Lake Matahina
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| Lake Matahina | |
|---|---|
 Lakeside view of Lake Matahina | |
  Lake Matahina Location of Lake Matahina in the North Island | |
| Location | Bay of Plenty, North Island, New Zealand |
| Coordinates | 38°7′5″S 176°49′0″E / 38.11806°S 176.81667°E |
| Type | reservoir |
| River sources | Rangitaiki River |
| Built | 1960 to 1967 |
| Construction engineer | Ministry of Works |
| First flooded | 1967[1] |
| Max. length | 6 km (3.7 mi)[2] |
| Surface area | 2.3 km2 (0.89 sq mi)[2] |
| Max. depth | 50 m (160 ft)[3] |
| Water volume | 55,000,000 m3 (1.9×109 cu ft)[2] |
Lake Matahina is a reservoir in the Bay of Plenty region of New Zealand, located immediately south of the settlement of Te Mahoe and 50 km east of Rotorua.[3] The lake was formed by the construction of the Matahina Power Station and its associated 86 m tall Matahina Dam on the Rangitaiki River, which was completed in 1967.[1]
In 1969, five children drowned after driving a car into Lake Matahina at a camp that New Zealand author Barry Crump helped to run.[4] Crump was charged with manslaughter over the deaths, but these charges were dropped.[5] Fleur Adcock, one of Crump's ex-wives, said that it was negligence on his behalf that the children died.[4]
The lake has a maximum depth of 50 metres (160 ft), a relative depth of 2.8%, and an annually fluctuating water level of only 0.5 metres (1.6 ft) to 0.75 metres (2.5 ft). Upper reaches of the lake are shallow (1 to 4 m), with a sinuous channel constricted by a narrow ignimbrite gorge. As the gorge widens down lake, the depth increases to15 metres (49 ft) along a delta front, and to 40 metres (130 ft) to 50 metres (160 ft) in the basin immediately behind the dam.[3]
Lake levels
The lake's operating levels are as follows:[6][7]
| Description | Level (referenced to the Moturiki Datum) | Comments |
|---|---|---|
| Design Flood Level | 76.8 m RL | Shall not exceed this level in all except “Emergency Condition” situations (as defined in Trustpower's “Lake Matahina Flood Management Plan”). |
| Maximum Lake level during floods of less than 200 cumecs | 76.4 m RL | This is the spillway date crest level. |
| Maximum Normal Operating Level | 76.2 m RL | Normal upper operating limit. |
| Minimum Normal Operating Level | 73.15 m RL | Normal lower operating limit |
| Minimum Level (flood pending) | 71.60 m RL | No generation below this level. Spillway gates reliant on mains power or back-up generator |
| Extreme Minimum Level (major flood >500 cumecs) | 70.0 m RL | Approval is required from Bay of Plenty Regional Council to go below 71.6. |
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