Tongariro trout protected in power project

Press, Volume CXII, Issue 33095, 9 December 1972, Page 12

Tongariro trout protected in power project

Tongariro and trout are synonymous so it is hardly surprising that their protection takes pride of place in the Ministry of Works’ programme to make the Tongariro Power Development as compatible as possible with its environment.

Specific works to protect the fish will cost about sl| million. Other works, worth several hundred thousand dollars, will help protect the trout but have not been designed just for this. In addition, die loss of power caused through bypassing 485 cusecs of water past the Poutu intake of the project may be regarded as an expenditure to protect fishing. This is estimated at $1 million a year in lost revenue from electricity. This water is needed to allow sufficient flow in the Tongariro River at all times to support the fish which spawn in the vicinity. The international reputation of the Taupo-Tongariro area for trout fishing and its contribution to the aura of the resort area, which lures visitors from various parts of the world, provided one good reason for the current special works.

On the Tongariro River, the location of the Moawhango tunnel outlet and the intake of the Poutu tunnel keep the stretch of flshable river that will be affected by the power project to a minimum. Natural barrier Water from man-made Lake Moawhango in the neighbouring catchment will discharge from a tunnel and augment the river above the Waikato Falls, which form a natural barrier to fish going upstream. Water for power is tapped at the Poutu intake structure just below the falls. The rest of the river will not be affected by the project apart from the reduction in flow. Water going through the Poutu intake will pass down a tunnel and discharge into the Poutu canal. As this canal cuts across the course of several streams which feed the T<»gariro, the streams are being carried under the canal at nine points by culverts.

Fish screens at the Poutu Dam at the Lake Rotoaira end of the canal stop rainbow trout from entering the canal from Lake Rotoaira.

Screens are being built on various other waterways to prevent fish from entering unsuitable areas. The most elaborate will be the drum screens under construtcion on the Wairehu canal, on the other side of Lake Rotoaira. Costing about $350,000, they are designed to keep brown trout, eels and lampreys in the Wanganui Catchment away from Lake Rotoaira and, subsequently, Lake Taupo, and are also selfcleaning. Combined bridge The most ingenious structure of all among the fish protection works is the combined road and fish bridge over the tailrace from the Tokaanu power station. This carries the renowned Tokaanu trout spawning stream over the tailrace. The stream flows through a channel to the combined bridge where it flows along an aqueduct beneath the road decking and then links up with its normal course on the other side of the tailrace. The channel to the bridge has a special spill weir, to take excess water in times of flood. This is fitted with screens to stop any fish from finding their way into the tailrace with the flood spillage. The whole construction job — spill weir, channels and combined bridgeaqueduct — will cost about $BOO,OOO. However, the protection of fish is not the only concern of the Ministry of Works in its construction work. The blending of the project into its surroundings, by landscaping and restorative planting, is another major activity. This is carried out with advice from the Lands and Survey Department.

Other concerns The Ministry also strives to keep discolouration of rivers and streams by construction works to a minimum, and is trying to cause as little disturbance as possible to wildlife in marsh country bordering Lake Taupo. In river beds on other parts of the project where

An artist’s impression of the Tongariro power development project, shown in relation to the fisheries protection works. These are designed to preserve the fishing in the area and the rainbow trout of Lake Rotoaira in particular. Velocity barriers, built into the scheme, are shown by the dam at the top of the picture, at the tunnel intake for the Poutu Canal, and where the Wairehu Canal enters Lake Rotoaira. Special measures taken to protect the fishing are shown thus: 1. Revolving fish screens to prevent brown trout, eels and lampreys migrating from diverted catchments into Lake Rotoaira and the Taupo system. 2. Wairehu Stream not used for carrying diverted waters—the stream is an important spawning stream for Lake Rotoaira rainbow trout. 3. Screens to prevent fish from entering the tunnel and going through the powerhouse turbines. 4. Screen to prevent spawners from Lake Taupo entering the tailrace. 5. Combined road and stream bridge. Tokaanu Stream — another good spawning one—is carried across the tailrace from the power-house. 6. Sulphurous Whangaehu waters not diverted to Lake Taupo. 7. Velocity barrier prevents trout from going upstream. 8. Screens to prevent rainbow trout leaving Lake Rotoaira. 9. Flow at Turangi not allowed to go below natural fipw or 1000 cusecs when the water is diverted.

metal has been taken, the work has been carried out in dry areas behind coffer dams wherever possible to avoid discolouration of the water. Another consideration has been to survey the power project sites for items of archaeological interest, as the district is rich in history. Mr T. J. Hosking, an archaeologist with the New Zealand Historic Places Trust, made a thorough investigation of the sites between 1966 and 1971 and, with local assistance, uncovered many artifacts which are on display at the Turangi Information Centre museum established by the M.O.W. public relations officer, Mr F. C. R. Ford, with Mr Hosking’s help. The survey was carried out so that the impact of the power scheme on archaeological work, now and in the future, would not be prejudiced. — From the Ministry of Works.