessarily those of WHHB.

Cyclone Gabrielle gave us a taste of global warming and it’s only going to get worse. 

The United States government, in its National Climate Assessment, said natural disasters cost the country $296 billion last year. President Joe Biden said that “denying the impact of climate change is condemning the American people to a very dangerous future … Impacts are only going to get worse, more frequent, more ferocious and more costly … None of this is inevitable.” 

The same goes for us, but unlike the US, New Zealand is too small to repeatedly fork out the colossal costs of events such as Gabrielle. 

Despite the obvious danger, we keep blaming cows, encouraging air travel, promoting gas-guzzling SUVs and voting-in governments that favour oil wells and gas platforms. Changing attitudes and behaviour isn’t easy.

The consents held by Water Holdings HB for a dam based on the Makaroro River in Central Hawke’s Bay are increasingly relevant as the situation worsens. The dam would generate hydro electricity, maintain a minimum flow of 5 cubic metres per second (cumecs) in our rivers, and give towns and irrigators enough water to survive and thrive.

And it could have an important role in reducing flooding, keeping shingle out of the riverbeds, and providing water for fire fighting.

If the dam had been built as originally planned, the heavy rain warning given ahead of Cyclone Gabrielle would have allowed the water level in the dam to be lowered by several metres before the storm hit, holding back floodwaters for crucial hours and reducing the flow down the Waipawa and Tukituki rivers. 

No precise measurements have been done as yet, but reducing the maximum flow by 10% dramatically reduces flood damage. 

Spilling water early from the dam could have reduced the bill for flood damage by many millions of dollars.

The build-up of shingle in a dam is a problem as it reduces long-term storage capacity. On the other hand, the build-up of shingle in river beds causes stop bank failure and bridges to be destroyed. 

Continuous shingle extraction is essential to safeguard assets and infrastructure throughout Hawke’s Bay. It is easier to extract shingle from one spot rather than removing it piecemeal from inaccessible kilometres of river bed. Taking shingle from the dam is a better, cheaper option than most alternatives.

Increased river flows allow fire-fighting ponds to be established throughout the province. They will be needed when our new pine forests catch fire. 

Few existing water bodies are suitable for helicopters and fire appliances, especially when rivers drop to 3 cumecs in summer. With scarce water, limited fire-fighting resources and steep untracked forests, there is a serious risk of out-of-control fires.

Water planning has been discussed for many years. Cyclone Gabrielle gave us a clear message: the time for action is yesterday.

The original Ruataniwha Water Storage Scheme, the 2022 Tukituki Water Strategy Plan and Water Holdings HB consents and our four councils know all we need for a lasting solution to the issues we face. 

Our children will be grateful if we provide them with plenty of water in a pristine landscape – a lot happier than if we condemn them to a very dangerous future because we ignored the danger signs for decades. 

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