Yemen is one of the five most water-stressed countries in the world, but is also a country with an extraordinary history of innovations in water management. One such innovation is the construction of cascades of check dams in wadis (ephemeral rivers). These check dams slow down the short-term flood flows in these dry rivers and maximize recharge. This enables the cultivation of very high-value grape farming in an area essentially dependent on only short floods.
The cascade check dams serve two purposes: (a) to reduce the speed of flow in the wadi; and (b) to impound excess water during flash floods.
The check dams divert water to spate irrigation canals on both sides of the wadi bed and increase the recharge of shallow groundwater. In semi-arid environments recharge most effectively occurs through riverbeds, as in these areas the alluvial deposits overlay sandstone and the cascade dams optimize the recharge effect.
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