waikato+river

=__**Waikato River**__=

The Waikato River is the longest river in New Zealand. In the North Island, it runs for 425 kilometres from the eastern slopes of Mount Ruapehu, joining the Tongariro River system and emptying into Lake Taupo, New Zealand's largest lake. It drains Taupo at the lake's northeastern edge, creates the Huka Falls, and then flows northwest, through the Waikato Plains. It empties into the Tasman Sea south of Auckland, at Port Waikato. It gives its name to the Waikato region that surrounds the Waikato Plains. The present course of the river was largely formed by the large volcanic eruption from the Lake Taupo volcanic complex 1800 years ago. The large outflow of volcanic debris blocked the old channel to the Firth of Thames at Lake Karapiro and **forced** the river to turn west and then north

=__**Eletricity Generation**__= The Waikato's first hydro-electric power station was the Horahora Power Station, now located under the Horahora bridge deep beneath the surface of Lake Karapiro. Horahora was built to supply electricity for the Martha gold mines at Waihi. The river has a series of eight dams and nine hydroelectric power stations that generate electricity for the national grid. These were constructed between 1929 and 1971 to meet growing demand for electricity. The power scheme begins at Lake Taupo, which has control gates to regulate the flow of water into the river. Once released through the gates it takes over 18 hours for the water to flow to the last power station at Karapiro. On its journey downstream it passes through power stations at Aratiatia, Ohakuri, Atiamuri, Whakamaru, Maraetai, Waipapa, Arapuni and Karapiro. Approximately 4000 gigawatt hours (GWh) of electricity is generated annually by the scheme, which is around 13% of New Zealand's total electrical generating capacity. The river also provides cooling water for the coal/natural gas fired thermal power station at Huntly. However, in order to protect aquatic life, conditions are imposed by its resource consent, specifying the quantity of water that can be removed by the station along with the maximum temperature of the water when returned to the river (25°C). These conditions mean that on very hot summer days the station cannot operate at maximum capacity, sometimes reducing their total output to 40 megawatts (MW). A new cooling tower has been built as part of expansion works at the site, which allows one 250 MW unit to run at full load even during such times. media type="custom" key="13085252"