Ngounié River

Ngounié
Ngounié
	Chaillu Mountains, Republic of the Congo
Mouth
• location	Lambaréné, Gabon
Length	680 km (420 mi)
Basin size	33,100 km2 (12,800 sq mi)

The Ngounié River (also Ngunyé,

Chaillu Mountains, along the border with Congo, and then turns northwest, flowing through the towns of Fougamou, Sindara and Mouila

before flowing into the Ogooué.

Etymology

The river name, Ngounié, is a French rewording of "Ngugni", which was originally used by

Eviya and Tsogo speakers know it as Otembo-a-Manga. The Kele speakers know it as "Melembye-a-Manga". The first part of these names means "body of water" in the given languages, and "manga" refers to dwarf palm trees which grow along its bank.^[1]

Geography

The Ngounié River, with a basin area of about 33,100 square kilometres (12,800 sq mi), is the second largest tributary of the

Massif due Chaillu. After meandering for more than 400 kilometres (250 mi) on the valley floor, it joins the Ogooué prior to Lambaréné. Development in the floodplain occurs mostly in the areas between Lébamba and Mouila, and again from the Fougamou area to the Ogooué at Lambarene. Conservatively, the estimated valley flood land area is approximately 150,000 hectares (370,000 acres). The left bank is characterized by sandy clay soils.^[2]

The Ngounié River Valley is formed between the forest-covered Du Chaillu Hills and the Ikoundou Mountains, and has grassy vegetation. The region within this valley is also known as Ngounié.^[3]

Its

tributaries include Louetsié, which passes through Lébamba and Mbigou; Ikoy, whose main tributary are the Ikobe River and the Oumba River; Dollé, which passes through Ndendé; as well as the Ogoulou, Ngongo and Ovigui rivers. Imperatrice Falls (also known as Samba Falls, or Empress Eugénie Falls),^[4] are approximately 10 metres (33 ft) in height. They are located in a river bend in the Ngounié Province, 5 kilometres (3.1 mi) from Fougamou. Here, the Ngounié measures approximately 150 metres (490 ft) in width and contains small islands. This is within the Peneplain Chaillu, which features granite gneiss and hills as well as rocky bays.^[5]

Climate

The climate is characterized by its equatorial humidity. The average temperature varies between 23–28 °C (73–82 °F). The relative humidity is commonly greater than 80%. Annual rainfall is measured around 2,000–2,200 millimetres (79–87 in). Wet seasons occur during September–December and March–May.[5]

Power development

The hydro-power potential of the Ngounié River has been proposed to be tapped by a hydroelectric project located on the Empress Eugénie Falls. The project is planned as a 56 MW run-of-the-river scheme with four units 14 MW capacity each. Two additional units of 14 MW have also been planned for completion in 2015, thus taking the total installed capacity of the station to 84 MW. The project utilizes the main Empress Eugénie waterfall of about 12 metres (39 ft) and a series of rapids in a river length of 2,000 metres (6,600 ft), creating a total head of 20 metres (66 ft) for power generation. The geology in the project area consists of granite gneiss formations.^[6]