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Using Thermal Infrared Imagery (TIR) for Illustrating the Submarine Groundwater Discharge into the Eastern Shoreline of the Dead Sea-Jordan

Many of thermal anomalies that are indicator of discharge zones of warmer water were observed along the Dead Sea shoreline at the areas of Zarka Ma’in, Zara and Al-Mujeb. The groundwater discharge locations were mapped along eastern shores of the Dead Sea by using aerial thermal infrared imagery (λ = 8-13 μm). A digital thermal infrared camera was used for this purpose in December 2005 at the nighttime. The principle of using this method is depending on the difference of the temperature between the sea surface water and the groundwater. The average groundwater temperature in the Dead Sea area is about 33 centigrade. It discharges into the cooler Dead Sea water 12 centigrade. The temperatures of the mixing two types of water (the discharge and the Dead Sea Water) were about 26 centigrade at some spots. These increasing of the Dead Sea temperatures are due to the groundwater discharge. The groundwater discharge was identified by thermal infrared images surveys. The survey provides sharp images of the shoreline of the Dead Sea (pixel size of about 4-5 m).


INTRODUCTION
The Dead Sea is a hypersaline terminal lake with a surface area of approximately 760 km 2 and a maximal depth of about 316 m. It is located in the central part of the Jordan Rift Valley, which extends from Lake Tiberias in the north to the Gulf of Aqaba at the south and includes The Jordan River at the North, the Dead Sea region, the southern Ghors (Haditha, Mazra, Safi), Wadi Araba and the Gulf of Aqaba. Geologically, the Dead Sea lake situated within the large Dead Sea basin. The Dead Sea is subdivided into two basins, the south very shallow basin and the deep North basin (Fig. 1).
The direct discharge of groundwater into the coastal zone has received increased attention in the last few years as it is now recognized that this process may represent a potentially important pathway for material transport (dissolved solids). Understanding SGD is important for both a component of the general water cycle, potential resource and to coastal environmental management. Generally almost all coastal zones are subject to flow of groundwater either as submarine springs or propagated seepage. In some deep aquifer, which has fractures or other breaches in the overlying, confining layers, allowing groundwater to flow into the sea? The groundwater might be flow directly to the sea wherever a coastal aquifer is connected to the sea, in addition to fresh groundwater from land. The recirculated seawater is driven through bottom sediments by a number of processes might be discharge into the sea. The groundwater seepage near shorelines is result from hydraulic gradients on land and this seepage may contribute to flow further out on the shelf from confined aquifers [1] . Submarine Groundwater Discharge (SGD) in general occurs everywhere through permeable sediments if the hydraulic head of aquifers is above sea level [2,3] .
The term SGD has been used in different ways over the years. SGD was defined by [4] as a direct groundwater outflow across the ocean-land interface into the ocean, which would include re -circulated seawater [5] . Considered SGD to be the sum of net groundwater discharge, outflow due to wave-setupinduced groundwater circulation and outflow due to tidally driven oscillating flow.
According to [6] in the coastal environment, total water discharge into the ocean consists of surface water discharge and SGD. Submarine pore water exchange occurs across the seabed by SGD and submarine groundwater recharge. The water depth, the Rundquist et al. [7] pioneered the idea of using the thermal infrared remote sensing for quantitative analysis of hydrology of flow-through lakes. They obtained the data from Thermal Infrared Multi Spectral (TIMS) airborne scanner in 8.2-12.2 micron range, from NASA National Space Technology Laboratory (NSTL). They selected four lakes in the Sand Hills with greater potential for inference of the zones on intensive groundwater seepage. They detected also the thermal variability and possible groundwater discharge zones to these locations.
The water discharge to the Dead Sea was estimated by [8] by using water balance calculations. They compared the water balance before (predevelopment) and after water resources development. They found that the amount of water that used to flow into the Dead Sea before development was 1980 MM 3 year −1 and after development (present day) is about 617 MM 3 year −1 for the total catchments area of the Dead Sea.
Burnett and Dulaiova [9] compared the results of the ground water discharge, which they obtained by using the continuous measurement of radon-222 for estimating groundwater discharge into the coastal zone with results of other studies in the same area using methods such as radium isotopes (Ra-223, Ra-224) and the automated seepage meters. They found that the results were comparable for the three approaches in the august readings. But in October the radon measurements indicate similar but slightly higher rates of flow than those calculated from the automated seepage meter. The estimate based on radium isotopes indicates a flow about a factor of two greater.
Erica et al. [10] used high-resolution airborne thermal infrared imagery to locate mine pools and discharges in Kettle Creek watershed-Pennsylvania.
The emitted Thermal Infrared Radiation (TIR) was used to measuring surface water temperatures by [11] . These methods were used to evaluate the accuracy of stream and lake radiant temperatures derived from airborne (MASTER, 5-15 m) and satellite (ASTER 90 m, Landsat ETM+60 m resolution) TIR images. They found that agreement between images temperatures and ground temperatures does not always imply that accurate temperatures have been recovered from TIR images. They concluded that an assessment of thermal stratification should be made in any field area before TIR images are use to measure water temperatures.
Shaban et al. [12 ] applied airborne thermal infrared to recognize groundwater discharge along coastal stretch of Lebanon and to compare the results which they got with the results which got by Food and Agriculture Organization (FAO) for the same area and using the same technique. They recognized twentyseven major SGDs. As well they did a correlation between SGDs and geologic controls on the land after doing interpretation of the satellite images. [13] used the thermal images taken by the Advanced Spaceborne Thermal Emission and reflection Radiometer and Reflection Radiometer (ASTER) in order to measure the temperature of the Yugama lake of crater on Kusatsu-Shirane volcano in Jaban. They found that the split-window algorithm applied to ASTER images are suitable for monitoring thermal changes in active volcanic lakes.
Geological settings: Most eastern part of the investigated area is covered by outcropping rocks of cretaceous age. While the west wards, the oldest formations of middle Cambrian are exposed. Close to the Eastern shoreline of the Dead Sea, Triassic and lower cretaceous rock restricted along the shoreline of the Dead Sea. Volcanic eruptions occur in many places Hydrogeological aspects: The bedrock at the Dead Sea area is typically highly fractured at the surface and subsurface extending greater than tens of meter. The fractures are often composed of two sets of fractures at approximately right angles to each other, they may be observed directly in exposed bedrock. These fractures are widely distributed throughout the Dead Sea area.
These fractures are the principal sources of secondary permeability in many bedrock aquifers. The recharge occurs chiefly through these faults and fractures. Then might be serving as paths for groundwater lateral and vertical movements.
Mountains, hills and wadies characterize the topography of the Dead Sea area; the topography of the mountains commonly having steep slopes from east to west toward the Dead Sea coast.
As well the Dead Sea area is characterized by high differences in the hydraulic head. It reaches about 1300 m above the shore of the Dead Sea, which provide the impetus for groundwater movement from the high head to the low head.
The main major aquifer systems within the Dead Sea basin are the upper aquifer Amman/Al Hisa/Wadi Es -Sir (B 2 -A 7 ) system and the lower aquifer system Kurnub and older age sandstone formations (Zarka, Ram and Disi).
Amman Al Hisa Wadi Es -Sir Aquifer system (B 2 -A 7 ) is form one of the most important and extensive aquifer system in the study area. It consists of two formations: The Wadi Es -Sir (A 7 ) and Amman silicifeid limestone (B 2 ). The B 2 and the A 7 formations are hydraulically connected due to its limited lateral extend.
This aquifer outcropping to the east of the Dead Sea area in the areas characterized relatively as high rainfall. The B 2 /A 7 formations consist of limestone, intercalated with laminas of marl. The upper part contains phosphatic limestone and silicified phosphate. The Wadi Ghudran (B 1 ) forms the middle part of this aquifer system consists of marl and chalky marl and consider as a minor aquitard within the system. The thickness of this system is ranging between 170 and 325 m.
The B 2 -A 7 aquifer system receives direct recharge from the rainfall and indirect recharge from the adjacent aquifer and from surrounding areas. But the direct recharge is limited at some areas located farther to the east of the Dead Sea due to the overlying by low permeability strata as Muwaqqar Chalk Formation (B 3 ).
The discharge occurred from the aquifer through the base flow of the wadies, spring flows and subsurface outflow toward the Dead Sea. Some amount leaks downward to recharge the deep aquifer. This aquifer is defined as unsaturated zone at the east of Dead Sea, because it crops out at this area and it is essentially an unconfined aquifer.
Lower Aquifer System This aquifer system includes the sandstone formations from different ages. The formations are Kurnub Sandstone group aquifer from the age of lower cretaceous, lower Zarka sandstone and shale from age of Triassic and Ram group sand stone from Cambrian age. These aquifers are connecting with each other. It crops out along the Dead Sea Shore and in the lower reaches of Wadi Zarqa Ma'in and Wadi Waleh/Heidan. The thickness of this aquifer system is more than 600 m in the north part of the Dead Sea at Wadi Zarka Ma'in area and Wadi Hidan and might reach to about 900 m.
The main component rock constituent of this aquifer is sandstone. The aquifer becomes extremely complex due to shale and clays contents. Because that the permeability are different in lateral and vertical directions. At some local areas lower Zarqa shale and clays form an aquiclude confining the underlying saturated Cambrian sandstone (Umm Ishrin and Disi). But in most of the study area the Zarqa shale and clays is absent from the formation. Therefore the whole sequence can be treated as one hydraulic connected aquifer. This lower aquifer system underlies the most of the study area with total thickness more than 600 m at some areas. As well it is exposed at the area of very low rainfall rates. Then the recharge of this aquifer system from the rainfall is very low and negligible because most of the recharge from the rainfall loss by the evaporation process. Then the main recharge source to this aquifer system is the downward leakage from the upper aquifer system and aquitards at the east of Dead Sea through the weakness zones as faults and fractured present in the A 1-6 . The major outflow from the aquifer takes place along the Dead Sea in the form of springs and seepages from Kurnub sandstone crops out along the Dead Sea shoreline. The main discharge as springs is from Zara and Zarqa Ma'in areas as thermal hot springs. As well the main discharge takes place as subsurface outflow toward the Dead Sea with different directions.
There are two minor aquifers in the Dead Sea area. Na'ur aquifer (A 1-2 ) consists of limestones intercalated with thick sequences of marl. It crops out at the Dead Sea area. This aquifer becomes as aquitard locally in some places to the east of the Dead Sea. The second minor aquifer is Hummar (A 4 ). It consists of dolomitic limestones with a secondary permeability due to the presence of fractures and joints within the limestone consist of this aquifer. Some springs issue from these aquifers to the east of the Dead Sea as Al Zarka spring at the upper of the Zarka Ma'in.
The formations of Fuheis (A 3 ) and Shueib (A 5-6 ) are forming a main aquitards in the area. In some places these include the minor aquifer mentioned above. They separate the Lower main aquifer and upper main aquifer.

MATERIALS AND METHODS
The thermal fingerprint is based on a pronounced thermal gradient between the groundwater and ambient surface conditions. The thermal infrared Imagery is an effective method to quickly assess large-scale areas and acquire information about specific locations of groundwater discharge.
This study exploited an idea of using temperature differences between groundwater and surface water in the Dead Sea to delineate zones of comprehensive groundwater-sea surface water exchanges. The groundwater temperature is relatively stable and it is as an average temperature of the area, while the temperatures of the surface water are changeable with changing the seasons. Thermal infrared only measures surface temperatures so its application is limited to the surface seawater.
To circumscribe the groundwater discharge zones, a thermal infrared survey was flown parallel over the study area at the eastern shoreline of the Dead Sea. The thermal Infrared Imagery was performed using a thermal infrared camera was fixed at the bottom of the small commercial plane. The survey was performing in December 2005 (winter season) and the time was between 19 and 20 h. This time and season were chosen to maximize temperature differentials between the groundwater and sea surface temperatures and to take an advantage of the lack of shadows cover, which can shield an anomaly from the TIR. The survey was performed at 1300-1600 m elevations. The TIR survey consisted high-resolution (4-8 m) imagery depending on the height of the plane. There was about 10-40% TIR image footprint overlap between adjacent flight lines and about 25-40% also footprint overlap between the images along the same flight line. Survey conditions were good for identifying discharge zones: clear sky, ambient air temperature 20-21°C and expected groundwater temperatures of 35°C at Zarka Ma'in, Zara and south Zara areas which have a hot springs and it expected about 26°C at Al-Mujeb and adjacent areas. The coordinates of the images were obtained from a stationary GBS stations. One of these stations was fixed inside the plane top of the thermal camera and the second GBS station was fixed on the ground at the airport. The coordinates were taken continuously from the starting point at the airport to the end point back to the airport.
The thermal infrared imagery was carried out as the following procedures: • The flight paths were drawn down on a georeferenced Land7 satellite image to determine the coordinates for each flight line at the office • The flight elevation from the standard sea level to obtain the require resolution, the overlapping percentage and ground coverage area of the images was determined • An initial site characterized was performed and the study area was reviewed for existing land use and irrigation areas • The thermal camera was prepared and calibrated for the sky temperature and the humidity and sharpness • Then the thermal camera was fixed at the bottom of the plane and the GBSs stations were also fixed After carrying out the Imagery many steps for interpretation and processing were carried out.
• Identification and cataloguing of discharge zones by thermal Imagery • Geological field investigations based on the identification of potential groundwater discharge zones, e.g., fractured zones, lineaments • Each images strip was calibrated relating to the flight elevation, the water temperature, atmo spheric temperature at the flight height and the relative humidity by using the camera software as showed in Fig. 3

RESULTS AND DISCUSSION
The thermal infrared imagery was succeeding to identify the submarine groundwater discharge zones in the Dead Sea area. Because the amount of the water that discharged into the Dead Sea is too large. As well, the difference of the temperature between the groundwater at the area and the surface temperature of the Dead Sea water in wintertime is high enough to recognize by the thermal infrared imagery. In wintertime, the temperature of the groundwater in the Dead Sea surrounding areas is higher than that of the surface water of the Dead Sea itself. As well, the field conditions for the imagery survey were ideal and the resolution of thermal signatures from upwelling groundwater was clear. On the other hand, the surface seawater temperatures were collected at the same time when the thermal infrared imagery was taking. The agreement between the temperatures from the aerial thermal infrared imagery and the temperatures measured directly by using the thermometer were quite good less than 1 centigrade.
The results of the thermal imagery survey indicate that there are groundwater discharge zones into the Dead Sea. These zones are characterized by high temperature compared to other zones where no discharges occur (Fig. 4-6).     Some discharge zones and the coordinates are shown in Table 2.

CONCLUSION
The Dead Sea area is very complicated in view of groundwater discharge. Because of the geological structures of the area. Using thermal infrared imagery was very useful to determine the zones of the groundwater discharge into the sea or the ocean.
Using thermal infrared imagery in the Dead Sea area showed many zones where the groundwater discharges into the eastern shores of the Dead Sea. The main zones of groundwater discharge located at three places. The first zone was at Al-Mujeb area at the southern part of the Dead Sea, the second zone was at Zarka Main area and the third main zone was at Zara area at the middle part of the Dead Sae. As well the thermal infrared imagery was very useful for determining the spring locations.