EAGE Workshop on Dead Sea Sinkholes – Causes, Effects and Solutions

This work deals with the creation of a sinkholes database for the Jordanian coast of the Dead Sea, Ghor Al Haditha area. Ground collapses inventories were carried out between 1991 and 2012. The lineament is replaced and analyzed in its structural setting at regional and local scales. Its direction (N 24 E) is sub-parallel to the ones displayed by most published focal mechanisms in that zone especially the one associated to the 23rd April 1979 earthquake (Mb = 5.1; N 20 E +- 5 deg, Arieh et al 1982), which is representative of all focal mechanisms calculated on a fault plane compatible with the general direction of the Jordan - Dead Sea Transform fault system for the east coast of the Dead Sea area. The alignment of sinkholes is constituted by thirteen minor linear segments separated by as many empty spaces. Their organization suggests the existence of a rotational effect caused by stress between two parallel strike-slip faults. Four minor linear units present an en-echelon arrangement from which one can deduce the presence of a local extensional stress field. In this context, sinkholes locations provide information of subsurface discontinuities interpreted as hidden fractures.

Unusual dolines are widely distributed in the northwestern part of Jordan along the western shoulder of wadi Sijin, a tributary of the Yarmouk River. The dolines are the result of dissolution of calcined carbonates. Lime (CaO) in wadi Sijin in Maqarin area is the result of the spontaneous combustion of the Bituminous Marl Formation that crops out at the southern bank of the Yarmouk River. Combustion took place after the drop in the groundwater level and the incision of the nearby wadi bottom. The volcanic activities during the Pleistocene time were probably the triggering factor for the ignition of the bituminous limestone. Combustion of bituminous marl has led to decarbonation and the formation of lime. Hyperalkaline groundwater activity and associated lime (CaO) -water interaction is evident along wadi Sijin and the Yarmouk River. High pH seepages are still flowing along the River. The groundwater discharges today is characterized by high hydroxide alkalinity, saturation with calcium sulphate and high concentrations of trace elements. The potential development projects in the karstified area are bringing more activities into the area. Sinkholes in the karstified area represent a very special geohazard and potential development projects should take it into consideration.

For essentially the last 30 year the water level of the Dead Sea has highly dropped. One of the major associated facts is sinkhole occurrences along the shoreline both in Jordan and Israel. As the principal invoked mechanism, many studies have concluded that sinkhole formation results from the dissolution of a previously immersed salt layer, progressively in contact with fresh to brackish water. In Jordan, the triggering of this phenomenon could also be the result of particular tectonic settings, associated with the Jordan-Dead Sea transform fault system. At Ghor Haditha (south–est Jordan), the consequences have been dramatic for farmers with the shrinking of temporary available lands and industry with the closing of at least one factory. The shallow material in this area is heterogeneous and composed of intercalated sand and clay layers of alluvial-colluvial origin, over a salt substratum, whose precise depth and thickness are yet partially hypothesized.

The Multi-channel Analysis of Surface Waves (MASW) is a recently developed seismic method to estimate S-wave velocity structure under the ground for geotechnical engineering purposes. The field setting of the survey uses a linear geophone array and a small seismic source such as sledgehammer or weight drop. It analyses the seismic waves in the frequency domain for the dispersion property of surface waves and estimates the distribution of the S-wave velocity below the surveyed area that is most responsible for the analyzed propagation velocity pattern of surface waves. After a relatively simple procedure, final Vs information is provided in 1-D, 2-D, and 3-D formats.

Sinkholes along the shores of the Dead Sea have been known since the 1960’s. Geophysical research indicates two major groups of sinkholes – those close to the edge of an evaporate layer and those that form away from a dissolution cavern. To date, no comprehensive geophysical survey of the Dead Sea has been performed. Airborne electromagnetic surveys can map the hydrogeology of the area surveyed including stratigraphy with unknown subsurface faults, the fresh water-salt water interface, and karstic cavities and existing and incipient sinkholes. Interpreted depth sections range from tens of meters to 100 m to 200 m or more in depth with the specific depth of investigation depending on the geophysical instrumentation used and how deep the very conductive Dead Sea water zone is. Design of an AEM survey over the Dead Sea includes a time-domain system flying with the sensor at 30 m above the ground surface with flight lines sub-perpendicular to known fault structures in the Dead Sea with line separations from 50 (detect sinkholes) to 200 (regional mapping) meters. Follow-up ground-based geophysical surveys would be conducted on both the Israeli and Jordanian sides of the Dead Sea by teams from those countries.

The Dead Sea is one of the saltiest lakes in the world with a concentration of halite and gypsum ten times higher than in the oceans. Its size is about 80 km long and 15 kilometers wide. Jordan, Israel and the PNA divided its shore in the following proportions: 60%, 25% and 15% respectively. The prevailing climatic conditions are of arid type and allow salt crystals to grow in the open air. The Dead Sea occupies the bottom of one of the pull-apart basins that punctuate the Jordan-Dead Sea strike-slip fault. The Dead Sea is composed of a northern and of a southern sub-basin. For centuries, they are separated by an emerging salt diapir (Lisan area) and connected by the shallow Lynch strait. However, since about 30 years, the southern sub-basin and the strait are dried-up (Figure 1). Indeed, since about 50 years the Dead Sea water level is dropping due to over pumping of its tributaries, especially the Jordan River. During the 1980's, early sinkholes and subsidence occurred. Currently they number several thousand.

The level of the Dead Sea (DS) has been dropping for the last five decades due to increasing extractions from its feeding sources (APC 2006, JVA 2006, Neev and Emery 1967, Baker and Harza 1955). As a theoretical result the hydrodynamic interface of the fresh/salt water bodies should readjust to a new equilibrium state through a seaward movement Ghyben 1988, Herzberg 1901, Glover 1959, Kremer 1977). Accordingly (Fig. 1), and in order to achieve system stability the groundwater levels of the surrounding areas should drop and the amounts of stored groundwater in excess of those necessary for keeping a hydrodynamic stability of the system will be discharged to the DS itself (Salameh und El-Naser 1999, 2000 a & b, Salameh and Udluft 1985).

The limited water resources in Jordan as well as the neighbourhood countries may cuase future conflicts among water resources because of rising water demands, aridity, climate change, and food security issues. The water topic in Middle East region is one way or another, finds its ways in the front. Scientists from Middle East region and abroad have always found it fascinating to tackle the subject of in Jordan, Israel and Palestine water condition. Determined to overcome water scarcity challenge, Jordan has embarked on a series of actions, policies, and projects to insure meeting future water needs. Working alongside international agencies, private sector, agreements with neighbourhood countries and academic institutions, Jordan has adapted several approaches in dealing with water scarcity: water resources planning and water demand management, water recycling (wastewater, grey water and brackish water); water desalination using renewable energy, national and international regional projects such as Disi and Red Dead Sea projects, respectively. Nonetheless, pressures and competition over the available water resources are mounting every year. Furthermore, demand management programs are yet to prove effective in a country in which the current water use per capita is already at a minimum compared to healthy standards. Apparently, several challenges set ahead in the future for Jordan as well as the neighbouring countries. The decrease in the Jordan River flow due to water diversion for domestic uses has also caused a lowering of the water line (a meter a year, 25 meters since 1980). The whole southern basin of the Dead Sea has dried up and has been turned into an industrial site, potentially life-threatening sinkholes (nature’s revenge) (Figure 1), Sewage/Pollution of the unique qualities of Dead Sea water, Moreover, no master plan is in place and plans for development are totally uncoordinated. Lastly, will water scarcity and fragile ecosystem in the region will be enough to be a bridge to take the region from conflict to peace in the Middle East?

Within the framework of a technical cooperation project between ACSAD and BGR a Decision Support System (DSS) for water resources management was developed and applied in two pilot areas.