Groundwater Potential Evaluation Research Articles

Evaluation of groundwater potential and eco-geological environment quality in Sanjiang Plain of Heilongjiang Province

Evaluation of groundwater potential and eco-geological environment quality in Sanjiang Plain of Heilongjiang Province

Evaluation of Ground Water Potential in Ekpri-Ikang, Bakassi Local Government Area, Cross River State, Nigeria. “A Case Study of Open Bible Standard Church Premises”

Electrical resistivity survey using Schlumberger Vertical Electrical Sounding (VES) field technique was carried out at Ekpri Ikang in Bakassi local government area of Cross River State. The survey is aimed at determining the water bearing formation of the area. Data acquired were interpreted using WinRes Program into a curve showing true resistivity and thickness of the subsurface layers. Result indicates that there are four distinct layers in the study area. Analyses of the data and interpretation of the sounding curve reveals that the water bearing layer exist in the layer two (2) and three (3) with resistivity values of 347.6Ω and 375.5Ω, also with thickness of 14.5m and 21.3m, depth of 39.6m and 61.0m. It is therefore recommended that boreholes for good drinking water be drilled to the layer two (2) and three (3) of the investigated area.

Groundwater Potential Evaluation in a Typical Basement Complex Environment Using GRT Index—A Case Study of Ipinsa-Okeodu Area, near Akure, Nigeria

This study is aimed at evaluating groundwater potential of Ipinsa-Okeodu area, near Akure, Southwestern Nigeria. A multi-criteria model was developed for achieving this aim; the GRT model which is based on geology of each sounding point, resistivity, and thickness of the aquifer across the study area was successfully used to evaluate the aquifer potential of the area for future groundwater development programme in the area. Geophysical investigation involving vertical electrical sounding was carried out across the study area. A total of one hundred and two (102) vertical electrical soundings (VES) data were acquired using Schlumberger array with maximum half-current electrode separation of 150 m. Three to five geoelectric layers were delineated across the study area. The predominant curve types are KH, H, K and A. The maps of aquifer layer resistivity and aquifer layer thickness were generated and synthesized with the geology of the study area in producing the GRT model map/groundwater potential map. The groundwater potential map shows that the area is characterized by five groundwater potential zones; poor, low, moderate, good and high. The northwestern regions, north central and part of the southwestern regions are high groundwater potential zones, the northern and most part of southeastern zone are of moderate potential, while small portion in the southeastern and northern zones are of low groundwater potential.

Evaluation of groundwater potential using geospatial techniques

The issue of unsustainable groundwater utilization is becoming increasingly an evident problem and the key concern for many developing countries. One of the problems is the absence of updated spatial information on the quantity and distribution of groundwater resource. Like the other developing countries, groundwater evaluation in Ethiopia has been usually conducted using field survey which is not feasible in terms of time and resource. This study was conducted in Northern Ethiopia, Wollo Zone, in Gerardo River Catchment district to spatially delineate the groundwater potential areas using geospatial and MCDA tools. To do so, eight major biophysical and environmental factors like geomorphology, lithology, slope, rainfall, land use land cover (LULC), soil, lineament density and drainage density were considered. The sources of these data were satellite image, digital elevation model (DEM), existing thematic maps and metrological station data. Landsat image was used in ERDAS Imagine to drive the LULC of the area, while the geomorphology, soil, and lithology of the area were identified and classified through field survey and digitized from existing maps using the ArcGIS software. The slope, lineament and drainage density of the area were derived from DEM using spatial analysis tools. The rainfall surface map was generated using the thissen polygon interpolation. Finally, after all these thematic maps were organized, weighted value determination for each factor and its field value was computed using IDRSI software. At last, all the factors were integrated together and computed the model using the weighted overlay so that potential groundwater areas were mapped. The findings depicted that the most potential groundwater areas are found in the central and eastern parts of the study area, while the northern and western parts of the Gerado River Catchment have poor potential of groundwater availability. This is mainly due to the cumulative effect of steep topographic and high drainage density. At last, once the potential groundwater areas were identified, cross validation of the resultant model was carefully carried out using existing data of dung wells and bore holes. The point data of dung wells and bore holes were overlaid on groundwater potential suitability map and coincide with the expected values. Generally, from this study, it can be concluded that RS and GIS with the help of MCDA are important tools in monitoring and evaluation of groundwater resource potential areas.

Quality Assessment and Evaluation of Groundwater Potentials in Parts of Buruku and Gboko Local Government Area Councils in Benue State

Hydraulic and layer parameters of groundwater aquifer have been evaluated in parts of Buruku and Gboko local government area councils, for the primary purpose of assessing quality and potential of groundwater in the areas. A total of 18 Vertical Electrical Sounding (VES) stations were occupied along traverse lines using the Schlumberger electrode configuration. The results revealed a characteristic QQA, QHH and QH type curves, with 6 - 7 geoelectric subsurface layers. The geoelectric layers are dominantly sandy with intercalations of shale at shallow depths in most stations. The aquiferous layers were delineated at the fourth and fifth geoelectric layers with average aquifer resistivity and depth of 420.56 Ω·m and 69.1 m, respectively. Groundwater flow is generally from the northeast to the southwest in line with the tectonics of the Benue trough. Two potential groundwater zones were delineated. These are the zone of poor quality water to the north (central) and east of the area of high potential and the zone of quality groundwater to the northeast, west and southwest of low potential. The study revealed that productive boreholes for excellent and sustainable yields were more viable in the northern (central) and eastern parts of the study area than in the northeast, west and southwest parts.

Integrated Landsat Imagery and Geophysical Exploration for Groundwater Potential Evaluation of Okene and Its Environs, Southwestern Nigeria

In this study, an integrated remote sensing and geophysical (aeromagnetic and geo-electric) methods was employed to assess the potential of groundwater in a basement complex terrain of Okene and its environs, Southwestern, Nigeria. Landsat imagery acquired over the study area was processed in the Geographic Information Systems (GIS) environment to delineate the surface lineaments, drainage networks and their orientations. Aeromagnetic data over the area were analyzed and its derivative maps were interpreted to further map the structures and the geology in the subsurface; depths to magnetic sources were determined using spectral analysis. Vertical Electrical Sounding (VES) of geo-electric method was interpreted to map the subsurface geology layers. The results of the integrated data were correlated with borehole yield data of the area for effective interpretation. Delineated lineaments from the azimuth, frequency plot showed dominant trends in the NE-SW and NNE-SSW directions. Radial average power spectrum revealed the depth to magnetic sources between 100 and 2500 m and the interpreted VES data characterized the area into three to four subsurface layers. In correlating the results with borehole yield data, the zones with high lineament density and low/negative magnetic anomaly were categorized as high groundwater potential zones while areas with low lineament density and high/positive magnetic anomaly as low groundwater potential zones. This study will guide efficiently subsequent groundwater drilling program in the study area.

Assessment of groundwater potential zones in an arid region based on catastrophe theory

Evaluation of groundwater potential is a multi-criteria and multi-level comprehensive assessment system that needs judgment of decision makers in making decision. To avoid subjectivity or the preference of decision makers in the assessment, catastrophe theory based evaluation method is proposed in this study which calculates the importance of one criterion over other by its inner mechanism and thus, avoid subjectivity. The proposed method is applied for the assessment of groundwater potential zones in the arid region of lower Balochistan province of Pakistan. The groundwater is considered as a system with five sub-systems namely, geology, soil, drainage density, slope and rainfall. Seventeen sub-system indicators of groundwater potential are selected for modeling groundwater potential zone. The catastrophe theory is applied to derive the relative weights of indicators in predicting groundwater potential. Thematic maps of sub-systems are integrated within a geographical information system and the groundwater potential zones of the integrated layer are calculated by using the weights of indicators. The results are verified by existing number of tube wells operating in the study area. It has been found that the number of tube wells is more in the area where the groundwater potential is high. The study reveals that catastrophe theory is suitable for assessing groundwater potential.

Groundwater potential evaluation of a part of Gidan Kwano campus of The Federal University of Technology, Minna, central Nigeria using geoelectric methods

Groundwater potential evaluation of Gidan Kwano campus of the Federal University of Technology, Minna, Central part of Nigeria was undertaken using Vertical electrical Sounding (VES) to provide information about the subsurface lithology and structures with the aim of evaluating its groundwater potential. A total of 48 VES was made along eight profiles with six sounding stations per profile within an area of about 10km2, using the Schlumberger array configuration. A combination of VES, Horizontal Resistivity Profile and Sounding – Profiling produced a subsurface geological appraisal of the study area. The results of the interpretations of VES data were used to produce the Isopach map of depth to Basement and the Fracture map of the study area. The results and the surface geologic map were found to be closely correlated. Fractures located within the study area coincide with the direction of stream flow suggesting that the drainage system is structurally controlled. The VES curves reveal that the area is generally characterized by three geoelectric layers. The top soil layers thickness ranges from 0.2m to 7.4m. The weathered layer has an average thickness of 0.3m to 58.8m. The mean depth to bedrock was computed as 35m. Out of the 48 VES made, 8 VES stations have been selected as priority locations for the development of groundwater resources. The study area has a very high potential for groundwater development. Despite all the limitations of the VES technique, it has been found to be reliable for groundwater exploration in the Basement Complex terrain particularly when the Schlumberger Configuration and combined with computer - aided interpretation for the survey data.Keywords: Vertical Electrical Sounding (VES), Horizontal Resistivity Profiling (HRP), Sounding-Profiling (Pseudosection), Groundwater Potential.

English

Pumping test was used for the appraisal and evaluation of groundwater potential and design of well. Pumping tests of the calcarious sedimentary rocks of Bhaskar Rao kunta watershed area were carried out for twenty five selected bore wells for quantitative understanding of the groundwater for crop water requirement and groundwater use efficiency. The tests were carried out independently for short duration under constant rate conditions. The acquisition of the drawdown data was interpreted by Jacob straight line method. The results of transmissivity vary from 2.67 to 236.9 m2/day with mean of 37 m2/day, whereas the specific capacity varies from 5.47 to 451.63 m3/d/m with a mean of 76 m3/d/m. Spatial variation of transmissivity values was further analyzed using statistical testing and Krasny’s classification systems; from the results of the statistical testing, 72% of the wells were under covered background transmissivity anomalies; 12% under positive anomalies; 8%, negative anomalies and remaining 8%, positive extreme anomalies. From the results of Krasny’s classification system, 12% of the wells was under  high magnitude (withdrawals of lesser regional importance), 40% of wells was under intermediate magnitude (withdrawals for local water supply), 48% was under low magnitude (smaller withdrawals for local water supply) and 100% of the wells was under covered moderate variations (fairly heterogeneous hydrogeological environment). Spatial variation of transmissivity magnitude and variation was identified as best useful in management practices. Key words:  Transmissivity, magnitude, variation, statistical testing, Krasny’s classification.

Groundwater Potential Evaluation of College of Engineering, Afe Babalola University, Ado-Ekiti, Southwestern Nigeria

Availability of water for daily activities has constituted serious challenge at the College of Engineering, Afe Babalola University, Ado-Ekiti. Hence, geophysical study of the College was conducted to investigate its groundwater potential with a view to proffer solution to water availability in the study area. Profiling and Vertical electrical sounding methods were employed using Dipole - Dipole and Schlumberger configuration respectively. Eight points were sounded along three traverses and one profile was occupied. Five different subsurface lithologic units were established namely; lateritic topsoil, sandy-clay, weathered basement, fractured basement and, fresh basement. The curve types range between simple K, H to complex HA, HK and KH. The topsoil, sandy-clay and weathered basement materials are characterised with relatively low resistivity values while the fresh basement materials are characterized with high resistivity values. The average resistivity and thickness values for the topsoil are 178Ωm and 1.0m respectively. Sandy-clay was encountered in six locations with average resistivity and thickness values of 23Ωm and 7.0m respectively. Weathered basement was encountered in six locations with average resistivity and thickness values of 231Ωm and 8.0m respectively. Fractured basement was encountered in four locations with average resistivity and depth to the top of fracture values of 294Ωm and 18.0m respectively. Basement is relatively shallow in the study area, it was encountered in three locations and the average resistivity and depth values to the top of basement are 1000Ωm, and 11.0m respectively. Overburden thickness was established in six locations with an average value of 11.0m. The combination of overburden materials with the fractured basement constitutes aquiferous units within the study area. The groundwater potential of the area is rated as medium with VES 2 and 5 more promising.

Delineating Aquifer Systems Using Dar Zarouk Parameters Determined from Surface Geoelectric Survey: Case Study of Okigwe District, Southeastern Nigeria

This study is aimed at delineating the aquifer systems in the study area and hence determining the parts with higher aquifer yield. To achieve this, 120 Vertical Electrical Soundings (VES) were carried out in Okigwe District of Imo State of Nigeria, using the Schlumberger electrode array and a maximum electrode spread of 900 m. Twelve of the VES stations were sited near existing boreholes to enhance interpretation. The resistivity of the aquifers zones varied across the study area. The highest thickness of 104.4m for the aquifer was recorded at Amonze (VES 95). Using an average transmissivity of 1032.0848 m2/day determined from pumping test data of the boreholes in the area, a mean conductance value of 91.222 m/day was obtained for the area. The hydraulic conductivity values obtained from the VES results varied from 9.8854 to 115.9646 m/day. The transmissivity values ranged from 992.04 to 10388m2/day. The storativity or storage coefficient determined for the area ranged from 1.59x10-4 to 7.80x10-3 while the specific capacity was fairly uniform with magnitude of about 877 m3/day. Using Dar Zarrouk parameters determined for the area, three aquifer systems had been identified viz: the Coastal plain sands aquifer, the Bende-Ameki sandstone/shale aquifer and the Ajali sandstone aquifer. The coastal plain sands aquifer serves the Southern part of Isiala Mbano, Ehime Mbano, Ihitte Uboma and the entire Obowo Local Government Areas (LGAs). The Bende-Ameki sandstone aquifer serves part of Ihitte Uboma, the Northern part of Ehime Mbano and Isiala Mbano. The Ajali sandstone aquifer serves the Northwestern part of the study area in Okigwe. Groundwater potential evaluation of the district based on the survey and borehole hydrogeological information revealed that the Southern part of the district is the most prolific in terms of groundwater exploitation and thus the most promising for siting productive boreholes.

Evaluation of Groundwater Potential of Baikin Ondo State Nigeria Using Resistivity and Magnetic Techniques: A Case Study

A combined electrical resistivity and Magnetic surveys was carried out to locate fissured zones and associated groundwater-bearing media at Baikin Area in Ondo State, Nigeria that is known to have acute groundwater supply shortage. One Hundred (100) Vertical Electrical Soundings were acquired along ten traverses using the Schlumberger array with maximum half current electrode spacing (AB/2) of 200 m. Magnetic data were acquired along the traverses at station interval of 10 m using the Proton Precession Magnetometer. Four geologic layers were delineated. These include the topsoil, weathered layer, fractured basement and fresh basement bedrock. The thickness of the topsoil ranged from 0.2 to 1.1 m while the resistivity values varied from 29 to 455 Ωm. The weathered layer thickness varied between 0.2 and 12.6 m while its resistivity ranged between 13 and 307 Ωm. The fractured basement delineated had resistivity value of 61 Ωm. The fresh basement resistivity ranged between 941 and α Ωm. The overburden thickness ranged between 1.1 and 12.9 m. The weathered and fractured aquifers constituted the main aquifer units. Aquifer thickness varied between 0.2 and 12.6 m. Quasi 3D magnetic models also showed that depth to bedrock in the study area was shallow. The study concluded that the groundwater potential of Baikin Area was generally low.

Geoelectrical evaluation of groundwater potentials of Bwari basement area, Central Nigeria

An investigation has been made of the groundwater potentials of Bwari basement area using solely geoelectric surveys. Twenty vertical electrical soundings along different transverses were conducted with maximum electrode spacing of 300 m. The results revealed that the area is characterized with 3 to 6 geoelectric subsurface layers with variability in resistivities and thicknesses of the different layers. The overburden thickness ranged from 6.9 to 72.9 m, with thinnest and thickest overburden observed at the central and western areas respectively. Dar Zarouk parameters (transverse resistance and coefficient of anisotropy), reflection coefficient, resistivity contrast, weathered layer thickness and overburden thickness were used as indices for evaluation of groundwater potentials. The area’s groundwater productivity potential was hence, classified into two zones namely; high and low. This study has revealed that no single factor (index) determines the groundwater productivity potential but a combination of two or more factors. For example, not all the areas with thick overburden or high weathered layer thickness correspond to high groundwater potential. Key words: Groundwater potential, electrical resistivity, transverse resistance, coefficient of anisotropy, Bwari.

Geoelectric Investigation of the Hydraulic Properties of the Aquiferous Zones for Evaluation of Groundwater Potentials in the Complex Geological Area of Imo State, Nigeria

Geoelectric Investigation of the Hydraulic Properties of the Aquiferous Zones for Evaluation of Groundwater Potentials in the Complex Geological Area of Imo State, Nigeria

Evaluation of Groundwater Potentials of the Calabar Coastal Aquifers

This article presents the results of groundwater site evaluation scheme and quality assessment of coastal aquifers in Calabar, South-eastern Nigeria based on ground water potential index (GWPI) scale, developed for this study. The GWPI consists of ten input parameters, namely: lithofacies (L), aquifer thickness (b), transmissivity (T), storativity (S), specific capacity (SC), static water level (SWL), formation resistivity (FR), chloride (Cl) contents, total dissolved solids (TDS) and Escherichia coli (E-coli). The groundwater potential index (GWPI) is computed as the sum of the products of weights and ratings assigned to each of the input parameters. The GWPI index varying between 20 and 60, is divided into three classes: high (> 40), medium (30-40), and low (< 30). The GWPI index, is then used to demarcate the study area into three hydrogeologic ground water potential zones. These are: (i) Northern zone 1 (transitional, low GWPI) (ii) Central zone 2 (coastal plain sands, high GWPI) (iii) Southern zone 3 (coastal alluvium, medium GWPI). The central zone 2 has the highest GWPI rating. The implication of this rating is that the aquifers in the central and southern zones 2 and 3 are more prolific water bearing than the transitional zone 1 that lies between the Coastal Plain Sands and the argillaceous sediments of the Calabar Flank. This is in agreement with the mean specific capacity (SC) and transmissivity (T) recorded for the central (355.6 m3/d/m, 2640 m2/d); southern (150.0 m3/d/m; 2150 m2/d) and northern (52.1 m3/d/m, 750 m2/d) zones respectively. Lithofacies, saturated thickness of the aquifer, static water level, transmissivity and storativity are the most important parameters which influence ground water availability in the study area. The GWPI results further reveal that E-coli (3-50counts/100ml), chloride (Cl-) (2.5-21.0mg/l) and static water level (SWL) (2.3-28.7m) remain the most significant parameters that contribute to groundwater pollution particularly in the southern zone of the study area. In the near future, water quality in aquifer will be affected due to poor management of human waste-disposal/salt water intrusion, thereby limiting the availability of potable water for domestic and industrial uses.

Very low frequency electromagnetic (VLF-EM) and electrical resistivity (ER) investigation for groundwater potential evaluation in a complex geological terrain around the Ijebu-Ode transition zone, southwestern Nigeria

Groundwater exploration in either a basement or sedimentary environment is often fairly well defined and focuses on delineating weathered/fractured rocks or saturated formations, respectively. Conversely, unique geological structures, the complex coexistence of different rock types and poorly defined basal/lateral contacts between basement and sedimentary rocks make groundwater development in a geological transition environment very challenging. Ijebu-Ode and its environs lie within such a problematic transition zone, between the Precambrian basement rocks and Cretaceous sediments of the Dahomey Basin, in southwestern Nigeria, where associated acute groundwater development challenges require adequate subsurface information to maximize its groundwater resource potential. This study integrated very low frequency electromagnetic (VLF-EM) and electrical resistivity (ER) geophysical prospecting techniques for a detailed terrain study of Ijebu-Ode in order to establish the reasons for the low groundwater resource potential in the area. Thirty five VLF-EM profiles, 140 vertical electrical soundings (VES) and relevant hydrogeological data were acquired along grids and profiles. Data were filtered, inverted and enhanced using appropriate software packages. The current density and geoelectric parameters of the VLF-EM and VES data were employed to generate terrain maps, the conductivity distribution and a subsurface basement model of the study area. Current density plots and geoelectric parameters identified up to three layers in the basement complex terrain which comprised lateritic topsoil, weathered basement and fresh basement rocks. The five layers encountered in the sedimentary terrain were topsoil, a lateritic unit, a dry sandy unit, a saturated sandy unit and fresh basement rocks. The hydraulic conductivity of the thick (3–18 m) lateritic unit was determined to be 1.32 × 10−5 mm s−1, while that of the underlying sandy units ranged from 2.65 × 10−4 to 1.36 × 10−3 mm s−1. The thick but less permeable lateritic unit which overlaid the more permeable rocks constituted a partial impermeable overburden that prevented an adequate groundwater recharge during and immediately after rainfall. Three zones were delineated as low, medium and high groundwater resource potential areas, located in the northern, central and southern part of the study area, respectively. The low groundwater resource potential around Ijebu-Ode is due to the less permeable lateritic overburden, which prevents an adequate recharge during rainfall and the rugged/undulating basement topography that controls the distribution and storage of the limited recharged water. The southern part of the study area can be developed to meet the water needs of the inhabitants.

Correlation of Self Potential (SP) and Resitivity Survey Methods for Evaluation of Groundwater Potentials: Case Study of Imo State, Nigeria

A total of seventeen vertical electric surroundings were carried out in Mbaitolu Local Government Area (L.G.A) of Imo State Nigeria, during which apparent resistivity and SP values were simultaneously measured. The field curves obtained reveals a multilayered earth with series of crest and trough for all the sounding stations. VES 6 showed only positive maxima and minima. The distribution of SP values for electrode spacing AB/2 = 100m divides the area into two zones of positive and negative potentials respectively. The anomaly high areas are those of favourable aquifer which form discharge zones with strong lateral flow and high aquifer thickness and transmissivity. Anomaly low areas correspond to areas of infiltration. The depth to aquifer determined from SP survey ranged from 40m to 115m and correlated fairly well with those obtained from resistivity result in 16 out of the 17 stations. The distribution of equipotential lines shown by the contour map divides the area into two zones by a zero potential line suggesting a possible ground water divided in terms of water quality or geologic setting or both. The cross-correlation coefficient computed statistically for each pair of depth points gave correlation significance at the 0.01 level, which validates the results.

Groundwater assessment in Salboni Block, West Bengal (India) using remote sensing, geographical information system and multi-criteria decision analysis techniques

An approach is presented for the evaluation of groundwater potential using remote sensing, geographic information system, geoelectrical, and multi-criteria decision analysis techniques. The approach divides the available hydrologic and hydrogeologic data into two groups, exogenous (hydrologic) and endogenous (subsurface). A case study in Salboni Block, West Bengal (India), uses six thematic layers of exogenous parameters and four thematic layers of endogenous parameters. These thematic layers and their features were assigned suitable weights which were normalized by analytic hierarchy process and eigenvector techniques. The layers were then integrated using ArcGIS software to generate two groundwater potential maps. The hydrologic parameters-based groundwater potential zone map indicated that the ‘good’ groundwater potential zone covers 27.14% of the area, the ‘moderate’ zone 45.33%, and the ‘poor’ zone 27.53%. A comparison of this map with the groundwater potential map based on subsurface parameters revealed that the hydrologic parameters-based map accurately delineates groundwater potential zones in about 59% of the area, and hence it is dependable to a certain extent. More than 80% of the study area has moderate-to-poor groundwater potential, which necessitates efficient groundwater management for long-term water security. Overall, the integrated technique is useful for the assessment of groundwater resources at a basin or sub-basin scale.

Groundwater potential evaluation using electrical resistivity method in a typical basement complex area of Nigeria

A geophysical survey employing the electrical resistivity method was carried out within the permanent site of the University of Agriculture, Abeokuta (UNAAB), Ogun state, Southwestern Nigeria. Atotal of 46 Schlumberger vertical electrical sounding (VES) stations were occupied using the ABEM Terrameter SAS 300B model with maximum inter-electrode spacing (AB) of 200m. The aquifer unitsare characterized by sand, sandy clay/clayey sand, weathered and fractured rocks. The plot of the aquifer resistivity against the coefficient of anisotropy shows that the basement in the study area is underlain by three types of rocks: Quartzite with aquifer resistivity in the range of 50 – 430
m and coefficient of anisotropy between 1.01 and 1.18. This weathered mainly to sand with good to high groundwater yield; Granite-gneiss with aquifer resistivity in the range of 40 – 90
m and coefficient of anisotropy of between 1.18 and 1.88. This weathered to a mixture of clay and sand with low to medium groundwater yield; Mica-schist with aquifer resistivity in the range of 16 – 40
m and coefficient of anisotropy of between 1.3 and 2.3. This weathered into more of clay because of its high ferromagnetic mineral content and as such has zero to very poor groundwater yield.

Hydrogeological interpretation and potential of the new magnetic resonance sounding (MRS) method

This study reviews the up-to-date hydrogeological contribution of the new, geophysical magnetic resonance sounding (MRS) method and presents new interpretation ideas and potential regarding various hydrogeological applications. The main advantage of the MRS method as compared to other geophysical methods is in its water selectivity. MRS is commercially available but is also the subject of R & D to minimize a number of limitations related not only to data acquisition but also to hydrogeological data interpretation. The two main MRS output data types are free water content ( Φ MRS) and decay time constant ( T d). Relations between Φ MRS and effective porosity, specific yield and specific storage are discussed in the framework of an original groundwater storage concept. T d is correlated empirically with hydraulic conductivity, however such correlation is not yet quantified for various rock types so T d has to be calibrated by borehole data. As an improvement of the data interpretation, a proposal of a new, multi-decay approach is presented. The advantage of such analysis is that it combines storage and flow property characteristics in assessing water content at various pore size fractions, and the disadvantage is that it is applicable only at large signal to noise ratios. Five case examples are used to show that combined interpretation of Φ MRS and T d can be used to evaluate subsurface hydrostratigraphy although such analysis is vulnerable to equivalence error and its resolution decreases with depth. MRS with large volume-averaging schema and current limitation to 1D approach is already suitable for groundwater modelling applications and for evaluation of groundwater potential in the MRS measurement scale (∼100×100 m 2) but is not yet optimized for well siting. MRS can detect water in the unsaturated zone, which can be potentially used in real time subsurface flux monitoring. Field experiments indicate that MRS is not appropriate for groundwater salinity detection. No field experiments have yet been made to detect hydrogenated compounds like hydrocarbons and tracers in the subsurface.