How about a tunnel between Manukau Harbour and the Hauraki Gulf to power turbines based upon the tidal differences between the two bodies of water?
Many people have suggested a tunnel between the Manukau Harbour and Hauraki Gulf to power turbines based upon the tidal differences between the two bodies of water. The concept is common in freshwater hydro schemes where tunnels are often used to give a strong and directed head of water, sometimes over long distances. Marine currents generally flow from west to east in the southern hemisphere, which means, for example, that some Pacific species are common on both sides of the tip of South America, but Atlantic species are far less common on the Pacific side. Current generally flow across the Tasman around NZ, meaning that Tasman species are found in the Gulf, but the reverse is less common. In the NZ context there are additional concerns from Maori around mixing water catchments. Given that there has been portage between the two harbours and ships have discharged foreign species from their ballast for generations, there is an argument to say that whatever damage that might be caused by
