Fires, floods: case for a dam has never been stronger
Cyclone Gabrielle gave Hawke’s Bay a taste of global warming, and it’s going to get worse. The US government has issued a National Climate Assessment: Natural disasters cost them US$296 billion over the past five years.
US President Joe Biden said those denying the impact of climate change are 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,” he said.
The same goes for us. Unlike the US‚ our economy is too small to fork out the colossal costs of repeated events like 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 Waterholdings 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 hydroelectricity, maintain a minimum flow of five cubic metres per second 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 firefighting.
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 per cent dramatically reduces flood damage.
Spilling water early from the dam could have reduced the flood damage bill 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 the river beds causes stopbank failure and the destruction of bridges.
Continuous shingle extraction is essential to safeguard assets and infrastructure throughout Hawke’s Bay.
It is easier to extract shingle from one spot than remove 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 firefighting ponds to be established throughout the province, and 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 3cu m in summer.
With scarce water, limited firefighting resources and steep untracked forests, there is a serious risk of out-of-control fires.
Water planning has been discussed for many years, but Cyclone Gabrielle gave us a clear message: the time for action is yesterday. 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 dangerous future because we ignored the danger signs.
Tim Gilbertson is the chairman of directors for Water Holdings Hawke’s Bay, the organisation that owns the consents for the Ruataniwha Dam.