Genesis quashes rumours

This graphic, using data collected by the Hawke’s Bay Regional Council river flow team, shows the rivers that feed into the Wairoa River upstream of the township and how much they contributed during Cyclone Gabrielle. The graphic also shows the lowest point controlled by Genesis Energy, which operates three power stations downstream of Lake Waikaremoana. Genesis’ last point of control is on the Waikaretaheke River at Piripaua Bridge. The graphic shows how just downstream of that the peak flow was only 170 cubic metres per second, while the peak flows in tributaries and further downstream were much higher. By the time the water reached Wairoa it was flowing at 6500 cubic metres per second. The Lake Waikaremoana figures show that inflows peaked at 434 m3/s, while Genesis discharged only 40 m3/s to preserve the dam structure and avoid uncontrolled and potentially far greater volumes of water being released.

Genesis Energy is concerned about ongoing speculation in Wairoa, particularly on social media, that it caused the devastating flood in North Clyde.

The company issued a second media statement to The Gisborne Herald yesterday, which it hoped would further reassure the community it wasn’t to blame.

It issued one on Tuesday when The Herald approached it for a response to some Wairoa residents’ concerns that the company might have opened a flood gate, causing the sudden inundation the morning after Cyclone Gabrielle.

In its further statement yesterday, the company said: “Genesis Energy acknowledges the tragic and catastrophic effects of Cyclone Gabrielle across the North Island and our hearts go out to all those affected.

“We understand in such trying times it is natural to look for answers as to how this situation could have occurred or if there are things we can do to prevent them happening again.

“We believe there should always be a forum for these types of questions to be asked and we are open to sharing information and cooperating with any reviews.”

Interim Chief Executive Tracey Hickman said the company was concerned about misunderstanding or misinformation circulating regarding Genesis’ management of water in the Lake Waikaremoana catchment before and during the cyclone.

“It is inaccurate to say the Waikaremoana Power Scheme was responsible for the flooding in Wairoa and surrounding areas.

“Genesis operates the level of Lake Waikaremoana at 5.5m below the natural lake level which enables flood flows to be stored and not passed directly downstream.”

In the days leading up to the cyclone Genesis reduced the level of Lake Waikaremoana by 6 percent to mitigate the effect of inflows from rain.

During the cyclone, lake inflows peaked at 434 m3/s (cubic metres per second). Genesis released only 40 m3/s as required by resource consents.

This requirement exists to ensure dam and public safety and to avoid uncontrolled and potentially far greater volumes of water being released.

“These outflows contributed less than 1 percent to the water which ended up at Wairoa township. The rest of the floodwater came from streams and rivers below the power scheme’s last point of control,” Ms Hickman said.

This was verified with independent river flow data from the Hawke’s Bay Regional Council, she said.

The council’s general manager asset management, Chris Dolley, said the discharge by Genesis at Lake Waikaremoana was minor in the scale of flood flows.

“At peak, the amount was less than 1 percent of the total flow at Wairoa River at the Railway Bridge,” Mr Dolley said.

“In terms of how the lake is operated during a major event such as Cyclone Gabrielle, the lake is able to buffer the outflow and store huge volumes of run-off, which reduces the peak flow in the major rivers compared to an uncontrolled outflow.”

Genesis monitors approaching rainfall events and releases water ahead of time as permitted by resource consent.

Hickman added the team at the Waikaremoana Power Scheme had been working extremely hard in difficult conditions to continue generating electricity for the East Coast and Hawke’s Bay region, working closely with Transpower to get power to homes and businesses.