Under the lead of scientists from the Helmholtz Centre for Environmental Research (UFZ) a 14-day field campaign in 11/2014 was pursued located north and south of the outlet of Wadi Darga (Deragot). During the campaign two aspects were in focus serving WP1 (Sinkholes) and WP2 (Water budget components).  

The first focus was set on submarine springs as the, to date, quantitatively unassessed component of the Dead Sea water budget. The foreseen quantification approach requires detailed and small scale physical data that need to be obtained in-situ or near in-situ. By these means, UFZ scientists cooperated with scientists from the Scientific Diving Centre at TU Bergakademie Freiberg and the company EvoLogics GmbH Berlin for the reason to 1) investigate and map in-situ the distribution and dimension of submarine springs through divers and additionally to sample the spring-water in order to attribute the spring outlet to the respective source aquifer, 2) map the sea-floor / water depths with a 0.5x0.5 m spatial resolution using an echosounder and a sidescan sonar mounted onboard an autonomously operating USV (unmanned surface vehicle), called Sonobot. First results reveal the expected congruence between the sea-floor mapping of the divers and the USV enabling us to effectively scan larger areas with the required level of detail. It furthermore shows indications to allow the derivation of 3D information of the shape of the buoyancy-driven jet within the water column that is generated by the outflow of the fresh- or brackish submarine springs. That ability would largely increase the chance to model the outflow, distribution and diffusion processes within the water column up to the sea-surface.

 

 

In order to combine those near in-situ information we furthermore applied a complementary airborne approach using a thermal system mounted onboard an UAV (unmanned aerial vehicle), called GeoX-8000. Submarine springs, differing in temperature from the ambient Dead Sea water, have a distinct thermal signature (pattern) at the sea-surface. We use this signature to localize discharge location, and perspectively, relate its shape and the ∆T (between water at the spring outlet and at the sea-surface) to the volumetric submarine groundwater discharge. The combination of all aided by planned small scale and long term hydrochemical investigations will converge within a model that allows us to predict the submarine discharge at the Dead Sea.

The second focus was set on sinkholes. In a complementary approach to the one conducted some weeks earlier at Ghor Hadditah the Geox-8000 was used to record the Mineral Beach sinkhole site. Within 10:20 min flight time and at a flight altitude of 50m, 500 images were recorded from which a high resolution digital elevation model (spatial resolution < 5cm) is calculated that serves as basis for future campaigns to monitor the subsidence over time at this site.

All this field work would not have been possible with the help of several people including Eldad Hazan (National Park Authority, Head of Enot Zukim reserve), Dr. Yossi Yechieli (Geological Survey of Israel), Assaf Tsabar (Dead Sea Works), Jake Ben Zaken (Kibbutz Ein Gedi), Mandy Hoyer, Dr. Thomas Pohl, Prof. Broder Merkel (all TU Bergakademie Freiberg), Thomas Tietz and Jevgeni Glushko (EvoLogics GmbH), thank you all for your efforts that made the campaign joy- and successful.

Contact

Dr. Ulf Mallast Helmholtz-Zentrum für Umweltforschung, UFZ Dept. Grundwassersanierung Theodor-Lieser-Straße 4 06120 Halle/Saale Germany Phone: +49-345-558-5210 Email: ulf.mallast@ufz.de

Dr. Christian Siebert Helmholtz-Zentrum für Umweltforschung, UFZ Dept. Catchment Hydrology Theodor-Lieser-Straße 4 06120 Halle/Saale Germany Phone: +49-345-558-5211 Email: christian.siebert@ufz.de