View of the leeward side of the Mangahao Upper #1 Dam from the end of Mangahao Road. Tararua Forest Park begins at this point.
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.