The hydro electric dam gates. It was interesting you could see the trout gathering at the bottom of the slides where the water comes down just before they opened because it stirs up the bottom and they now that means lots of food. The power company opens the gates and roars water down the gorge 3 or 4 times a day in treaty with the Maori in the area to continue to allow the water to flow freely some of the time. It means a loss of income to them but more power to the company for being sensitive to the needs of the environment and to the needs of Maori.