Jordan is located in an arid to semi-arid region with variable topography features. The far western part of the country is mountainous terrains, while the eastern and southeastern parts are dominated by flat-desert terrains. Due to these topographic variations, rainfall distribution varies considerably. The annual rainfall intensity ranges from 600 mm in the northwest to less than 50 mm in eastern and southern parts of the country [1] . Jordan is suffering from scarcity and shortage of water resources. The available per capita water resources are projected to decline from about 150 m³/year to only 90 m³/year by the year 2020, putting Jordan in the category of absolute water shortage [2] . The political situations in the region, especially the recent waves of Syrian refugees have added an extra pressure on the natural resources and in particular the water resources. During winter times, the eastern and desert areas received extensive rain storms and monsoons, by which, a large quantity of surface water are drained through wadis and spread over low lands, surface and flat areas and eventually lost to evaporation. In recent years, several studies have been conducted on water harvesting and capturing surface water in dams in the eastern and northeastern Jordan (e.g. [3] - [6] ). During the last four decades, the groundwater table has declined dramatically due to the extensive pumping (either for domestic and agricultural activities). Groundwater artificial recharge is an effective technique to fill aquifers using different types of water, and to augment ground- water level. It has many advantages over water harvesting, as it is less affected by the climatic conditions and evaporation. In addition, the recharged water is subjected to self-purification (natural attenuation) which will be enhanced naturally through percolation. Groundwater artificial recharge studies have been done using different geophysical and GIS techniques in several areas worldwide as well as in Jordan (e.g. [4] [7] - [13] ).

TDEM technique has been previously used in numerous hydrogeological applications (e.g. [14] - [21] ). In this study, the TDEM technique and hydrological study were integrated to investigate the potentials for artificial groundwater recharge at the dam downstream area of at Alasra Dam site as a tool for conservation of the harvested and flooding water to be used at times of dry and hot summer seasons.

The investigated area- which is part of Jordan’s eastern plateau - is located in the northwestern part of Azraq basin between [480000 - 492000] E, [550000 - 575000] N according to Jordan Transverse Mercator (JTM) (Figure 1). Relief topography of Alasra watershed area shows that the elevations are ranging from 740 - 1000 m above sea level (masl). The average annual rainfall varies from 70 mm in the far eastern and southern part of the study area to about 150 mm in the northwestern part. The temperature may reaches more than 40˚C during summer days and drops to a few degrees below zero in winter, especially during the night [1] . The relative humidity in eastern plateau is low. In winter, it is generally around 50% - 60% and drops to 15% in summer [1] . The potential evaporation rates increase east and south-wards directions and may exceed 4000 mm/y in the center of plateau [1] .

The geological setting of Neogene continental basalts exposed at NE-Jordan have been investigated by several researchers (e.g. [22] - [35] ). The study area is part of Harrat ash-sham Basalts super Group and forms the northern extension of Arabian Volcanic province [35] . A brief description of the major geological formations found in the study area (Figure 2) can be summarized as follows [35] [36] .

TDEM’s sounding points have been individually interpreted as a 1-D layering model using the available surface and subsurface geological information and the static water level map of basaltic aquifer (Figure 4(a) and Figure 4(b)). Table 2 lists the multi-layering model interpretation for each TDEM sounding point. Figures 5-7 show N-S 2-D resistivity cross-sections and Figures 8-10 show an E-W 2-D resistivity cross-section over the investigated area. In order to facilitate the geological interpretations, the inverted models were typically represented in thematic maps and cross-sections [40] . The resistivity distributions at selected depths (20 m, 75 m and 120 m) are outlined in Figures 11-13 respectively. Figure 14 shows a 3-D resistivity visualization model of TDEM’s results. The TDEM’s results suggest three principal subsurface layers. The top surface layer has intermediate resistivity values which could be attributed to super facial deposits such as alluvial mud flat (Alm), alluvial fans (Alf), wadi deposits and clay intercalated with basalt boulders. The thickness of this layer is ranging from a few meters to around 50 m at TDEM-8 and TDEM-4 (Figure 7 and Figure 5). The second subsurface layer has high resistivity values and is composed of unsaturated massive basalt layer. It could belong to MOB of Asfar Group. It is characterized by a variable thickness as shown in different 2-D cross-sections. For instance, it has a thickness of about 100 - 110 m at TDEM-4 (Figure 5 and Figure 8), 70 m at TDEM-5 (Figure 6 and Figure 8), and 80 m at TDEM-8 (Figure 10). Moreover, significant lateral variations in the resistivity of this layer were apparent. It has a resistivity of 90 - 100 Ω∙m at TDEM-1, TDEM-2 (Figure 5), TDEM-7 (Figure 6), TDEM-9 and TDEM-10 (Figure 7) and it was identified as an intermediate resistivity zone composed of basalt with higher

degree of saturation. Additionally, it was found that the same layer has a resistivity of 1000 Ω∙m at TDEM-3 and TDEM-4 (Figure 5), TDEM-5 and TDEM-6 (Figure 6) and TDEM-8 (Figure 7). The large variation in resistivity could be ascribed to the degree water saturation as a result of groundwater recharge from the nearby harvested water dam, or due to lithological variations (clay content) or structural control. The third subsurface layer was with low resistivity values and observed in the majority of TDEM’s soundings and the bottom of the hydro-geophysical cross-sections (Figures 5-10). It was also observed in the 3-D model visualization (Figure 14). This layer was found at depths ranging from 120 to 150 m below ground surface in the investigated area, and has resistivity values ranging from <10 Ω∙m to 40 Ω∙m. This layer could be interpreted as a saturated basalt layer and/or containing high ratio of clay. In addition, several lenses-like zones have been identified with different resistivities at different depths, which reflect the nature of basalt flow successions and subsurface structures.

There is probably a significant NNW-SSE fault identified at different cross-sections, between TDEM-7 and TDEM-8 (Figure 10), between TDEM-6 and TDEM-9 (Figure 9), and between TDEM-5 and TDEM-10 (Figure 8). It can be seen also in the thematic maps (Figures 11-13). This fault is extending along the course of the downstream valley of Alasra dam site. Moreover, it could be the extension of the well-known Fuluq fault when compared with the surface geological map (Figure 2). This fault is likely to play an important role in groundwater recharge through percolation of surface water into the groundwater aquifer through conduits and fractures. A principal NW-SE fault is probably found between the TDEM-9 and TDEM-10 soundings (Figure 7), between TDEM-6 and TDEM-7 (Figure 6), and below TDEM-2 (Figure 5). It can also be seen in the the-

matic maps at different depths (Figure 12 and Figure 13). A NE-SW fault extending over the investigated area has been identified and is clearly shown in thematic maps (Figures 11-13).

There are several artificial groundwater techniques that have been developed and applied in various parts of the world. The description of these methods is mentioned in [41] - [43] . Based on the resulted hydro-geophysical models, structural pattern and interpreted multi-layering models at downstream of Alasra dam site, the techniques that could be utilized within the study area are:

1) Direct Surface Recharge: It is the simplest and most widely applied technique. In this method, water moves from the land surface to the aquifer by means of percolation through the soil. It has relatively low construction costs and is easy to operate and maintain. However, this technique cannot be applied in the study area for the following reasons:

a) It requires longer time for the recharge water to reach the aquifer. This might lead to evaporation problem, especially in arid environment as that of the study area, where the evaporation rate is high.

b) The groundwater aquifer in the study area is deep (above 150 m) which means that the surface water will need more time to reach the groundwater.

c) There are indications of a clay layer above the water table in the study area which prevents the groundwater

recharge using such technique.

2) Direct Subsurface Recharge: This technique is used for recharging deeper aquifers which is the case within the study area. It is based on digging injection wells when aquifers are deep and separated from the land surface by low permeability materials. This technique is expensive but might be a solution to replenish groundwater in the study area. The problem with the clay layer above the groundwater table can be overcome by digging injection wells to penetrate this layer and establish a path between surface and the groundwater.

3) Combining Surface-Subsurface Methods: Both techniques mentioned above could be combined to have a better groundwater recharge. The surface water dam in the area could help in applying a direct surface recharge through the wadi bed. Also, having injection wells close to the dam will accelerate and maximize the potentials for replenishing the groundwater in the area.

This research was carried out by Hani Al-Amoush while on sabbatical leave from Al al-Bayt University for the academic year (2015/2016). The authors would like to thank Al al-Bayt university presidency, the dean of Institute of Earth and Environmental Sciences. The authors also acknowledge the help and supports of the dean and staff of The Scientific Research Deanship at Al al-Bayt University. Critical and constructive review of the manuscript by the reviewers is greatly treasured.

Hani Al-Amoush,Abdel Rahman Al-Shabeeb,Saad Al-Ayyash,Rida Al-Adamat,Majed Ibrahim,A’kif Al-Fugara,Jaafar Abu Rajab, (2016) Geophysical and Hydrological Investigations of the Northern Wadis Area of Azraq Basin for Groundwater Artificial Recharge Purposes. International Journal of Geosciences,07,744-760. doi: 10.4236/ijg.2016.75057