How it began
The Mozabites settled the M'zab Valley in the northern Sahara in the 11th century and built fortified towns adapted to a hyper-arid climate. To live there they devised a system for collecting and redistributing the water of occasional flash floods. A hydraulic study of the oases of Ghardaia and Berriane reports that the Ghardaia system for sharing flood water has worked for seven centuries and has been renewed several times.
How it works
When a flash flood comes down the wadi, hydraulic structures divert and regulate the flow. Channels lead the water and runoff from the surrounding hills into the palm groves, where it irrigates the gardens and recharges the shallow aquifer that feeds the wells. Each system is made up of several structures that share the flood among users according to fixed rules. A community organization manages the channels, and floodable areas were occupied only by temporary structures, not dwellings.
What lasted
The system has been managed for hundreds of years by the same customary laws and groups, and it is still in use. Researchers describe it as tangible water heritage adapted to a harsh environment and to local society. The M'zab Valley was inscribed on the UNESCO World Heritage List in 1982, and water infrastructure is treated as a core part of that heritage.
Where it stands today
The works are threatened by climate change, which increases flood risk, and by unsustainable urbanization. The local management authority promotes the traditional practices through workshops and guides, and UNESCO presents the valley as a case study in using traditional environmental knowledge for water management and climate adaptation.
