Hydrogeological Regime Research Articles

Complexity of hydrogeologic regime around an ancient low‐angle thrust fault revealed by multidisciplinary field study

AbstractCo‐located and integrated observation of the surface and subsurface is necessary to characterize fault zone hydrogeology. The spectacular cliff‐face exposure of the Champlain Thrust fault at Lone Rock Point, Vermont, and a nearby well‐field site provides the opportunity for co‐located structural and hydrogeologic field observations. We mapped the prominent structural features of the Champlain Thrust fault and discrete groundwater seeps in outcrop, and also drilled through the fault near the outcrop and determined aquifer parameters from aquifer pumping tests. In outcrop, the fault core thickness varies on the meter scale, splays out into multiple strands, and is offset by a minor normal fault. Groundwater seeps are prevalent in the heavily fractured footwall, but limited in the fault core and hanging wall, suggesting that at the cliff face the water table is generally near the fault core and groundwater flow in the hanging wall is limited. Enrichment of more soluble minerals in cemented fault rock associated with older strands of the fault system may play an important role in localizing karst features in the hanging wall. At the well‐field site, the Champlain Thrust fault is offset significantly by a high‐angle normal fault, the water table is near the surface, and aquifer pumping tests reveal a complex hydrogeologic system, with karst and steep fractures as strong hydraulic conduits in the hanging wall and fault core. The most salient features of the fault zone hydrogeology in the surface and subsurface data are different, but can be integrated into a preliminary conceptual model. Together, the surface and subsurface methods underscore and emphasize the complexity and heterogeneity of the hydrogeology of this low‐angle sedimentary fault.

The contribution of cluster and discriminant analysis to the classification of complex aquifer systems.

This paper presents an innovated method for the discrimination of groundwater samples in common groups representing the hydrogeological units from where they have been pumped. This method proved very efficient even in areas with complex hydrogeological regimes. The proposed method requires chemical analyses of water samples only for major ions, meaning that it is applicable to most of cases worldwide. Another benefit of the method is that it gives a further insight of the aquifer hydrogeochemistry as it provides the ions that are responsible for the discrimination of the group. The procedure begins with cluster analysis of the dataset in order to classify the samples in the corresponding hydrogeological unit. The feasibility of the method is proven from the fact that the samples of volcanic origin were separated into two different clusters, namely the lava units and the pyroclastic-ignimbritic aquifer. The second step is the discriminant analysis of the data which provides the functions that distinguish the groups from each other and the most significant variables that define the hydrochemical composition of the aquifer. The whole procedure was highly successful as the 94.7% of the samples were classified to the correct aquifer system. Finally, the resulted functions can be safely used to categorize samples of either unknown or doubtful origin improving thus the quality and the size of existing hydrochemical databases.

The Chicxulub impact and its different hydrogeological effects on Prehispanic and Colonial settlement in the Yucatan peninsula

The Chicxulub impact ~66 million years ago and subsequent geological processes have created different hydrogeological regimes in the Yucatan peninsula, Mexico. These regimes have affected settlement patterns on local and regional scales. This study focuses on the intersection between three of these regimes; the Buried Ejecta within Saline Intrusion Zone, the Albion Formation, and the Ticul Fault Zone. Lake Chichancanab is located in the intersection between these zones. The Prehispanic settlement east of Chichancanab, in the Cochuah region, is distributed evenly whereas the Colonial period settlement of the same area largely stays within the Buried Ejecta within Saline Intrusion Zone. Colonial socioeconomic conditions and the Church limited the Spanish control of the Cochuah region, partially because groundwater access became increasingly more important during the Colonial period. WIREs Water 2016, 3:871–884. doi: 10.1002/wat2.1170This article is categorized under: Engineering Water > Planning Water Science of Water > Water and Environmental Change Human Water > Water Governance

Hydrogeological Properties of the Rocks in Adansi Mining Area, Ghana

Groundwater is an important resource in the Adansi mining area as some communities in the area are not connected to the Ghana national water network. These communities therefore utilise groundwater for potable water supply. The hydrogeological properties of an aquifer coupled with climatic conditions and geomorphology determines how much groundwater exists in that location. A hydrogeological study of the rocks in the Adansi area was carried out to obtain the aquifer hydraulic properties. Drilling and pumping test analysis information were used to assess these properties. The average borehole depth in the area was 44.3 m whilst the average static water level is 10.75 m. There is a general decrease in yield with an increase in borehole total depth. There is also no strong correlation between aquifer saturated thickness, yield and drawdown. Transmissivity of the aquifer decreases from the phyllite, argillitc sediments, granites to sandstone. Three hydrogeological regimes (> 0.9 m/day, 0.9 – 0.09 m/day and < 0.09 m/day) were also realised based on the hydraulic conductivity. The spatial distribution of the hydraulic properties suggests the influence of geological structures on the occurrence of groundwater in the area. Keywords : Hydrogeological Properties, Mining, Hydraulic, Drilling, Groundwater

A simple, low-cost approach to predicting the hydrogeological consequences of coalfield closure as a basis for best practice in long-term management

The closure of individual coal mines usually entails a cessation of mine dewatering, which can give rise to significant changes in the local and regional hydrogeological regime. Where the last colliery in an entire coalfield closes, these changes can be very large-scale and potentially damaging, with potential for pollution of major rivers and aquifers. While a number of modelling approaches have been developed in recent decades to predict these changes and facilitate their proactive (and prophylactic) management, when the last mine in a given coalfield is closing the mine owners typically have neither the time nor money to commission extended and sophisticated numerical modelling studies. In such circumstances, a simplified, lower-cost approach is required to provide regulators with predictions of rates of water level rise, future equilibrium water levels and the rates and quality of any future outflows of mine water to rivers and/or aquifers. These predictions can also be useful in guiding the decisions of future site owners over alternative uses of colliery infrastructure after the cessation of coal production. An approach to such predictions has been developed which is based on summary information on the extent of workings, dewatering pumping rates, locations and collar elevations of unfilled shafts and adits attached to the deep workings, as well as surface topography and the geometry of any overlying aquifers. Uncertainties over hydraulic gradient after the completion of water level recovery are handled by analogy to a range of post-recovery gradients from similar large coalfields. A brief example of the application of the approach to a real coalfield is presented. This approach could be used either on its own or as a prelude to more detailed modelling and monitoring during the years following mine closure. The insights into system behaviour gained from such exercises could well be valuable in future re-use of flooded voids as resources for heat recovery or disposal as part of low-carbon heating systems.

Regional Geochemistry and Fluid Flow in the Palaeogene Aquifers of the Gaoyou Subbasin in the Southern Part of North Jiangsu Basin, China

AbstractChemical analysis of groundwater in petroliferous basins can be an effective way to determine the regional hydrogeological regime and to evaluate the preservation conditions of hydrocarbons. This paper presents the hydrochemical distribution of both individual aquifers and different structural units within the Palaeogene strata of the Gaoyou subbasin in the North Jiangsu Basin, east China. The results show that the salinity of the Palaeogene aquifers in the Gaoyou subbasin displays a systematic increase from the central deep depression to the periphery areas, and shows a reverse trend as the burial depth increases. Salinity maps of individual aquifers suggest that formation water in the deep layers at the centre of the study area probably retains original features of fresh lake water. Geofluids near the central deep depression of the Gaoyou subbasin migrate vertically through the Zhenwu and Hanliu faults, while those of the northern slope belt mainly flow laterally through aquifers. Both low and high salinity formation water can be found in the hydrocarbon producing areas. The low salinity zones commonly affected by infiltrated meteoric water are unfavourable conditions for the preservation of trapped hydrocarbons.

Hydrogeophysical and structural investigation using VES and TDEM data: A case study at El-Nubariya–Wadi El-Natrun area, west Nile Delta, Egypt

The geoelectric survey includes 93 Vertical Electric Soundings (VES) and 26 TEM stations were conducted to delineate the subsurface structures and hydrogeological regime of El-Nubariya–Wadi El-Natrun area. The VESes AB/2 was varying from 1 up to 700m in successive steps, while TEM stations were measured using coincident loop of 50m side length.The interpretation of the geoelectrical data shows that the depth to the main aquifer ranges from 6m at the northern part near the Nubariya city to about 90m at the southern parts where it increases to the south and southeast directions. Generally the aquifer system in the area can be divided into Pleistocene and Pliocene aquifers. The Pleistocene aquifer is the shallower aquifer in the area and it consists almost of gravelly to clayey sand deposits. The Pliocene aquifer is the main aquifer where it is composed of sand to gravelly sand deposits.Depending on the results of the geoelectric prospecting represented by the true resistivity map, we can infer the quality of the groundwater. A brackish groundwater can be found at the northern and northeastern parts of the study area at shallow depths whereas relatively fresh water can be detected at the southern and southeastern parts around Wadi El Natrun city at deep depths.The area under consideration is affected by a group of normal faults that divided the investigated area into five main divisions, northern, eastern, western, southern and central divisions. The inferred faults from the geoelectric sections are traced and collected to construct a structure map. It is worth to mention that Wadi El Natrun and its lakes are structurally controlled by faulting systems trending NW direction.

Delayed signatures of underground nuclear explosions.

Radionuclide signals from underground nuclear explosions (UNEs) are strongly influenced by the surrounding hydrogeologic regime. One effect of containment is delay of detonation-produced radioxenon reaching the surface as well as lengthening of its period of detectability compared to uncontained explosions. Using a field-scale tracer experiment, we evaluate important transport properties of a former UNE site. We observe the character of signals at the surface due to the migration of gases from the post-detonation chimney under realistic transport conditions. Background radon signals are found to be highly responsive to cavity pressurization suggesting that large local radon anomalies may be an indicator of a clandestine UNE. Computer simulations, using transport properties obtained from the experiment, track radioxenon isotopes in the chimney and their migration to the surface. They show that the chimney surrounded by a fractured containment regime behaves as a leaky chemical reactor regarding its effect on isotopic evolution introducing a dependence on nuclear yield not previously considered. This evolutionary model for radioxenon isotopes is validated by atmospheric observations of radioxenon from a 2013 UNE in the Democratic People’s Republic of Korea (DPRK). Our model produces results similar to isotopic observations with nuclear yields being comparable to seismic estimates.

Relação entre o escoamento de base e os diferentes sistemas hidrogeológicos do Estado de Minas Gerais

Estimativas da separação do escoamento superficial em escoamento superficial direto e escoamento de base são importantes para avaliar, entre outros aspectos, a capacidade de manutenção de vazões em períodos de estiagem e a análise das relações entre o escoamento de base e as classes hidrogeológicas pode contribuir para o entendimento dos processos hidrológicos envolvidos. O presente trabalho objetivou estimar o escoamento de base em oito seções de cursos d’água que caracterizam os sistemas hidrogeológicos do Estado de Minas Gerais. Para isto foi utilizado um filtro numérico de modo a avaliar a relação entre sistemas aquíferos e regime de fluxo d’água. Foram utilizados dados diários de vazão, no intervalo de 01/10/1981 a 30/09/1991. Em todos os casos, o escoamento de base foi responsável por mais de 50% da vazão dos cursos d’água. Os aquíferos compostos por litotipos xistosos, pelíticos e por cobertura detrítica apresentam relação entre o escoamento de base e o escoamento superficial menor do que os demais e, portanto, a mesma classificação estatística. Com base nos resultados apresentados, conclui-se que a hidrogeologia exerce influência indireta na relação entre o escoamento de base e a vazão dos cursos d’água.

The Emperor's Old Clothes: An Inconvenient Truth About Currently Accepted Vapor Intrusion Assessment Methods

The Emperor's Old Clothes: An Inconvenient Truth About Currently Accepted Vapor Intrusion Assessment Methods

The 22 March 2014 Oso landslide, Washington, USA

The Oso, Washington, USA, landslide occurred on the morning of Saturday, 22 March 2014 and claimed the lives of 43 people. The landslide began within an ~200-m-high hillslope comprised of unconsolidated glacial and previous landslide/colluvial deposits; it continued as a debris avalanche/debris flow that rapidly inundated a neighborhood of 35 single-family residences. An intense three-week rainfall that immediately preceded the event most likely played a role in triggering the landslide; and other factors that likely contributed to destabilization of the landslide mass include alteration of the local groundwater recharge and hydrogeological regime from previous landsliding, weakening and alteration of the landslide mass caused by previous landsliding, and changes in stress distribution resulting from removal and deposition of material from earlier landsliding. Field reconnaissance following the event revealed six distinctive zones and several subzones that are characterized on the basis of geomorphic expression, styles of deformation, geologic materials, and the types, size, and orientation of vegetation. Seismic recording of the landslide indicate that the event was marked by several vibration-generating episodes of mass movement. We hypothesize that the landslide occurred in two stages, with the first being a sequential remobilization of existing slide masses from the most recent (2006) landslide and from an ancient slide that triggered a devastating debris avalanche/debris flow. The second stage involved headward extension into previously unfailed material that occurred in response to unloading and redirection of stresses.

Quality characteristics and hydrogeochemistry of irrigation waters from three major olive groves in Greece

Surface and groundwater samples were collected from three key olive grove regions in Greece in order to assess their overall quality and outline major hydrogeochemical characteristics. The three study areas were selected for their significance to the national olive production as well as for their diverse physiographic characteristics and imposed cultivation practices. Results suggest that quality status in general is acceptable with few exceptions; however, issues related with salinization were identified which in turn could potentially lead to environmental degradation. Hydrogeochemical characteristics are affected by geogenic (natural) factors and anthropogenic influences to some extent. Results were confirmed by PoS index which classified samples according to their quality status. Overall, the controlling factors appear to be the geological setup, the hydrogeological regime, as well as the irrational cultivation practices and groundwater overexploitation. Environmental sustainability in the three examined regions is considered feasible on the grounds of a critical balance between environmental protection and production optimization. This balance may be achieved through the implementation of tailored actions and management measures, designed for each of the three cultivated areas and every plot participating in the study.

Identifying the impact of climate and anthropic pressures on karst aquifers using wavelet analysis

This paper assesses the implications of climate and anthropic pressures on short to long-term changes in water resources in a Mediterranean karst using wavelet analysis. This approach was tested on 38-year (1974–2011) hydrogeological time series recorded at the Lez spring (South France), which is exploited for water supply. Firstly, we investigated inter-relationships in the frequency domain by cross-correlation across multiresolution levels. Our results showed that rainfall and spring discharge are highly correlated in the high frequency domain which reflects the hydrogeological response during flood events of typical highly karstified systems. Pumping and groundwater level are correlated in a lower frequency domain, illustrating seasonal to multi-year relationships. Secondly, continuous wavelet transform was applied to characterize the temporal variability of the inter-relationships involved. On the contrary to examples of “non-managed” karst aquifers in the literature, our results showed that the 10-year rainfall component was attenuate in the discharge signal. We assume that the reason is that the storage variations are strongly affected by pumping. This interesting result shows that possible long-term impacts of rainfall variability due to climate change may be masked by a high pumping rate. We showed also that despite an increase of the pumping rate from the 1980s, the stress on the groundwater resource does not increase from year to year. The present pumping strategy does not affect the drawdown in the long term, avoiding an over-exploitation of the aquifer. Finally, this study highlights the effectiveness of wavelet analysis in characterizing the response variability of karst systems where the hydrogeological regime is modified by pumping.

Airborne and ground‐based transient electromagnetic mapping of groundwater salinity in the Machile–Zambezi Basin, southwestern Zambia

ABSTRACTThe geological and morphological evolution of the Kalahari Basin of Southern Africa has given rise to a complex hydrogeological regime that is affected by water quality issues. Among these concerns is the occurrence of saline groundwater. Airborne and ground‐based electromagnetic surveying is an efficient tool for mapping groundwater quality variations and has been used extensively to explore the Kalahari sediments, e.g., in Botswana and Namibia. Recently, airborne and ground‐based mapping of groundwater salinity was conducted in the Machile–Zambezi Basin, southwestern Zambia, using the versatile time‐domain electromagnetic system and WalkTEM system, respectively, incorporating earlier ground‐based ProTEM 47D measurements. The data were inverted using the laterally constrained inversion technique followed by a separate spatially constrained inversion scheme. WalkTEM data were inverted as ordinary single‐site one‐dimensional inversions. The regional electrical resistivity signature of the Machile–Zambezi Basin was found to be characterized by high elevation (1000 m–1050 m above mean sea level), high electrical resistivity (above 100 Ωm) areas that form the western and eastern boundaries of a low‐resistivity (below 13 Ωm) valley that extends southwestwards into the Makgadikgadi salt pans. The electrical resistivity distribution is indicative of a full graben related to the Okavango–Linyati Fault system as a result of propagation of the East African Rift Valley System into Southern Africa. The saline lacustrine sediments infilling the Machile Graben are responsible for the low formation resistivity (below 13 Ωm) and high salinity (above 7000 μS/cm) observed in the groundwater and are probably related to the complex evolutionary history of Palaeo‐Lake Makgadikgadi.

Hydrogeochemical evolution of inland lakes’ water: A study of major element geochemistry in the Wadi El Raiyan depression, Egypt

Wadi El Raiyan is a great depression located southwest of Cairo in the Western Desert of Egypt. Lake Qarun, located north of the study area, is a closed basin with a high evaporation rate. The source of water in the lake is agricultural and municipal drainage from the El Faiyum province. In 1973, Wadi El Raiyan was connected with the agricultural wastewater drainage system of the Faiyum province and received water that exceeded the capacity of Lake Qarun. Two hydrogeological regimes have been established in the area: (i) higher cultivated land and (ii) lower Wadi El Raiyan depression lakes. The agricultural drainage water of the cultivated land has been collected in one main drain (El Wadi Drain) and directed toward the Wadi El Raiyan depression, forming two lakes at different elevations (upper and lower). In the summer of 2012, the major chemical components were studied using data from 36 stations distributed over both hydrogeological regimes in addition to one water sample collected from Bahr Youssef, the main source of freshwater for the Faiyum province. Chemical analyses were made collaboratively. The major ion geochemical evolution of the drainage water recharging the El Raiyan depression was examined. Geochemically, the Bahr Youssef sample is considered the starting point in the geochemical evolution of the studied surface water. In the cultivated area, major-ion chemistry is generally influenced by chemical weathering of rocks and minerals that are associated with anthropogenic inputs, as well as diffuse urban and/or agricultural drainage. In the depression lakes, the water chemistry generally exhibits an evaporation-dependent evolutionary trend that is further modified by cation exchange and precipitation of carbonate minerals.

Geographic Information Systems (GIS) as a tool for interpretation of neotectonics in the Podhale area, Poland

A combination of approaches to the study of neotectonics is discussed. As an example, an analysis is presented for part of the Podhale region, where changes in the hydrogeological regime were observed. Comments are made on the manifestation of geological processes and principles in investigations of neotectonics, due to the results of precise digital terrain modelling (DTM) and geodetic surveys. The results obtained lead the authors to the conclusion that a reliable study on the geological activity of an area evaluated from considerations of river-channel morphology requires attention to changes in spatial development as a factor controlling the intensity of the hydrological regime. In such cases, a database of complex geodata information is required. A geodetic approach is presented, based on GNSS observations that become a new standard in geomorphologic studies. The results of GNSS observations provide quantitative estimates of displacements in the study area and allow assessment of their kinematics. The Liesek1 and Nowy Targ GNSS stations reveal a significant variation in the annual rate of uplift changing from 0.8 to 0.2 mm/yr, respectively. The difference in displacement azimuths (30° at Liesek1 and 300° in Nowy Targ) indicates rotation of the Podhale area. The GNSS-derived dissimilar displacement vectors imply the impact of neotectonic movements on the channel geometry of the Czarny Dunajec River. However, according to the analysis presented, this geometry is strongly influenced by land use and climate, resulting in the incision of river channels in Quaternary sediments. The annual rate of channel indentation reached a mean value of 1.4 cm, and a maximum value 5.5 cm during the studied period from 1965 to 1975. This outcome corresponds to a cumulative effect of neotectonic uplift combined with the results of human activity and climatic changes. Consequently, our study shows that a particular attention must be exercised in drawing conclusions on neotectonic displacements based solely on geomorphological observations.

Groundwater conservation and monitoring activities in the middle Brenta River plain (Veneto Region, Northern Italy): preliminary results about aquifer recharge

In the middle Brenta River plain there is a unconfined aquifer that represents an important groundwater resource in Veneto region. In this area the main groundwater recharge factor is related to the stream seepage: the water dispersion from the Brenta river is active with variable intensity from the foothill to the alignment Nove di Bassano - Cartigliano (Province of Vicenza). In order to mitigate the expected groundwater effects, due to future important waterworks withdrawals provided by the regional water resources management plans, an experimental project of Managed Aquifer Recharge has started, by means of the realization of some river transversal ramps. The construction of pilot works, partially completed, were preceded by a specific hydrogeological monitoring program, aimed to the evaluation of the effectiveness of the MAR actions in terms of comparison between pre-and post-operam conditions. Thanks to the development of a site-specific methodology, aimed to the quantification of the artificial infiltration rate, and after some years of monitoring controls of the hydrological and hydrogeological regimes, it is now possible to evaluate the extent and the rate of the recharge effects in groundwater due to ramps realization. The monitoring plan will be continued in the medium-long term. Some innovative approaches, based for example on the use of groundwater temperature measurements as recharge tracer, will help to validate the preliminary results.

Characterization of Ethiopian mega hydrogeological regimes using GRACE, TRMM and GLDAS datasets

Understanding the spatio-temporal characteristics of water storage changes is crucial for Ethiopia, a country that is facing a range of challenges in water management caused by anthropogenic impacts as well as climate variability. In addition to this, the scarcity of in situ measurements of soil moisture and groundwater, combined with intrinsic “scale limitations” of traditional methods used in hydrological characterization are further limiting the ability to assess water resource distribution in the region. The primary objective of this study is therefore to apply remotely sensed and model data over Ethiopia in order to (i) test the performance of models and remotely sensed data in modeling water resources distribution in un-gauged arid regions of Ethiopia, (ii) analyze the inter-annual and seasonal variability as well as changes in total water storage (TWS) over Ethiopia, (iii) understand the relationship between TWS changes, rainfall, and soil moisture anomalies over the study region, and (iv) identify the relationship between the characteristics of aquifers and TWS changes. The data used in this study includes; monthly gravity field data from the Gravity Recovery And Climate Experiment (GRACE) mission, rainfall data from the Tropical Rainfall Measuring Mission (TRMM), and soil moisture from the Global Land Data Assimilation System (GLDAS) model. Our investigation covers a period of 8years from 2003 to 2011. The results of the study show that the western part and the north-eastern lowlands of Ethiopia experienced decrease in TWS water between 2003–2011, whereas all the other regions gained water during the study period. The impact of rainfall seasonality was also seen in the TWS changes. Applying the statistical method of Principal Component Analysis (PCA) to TWS, soil moisture and rainfall variations indentified the dominant annual water variability in the western, north-western, northern, and central regions, and the dominant seasonal variability in the western, north-western, and the eastern regions. A correlation analysis between TWS and rainfall indicated a minimum time lag of zero to a maximum of six months, whereas no lag is noticeable between soil moisture anomalies and TWS changes. The delay response and correlation coefficient between rainfall and TWS appears to be related to recharge mechanisms, revealing that most regions of Ethiopia receive indirect recharge. Our results also show that the magnitude of TWS changes is higher in the western region and lower in the north-eastern region, and that the elevation influences soil moisture as well as TWS.

Catalog of geothermal play types based on geologic controls

Abstract The key element in the characterization, assessment and development of geothermal energy systems is the resource type. Throughout the past 30 years many resource type schemes and definitions were published, based on temperature and thermodynamic properties. An alternative possibility to cataloging geothermal energy systems is by their geologic characteristics, referred to as geothermal plays. Applied to worldwide case studies, a new catalog is developed based on the effects of geological controls and structural plate tectonic positions on thermal regime and heat flow, hydrogeologic regime, fluid dynamics, fluid chemistry, faults and fractures, stress regime, and lithological sequence. Understanding geologic controls, especially of geothermal plays without surface expression, allows the comparison with hydrocarbon reservoirs through their ratio of porosity and permeability. This analog has implications on site-specific, first class exploration strategies and reservoir improvement through technologies specifically suitable for unconventional sustainable energy reservoirs. This article aims to introduce geothermal plays to a wide geoscientific community and to initiate a geologically based cataloging of geothermal resources. With this new catalog of geothermal plays, it will be ultimately possible to transfer lessons learned not only within one specific catalog type, but also technology from geothermal plays to unconventional hydrocarbon plays and vice versa.

Geophysical evidence for the hydro‐tectonic origin of the Sabkha El Sheikh Zwayed Lake and the shallow fresh water supplies, Northern Sinai, Egypt

ABSTRACTThe El Sheikh Zwayed Lake is a saline lake located in northern Sinai Peninsula. The origin of the lake as well as the shallow fresh water supplies between the lake and the Mediterranean are the subject of many geological, hydrogeological, and geophysical studies. Two main hypotheses have been sug gested to explain the phenomenon of the lake (i.e. hydrogeological and/or tectonic). Using direct current resistivity (DCR) and gravity data, we investigated which of these processes explain the jux taposition and the contradiction between the location of freshwater between the sea and a saline lake to the south which is supplied by a saline aquifer. We infer from the 1D and 2D resistivity inversions that a shallow grabenal structure exists between the lake and the coast. The gravity measurements enable a subsurface NE‐SW doubly plunging anticline to be suggested (and related to Syrian arc system) to the south‐west side of the lake as well as a NE‐SW associated deep inferred fault‐line crossing the lake. The results show that the hydrogeological regime in the study area is tectonically con trolled; whereby the graben structure works as a hydrogeological barrier between the lake and the sea.