Reconnaissance Studies for the Design of 6 Dams – Yemen

Project Name: Reconnaissance Studies for the Design of 6 Dams (Al Lafij A’ala, Beyt Beni Hajib, Madkhal, Al Aqiq, Hadjar Alitri, Beni Dalia’a)

Country: Yemen Arab Republic

Client: Ministry of Agriculture

Finance Source: Local

Tags: Yemen, Local, HEPP, Assesment

The 6 dam sites had been investigated from hydrological, topographical and geological points of view. The main purposes for the construction of the dams are flood control and irrigation. Two of them are located in the central region, very near to Sana’a, namely Beyt Beni Hajib and Beni Dalia’a. The remaining four, namely Al Aqiq, Madkhal, Hadjar Alıtrı and Al Lafij Al A’ala are located in the northern, eastern, western and southern regions respectively.

1) Al Lafij Al A’Ala: There are measured hydrological data records throughout the study area; well hydrographs or stream flow records of two or more years for precipitation and groundwater whereas some information exists for evaporation and present water use at reconnaissance level. The formation at the dam site is quaternary volcanic rocks mainly alkali flows and pyroclastic rocks. River flow is approximately 80-100 m3/s. At the dam axis, the width of the wadi bed is 40m.
2) Beyt Beni Hajib: In Raydah area, there are some measured records available for precipitation and evaporation and also for groundwater. Some information exists on present water use at reconnaissance level. The geological formation around the dam site is quaternary basalts and lithic tuff. Drainage area of the dam axis is 3.6km2. Wadi bed is 30m wide at the axis and proposed height of the dam is 15-20m at this axis. Area of the reservoir is estimated as 35 000 -40 000m2.
3) Madkhal: The measured records are available for precipitation and evaporation. Formation at the dam site is precambrian basement, abutments are formed of gneiss derived from granite. The drainage area is 1044km2. Area of the reservoir is approximately 100 000m2. The wadi bed is 50m wide at the dam site.
4) Al Aqiq: The measured records are available for precipitation, evaporation, surface water, ground water and present water use. At the dam axis the formation is precambrian basement, gneiss at the left abutment and greenschist at the right abutment. The drainage area of the dam is 192km2. The dam height is proposed about 25m and the reservoir area is about 80 000m2. There is a deep saddle at the right abutment along the axis that should be closed and used for diversion and spillway structures.
5) Hadjar Alitri: From the isohyetal map of Yemen Arabic Republic, the annual precipitation at the dam site is estimated about 800-820mm. The geological formation at the dam site is jurassic limestone with marn and shale. The drainage area of the dam axis is 25.9km2. At the upstream, there are terraces on the abutments descending down to the river bed that are used for agriculture
6) Beni Dalia’a: The measured records are available for precipitation and ground water. The geological formation around the dam site is quaternary volcanic rocks, mainly pyroclastic rocks. The drainage area is 2.6km2. The area of the reservoir is 15 000m2. Width of the riverbed at the axis is 40m and the height of the dam is proposed as 12m. Agriculture is intensively executed at the downstream of the dam axis. 60 000m3 of water will be stored in the reservoir.