Badush Dam : Controversy and Future Possibilities

The Journal of the University of Duhok

Badush Dam is uncompleted combined earthfill and concrete dam, it is located on the Tigris River. The dam is planned and designed to be a protection dam downstream of the already existing Mosul Dam to protect population and infrastructure downstream of Mosul Dam. Thisa is attributed to the safety concerns of Mosul Dam which suffers from severe karstification in its foundation due to the presence of thick gypsum beds. The safety of Mosul Dam is a matter of debate since its construction and commissioning in 1986. The construction of Badush Dam started in 1988 and suspended in 1991, although (30-40) % of the dam was already built. The geological setting of Badush Dam is almost similar to that of Mosul Dam. Therefore, the foundation of Badush Dam will suffer from the same problem which is karstification because they are located on gypsum beds which are the same rocks under the foundations of Mosul Dam. The thin inclined clay core and foundation treatment works indicate clearly that Badush Dam is designed to have temporary nature which is to contain the volume of Mosul Dam wave (11 × 11 km 3) in case of collapse of Mosul Dam and to pass the wave downstream without flooding.

Engineering, 2019

Badush Dam is a partially completed dam and a unique case of flood retention dams. Its intended main function is to perform flood protection once in its lifetime; that is if Mosul Dam would collapse. In such a case, the Badush dam would temporarily store the whole flood wave and route it safely to the downstream. For this end, the bulk of the reservoir is left dry, while the remaining volume at the lower part which is intended for power generation does not give an economic justification for building the full height of the dam. The short duration of the intended use as a protection dam has led to relaxing many design assumptions which have raised concerns over the dam integrity. The current controversy rages now over whether to continue the construction of the dam as it was first designed or to change all that in view of the similar site geology of Mosul Dam. Mosul dam foundations suffer at the moment from the severe continuous dissolution of the soluble materials in its foundation leading to continued maintenance grouting of that foundation. This paper gives an overview of the history of Badush dam, its current design and what new requirements which are needed if it is to replace Mosul Dam itself.

Mağallaẗ Tikrīt li-l-ʻulūm al-handasiyyaẗ/Tikrit journal of engineering sciences, 2024

In this study, a program was built to simulate the sudden and complete collapse of the Mosul and Badush Dams behavior towards this collapse and predict the level at which the water will balance in the two dams after the collapse, compared to different levels at the Mosul Dam before the collapse. Two mathematical models were built as inputs to this program. The first predicted the water level in the Mosul Dam reservoir in terms of its storage volume before the collapse, and the second predicted the water level in the Badush reservoir after the collapse, according to the level in the Mosul reservoir before the collapse. For each collapse scenario, the program was organized according to sequential steps summarized assuming the water level in the Badush Dam reservoir when the level stabilizes, and from it determining the water volume in Badush reservoir based on the geometric analysis of the reservoir, then the volume of water transferred from Mosul reservoir to Badush reservoir, and thus the volume of water inside Mosul reservoir before the collapse. From the first mathematical model, the level of the Mosul Dam reservoir was determined before the collapse. The second mathematical model determined the level of the Badush Dam reservoir after the collapse. The results showed that the program has high flexibility in predicting what will happen in the Badush Dam reservoir after the collapse based on the water level in the Mosul Dam reservoir before it collapses and that the limits of the program's work extend from the minimum to the maximum level in Mosul Dam at which the failure can occur. Also, the storage volume in Mosul Dam will be distributed to the two reservoirs after the failure until the level stabilizes. Badush Dam, at a level of 330.4 m (a.s.l), can expand the maximum flood wave resulting from the total and sudden collapse of Mosul Dam at its maximum level of 333 m (a.s.l).

During and after the construction of Mosul Dam, in Iraq, all the studies expressed a clear concern on the fact that the region of the dam suffers from extensive presence of soluble rock formations that might undermine the safety of the dam with its large reservoir. Most of the studies dealt with foundation treatment and safety hazards due to the dissolution of gypsum and anhydrite. To overcome the problem, grouting operations were performed. The seepage of water continued and this highlighted the possibility of the dam failure. Different grouting techniques and methods were suggested but the results were the same. Finally, it was decided to limit the maximum operation water level to EL. 319 m (a.s.l.) instead of EL.330 m (a.s.l.). This recommendation has remained in force up to now with the loss of sizable storage of irrigation water and power potential

Mosul Dam is an earth fill dam located on the Tigris River in North Western part of Iraq. It is 113 m in height, 3.4 km in length, 10 m wide in its crest and has a storage capacity of 11.11 billion cubic meters. It is, constructed on be-drocks which consist of gypsum beds alternated with marl and limestone, in cyclic nature. The thickness of the gypsum beds attains 18 m; they are intensely karstified even in foundation rocks. This has created number of problems during construction, impounding and operation of the dam. Construction work in Mosul Dam started on January 25 th , 1981 and started operating on 24 th July, 1986. After impounding in 1986, seepage locations were recognized. The cause of seepage is mainly due to: 1) The karsts prevailing in the dam site and in the reservoir area. 2) The existence of gypsum/anhydrite rock formations in the dam foundation alternating with soft marl layers and weathered and cavernous limestone beddings. 3) The presence of an extensive ground water aquifer called Wadi Malleh aquifer, which affects considerably the ground water regime in the right bank. The dissolution intensity of the gypsum/anhydrite ranged from 42 to 80 t/day which was followed by a noticeable increase in the permeability and leakages through the foundation. Inspection of the dam situation in 2014 and 2015 indicates that the dam is in a state of extreme unprecedentedly high relative risk. In this work, possible solutions to the problem are to be discussed. It is believed that grouting operations will elongate the span life of the dam but do not solve the problem. Building another dam downstream Mosul Dam will be the best protective measures due to the possible failure of Mosul Dam, to secure the safety of the downstream area and its' population.

Mosul Dam is multipurpose earth fill dam. It is 3.4km long, 113m in height and its storage capacity reaches 11.11 km 3 of which 2.95 km 3 is dead storage. The dam is located on the River Tigris in the northern part of Iraq about 60 km in north west Mosul city. The dam was built on highly karstified alternating beds of gypsum, marl and limestone. The dam was operating in 1986 and since then, seepage problems started due to the solubility of the gypsum beds, presence of karstification and the effect of the local groundwater aquifer. Insensitive grouting program was put to stop the seepage and ensure the stability of the dam but it did not stop. The situation became worse in 2014 when ISIS occupied the dam area and grouting operations which were halted. Recent evaluation of the conditions indicates that the dam is in its worst conditions. The failure models of the dam indicate that 6 million people will be affected , and 7202 km 2 of land will be inundated. To stop this catastrophe, grouting operations should be continued intensively to elongate the span life of the dam. Water level within its reservoir should be kept at a very low level to minimize the damages in case of dam failure. As a permanent solution, another dam should be built downstream Mosul Dam so that it can take the wave of Mosul Dam in case of its failure.

Mosul Dam is an earthfill multipurpose dam. It is located on the River Tigris in northwestern Iraq. The dam is 3.65 km long and its crest elevation is at 341 m above sea level. The storage capacity at normal operation level (330 m above sea level) is 11.11km3. The work to build the dam started on 25thJanuary, 1981 and finished on 24thJuly, 1986. The total cost of the development was estimated at 2.6 billion US$. The foundation of the dam lies on the Fatha Formation. This formation is composed of alternating beds of marls, limestone, gypsum and claystone. It is highly karstified, which has which created a lot of problems during the construction, impounding and operation phases.

Mosul Dam is the second biggest dam in the Middle East due to the capacity of its reservoir. Since the operation of this dam in 1986, it is suffering from seepage problems in the foundation of the dam due to the dissolution of gypsum and anhydrite layers under the foundation. This phenomenon has raised concern about the safety of the dam. Studies done during the recent years showed that grouting works can only be considered as a temporary solution at its best. It is clear now that while grouting must be continued search for long term solution must be sought if dam failure consequences are to be avoided. This must be done as soon as possible as the dam is showing more and more signs of weakness. It is further considered that the suggestions and recommendations forwarded by the team of Lulea University of Technology and the Panel of Experts in the Stockholm Workshop 24-25 May, 2016 give the most practical and suitable solutions for this problem.

Worries concerning the possibility of the dam failure due to the seepages under the foundation of Mosul Dam during its construction and operation phases enhanced the application of several dam failure models on Mosul Dam case. All the applied models gave similar results. It was noticed through the models that the wave in case of the dam failure will have a height of 54m and the discharge will be of the order of 551000 m3/sec. This wave will reach the capital city of Iraq “Baghdad” after about 38 hours. The discharge of the River Tigris at Baghdad will be 46000m3/sec and the height of the wave will reach 4m. The propagation of the wave along this distance will cause a catastrophe. About 500000 civilians will die in addition to the unbelievable damage that will be caused to the infrastructure of the country.

Mosul dam was built on the River Tigris northern part of Iraq during the period 25th January, 1981 and finished on 24th July, 1986. The foundation of the dam lies on the Fatha Formation. This formation is composed of alternating beds of marls, limestone, gypsum and clay. The beds of this formation are highly karstified. After impounding, several sinkholes developed within the vicinity of the dam site. The surface expression of the sinkholes suggests that they are caused by underground collapse.The appearance of the downstream sinkholes is most likely related to fluctuations in the tail water level of the main dam during operation of the dam and the downstream regulating reservoir. In addition, water seepage also was noticed in various areas indicating the dissolution of gypsum and anhydrite from the foundation. During the period February-August, 1986 the dissolution intensity ranged from 42 to 80 t /day.