Al Wahda dam (M'jara)

Name of Project:

Al Wahda dam (M'jara)



Country:
Morocco

Client:
Ministry of Public Works, Hydraulic Administration Ministry of Energy, National Office of Electrical Power

Construction period:
January 1992 – December 1998

Agriculture plays a prominent role in the Moroccan economy, employing a considerable portion of the country's work force. In keeping with agro-energy infrastructure plans in the M'Jara region, Sidi-Kacem province, the Hydraulic Administration of the Ministry of Public Works (AH), in agreement with the National Office of Electrical Power (ONE), had an earth dam built on the Ouergha River measuring 88 m high, which created a basin containing 3,800 million cubic meters of water and a plant at the base of the dame with a total installed capacity of 247.5 MW.
In this regard, it should be noted that the installed power of just this one plant accounts for 22% of all the installed power in Morocco.
The basic objectives of the project were:
Protection of the Gharb plain against devastating periodic flooding.
The irrigation of more than 100,000 hectares in the Gharb plain and the lower Ouergha valley.
The production of 400 million kWh of electrical power per year.
The transfer of more than 600 million cubic meters of water to the souther regions of the country, which will experience a water deficit in coming years.
The site where the Al Wahda dam is located is, as the crow flies, about 35 km from the city of Ouezzane, some 5 km from the village of M'Jara, which can be reached by provincial road RP No. 26, which connects the cities of Ouezzane and Fes.

The work on the civil engineering portion can be summarized as follows:

  • a main dam consisting of a core of clay and an earth transition zone, and upstream protection made of rock, 1,600 m long, 88 m high;
  • a secondary dam consisting of two earth-fill transition zones and upstream protection made of rock, 1,000 m long, 26 m high;
  • a concrete plant for housing 3 Francis turbines, 82.5 MW each;
  • a concrete intake tower, 71 m high, located on the right bank of the dam, with 4 intake grids having a total cross-section of 384 m²;
  • a bottom outlet, located under the headrace tunnel, consisting of a double tunnel measuring 750 m long, made using the "cut and cover" technique;
  • a canal-type spillway located on the right bank, measuring 700 m long, 100 m wide, and with 17 m high side walls.

The spillway structure consists of six sector gates, each 14.70 m wide, with a total capacity of 13,000 m³/sec;

  • a headrace tunnel measuring 376 m long and 11.50 m in diameter, made of high-strength steel.
MAIN TECHNICAL DATA:
Surface excavation: 14,000,000 m3
Embankments: 27,000,000 m3
Concrete: 750,000 m3
Earthmoving: 40,000,000 m3
Diaphragms: 5,300 m3
Reservoir volume: 3,800,000,000 m3

OTHER PROJECTS: Morocco

Last update: 18/09/2013