III. Wadi Floodwater Harvesting

This system depends on harvesting water from wadis. Water flow in the wadis is seasonal, erratic, and occasionally torrential. Several methods are used to harvest water from the wadi which depends on slowing water flow during peak discharge to allow water infiltration and divert water flow to fields or cisterns.
Jessour (pl.), Jisr (sing.).

Wall built across step wadi (e.g., in Tunisia). Spillways may be used.

 

 

Wadi cross walls, dams, dykes (Marbid, Arabic, Yemen),

Stone wall constructed across gentle-sloping wadi bed. Dams are rarely above one meter. A series of check dams may be used to slow water down and increase infiltration, or for water storage in cisterns or tanks.

 

           

 

 

 

Wadi Terracing

A series of dams is constructed in the wadi bed to direct water for cultivation on wadi bank terraces.

 

Wadi High Dams & Reservoirs

  High dams more than 10 meters in height have been constructed since Antiquity. Among the oldest high dams is Sadd el-Kafara in Wadi Garawi, Egypt, the Sadd at Jawa, Jordan, and the Ma’arib dam in Yemen.

 

Sadd el-Kafara, Wadi Garawi, Egypt (photo Fekri Hassan)

 

Tabia: Large (semicircular) bunds, Rabat

  Term used in Tunisia referring to the use of large earthen bunds in circular, trapezoidal or V-shape, about 10-100 meters in length and 1-2 m in height. They are staggered facing upslope.

 

Water Diversion Levee & Dam (Water Speeding System)

Water in a wadi is diverted by a dam or dyke to raise its level so that it can be channelled to the banks of the wadi. A levee is used on the side of the wadi to direct the water.

 

 

Faydah

Flat area of wadi where water collects.

 

 

Reservoirs                 
Large basins, often at high elevations where water is collected behind dams.

 

 

 

 

Waterfall Harvesting Cistern
 

A cistern constructed to receive water cascading from a waterfall.

<< back | continue reading >>