Aquifer Layer Research Articles

Deployment of Geophysical Technique in Groundwater Search at Guinueaworm Endermic areas in Obubra local government area of cross river state, Nigeria

This study was conducted in the Guineaworm prone areas in Obubra Local Government Area, the study entails the deployment of vertical electrical sounding technique in the search for groundwater. In doing this, measurement was made in 14 profiles of 500m long each, using the IGIS resistivity meter model SSR-MP-ATS. Resist software was used for analysis. The Geoelectric sounding data interpretation revealed characteristic curves with two to six geoelectric layer thicknesses. The predominant curve types in the area were the KH, HKH, and HK. The electrical resistivity of the first layer ranged between 15.8to1626Ωm, which was indicative of clay, shale, or sandy silt, three to six geoelectric layers were obtained from the interpretation of the sounding data. The resistivity of the second layer ranged from 52.3 to 370.7Ωm. This was assumed to be shalestone/shale, and it was overlain by the third layer, which had resistivity values between 121 m to 1491.9Ωm, which was assumed to be sandstone (sandstone materials make good aquifers).The fourth layer, had values between 12.3Ωm. m to 1052.7Ωm, the fifth layer, had values between 11.21Ωm. to 2277.2Ωm, and the last layer, which had a value of32Ωm.The Transmissivity measurements ranged from 16 m2/day to 171 m2/day, Porosities were high with strong storactivity which show that the studied area contains thick and abundant aquiferous zone. Protective capacities (PC) values of (0.01-1.260 seimens) were obtained from the VES data. Borehole depths were recommended for each profile for borehole development. The study was identified to have confine aquifer terrain because of the confining clay layer which had a large vertical extend in the adjacent layers that enclosed the aquifer layer.

Groundwater pollution and risk assessment using indexed-based models: a case study of Igbo-Etiti area, eastern Nigeria.

Water is one of the most abundant resources on earth not evenly distributed. Due to the high shortage of water sources in Igbo-Etiti and intensive agricultural practices in the area, assessment of groundwater pollution and its potential risk to contamination is imperative, as its remediation when contaminated is extremely challenging. Vertical electrical sounding (VES) and physicochemical analysis were carried out in twenty (20) locations and five groundwater samples, respectively, with the aim to evaluate the groundwater pollution indices and the ecological and human health risk associated with its pollution. The VES results delineated five geologic layers and ten characteristic curve types. The fourth layer with the aid of the VES results constrained by the borehole lithologic information on the water bearing geologic unit was delineated as the major exploitable aquifer layer. Results of groundwater vulnerability to pollution classified the area into low (15%), moderate (60%), and high (20%) vulnerability. Physicochemical analysis results on the studied groundwater revealed acidic (pH 4.6) to alkaline (pH 7.2) groundwater conditions. Pollution index of groundwater results delineated a moderate to very high pollution index, with cadmium and arsenic consistently identified as the heavy metals contaminating the groundwater. Ecological risk assessment revealed a moderate to very high integrated potential ecological risk, while human health risk results delineated a target hazard index greater than one in all the studied groundwater samples. This study will serve as a guide to the residents and society in sustainable development decision-making that will preserve the quality of the study area groundwater.

Implementing Vertical Drainage to Reduce Flood Risk at Settlement Area in Medan


 With the increasing number of residents in a city, there will be excessive exploitation of nature, uncontrolled land use changes and a decrease in the carrying capacity of the environment. These various results have a potential to increase the frequency and severity of flood disasters. Flooding is a problem for the town because it leads in losses of property and lives, the emergence of health issues, damage to different infrastructure facilities and infrastructure, among other things. Although the government has been developing a horizontal drainage system for years, it has yet to decrease urban flooding. Consequently, a new technique is required to overcome flooding, specifically the use of vertical drainage. In an attempt to improve the community's living conditions, this activity's goal is to reduce the risk of flooding in Kelurahan Pasar Merah Timur settlement area. The advantages of this program include an improvement in the community's quality of life as a result of less intense flooding following the installation of vertical drainage. According to the test, 2 liters of water can be drained into the aquifer channel every second by the vertical drainage. So it can be assumed that if there is a puddle of water that cannot be drained by horizontal drainage of 4000 liters or 4 m3, it will take 34 minutes to deliver the water into the aquifer layer.

Aquifer layer in Muara Batu and Dewantara Sub-district based on resistivity cross-sectional model

This study aims to determine the depth of the aquifer layer in the Muara Batu and Dewantara sub-district as a source of groundwater that can be used continuously. The identification of this aquifer layer is based on the results of the resistivity values of subsurface rocks measured using the electrical resistivity method of the Schlumberger array. Data acquisition was carried out on 3 lines (MB1, MB3, and MB4) with a length of 330 m each. The variations in the resistivity values of the rocks obtained were modeled in the form of a 2D cross-section using the Res2DInv software, thus providing an overview of the subsurface for groundwater exploitation. The cross-sectional model obtained shows that the shallow aquifer layer is at a depth of 20-52 m (2-12 Ωm) on the MB1 and a depth of 60 m on MB3 and MB4. The low resistivity value 12 Ωm on the MB1 indicates that the subsurface is generally composed of water-saturated rock layers.

Effects of Boundary Conditions on Performance Prediction of Deep-Buried Ground Heat Exchangers for Geothermal Energy Utilization

An accurate prediction for deep-buried ground heat exchangers (DBGHEs) is the premise for efficient utilization of geothermal energy. Due to the complexity of the geological composition spanning thousands of meters, the configuration of boundary conditions plays a critical role in evaluating DBGHE thermal performance. This paper proposed a three-dimensional model of full-scale DBGHE involving both conductive and convective heat transfer in aquifuge and aquifer layers. The constant inlet temperature and constant heating power boundaries in the DBGHE domain, and the surface–bottom temperature and heat flux boundaries in the rock-soil domain were examined. It was found that the differences in the performance prediction caused by different DBGHE boundary conditions were closely related to the system’s operating time. The relative differences in heat extraction amount and average borehole temperature of 2000 m DBGHE caused by the two inlet boundaries on the 30th day were, respectively, 19.5% and 18.3%, while these differences on the 120th day were decreased to 8.4% and 9.9%, respectively. It was found that the constant inlet temperature boundary was more appropriate than the constant heating power condition for estimating aquifer effects on the performance of DBGHE. For the rock-soil domain, the results showed that the heat extraction amount of DBGHE under the heat flux boundary was 12.6%–13.6% higher than that under the surface–bottom temperature boundary. Particularly, when considering the velocity change of groundwater in the aquifer, the relative difference in heat extraction amount increments caused by the two types of rock-soil boundaries can reach 26.6% on the 120th day. It was also found that the thermal influence radius at the end of a heating season was hardly affected by either the DBGHE inlet or rock-soil domain boundary conditions.

Improving the representation of groundwater processes in a large-scale water resources model

ABSTRACT This study explores whether incorporating a more sophisticated representation of groundwater, and human–groundwater interactions, improves predictive capability in a large-scale water resource model. The Global Water Availability Assessment model (GWAVA) is developed to include a simple layered aquifer and associated fluxes (GWAVA-GW), and applied to the Cauvery River basin in India, a large, human-impacted basin with a high dependence on groundwater. GWAVA-GW shows good predictive skill for streamflow upstream of the Mettur dam: Kling-Gupta efficiency ≥ 0.3 for 91% of sub-catchments, and improved model skill for streamflow prediction compared to GWAVA over the majority of the basin. GWAVA-GW shows some level of predictive skill for groundwater levels over seasonal and long-term time scales, with a tendency to overestimate depth to groundwater in areas with high levels of groundwater pumping. Overall, GWAVA-GW is a useful tool when assessing water resources at a basin scale, especially in areas that rely on groundwater.

Estimating The Distribution of Sea Water Intrusion in Sengkubang Village Based on The Resistivity Value

The fulfillment of clean water needs in Sengkubang Village is done by utilizing groundwater, which in some locations still has a brackish to salty. This situation is one indication of seawater intrusion into groundwater because Sengkubang Village is a coastal area. This study aims to estimate the distribution of seawater intrusion based on the subsurface resistivity value. The method used is the resistivity method with dipole-dipole configuration. Measurements in the field apply six lines with a length of 55 m and the smallest electrode distance of 5 m. The distance of each line from the coastline is approximately 410 m, 485 m, 560 m, 635 m, 710 m, and 785 m. The interpretation results show that the seawater intrusion at the study area has a resistivity value of 0.223 Ωm - 5.03 Ωm at a depth of 0.854 m to 10.9 m. The subsurface layer at the study site is composed of sand, sandy clay, and gravel sand mixed with silt. The unconfined aquifer layer, which is interpreted as sand, is thought to have experienced seawater intrusion to 785 m from the coastline.

Groundwater exploration using 2D resistivity method in water supply for prevention of peatland fire at Kahayan Kuala area, Central Kalimantan

Resistivity data acquisition using the two-dimensional (2D) resistivity method has been carried out at 8 locations in the Kahayan Kuala area, Pulang Pisau District, Central Kalimantan. The aim of the study was to identify the distribution type and depth of aquifer layers and other geological materials in subsurface based on their resistivity characteristics. The study results showed that resistivity values at the northern part of the study area ranging from 13.28–282 and 2.09–88.37 ohm-meter, while at the southern part, the resistivity values ranging from 0.32–25.75 ohm-meter. At the northern part of the study area, the resistivity values range of 41.77–88.37 to 67.7–187.79 ohm-meter are peat and mud layers, range of 25.35–88.37 to 55.29–282.28 ohm-meter are sandstone layers, and range of 2.09–34.31 to 13.28–67.78 ohm-meter were clay and sandy clay layers. At the southern part, the range of resistivity values from 5.97–25.75 ohm-meter are peat and mud layers, range of 4.46 - 25.75 ohm-meter are sandstone layers, and range of 0.32–5.97 ohm-meter are clay and sandy clay layers. Sandstone layers are interpreted as confined aquifers, peat and mud layers as unconfined aquifers, and clay and sandy clay layers as non-aquifer or sealing layers. At the northern part of the survey area, the depth of aquifer layers ranging from 10–40 meter and at the southern part the depth of aquifer layers ranging from 20–50 meter.

Detection of groundwater aquifers using geoelectrical resistivity method (case study : Plupuh Sub-district, Sragen District )

An aquifer is a layer below the ground surface that contains groundwater. Inside the earth there are unconfined aquifers and confined aquifers, where unconfined aquifers are located near the surface while confined aquifers are located very deep beneath the earth. This study aims to find the location, depth, and thickness of aquifers that have the potential to contain large amounts of groundwater. The instrument used in this research is a resistivity meter OYO Model 2119C Mc OHM-EL, with a Schlumberger configuration with a current electrode length of AB/2 to 350 meters. Data acquisition were carried out in the Plupuh sub-district, Sragen district as many as 5 sounding points, and data processing using IP2win software. Based on the interpretation of resistivity geoelectrical data, it can be concluded that the area has the potential to have a lot of groundwater content, for unconfined aquifers at the TS1 sounding point with a depth of 7.7 meters to 19.2 meters with a thickness of 11.5 meters. and TS4 with a depth of 15.4 meters to 30 meters with a layer thickness of 14.6 meters. This aquifer layer is dominated by sand layer lithology, while the confined aquifer layer is located around TS1 and TS2. The two sounding points are located in the east and northeast of the research area. TS1 was detected at a depth of 39.9 meters to 110 meters with a layer thickness of 60.1 meters and TS2 was at a depth of 40.2 meters to 66.5 meters and 80.2 meters to 139.7 meters with a thickness of 84.8 meters. This aquifer layer is dominated by the gravel sand layer in TS1 and the sand layer in TS2.

Delineation of aquifer promising zones and protective capacity for regional groundwater development and sustainability

Water security is the central mission of the sustainable development goals. The demand for potable and clean water has skyrocketed due to frequent borehole failures and population expansion, which requires adequate groundwater resource management strategies. Identifying groundwater potential zone, overburden protective index capacity and installations of alternative/artificial storage support mechanisms for water security and sustainability under the growing water challenge and demand is critical. This study identifies; (i) aquifer promising zones (ii) aquifer protective capacity through geophysical investigation and suggests (iii) improving aquifer recovery management strategy as the top three targets for groundwater development. An electric resistivity technique was applied to acquire a total of sixty (60) vertical electrical sounding points with Schlumberger arrays. The study indicates the resistivity layer of the aquifer unit ranges from 21 to 294 Ωm, while the aquifer layer thickness values spread from 8 to 59 m and the overburden thickness overlays the aquifer unit extends from 3 to 20 m. The deeper aquifer zones were encountered between 30 and 59 m, which could be suitable for groundwater development, and the shallow aquifer occurs between 8 and 14 m, which is not encouraging for groundwater development and may be susceptible to surface contaminations. However, for water security and sustainability, multiple boreholes should be sited at the delineated aquifer promising zone where the aquifer is fractured and occurs within a depth of 30 m and above. The weathered/fractured units constitute the regional aquifer units, which are largely responsible for the groundwater potential. The hydraulic conductivity of the regional aquifer was estimated to vary between 0.337 and 10.62 m/day, which invariably enhances the aquifer recovery processing. Groundwater quality and the risk of surface contamination were examined through overburden protective index capacity.

Application of the RAPS Method for Determining the Dependence of Nitrate Concentration in Groundwater on the Amount of Precipitation

Protecting groundwater from contamination is today’s most current environmental protection topic. What can man do in his environment to reduce the harmful impact of contamination on the environment, and thus the immediate effect on groundwater? Agricultural production is an ongoing source of groundwater contamination due to the increasingly frequent use of nitrates in fertilizers, which are washed out from the soil into groundwater due to precipitation. This paper investigates three wellfields in the north of the Republic of Croatia near the town of Varaždin. With the application of the RAPS method, the dependence of nitrate concentration in groundwater on the amount of precipitation was established. The analysis results show the connection of the observed parameters, especially in the upper aquifer layer. In this layer, the coefficients of correlation are greater than 0.80 at all locations, which shows a strong positive connection between the parameters. In the lower aquifer, the values of the coefficients of correlation are lower, and the results mostly indicate a weak correlation. The obtained results will serve as a starting point for future studies, which will aim to precisely determine the factors that influence groundwater quality in the observed area.

AQUIFER SYSTEMS CHARACTERIZATION FOR GROUNDWATER MANAGEMENT IN ILE-OLUJI, SOUTHWESTERN NIGERIA, USING MCDA GIS-BASED AHP

Multicriteria decision analysis for groundwater potential mapping utilizing analytical hierarchical process of six hydrogeologic parameters including aquifer layer thickness, aquifer layer resistivity, overburden thickness, transverse resistance, transmissivity, and coefficient of anisotropy; in relation to groundwater yield was carried out in Ile Oluji, Southwestern Nigeria. The aim was to develop groundwater potential map using calculated groundwater potential index values (GWPIV). The obtained GWPIV which ranged from 1.53 (granite) – 3.50 (migmatite) with an average of 2.18 suggestive of moderate groundwater potential (90 % of the study area). The low potential zone (10 %) are observed sporadically in the central and northwestern parts. All the geological units recorded overlapping hydrogeologic properties. The longitudinal unit conductance recorded regional average of 0.219876 mhos. Therefore the protective capacity of groundwater system in the study area is weak, and relatively less-weaker in granite environment; and in northwestern and central parts. Nevertheless, the water table aquifer (accounts for 80%) and the fracture basement (constitutes 20%, frequently occurring in gneissic environment) are the water bearing units, with average overburden thickness in migmatite, granite, and gneiss 24.3 m, 24.5 m, and 27.9 m respectively. The average coefficient of anisotropy (1.12); hydraulic conductivity (0.37 m/d), transmissivity 6.86 m2/d (migmatite: 7.17 m2/d, granite: 7.14 m2/d, and gneiss: 6.02 m2/d). Hence gneissic offered both thick weathered layer and fractured aquifer. Empirical model for plot of formation factor and hydraulic conductivity in migmatite, granite, and gneiss, showed positive correlations in descending order as: granite (0.3778), migmatite (0.1057), and gneiss (0.0641).

Solving subsurface flow toward wells in layered soils using hybrid method of fundamental solutions

In this article, numerical solutions of three–dimensional subsurface flow toward wells in layered soils using a hybrid method of fundamental solutions is presented. The proposed boundary–type meshless method is based on using the superposition of the fundamental solution and general solution of governing equations from the subsurface flow and the radial flow to a well, respectively. To deal with the subsurface flow in a layered aquifer system, the method of domain decomposition is employed in which the continuity conditions of head and flux at the interface between layers can be satisfied. The validation of the proposed approach is conducted comparing with exact solutions and the USGS's modular hydrologic model, MODFLOW. The approach is then applied to investigate the leakage of the aquifer under pumping conditions for a real layered aquifer system in Taiwan. Results illustrate that the proposed approach exhibits high accuracy over the mesh–based numerical technique. We also demonstrate that the boundary–type meshless method is beneficial for the boundary discretization technique and reduces the computational complexity.

Interpreting Concentrations Sampled in Long-Screened Wells with Borehole Flow: An Inverse Modeling Approach.

New approaches are needed to assess contaminant mass based on samples from long-screened wells and open boreholes (LSW&OB). The interpretation of concentration samples collected in LSW&OB is complicated in the presence of vertical flow within the well. In the absence of pumping (i.e., ambient conditions), the well provides a conduit for flow to occur between aquifer layers or fractures as a result of head differences. Under pumping conditions, vertical borehole flow may vary with depth depending on far-field heads and hydraulic conductivity; furthermore, if pumping fails to overcome ambient gradients, outflow from the well to the aquifer may occur. Concentration samples thus represent flow-weighted averages of formation concentrations, but the averaging process is commonly unknown or difficult to identify. Recognition of the importance of borehole flow has motivated the use of multi-level wells, packers, and well liners; however, LSW&OB remain common for numerous reasons, including cost, multi-purpose design requirements (e.g., pump-and-treat, water supply), logging, and installation of instrumentation. Here, we present a simple analytical model for flow and transport within a well and interaction with the surrounding aquifer. We formulate an inverse problem to estimate formation concentration based on sampled concentrations and data from flowmeter logs. The approach is demonstrated using synthetic examples. Our results (1) underscore the importance of interpreting sampled concentrations within the context of hydraulic conditions and aquifer/well exchange; (2) demonstrate the value of flowmeter measurements for this purpose; and (3) point to the potential of the new inverse approach to better interpret results from samples collected in LSW&OB.

Modelling Plume Development with Annual Pulses of Contaminants Released from an Airport Runway to a Layered Aquifer, Evaluation of an In Situ Monitoring System

In cold climates, the use of de-icing chemicals in the winter can lead to groundwater contamination, especially when used in large quantities, such as at airports. Oslo Airport, Gardermoen, is situated on Norway’s largest rain-fed aquifer. Potassium formate is used to remove ice from runways and propylene glycol from airplanes; the organic parts are degradable. Most of the wells to monitor the spread of de-icing chemicals in the underlying aquifer have well screens near the groundwater level, while the runways and the source of de-icing chemicals are near the groundwater divides, where vertical flow is expected. The objective of this study is to demonstrate the importance of layers and time-varying recharge on the spreading of contaminant plumes in an aquifer near a groundwater divide. This is done with numerical modelling. The model results show increased vertical transport of the added tracer in the presence of horizontal layers, both continuous and discontinuous, in the aquifer. With certain distributions of hydraulic conductivity, Ks, we demonstrate that deeper monitoring wells are required. With the scenarios modelled here, time-varying recharge has a weaker effect on plume distribution. Measured concentrations of potassium and total organic carbon show the cyclic effect of seasonally varying recharge of contaminants, and an asymptotic accumulation of concentration over time, that is consistent with the model runs. In conclusion, groundwater monitoring systems near a groundwater divide should include multi-level samplers to ensure control of the vertical plume movement.

Evaluation of submarine groundwater discharge and associated beach groundwater dynamics

ABSTRACT This paper reports the dynamism of a submarine groundwater discharge (SGD) zone in SW India. Two electrical resistivity tomography (ERT) surveys were conducted in the project area to delineate the seawater-fresh water interface and characterize the subsurface aquifer layers. Beach groundwater dynamics were also studied by continuously monitoring salinity, temperature, and nutrient concentration in the groundwater from three shallow dug wells on the beach. The ERT surveys were planned in such a way as to fall between these dug wells. The flow domain was modeled using a numerical modeling approach, and the rate of fresh SGD flux and its spatial variation along the coastline has been estimated. The study proves that the numerical modeling approach combined with other field measurements and observations, such as ERT and continuous monitoring gives a comprehensive understanding of SGD and associated processes.

Application of improved stratigraphic modified Lorenz plot and flow zone indicator in discriminating the Igbo-Etiti aquifer into hydraulic flow units, eastern Nigeria

Discriminating the Igbo-Etiti aquifer sequence into hydraulic flow units was carried out employing integrated method. The method demonstrated an excellent potentiality in delineating and classifying the aquifer into hydraulic flow units (HFU). Results of electrical resistivity survey identified five geoelectric layers in the study area. The fourth layer with the aid of the layer's geologic unit characteristics and borehole lithology was delineated as the aquifer layer. Results from improved stratigraphic modified Lorenz plot (ISMLP) identified the slope, angle and percentage contributions of the established HFUs to range from 0.0029 to 3.1455, 0.1660° to 72.364° and 1.3–76.2% respectively. ISMLP result analysis delineated a total of five (5) classes of hydraulic flow units. These classes of HFUs based on efficiency ranking and classification, range from barrier unit with tight flow capacity efficiency to super conductive unit with good flow capacity efficiency. Results of ISMLP delineated group 4 HFU (G4 HFU) with a total flow capacity percentage contribution of 5.6% as a super conductor unit and the best flow capacity efficiency unit in the study area. G2 HFU described to be a conductor unit was identified as the dominant class of HFU in the study area with a total flow capacity contribution of 76.2% to the overall aquifer flow capacity. Results from flow zone indicator (FZI) method revealed a total of five (5) hydraulic flow units with FZI unique values of 16, 17, 18, 19 and 20. FZI results, identified HFU3 and HFU4 as the most occurring HFU in the aquifer layers, with HFU1 and HFU2 outlined as the least occurring HFU. The integrated approach successfully and uniformly identified five (5) classes of HFUs in the study area. Dykstra-Parson's coefficient of 0.618 revealed very high heterogeneous aquifer layers.

VES Geoelectrical Method for Identification of Aquifer Depth in Coastal Area of North Lombok Regency, Indonesia: Implications for the Sustainable Utilization of Water Resources

Measurement of the resistivity value distribution of subsurface rocks has been carried out in Mumbul Sari Village, Bayan District, North Lombok, which is one of the drought-prone areas in NTB Province, Indonesia. This research was conducted to identify the presence of groundwater aquifer layers in the study area based on the distribution of resistivity values. Data collection was carried out at two measurement points, namely the MBLS-1 Point with a track length of 700 m and the MBLS-2 Point with a length of 750 m. Data processing was carried out using IP2WIN Software to obtain a one-dimensional subsurface cross-sectional model, then interpreted using a resistivity log to make it easier to draw information on the subsurface point of measurement. Based on the distribution of resistivity values, it is known that the geological layers in the study area consist of pumice tuff, silty silt, sandy silt, and lava. The inversion results from the IP2WIN software show that the depth of the aquifer zone at Point MBLS-1 is 15.6 – 70.2 m with a resistivity value of 90.3 Ωm and a thickness of 54.5 m, while at Point MBLS-2 it is located at a depth of 21.9 – 86.1 m with a resistivity value of 112 Ωm and a thickness 64.3m. The aquifer zone at both measurement points is interpreted as a sandy silt layer. Groundwater drilling is recommended at the MBLS-1 point to a depth of 70 m and at the MBLS-2 point to a depth of 86 m. The geological structure that forms the boundary of the aquifer zone is a layer of compact and hard lava, so for groundwater utilization in the study area, it is recommended to use drilled wells to a depth of 70 – 86 m which is the lower limit of the aquifer layer.

Remote sensing and geophysical methods for delineating groundwater resources in schists hard rocks of the Adamawa Yadé Domain, Cameroon

The combination of remote sensing and geophysical techniques is a practical approach for mapping environmental hydrogeological setting and delineating groundwater zones. This paper applies an integrated approach to identify and extract the subsurface structures that act as conduits for the groundwater flow in the highly deformed area of the Adamawa region. Remote sensing data through the lineament’s extraction technique highlights topographic lineaments along which rivers flow in the area. The distribution of these lineaments according to the lineament density map indicates the degree of permeability or porosity of each region and thus the capability in terms of groundwater potential. The filtering of aeromagnetic data enables to produce a structural map showing various geophysical lineaments interpreted as the fault systems of the study area. These faults are the main conduits through which magnetized rocks of granitoid type intruded into the basement and groundwater flows to the subsurface. Local application of the vertical electrical sounding (VES) shows that the study area is highly fractured/faulted and composed of multiple lithologic units including two aquifer layers (clayey sands and fractured schists) with thickness ranging from 5 to 15 m and from 34 to 82 m, respectively. Geoelectric cross-sections reveal that the subsurface structures consist of horsts, followed by a progressive subsidence depicted by the NE-trending faults towards the southern depression and grabens bounded by NW- and NE-trending normal faults. These prominent structures (faults, fractures, and grabens) are considered as the conduits for the groundwater flow into hard rock aquifers of the study area.

Delineation of Paleochannel and Groundwater Resources in the Khari River Basin, Kachchh using Transient Electromagnetics

Abstract The paleochannels are riverine geomorphic features, which are either buried or shifted due to tectonic, climate, and anthropogenic activities. In general, these channels serve as potential groundwater repositories, and their identification can help in developing potable groundwater sources. Here, the results of transient electromagnetic (TEM) study carried out near and around the Khari river basin of the tectonically active Kachchh intraplate region, western India are presented. The TEM investigations at 22 sites along three traverses have been carried out in the river basin that cut the present-day river channel and its presumed paleochannel. The geoelectric sections of the three profiles decipher information down to 300-350m and suggest a multilayer aquifer system. The sub-surface model infers a deeper confined aquifer at variable depths from 100-150m associated with the river as well as its paleochannel. The paleochannel aquifer is observed to be buried under 15-20m thick unconsolidated sediments that overlie a Mesozoic sandstone layer of the Bhuj Formation. The resistivity sections across the paleochannel suggest a relatively fresh aquifer layer with higher storage capacity. A vertical bedrock offset of 100-120m and the discontinuity of lithostratigraphic layers observed from the study suggest the dominant tectonic control in the formation of the paleochannel that correlated with the location of the reactivated splay of the Katrol Hill Fault.