Arapete camp looking upstream, much of the surrounding bush has been felled. Later this area was flooded and called 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 the first world war construction began in late 1919 and the station opened in November 1924.