Airborne Thermal Data Identifies Groundwater Discharge at the North-Western Coast of the Dead Sea

Abstract

Abstract:A qualitative and quantitative monitoring of groundwater discharge was conducted based on an airborne thermal campaign undertaken along the north-western coast of the Dead Sea in January 2011 to contribute to the relatively scarce information on groundwater discharge to date in the region. The application of airborne thermal data exploits thermal contrasts that exist between discharging groundwater and background sea surface temperatures of the Dead Sea. Using these contrasts, 72 discharge sites were identified from which only 42 were known from previous in situ measurements undertaken at terrestrial springs by the Israel Hydrological Service. Six of these sites represent submarine springs and at a further 24 locations groundwater appears to seep through the sediment. Although the abundance of groundwater seepage sites suggests a significant, but so far unknown groundwater source, the main contribution appears to originate from

Response of a coastal hydrogeological system to a rapid decline in sea level; the case of Zuqim springs – The largest discharge area along the Dead Sea coast

“…Their waters drain into several high discharge channels that are deeply incised in the mud flats. In contrast, most outlets south of the ''bay" are located adjacent to the shore (seeping or diffuse springs; Mallast et al, 2013b) and emerge from coarse-grain sediments at the land/water interface. Sampling density is thus much higher south of the ''bay" (Fig.…”

“…This young faulting system controls also the distribution of the collapse-sinkholes that are presently developing along the Dead Sea coastline (Abelson et al, 2003). Water that emerges on the sea floor, close to the shore, has been observed, creating circular patterns on the lake surface (Ionescu et al, 2012;Munwes et al, 2010;Mallast et al, 2013b). This upward flow is triggered by the density differences between the emerging, relatively fresh groundwater and the Dead Sea brine.…”

“…Due to the complex nature of this system, direct measurement of the discharge of the subsurface leakage into the Dead Sea is impractical. Based on airborne thermal data, Mallast et al (2013bMallast et al ( , 2014 estimated that groundwater contribution from submarine springs appears to be <10% of the total spring abundance.…”

“…The difference is due to lithological variations. All springs in the northern part emerge far from the shore (terrestrial springs; Mallast et al, 2013b), behind the muddy plain (up to 1000 m from shore). Their waters drain into several high discharge channels that are deeply incised in the mud flats.…”

“…We assume that all the water in these channels and seepages flows directly to the Dead Sea; the potential losses through evaporation and infiltration are considered insignificant due to: (i) short and rapid flow from emergence to the coast, and (ii) streambeds are built of impermeable clays which prevent infiltration. Although a few in-lake springs were documented during the sampling campaigns, their contribution to the amount of total discharge is assumed to be rather small (see also Mallast et al, 2013b). Based on all the above assumptions, measurement of the discharge was carried out along the shore by a team of the Hydrometric Department of the Hydrological Service of Israel by applying routine procedures of measurement of water flowing in channels (Rophe, 2003).…”