Waikaremoana Power Scheme

The Waikaremoana Power Scheme is located between the Te Urewera National Park and Wairoa, along the Waikaretaheke River. The Waikaretaheke River begins in the south-eastern corner of the Lake Waikaremoana and joins the Waiau River at Ardkeen. The Waikaremoana Power Scheme is located along the upper 7 km of Waikaretaheke River.

The scheme uses water from Lake Waikaremoana, Waikaretaheke River, Mangaone Stream and Kahuitangaroa Stream to generate electricity and incorporates three power stations: Kaitawa (36MW), Tuai (60MW) and Piripaua (42MW).

Water is taken from Lake Waikaremoana via tunnels to Kaitawa Power Station, before being discharged into Lake Kaitawa. Water is then passed through Tuai Power Station and discharged into Lake Whakamarino. From there, water is carried by tunnel to Piripaua Power Station and is discharged into the Waikaretaheke River.

Description of the Waikaremoana Power Scheme.

KEY FACTS

WAIKAREMOANA POWER STATION
Year Commissioned	Tuai - 1929 Piripaua - 1943 Kaitawa - 1948
Total Capacity	Tuai - 60MW Piripaua - 42MW Kaitawa - 36MW
Generation Units:	Tuai - Three 20MW units Piripaua - Two 21 MW units Kaitawa - Two 18MW units

Contribution to the National Grid

The electricity generated at the Waikaremoana Power Scheme goes into the national grid. The current overall scheme capacity is 138 MW. The annual energy generation of the scheme varies from year to year.

Challenges faced in operating the scheme

Effective water management is a critical feature affecting the operation of the Waikaremoana Power Scheme. Apart from the fact that Lake Waikaremoana is a conservation area with strictly controlled operation parameters, the two smaller head lakes for Tuai and Piripaua Power Stations are quite small and contain minimal storage capacity. This essentially requires that the three stations be run in tandem as a "run of the river" scheme.

Another operational peculiarity of the Waikaremoana Power Scheme is the presence of leakage flow from Lake Waikaremoana through the natural earth dam to the Waikaretaheke River. Initially the leakage was reasonably constant at around 15 to 17 cubic metres per second and it was this water that was used to supply Tuai and Piripaua Power Stations before Kaitawa Power Station was built. After the construction of Kaitawa, a project was initiated to seal the bed of the lake where most of this leakage was occurring, resulting in the reduction of leakage from around 15 to 5 cubic metres per second. Leakage still occurs today and ensures an ongoing water supply is maintained to the various springs in the area.

However, the leakage requires a careful operational strategy, given that it can rapidly fill Lake Kaitawa. To account for this constant and uncontrolled inflow to Lake Kaitawa, the Waikaremoana Power Scheme is continuously operated at approximately 12MW.

Genesis Energy has many resource consents to operate the scheme and these require ongoing monitoring and reporting of the environmental effects. Genesis Energy also has mitigation agreements in place to manage its effects on the environment. In addition, environmental initiatives have been set up to enhance the surrounding environment and these are over and above the consent related legal obligations.
Monitoring river flows to ensure compliance forms a significant part of the operation of the scheme.