Mosul Dam: The most dangerous dam in the world.

OVERVIEWNadhir Al-Ansari

Professor, Lulea University of Technology, SwedenMember of the Iraqi Forum for Intellectuals and Academics

Tigris River

Mosul reservoir reservoir

Spillway Mosul dam site

North Al-Jazeera pumping station

Hydropower generation

Mosul Dam Scheme

Mosul dam project (1986)

Main spillway

Mosul Dam is one of the biggest water projects in Iraq.

Purpose•Flood control•Irrigation of area (2500ha projected)directly from Mosul Reservoir and 750000ha from dam releases at middle and south Iraq.

•Hydropower generation(4 turbines with total generating capacity of 750 MW) + 300 MW (Pump storage and Reregulating Dam).

• The total volume of material for the embankment is reported to be around 37.7 million m3

• The upstream and downstream embankment slopes are inclined 2.5:1 (horizontal: vertical) below El. 330 m, which is the normal high operating pool level.

• Above El. 330 meters, both slopes are inclined at 1.73:1.

Total Storage Capacity 11.11km3

Live Storage 8.16km3

Dead Storage 2.95km3

Geotechnical• Site selection• Foundation

Problems

Karstified limestone and gypsum in the foundations of the dam

Solution crack

Sinkhole under a concrete pavement

Soil failure in a village on left abutment

Upstream right abutment, open fissure resulting fromslab slide

Sinkholes and Dissolution Phenomena

In March 2002 a large dissolution tunnel was discovered in a gypsum/ anhydrite layer in the right bank of the reservoir . The height of the cave was 1.3 meters with a floor level of 315 compared to 330. which was the maximum operation water level

Seepage from left abutment (photos taken in 2003)The situation was stable with continuing dissolution .

Discharge showed strong correlation with reservoir water level

Sinkholes and Dissolution Phenomena

The existence of (Wadi Dermalih) under ground aquifer was established during the construction of the underground caverns and tailrace tunnel of the PS scheme . The excavation of the caverns was only possible after completing grout shields and drainage tunnels around them. This photo shows the huge spring which had erupted from a gypsum- breccias layer during the tailrace tunnel excavation . A great amount of grouting was done to plug this spring

The Reservoir

W. A - 380 Km2

Boat path

Mosul reservoir boundary at 300 m a.s.l

Areas of sedimentation

Why we are worried now?

1.Continuous seepage: It seems that the seepage is increasing in 2015 (USACE)

2.Development of sinkholes downstream and upstream the dam.

3.One of the two bottom outlet gates in not functioning since 2013.

4.Indications of settlements (USACE and Richard Coffman, University of Arkansas ).

Globesar: settlement rate 5-10 mm/year

5.Expected flood.

Consequences

Mosul

Tikrit

Water Depth: 24 m Time: 4 hrQ: 405000m3/sec

Water Depth: 4 m Time: 38 hrQ: 46000 m3/sec

Water Depth: 15 m Time: 22 hrQ: 185000 m3/sec

Projected loss of life from dam failure 500,000 (U.S. Embassy est. 1.47 million)

Flood wave will destroy the infrastructure of the cities on both banks of the River Tigris downstream the dam to Baghdad.

Solution

Grouting

Mosul

Tikrit

Badush dam