Ämmä was built in the built-up area of Ämmänsaari and was the first power plant finished the River Emäjoki. The power plant designed by Aarne Ervi has a maximum capacity of 16 MW.
The construction started in 1957 by building service buildings, concrete mixing plants and housing in the area. The construction of the power house, foundations for the dam and excavations for the headrace and tailrace started in the same year. The canal that reached Kiantajärvi (Lake Kiantajärvi) was also digged. 
The construction of the concrete framed power house advanced quickly. So did all the other concrete works. Water could be released to the headrace at the end of the year in 1958. At the same time, the other branch of the river, Jalonhaara, was closed with an embankment. The power plants on the Emäjoki - Ämmä, Seitenoikea and Aittokoski - were built in series, so that the workforce and machines moved from one site to another as soon as different stages were finished. Ämmä hydroelectric plant was finished in 1959 and the machinery connected to the power grid on 14 November 1959.
 Mauri Kuuskoski, Pekka Salminen, Jouko Vahtola, Paavo Vasala. Vesivoimaa Oulujoesta 50 vuotta: sähkölla eteenpäin. Oulu: Oulujoki Oy, 1991, 49-50
 Ibid, 50
Owner: Fortum Power and Heat
Designer: Aarne Ervi, architect
Capacity: 16 MW, head 10-13 m
Power house: In-situ concrete frame, cladded with fibre-reinforced cement board
Special features: Located in Ämmänsaari conurbation
Protection status: Classified as RKY (Nationally significant built cultural environment – RKY 2009: Hydropower plants on the River Oulujoki and Sotkamo Route).
 Veli-Pekka Huhmo. Oulujoen vesistön voimalaitosarkkitehtuuria. Oulu: Humanpolis Oy, 2017
Ämmä has a medium sized residential area with wooden detached houses.
All pictures below are part of the power plant's history. All images are copyrighted. You may use the images for personal use but the images may not be used in commercial contexts or printed matter without our permission. Click on the pictures to enlarge them.