Hawke’s Bay Regional Council investigates Ngāruroro tributary dam sites
The braided portion of the Ngaruroro River. The Hawke’s Bay Regional Council is studying the construction of a dam on a tributary halfway up the Ngāruroro to supplement flows. Photo / Paul Taylor
A dam on a tributary of the Ngāruroro River at Hawke’s Bay is being investigated as a possible solution to future summer water shortages in the area.
Draft Hawke’s Bay Regional Council Regional Water Assessment
predicted an annual shortage of 32 million cubic meters of water in the region by 2040.
Leaders have long warned that climate change could turn the Heretaunga plains, known as ‘New Zealand’s fruit bowl’, into a dust bowl during summers as water users compete for a scarce resource.
A Hawke’s Bay Regional Council spokesman said the council was investigating sites for a small to medium-sized public dam of up to 20 million cubic meters on a tributary halfway to Ngāruroro, near the Whanawhana Cable Car , but they are still determining if one of the sites is doable.
A 2019 water conservation order on the upper Ngāruroro, still under appeal by private stakeholders, would mean dams were not possible in those stretches, but an order was not granted by the environmental court for the lower sections, under the cable car.
“A dam is being studied as an option to supplement the flows of the Ngāruroro and lowland streams of the Heretaunga Plains in summer, to balance the cumulative impacts of water withdrawn from aquifers by all users during the hot summer months,” the regional council said. said the spokesperson.
Dams are a hot topic in Hawke’s Bay right now.
Proponents of the failed Ruataniwha Dam in central Hawke’s Bay are seeking to extend its consents until 2030, with a view to reigniting it in a new form. Currently, consents expire in 2024.
Hawke’s Bay Regional Council said the proposed dam on the Ngāruroro tributary was an extension of work done in a plan change process known as TANK, which focused on the future of the waterways navigable from Tūtaekurī, Ahuriri, Ngaruroro and Karamū.
The council was working with landowners, mana whenua and other stakeholders around the proposal, the spokesperson said.
“Any viable option would require strong community input before becoming part of the suite of tools available to our region to combat the impacts of climate change.”
Hawke’s Bay Regional Water Assessment Project, commissioned by the council and yet to be released in full form, projects an annual water shortfall to demand of 32 million meters cubic meters by 2040 and a deficit of 46 million cubic meters by 2060.
The regional council spokesman said that as climate change reduces the amount of water available to Hawke’s Bay, demand reduction alone may not be enough and supply options will provide more water to sustain the environment and meet demand.
Hugh Ritchie, director of Water Holdings Hawke’s Bay, said he believed the Ruataniwha Dam consents they held and planned to use for the Makaroro storage system were still the most effective way to to ensure water safety throughout the region and to ensure environmental flow in the center of Hawke. Bay.
He said the Makaroro storage system would be capable of holding 100 million cubic meters of water and using about 20 million of that to provide an environmental flow of 5,200 liters per second, compared to a minimum of 800 liters per second. second in 2019.
The regional council sold the permits to Water Holdings Hawke’s Bay after the Supreme Court found in 2017 that the Minister of Conservation had acted unlawfully in trying to make 22ha of Ruahine Forest Park available to Hawke’s Bay Regional Investment Company Ltd (HBRIC) for $330. million from the Ruataniwha dam project, after about $20 million of taxpayers’ money has already been invested in the project.
Tom Kay, freshwater advocate for Forest & Bird, said dams tend to have a negative environmental impact, citing a 2017 article, Damn the Dams by Mike Joy of Victoria University of Wellington and Kyleisha Foote from Concordia University in Montreal.
“A review of 165 scientific papers found that 92% of them reported a decrease in ecological health in response to flow regulation. This suggests that altering natural flows by dams is detrimental,” the paper says. .
Kay said the dams also impede the free movement of native fish along the river and he would prefer to see solutions such as wetland restoration and reforestation.
“Even when fish passage is scheduled to allow fish to move upstream, fish still have to move downstream and tend to swim through turbines or a dam outlet and be killed by the pressure,” said Kay.
“If they can’t swim out to sea to reproduce, then we lose those tunas and their bloodlines forever.”
Trevor Le Lièvre, spokesperson for Wise Water Use, said technical solutions were a last resort.
“If a water problem persists, only then should engineering solutions be investigated,” Le Lièvre said.
The Hawke’s Bay Regional Council’s Interim Water Assessment of the Hawke’s Bay Area highlighted several possible ways to ensure water security in the region on the supply side.
Another potential solution, managed aquifer recharge, involves capturing water from rivers and streams when flows are high and using it to recharge aquifers.
The regional council spokesman said a test site for recharge trials of the managed aquifer had been identified and a cultural impact assessment had been carried out.
“We are finalizing resource consent requests and expect to file them in the near future.”
The spokesman said the regional council was also looking at opportunities to encourage industry to develop in areas, such as Wairoa, which have a relative abundance of water.
The spokesman said the Kotahi plan for the regional council would be an opportunity for the community to have a say in how to approach the water supply.
“The Kotahi Plan, which is due for approval by the end of 2024, is an opportunity for the community to decide how water is managed in Hawke’s Bay, including allocation policy and how we apply water efficiency, conservation and demand reduction initiatives,” the spokesperson said. said.