Workmen working on a new pole on the Mangahao Line. The men are W. Weastell, top of the pole; at left on the ground G. Clark; Caneen and Gastern hold the wires at the right.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.