At a Glance
The Matahina dam creates Lake Matahina — a distinctive entrance to the Eastern Bay of Plenty, when travelling from Murupara.
The Rangitaiki River has three hydro-electric power schemes along its length, each having the ability to alter flows in the river. Extreme care should always be undertaking when pursuing recreational activities in the river, including while swimming, fishing or boating. It is always advised that you use the appropriate safety equipment and check the river conditions before you undertake your desired recreational activity.
Resource Consents and the Environment
Matahina’s Resource Consents were successfully renewed in 2013. Our re-consenting project set out to maximise the efficiency of the power station and its water use. The scheme is now better placed to meet varying electricity demands, inflow volumes, and the physical constraints of the plant.
River Flows and the Modified Operating Regime
In June 2016, the Modified Operating Regime was implemented. This meant a new minimum flow came into effect. The minimum flow of 35 m3/s must be maintained as measured at the flow recording site at Te Teko.
Real time information on the flows and levels within the Rangitaiki River as measured at Te Teko can be found on the Bay of Plenty Regional Council monitoring page, by clicking here.
||Modified Operation Condition
||When flows into the lake are above 35 m3/s
||Minimum Flow must not be less than 35 m3/s as measured at Te Teko Flow recording site
|| Maximum flow from the power station cannot exceed 160 m3/s except during flood conditions.
|Low Flows (flow into Lake is less than 35 m3/s)
||When flows into the lake are between 35 m3/s and 25 m3/s
||The daily outflow from the power station must equal the average inflow over the previous 24 hour period.
For example if on the Monday the inflow over the day averaged 32 m3/s, then on the Tuesday an average of 32 m3/s must be released from the power station. In addition to the daily requirements, the instantaneous flow must not go below 25 m3/s.
||When flows into the lake are less than 25 m3/s
||The instantaneous flow at Te Teko is to equal the previous days average inflow.
For example, if on the Wednesday, the inflow into the lake averaged 23 m3/s, than the instantaneous flow at Te Teko must not fall below 23 m3/s on Thursday. It is extremely rare that inflows fall below 25 m3/s.
|Operating Peaks during Low Flows
A maximum of 1 operating peak in a 24 hour period, and a maximum increase of 15 m3/s above the flow immediately prior to the peak commencing.
For example, if the current flow is 32 m3/s then the operating peak cannot cause the flow to exceed 47 m3/s.
|Operating Peaks during Normal Flows
||No limit to amount of peaks during normal flows
|| Maximum increase of 97 m3/s per hour
||Maximum decrease of 30 m3/s per hour
The term ‘operating peak’ is defined as an increase in the discharge from the Matahina Dam (being a combination of discharges from the power station and over the spillway) to a constant flow for no less than 30 minutes followed by a subsequent decrease in the flow being discharged.
A trap and transfer programme has been operating at Matahina since 1983, and assists elver and other native fish species to migrate upstream of the dam. The trap and transfer programme is operated by the Kokopu Trust on behalf of Trustpower.
The majority of fish caught in the trap are transferred upstream to Lake Aniwhenua and the upper Rangitāiki River, with the remainder transferred to Lake Matahina. On average, 2 million elver are transferred upstream each year. In addition, a number of adult eel migrating downstream are caught at the dam and transferred to the lower Rangitāiki River.
Trustpower is currently developing new technology to limit human interaction with migrating elver, with the hope that elver will be transferred from the station tail race into a holding tank inside the power station using a transfer machine based on the concept of the Archimedes screw. Development in this area is continuing, but more information about the test system can be found here.