A view of Arapete workmens camp from further up the ridge line. The area was later flooded and became Tokomaru No 3 Reservoir. The Mangahao Power Station provides hydroelectric power and is situated near the town of Shannon. It serves Wellington, Horowhenua, Taranaki, Hawkes Bay, and the Wairarapa. After being delayed by WWI, construction began in late 1919 and the station opened in November 1924.