Karstification Problems in the Haditha Dam, West Iraq

Abstract

Haditha Dam is constructed on the Euphrates River in the western part of Iraq completed in 1988 and located 14 km west of Haditha town. Haditha Dam is a combined earthfill and concrete dam with a total length of 9064 m. The maximum height of the dam is 57 m from the deepest point at the river channel and dam crest level is 154.00 m (a.s.l.). The storage capacity is 6×109 m3 at normal operation water level of 143 m (a.s.l.). The exposed formations in the dam site and reservoir area are the Euphrates (Lower Miocene) and Fatha (Middle Miocene) formations. Both formations are well known in Iraq to be karstified at different intensities. The right bank of the Euphrates River is severely karstified with tens of sinkholes of different shapes, dimensions and activities. The presence of the karstified rocks is the main reason the dam has a very long grout curtain which extends along its entire length and includes the concrete powerhouse and spillway structure in the river channel, and the right and left bank extensions. The right bank extension of the grout curtain is exceptionally long due to the extent of the sinkhole area. Grouting was performed here in boreholes drilled at one-meter spacing to reduce water penetration and movement through the flank of the dam. The grout curtain under the embankment in the river section was done in two rows, while under the concrete structure it is comprised of three rows of holes. The left bank extension has two rows. The depths of all parts of the curtain varied following the karstification zones and intensities. The main aim of the current study is to elucidate and discuss the influence of the karstified rocks at the dam site and reservoir on the design and especially the length of the dam and the need for side extensions.