Exploration Of Groundwater Resources Research Articles

Modeling and analysis of temporal dynamics in groundwater aquifers of New Valley Oases, Egypt

Water scarcity poses a significant challenge in arid and semi-arid regions, necessitating a focused exploration of groundwater resources. Egypt, confronted with various water challenges, particularly in its Western Desert, relies heavily on groundwater as the exclusive water source due to the presence of the Nubian Sandstone aquifer. Effective groundwater management in this region is imperative. This study delves into the hydrogeological characteristics of the Nubian Sandstone aquifer system (NSAS) in the prominent New Valley Oases—Kharga, Dakhla, and Farafra—where agricultural activities heavily depend on groundwater. The primary objective entails a meticulous temporal assessment of the impact of groundwater development on aquifer behavior, groundwater levels, and drawdown. Employing a remote sensing approach, agricultural expansion from 1995 to 2020 was scrutinized. The Visual MODFLOW package served as a robust tool for simulating groundwater flow in the study areas. Noteworthy findings reveal an upward trajectory in agricultural crop areas, escalating by approximately 6% from 1740 km² in 1995 to 1850 km² in 2020. Concurrently, drawdown, influenced by current groundwater extraction, is anticipated to range from 0.5 to 5 meters per year. To ensure the sustainable development of these areas, stringent regulations must be implemented, underscoring the imperative for judicious groundwater management practices. This research underscores the critical need for informed decision-making and proactive measures to address the evolving dynamics of groundwater resources in the New Valley Oases.

Groundwater resource exploration and mapping methods: a review

Groundwater, a vital resource for various human activities and ecosystems, necessitates efficient management and sustainable utilisation. Groundwater potential zone mapping plays a pivotal role in identifying areas where groundwater resources are abundant, thereby aiding decision makers in optimal resource allocation. This review paper presents an in-depth analysis of diverse methods employed for groundwater potential zone mapping, offering a comprehensive overview of their strengths, weaknesses and recent advancements. The review covers traditional methods rooted in hydrogeological principles, as well as modern techniques that harness the power of geospatial technologies and machine learning. Furthermore, the paper explores the integration of remote sensing and geographic information systems for spatial data analysis, emphasising their role in enhancing the accuracy of potential zone mapping. In the context of recent advancements, the review sheds light on the emergence of hybrid methods that combine the strengths of multiple approaches, resulting in improved prediction accuracy and robustness. Challenges associated with each method, such as data quality, model complexity and interpretability, are critically examined, providing insights into the potential limitations and avenues for improvement. The review also emphasises the importance of validation and uncertainty assessment, ensuring the reliability of potential zone mapping results. Finally, this review paper serves as a comprehensive guide for researchers, practitioners and policymakers engaged in groundwater resource management. By offering a holistic understanding of the diverse methods available for groundwater potential zone mapping, this paper contributes to informed decision making and the advancement of sustainable groundwater-management practices.

Groundwater potential assessment in the Blue Nile River catchment, Ethiopia, using geospatial and multi-criteria decision-making techniques

Groundwater supplies have been exploited because of global water shortage. Therefore, effective management of water resources is crucial. Identifying potential groundwater regions in arid and mountainous terrains is challenging for many developing nations because of a lack of financial and human resources. An integrated strategy using remote sensing, geographic information systems, and multi-criteria decision analysis of the hierarchical analytical process was used to identify potential zones for groundwater in the Gulufa Watershed, Blue Nile River Basin, Ethiopia, which covers 1700 km2. Nine groundwater-influencing thematic layers were produced from conventional and satellite data, including lineament density, lithology, slope, geomorphology, soil, land use/land cover, drainage density, rainfall, and elevation. Satty scale values for the thematic layers and their classes were determined based on experts' opinions and literature. Thematic maps were integrated based on their weights and rates to produce a potential zone map using ArcGIS weighted overlay spatial function tool. According to the results, the prospect zone map consists of 383 km2 of very high, 865 km2 of high, 350 km2 of moderate, 58 km2 of low, and 0.3 km2 of poor zones. Validation of the potential zone map using existing boreholes yielded a close agreement, demonstrating the method's accuracy. According to the map removal sensitivity analysis results, the potential zone was more sensitive to lithology than other thematic layers. The map created in the research region can be an essential reference for identifying potential locations for additional groundwater resource exploration, planning, and management.

Aquifer characterization using geophysical and pumping test data in Kericho, Kenya

The exploration of groundwater resources has considerable potential for boosting water supplies in Kericho County, Kenya. However, it is underused due to limited knowledge caused by lack of adequate research in this field. As a way to fill this gap, this study aimed to characterize hydraulic and hydrogeological parameters controlling groundwater occurrence in the Kericho aquifer in Kericho County, Kenya. To achieve this objective, the study utilized a combination of geophysical and pumping test data. Consequently, fifty Vertical Electric Soundings (VES) were carried out to determine the aquifer properties of the study area. Further, seven out of fifty surveyed sites were drilled to depths ranging between 30m and 230m, and test pumping was done for 24 hours. Geophysical results show that the average hydraulic conductivity in the study area varies from 1.96 m day-1 to 6.2 m day-1 . The transmissivity ranged from 35.83 m2 day-1 to 5166.4 m2 day-1 , while the yield ranged between 0.7 and 9.7 M3 /hr. The aquifer hydraulic parameters determined from geophysical and pumping test data were analysed using one-way analysis of variance (ANOVA). The results show no significant difference (p = 0.948151> 0.05) on hydraulic conductivity between geophysical and pumping test methods. Therefore, this study confirmed the reliability of both methodologies for groundwater assessment. Identifying prospective groundwater zones in the research area demonstrates that the combination of these methods is efficient and suited for groundwater exploration. It is suggested that observation wells be added in future studies to allow for the computation of storativity.

Steady-state Assessment of Hydraulic Potential at Water Scarce regions of Agniyar River Basin, India using GMS-MODFLOW

Although the Agniyar river basin, a segment of the Cauvery River basin, hosts a sizable agricultural community whose primary source of income is underground water supply, the area has been experiencing escalating water scarcity for decades. The present research work is carried out to address the lack of a research base in this region and to create a comprehensive groundwater baseline information system for studying the impacts of natural and anthropogenic activities, using GMS MODFLOW with Monte-Carlo simulation-based groundwater level dataset. The model, thus developed, can be calibrated with contemporaneous recharge and discharge data regularly so that the output may be used to make policy decisions in sustainable exploration of groundwater resources. The model also provides the locations of subsurface flood cells which can be potential water harvesting sites. Besides, the present modelling framework can be extended to other water-scarce regions as well.

Sustainability of Groundwater Potential Zones in Coastal Areas of Cuddalore District, Tamil Nadu, South India Using Integrated Approach of Remote Sensing, GIS and AHP Techniques

This paper aims to identify the groundwater-potential zones in coastal zones of the Cuddalore district by integrating remote sensing, Geographic Information System (GIS), and Analytical Hierarchy Process (AHP) techniques. The thematic layers such as geomorphology, landuse/land cover, lineament density, geology, soil, drainage density, rainfall, and slope are considered for the identification of groundwater-potential zones. The groundwater-potential zones are categorized into five zones as ‘very good’, ‘good’, ‘moderate’, ‘poor’, and ‘very poor’. From the study, it is observed that the rainwater/surface water infiltration to the aquifer is high in the eastern region due to flat topography, and thus, these zones possess ‘very good’ and ‘good’ groundwater-potential zones. The groundwater potential in the central region of the study area possesses moderate infiltration capacity, which is suitable for agricultural practices. Moreover, it is also observed that the groundwater potential is ‘poor’ and ‘very poor’ in the northwest region due to steep slopes in which suitable recharge structures should be constructed in these zones to harvest the rainwater. Eventually, the obtained results are validated with existing bore wells in the study area, and it reveals that a GIS-based integrated method is an effective tool for the exploration of groundwater resources with high accuracy.

Investigating fault zone hydraulic properties and groundwater potential in a fault-dominated aquifer system: A case study of the Dili fault in Central Taiwan

Discovering groundwater resources in a fault-controlled aquifer system appears to be a viable solution to water scarcity in the mountainous areas of Taiwan. Regoliths, fractured bedrock, and faults commonly exist in such aquifer systems. To investigate the groundwater behavior in the three subsurface media, a 3-D hybrid model (equivalent porous media/discrete fracture network) involving various in situ investigation techniques (borehole drilling, outcrop investigation, borehole televiewer logging, sonic logging, and downhole hydraulic tests) was proposed to assess the hydraulic properties and groundwater storage of the Dili fault zone of Central Taiwan and its surrounding formations. Subsequently, the model was verified through a case study of a simple fracture network. Based on the validated model, flow path analysis was successfully performed to reveal the hydrogeological role of the fault zone, which acts as a conduit for groundwater flow. To ensure the simulated result regarding the hydraulic properties of the fault zone, this study proposes three additional cross-checking techniques, namely stable water isotopes, derivative plots of pumping test data, and identification of hydraulic gradients. The results of the investigation show that the hydraulic properties of the fault zone obtained by the three approaches are consistent with those determined by the numerical method, and the use of the three cross-checking techniques has been confirmed to be suitable for effectively exploring the hydraulic properties of a fault because the site characterization data are insufficient. Finally, the developed hybrid model was used to calculate the groundwater storage of each geological zone, indicating its great potential for the development of groundwater resources in the study area. Therefore, this study integrates in situ investigation techniques, numerical models, and three evaluation approaches of fault zone hydrogeology to construct a systematic, feasible, and applicable exploration methodology that can be employed for groundwater resource exploration in a fault-dominated aquifer system.

Identification of Groundwater Potential Zones Using Remote Sensing and GIS for Gautam Buddha Nagar

Abstract: With an escalatory growth of human population in the 21st century there has been a significant increase in demand of water for human survival. With the limitation of Surface water sources now ground water that contributes to the total annual supply of water consumption and outshines as one of the major sources. The objective of this paper is to review and analyze the area of Gautam Buddh Nagar, Uttar Pradesh using remote sensing and Geographic Information System for identification of groundwater potential zones. There is various expertise which are used for different water zones for its mapping and its analysis. Parameters like density, soil, land use\cover, geology, drainage, rainfall, contour and terrain are used for controlling groundwater zones. These Groundwater mapping methods are explained and extracted from data sources of satellite images. These techniques include methods which are advance and conventional. For identification and mapping of groundwater potential analysis the thematic layers are used. The significance of each layer is discussed for the location groundwater potential zones using the conditions present. For effective exploration and identification of appropriate locations for water extraction this groundwater potential information will be helpful. For analysis exploration and study of a location remote sensing data is a fast, cost-effective and economical way of doing it. With the Integration of these data for the exploration of groundwater resources has been seen as a breakthrough in the field of its research, and plays a significant role for providing assistance in monitoring, accessing, and preservation of groundwater resources. In the present paper, the assessment of groundwater availability in Gautam Buddha Nagar, Uttar Pradesh, India have been conducted using these techniques. Various maps were prepared like base map, DEM, drainage density map, contour map, land use map, lineament density map and groundwater potential zones using the data of remote sensing and the existing maps. Raster data was transformed from base map and DEM using feature to raster converter tool in ArcGIS 10.3 version

El rol de la exploración geofísica en acuíferos profundos en ambientes semiurbanos y rurales en cuencas de ante arco Andino, caso de estudio en acuífero del río Ñuble, Valle Central de Chile

The hydric resource coming from groundwater has a strategic nature at global scale, within a context of overpopulation and over exploitation of the resource and climate change. Chile doesn’t scape to it, where climate models predict a drought for most of the country, including partially, the agriculture region of the Central Valley between Santiago and Puerto Montt. The adaption process to global change demands the exploration new sources of provisions of this resource, being strategic the one coming from aquifers. To date, the knowledge of these resources is limited to depths below 200 m in each aquifer. However, in the Central Valley between Santiago and Chiloé, the geophysical evidences allow to infer the existence of a thick volcano-sedimentary basin growing in thickness southward well above 500m, with good potential for occurrence of large groundwater resources. 
 The characterization of deep aquifers, 200-1,000 m of depth, demands to have an exploration tool economic, non-invasive, and reliable, able to be applied in semi-urban and rural environments, where the water resource need is higher.
 The geophysical methodologies meet these characteristics and have been applied in Chile and elsewhere as an exploration tool of ground water resources. However, its application have not been described in Andean environments, of large population and/or agro-industrial activity. In consequence, the present work raises a methodological strategy for the characterization of groundwater resources, in particular for the detection of deep resources. We propose the application of a combination of complementary geophysical techniques, including electrical, electromagnetic, and gravimetric methods (to determine the aquifer geometry) along with complementary techniques, like magnetometry, to reduce interpretation ambiguity and , constrained by hydrogeological information and petrophysics of rocks and sediments of the basin and basement. Complementary, we include an analysis of the potential effects of cultural noise and its effects on geophysical observations, given the focus of exploration in semi-urban and rural places.
 With the aim to validate the proposed methodology we use as a case study the aquifer of Ñuble river, in the Ñuble region, Chile. This aquifer properly represents an Andean forearc environment in rural and semi-urban condition, and potentially hosting a deep seated aquifer. The results allow the characterization of an aquifer with hydrogeological potential between 50 and 300-500 depth, overlying a sedimentary basin of more than 1,000 m thickness. The application of the proposed methodology for the exploration of groundwater resources will provide, in consequence, the recognition of a vital relevance resource for the sustainability of Chile during the following decades.

Groundwater potential zones mapping by applying GIS, remote sensing and multi-criteria decision analysis in the Ghiss basin, northern Morocco

The Ghiss watershed, located in a Mediterranean semi-arid area, is currently experiencing a prolonged drought. The scarcity of potable surface water has driven the population and the government to intensify the exploration of groundwater resources. Conventional methods used for groundwater exploration are generally expensive, time-consuming and are limited in space. Therefore, we suggest with the present study the application of geospatial techniques (Geographical Information Systems (GIS) and Remote Sensing) and Multi-criteria decision analysis as a non-conventional and more accessible method of groundwater exploration in the Ghiss basin. Accordingly, eleven factors of high importance concerning the delineation of groundwater potential zones were weighted depending on their relative importance using the Analytical Hierarchy Process's (AHP) pairwise comparison matrix. The GIS-based analysis of multiple thematic layers (drainage density, lineament density, roughness, lithology, land use and land cover, elevation, curvature, topographic wetness index, topographic position index, rainfall and slope) has revealed that “poor” and “moderate” groundwater potential constitute respectively 7% (58.59 km2) and 55% (460.35 km2) of the area, while “good” and “very good” groundwater potential represent respectively 35% (292.95 km2) and only 3% (25.11 km2) of the area. Our model results were validated using depth to water level (DWL) data of the Ghiss watershed and this comparison showed an acceptable conformity (70%) with GWPZs mapped for the Ghiss basin. It was also determined that the degree of conformity to generated GWPZ models using fewer parameters is comparable to those using more parameters. Our results indicate that two parameters (Lineament Density and Lithology) were sufficient to obtain a similar conformity (68%) with depth to water level data.

Groundwater resource exploration & development – Focus on groundwater to support surface water supply in the Lower Olifants River, South Africa

Many South-African towns in the Western Cape Province are dependent on surface water resources to satisfy the ever-increasing water demand. In recent years, the effects of climate change on the environment has challenged these areas continually and recently led to calls for major changes in water management. The Lower Olifants River Water Management Area experienced an extreme drought that persisted from 2016 to 2018, which led to the need for development of groundwater resources. The local economy of the Lower Olifants River is dependent on water releases from the Clanwilliam and Bulshoek Dams, located within the Olifants River Syncline (ORS), where ‘megafault’ zones form preferred flowpaths for groundwater in the Table Mountain Group (TMG) aquifers. The Lower Olifants River Water User Association (LORWUA) was mandated to proceed with the exploration and development of these aquifers to supplement the existing water use of the LORWUA. This will be available during periods of less rainfall and therefore increase the security of the water supplied. The groundwater project aimed at exploring and developing the fractured rock aquifers of the Peninsula (Op) and Skurweberg (Ss) Formations contained within the TMG. Through a high-level desktop assessment, remote sensing investigations and geophysical ground surveys, several target areas and drilling priorities were identified to obtain high borehole yields that access the resource in proximity to existing surface infrastructure. The projected water need from the groundwater resource was 8.6 million cubic metres per annum (Mm3/a). Faults/structure zones were the main hydrogeological targets, with drill target depths of structures planned for intersection deeper than 100 m below ground level (mbgl). Down-hole camera work and initial aquifer testing concluded that deep geological contact zones are prone to collapse when flow is induced in water-bearing fractures. This indicated the need for production borehole construction, even prior to aquifer testing for yield estimates. A major concern still to be resolved is the availability of water in storage and the realistic expectations of the well field over time. Although individual borehole testing provided information on the properties of specific water-bearing structures, long-term monitoring will provide a better understanding of the aquifer in response to abstraction and recovery in times of rest. The operating rules for the conjunctive use of the well field developed, with the existing surface water scheme, is still to be defined and modelled for optimisation, pending long-term monitoring.

Simple method for estimating well yield potential through geostatistical approach in fractured crystalline rock formations

In inland Tanzania, because of the low annual rainfall and poor surface water runoff, increasing the supply of safe drinking water is a major issue. To solve the issue and to design for the drinking water supply at region of fractured zones in crystalline rocks, the simple method is applied to find the relationships between the pumping discharge of drilling wells and the field survey data in the Tabora Region, Tanzania. The field data used included results of electrical resistivity tomography (ERT) survey, electric resistivity borehole logging, the geological column (as geological information) and size of lineaments (as spatial information). A multiple correlation equation developed in this study demonstrates that the pumping discharge of a drilling well can be determined from two surface data sets: ERT survey results and lengths of topographic lineaments. This study also demonstrates that surface hydro-geophysical surveys are highly effective for exploration of groundwater resources in Tabora Region, and thus assist in locating potential drilling sites where water resources are scarce. Application of this equation enables prediction of the well yield potential in developing areas and is expected to increase the water supply in the Tabora Region, where water resource surveys are being conducted. Areas suitable for residential use, which are identified as regions on the application map where the well yield potential exceeds 5 m3hr-1, are found at the northern part of the Tabora Urban and Tabora Rural east and north from Tabora Urban. From the case study in the Tabora Region, this proposed simple method has possibilities to be able to apply for other regions in Tanzania and surrounding countries of Tanzania where are under similar conditions and environments to the Tabora Region.

Delineation of groundwater potential zones in Karha river basin, Maharashtra, India, using AHP and geospatial techniques

Groundwater is a life-sustaining resource catering the daily water requirements of mankind, aids in industrial development, influences agricultural activity, and maintains the ecological balance. The present study was carried out in the Karha river basin, Maharashtra State, having an area of 1314.98 km2. In hydro-geological research, for the exploration of groundwater resources, the integration of remote sensing data and GIS plays a remarkable role in monitoring, assessing, and conserving groundwater resources for water resource management and development. A total ten thematic layers such as geomorphology, geology, land use/land cover, drainage density, slope angle, lineament density, rainfall distribution map, curvature, topographical wetness index, and soil map were integrated into a GIS platform, using the spatial analyst tool in Arc GIS 10.0 to delineate the Ground Water Potential Zones in Karha river basin area. The analytical hierarchy process (AHP) technique is used to determine the weighted value for each parameter and their sub-parameters, based on their relative importance of influencing factors for groundwater recharge. The final groundwater potential zonation map of the study area was categorized into four classes namely, poor, moderate, good, and excellent potential zones. The western part of the basin, particularly in Ghorawadi, Garade, and Saswad regions, have been identified as excellent potential zones for groundwater exploration. The result has shown about 21.96% (285.43 km2) and 28.82% (374.49 km2) of the study area falls under “excellent” and “good” groundwater potential zone, respectively, whereas about 10.81% (140.46 km2) area falls under the poor potential zone.

Deep insight to the complex aquifer and its characteristics from high resolution electrical resistivity tomography and borehole studies for groundwater exploration and development

Discovering and locating the source and availability of groundwater in a plateau region of Chhotanagpur gneissic complex, where there is a varied hydrogeological characteristics, is a crucial task for earth scientists. One such region located at Garh Khatanga near Ranchi, Jharkhand, India was closely studied for groundwater assessment and exploration. High resolution electrical resistivity tomography 2D data were acquired to probe deep inside the earth up to a maximum depth of 220 m using state-of-the-art electrical resistivity tomography technique and mapped geoelectrical subsurface images at 16 sites in three different blocks along a 7.2 km line for prospecting and exploration of groundwater resources. The geophysical inversion of the 2D resistivity data revealed prospect groundwater scenario at six sites based on the hydrogeological interpretation and the significant resistivity contrast between the highly weathered/fractured and the massive rocks. The modelled resistivity sections revealed different degree of weathered, fractured and saturated weathered/fractured strata as well as clearly indicated the presence of a totally hard massive rock within the subsurface lying between ~30 and 220 m depths. The geophysical anomalies were confirmed and validated by borehole drilling at four sites up to a maximum depth of 215 m with yields ranging from 2.0 to 4.25 inch, which is equivalent to 5632–63769 l/hr of groundwater exploitation. These yields of groundwater resources are rated as good aquifer(s) in the plateau region of Chhotanagpur gneissic complex. The characteristics resistivity for fracture zone varies from 140 to 1300 Ωm, while for saturated weathered/fractured it ranges from 10 to 1000 Ωm. On joint interpretation of the 2D resistivity models and the borehole lithology data, it clearly shows the average resistivity of the aquifer zone lies in the range 50–500 Ωm. The present study along with the conceptual geological models provided a sound knowledge of hard rock hydrogeology in the plateau region with complex geological settings and these helped to achieve significant results for groundwater exploration and development of the resources of the studied area as well as take up such challenging work in exploring the prospect groundwater resources in other similar geological setting of the country.

Comparison of AHP and FAHP methods in determining suitable areas for drinking water harvesting in Birjand aquifer. Iran

Due to the decrease in groundwater quality, as a result of irregular exploration of groundwater resources, the recognition of areas for obtaining groundwater suitable for drinking has become an important and significant topic. In this study, two multi-criteria decision making (MCDM) methods were compared to determine suitable areas for drinking water harvest (AHP and FAHP). Also, ten parameters were used for the decision criteria: applied sodium, calcium, magnesium, Nitrate, TDS, SO4, Electrical conductivity (Ec), Chloride (Cl), drawdown(S) and Transmissivity coefficient. Their values were calculated using AHP and FAHP Based on the influence of the value of each parameter on the raster layer, all raster layers in the GIS were merged into two final layers. By comparison, the final layer of the FAHP is more in conformity with reality as compared with the ultimate layer of AHP.

Geophysical assessment of aquifer vulnerability and management: a case study of University of Nigeria, Nsukka, Enugu State

Seventeen vertical electrical soundings and seven electrical resistivity tomography profiles were carried out at the University of Nigeria, Nsukka, Enugu State, Nigeria. The study involves the use of Schlumberger and Wenner electrodes configuration. The thrust of this work is on determining the vulnerability of the hydrogeological units by employing the aquifer vulnerability index (AVI) method. The resistivity data measured were interpreted manually and with computer software packages, which gave the resistivity, depth and thickness for each layer within the maximum current electrodes separation. The hydraulic conductivity (K) and hydraulic resistance (C) of the protective layers estimated from the primary parameters estimated have values ranging from 0.0434 to 0.4890 m day−1 and 38.37 to 1005.84 day−1, respectively. AVI of the study shows that the study area is characterised by low to high AVI with moderate AVI as dominant. This is to help in delineating aquifer protective zones and also possible locations, which further helps in groundwater resource exploration and management.

Identification of Potential Groundwater Zones Using RS and GIS.

Exploration of groundwater resources requires recognition of regions and their potential sources. Because of high importance in the karstic regions and their significant role in providing needed water, efforts to explore new sources of Karst is inevitable. Checking discontinuities is always an important issue in karst studies. Because of high discontinuities in rock masses, permeable areas will be created, they cause appropriate groundwater paths to flow methodology: Recognition of these regions is possible through geophysical methods based on physical characteristics of these areas such as density or resistivity. Using geophysical methods in water and geotechnical methods have less history to oil field investigations and mining exploration but have been accelerated in recent years. Results: In this research, we have tried to investigate the usage of various geophysical methods, such as how to detect and identify underground water using these methods.Conclusion: We can note of geophysical applied methods for groundwater potentiometric such as geoelectric methods, ground penetrating radar, electromagnetic, gravimetry, magnetic and seismic surveys.

Discriminating Weathering Degree by Integrating Optical Sensor and SAR Satellite Images for Potential Mapping of Groundwater Resources in Basement Aquifers of Semiarid Regions

Unlike in coastal and sedimentary basins, regional-scale exploration of groundwater resources using only geophysical methods is costlier in consolidated rocks such as volcanic rocks and crystalline basement complexes in Africa because of the highly heterogeneous structure of aquifers. Therefore, advanced analysis of remotely sensed images and an accurate assessment of groundwater resources are crucial before carrying out a geophysical prospecting survey. This study proposed a joint analysis of satellite images from optical sensors and synthetic aperture radar (SAR) which aimed to enhance potential mapping accuracy of groundwater resources in crystalline rock areas in a semiarid region. The backscattering coefficient of the SAR data analysis effectively detected the zones of relatively high weathering degree and thus having thick permeable regolith. In addition, a modified clay index calculated from the four band reflectances of the optical sensor image—red, near infrared, and two shortwave infrared bands—was applied to discriminate clay-rich zones from high vegetation activity zones. The clay-rich zones detected corresponded with the highly weathered zones estimated from the small SAR backscattering coefficients. The zones also corresponded with a large density of faults and lineaments and furthermore were verified by high potential yields from groundwater wells. The thickness of weathered zones was likely to increase with a decreasing backscattering coefficient and higher modified clay index values. Conversely, large backscattering coefficients in the narrow zones along the major lineaments from large volumetric scattering because of high vegetation activity, as confirmed by the large vegetation index values, suggested that high moisture content was retained in the soils. In fact, the potential yields of the groundwater wells tended to increase near the lineaments. Accordingly, shallow groundwater occurrence is plausible in those zones.

Geologic controls on hydraulic conductivity in a karst-influenced carbonate bedrock groundwater system in southern Ontario, Canada

A large set of hydraulic conductivity values has been integrated with the geologic characterization of a Paleozoic-age carbonate groundwater system to assess the relative influence of specific geologic features on hydraulic conductivity. Three geologic controls are investigated: (1) proximity to bedrock valleys within a regional stress field; (2) carbonate rock texture; and (3) sequence stratigraphic breaks. Results demonstrate that high hydraulic conductivity values do not correlate with a single geological feature, but are associated with various features that have been enhanced by carbonate dissolution. Predicting the spatial distribution of hydraulic conductivity in carbonate rocks requires a regional understanding of the geological history with a conceptualization of where and when waters have interacted with the rocks to dissolve and enhance porosity through geologic time. This investigation focused on a region in southern Ontario, Canada, and concludes with a map identifying the area with the greatest probability of encountering high hydraulic conductivities in the main hydrostratigraphic unit, the Gasport Formation. The map supports the selection of groundwater resource exploration targets for a local municipality. Beyond the local benefits of this work, this investigation offers an approach that can be adopted by practitioners exploring for bedrock groundwater resources or characterizing contaminant transport pathways in complex karst-influenced, carbonate bedrock groundwater systems.

Physical characterization to estimate the hydraulic conductivity of the aquifer case study: wadi Izerzi (Tamanrasset-Algeria)

The groundwater exploitation requires the evaluation of groundwater potentiality of the aquifer, particularly from the various studies such as the study of its physical characteristics. A complete hydrodynamic study requires knowledge of the properties of the aquifer system: its characterizing configuration and structure, functions of the reservoir, and its behavior. The aquifer is a complex interaction of two main functions: the storativity function and the conductivity function. This research is an integral part of a long-term research development and of a short-term operation, typically for medium- and long-term exploration of groundwater resources. In order to achieve this target, a substantial number of well-developed methods of evaluating the hydric potential and statistic calculations are currently being established. It is generally accepted that the method of estimating hydraulic parameters such as hydraulic conductivity of the aquifer is a very effective way, in case it is correlated to the results of the physical properties characterizing this aquifer. The laboratory study has been realized on an adequate sample of the soil from the aquifer by using appropriate techniques, to define its properties such as particle size, porosity, and measurements. For this case study, the physical properties of the aquifer materials are based on analysis of the test results obtained from 18 samples of the soil aquifer material, weighing from 2500 to 3000 g each, with the total mass of about 50 kg. Resulting values of the hydraulic conductivity are quite similar; all of them meet the range of the hydraulic conductivity from medium to coarse sand (8.8 E-05 to 3.27 E-03 m/s), an average value of (1.5 E-3 m/s). Nevertheless, it is possible to show the linear relationship between hydraulic conductivity and other physical properties such as void ratio (e) and the effective diameter (d10) of the aquifer material which its mean values are respectively 52% and 0.52 mm. The hydraulic conductivity of soil depends on a variety of physical factors, including porosity, particle size and distribution, shape of particles, and arrangement of particles. Thus, it is complicated to identify a method to estimate values of hydraulic conductivity yielding a priori reliable ranges of results, when they are compared with results obtained by other methods of in situ measurement and laboratory. However, this method of empirical expression based on the particle size we have used provides satisfactory results.