Main Aquifer Research Articles

Hydrogeology of a landslide: a case study in the Montagne de Reims (Paris basin, France)

Investigations of hydric and hydrogeological mechanisms that contribute to the current reactivation of mass-movements feed predictive models that can be useful for risk management. Our model is based on an approach combining (1) a large-scale analysis of the landforms, using LiDAR imagery and field observations, (2) a characterization of the groundwater (piezometry, conductivity and temperature), both in the landslide and in the stable slope, and (3) electrical resistivity profiles. These combined data allow the reconstruction of the structure of the landslide to determine its influence on groundwater flow. The Saint Maur landslide bars the main aquifer of the Upper Ypresian sands whose slow flow results in lower piezometric level fluctuations and stronger mineralization than found in the unconfined aquifer on either side of the slip. The confined aquifer emptying occurs through the sliding plane so that the landslide aquifer is fed essentially by capillary rise from the shear plane and to a lesser extent by surface infiltration. Therefore, the amount of water in the landslide and the resulting probability of mass movement are weakly correlated with rainfall events. In addition, the wide dispersion of the conductivity values of the landslide aquifer reflects a weak mixing of the water. Groundwater circulation modelling allows us to correct in situ (i.e. underground) the flows causing reactivations, and confirms that stabilization by hydrogeological action is more efficient than a surface drainage. Thematic collection: This article is part of the Role of water in destabilizing slopes collection available at: https://www.lyellcollection.org/cc/role-of-water-in-destabilizing-slopes

Hydrogeological Conditions and Mathematical Model of the Area Surrounding Hatra Suggested dam, Northwest Iraq

The area was hydrogeologically studied, it was found that the main aquifer is unconfined, it is located within Fat’ha Formation, and the hydraulic properties of this aquifer were also studied from the analysis of pumping tests data to determine the averages of transimissivity (T=671.027 m2/day), hydraulic conductivity (K=45.449 m/day), and storage coefficient (Sc=0.226). The groundwater levels and flow direction map was drawn, and it was found that the flow corresponds to the topographical slope of the land surface towards Tharthar valley, from the east - west towards the center of the study area, with a slight slope towards the south.These are some data represent a database that can be used in the design of the proposed dam on Tharthar valley, and the policy of storage and water management in the dam, reservoir as well as to build a mathematical model to predict the future behavior of groundwater in the region.Especially under the body of the dam to simulate the changes in groundwater conditions in the area of the small Hatra Dam Suggested on Tharthar valley, when storing water in front of a dam, and the expected engineering problems that would occur due to groundwater seepage under or on both sides of the dam body, by raising the water level within the valley – hypothetically, by 1m, 2m, 3m, 4m, 5m, 7m, 9 m and 11 m, assuming no pumping from the Aquifer during the rise of the level in the valley. as well as re-calculation with the same ranges of raising the level on another assumption, which is pumping from the wells in the area by 9 m3/ hour, for a period of time 6 hours per day, and determining the affected area by raising the level for each of the cases. The study indicated that the expected effect on the groundwater level starts when raising the water level inside the valley to four meters, and the clear increase continues at five meters, but the cumulative effect of raising the level from (7-11)m is slight. It also identified the sites that would allow the underground water to be pumped under the dam’s body, and the results were consistent with the geological reality of the area. These results will help in establishing an appropriate design for the foundations and structure of the dam.The current study is one of the requirements for building a small dam within the plan for managing water resources and developing the region that suffers from desertification, drought and environmental degradation.

Integrated geophysical methods and techniques for studying the perennial springs in Ikanje- Share, Kwara State, Nigeria

An integrated magnetic, self-potential (S.P.) and electrical resistivity survey involving magnetic profiling and 1D Vertical Electrical Sounding (VES) electrical imaging techniques were carried out in the transition environment between the Nupe Basin and Southwestern Nigeria Basement Complex at Ikanje-Share in Kwara State, Nigeria. The Ikanje-Share perennial springs started gaining a lot of attention after many travelers and tertiary institutions in Nigeria made it a good choice for their fieldwork exercise. The surveys were done in order to delineate the subsurface layers, determine the geoelectrical characteristics and identify geological structures (e.g., faults and fractures) that are responsible for the perennial spring formation. The magnetic profiling was used as reconnaissance technique to identify lineament features that are favourable to groundwater accumulation and transmission. Some magnetic lineaments were qualitatively inferred from some profiles in the study area. The fault locations coincide with inflection points in S.P. curves and occur as horizontal and consistent planes of discontinuities at depths of approximately 1.25, 4.25, 8.75, 13.15 and 21.25 m, respectively. The VES interpretation results indicated four to five major geologic units, which include: the topsoil/clay/lateritic layer, the lateritic layer, the weathered basement, the weathered/fractured basement and the fresh bedrock. The weathered and fractured basements constitute the main aquifer units and the overburden thickness varies from 5.0 to 16.8 m. The study has shown the usefulness of integrated geophysical methods and techniques in subsurface structural and groundwater development study over the perennial springs in the transition environment between the Nupe Basin and the Southwestern Nigeria Basement complex.

Estimation of unrecorded groundwater abstractions in Jordan through regional groundwater modelling

Jordan suffers from water scarcity and groundwater covers the majority of Jordan’s water supply. Therefore, there is an urgent need to manage this resource conscientiously. A regional numerical groundwater flow model, developed as part of a decision support system for the country of Jordan, allows for quantification of the overexploitation of groundwater resources and enables determination of the extent of unrecorded agricultural groundwater abstraction. Groundwater in Jordan is abstracted from three main aquifers partly separated by aquitards. With updated geological, structural, and hydrogeological data available in the country, a regional numerical groundwater flow model for the whole of Jordan and the southernmost part of Syria was developed using MODFLOW. It was first calibrated for a steady-state condition using data from the 1960s, when groundwater abstraction was negligible. After transient calibration using groundwater level measurements from all aquifers, model results reproduce the large groundwater-level declines experienced in the last decades, which have led to the drying out of numerous springs. They show a reversal of groundwater flow directions in some regions, due to over-abstraction, and demonstrate that documented abstractions are not sufficient to cause the observed groundwater-level decline. Only after considering irrigation water demand derived from remote sensing data, the model is able to simulate these declines. Illegal abstractions can be quantified and predictive scenarios show the potential impact of different management strategies on future groundwater resources.

A Stepwise Modelling Approach to Identifying Structural Features That Control Groundwater Flow in a Folded Carbonate Aquifer System

This paper concerns a stepwise modelling procedure for groundwater flow simulation in a folded and faulted, multilayer carbonate aquifer, which constitutes a source of good quality water for human consumption in the Apennine Range in Central Italy. A perennial river acts as the main natural drain for groundwater while sustaining valuable water-related ecosystems. The spatial distribution of recharge was estimated using the Thornthwaite–Mather method on 60 years of climate data. The system was conceptualized as three main aquifers separated by two locally discontinuous aquitards. Three numerical models were implemented by gradually adding complexity to the model grid: single layer (2D), three layers (quasi-3D) and five layers (fully 3D), using an equivalent porous medium approach, in order to find the best solution with a parsimonious model setting. To overcome dry-cell problems in the fully 3D model, the Newton–Raphson formulation for MODFLOW-2005 was invoked. The calibration results show that a fully 3D model was required to match the observed distribution of aquifer outflow to the river baseflow. The numerical model demonstrated the major impact of folded and faulted geological structures on controlling the flow dynamics in terms of flow direction, water heads and the spatial distribution of the outflows to the river and springs.

Effects of Confining Pressure on Permeability in a Single Fracture Based on the Deformation of Hydraulic Aperture at Low Fluid Velocities

Abstract The fluid flow in fractured rock was determined by the aperture of fractures, which is influenced by the complex variation and wide distribution of in situ stress conditions. While extensive studies focused on qualitative analysis of the experimental phenomena, much less was the quantitative mechanism of permeability under confining pressure in theory, which is frequently required in rock engineering projects. In this work, we proposed a new negative exponential model to quantitatively describe the flow rate Q, seepage pressure Ps, hydraulic aperture eh, and permeability k under different confining pressures Pc at a low flow rate. Hydromechanical tests with two experimental modes (constant Q test mode and constant Ps test mode) were conducted on cutting shale samples, and test data were collected. Furthermore, regression analyses were performed on the test data, based on the proposed model. Results suggest that the negative exponential model quantitatively predicts the seepage properties (Q, Ps, eh, and k) under the changeable in situ stress conditions in the application of low flow velocities in natural fractures, such as the development of oil/gas reservoirs and controlling of solute transport in the main aquifer. The proposed model assists in understanding and applying the behavior of the fluid flow in fractured rock under in situ stress conditions at low flow velocity.

Hydrogeochemistry of the groundwater system of the transboundary basement and volcanic aquifers of the Bulal catchment, Southern Ethiopia

The evaluation of groundwater geochemistry of transboundary aquifers has an important role in the management and sustainable use of groundwater resources in arid and semi-arid regions. This study presents the results of an integrated hydrogeochemical study of the Bulal transboundary aquifers located in the Borena zone, along the Ethiopia-Kenya border. The main aquifers are basic volcanic rocks, subordinate felsic pyroclastic deposits, and metamorphic basement rocks. These aquifers are overlain by alluvio-lacustrine sediments, eluvial soil and regolith. The groundwaters are dominated by Na+ and HCO3− and mixed water types. Silicate weathering and evaporation are the dominant hydrogeochemical processes controlling the chemistry of the groundwaters in most parts of the catchment. However, dissolution of evaporitic minerals might have also played a significant role in adding major ions into the groundwater system. Groundwater in the volcanic aquifers are Na–HCO3, Ca–Mg–HCO3, Na–Ca–HCO3 and Na–Cl–SO4 water types while Ca–Mg–HCO3, Na–Ca–Cl–SO4 and Ca–Mg–SO4 water types are dominant in the metamorphic basement aquifers. The groundwater in the catchment mainly evolved from Na–HCO3 in the west, Ca–Mg–HCO3 in the north, and Na–Ca–Cl–SO4 in the central east and southeast to Na–Ca–HCO3 type in the southern low-lying areas along the groundwater flow direction. The study has significant implications for the management of groundwater quality in the region.

Characterization of Shallow Groundwater Circulation Based on Chemical Kinetics: A Case Study of Xiong’an New Area, China

Xiong’an New Area, located in the middle of the North China Plain, will have been built as a “city of the future.” Urban planning and construction need to comprehensively consider the constraints of hydrogeological conditions such as aquifer structure and parameters. As the main aquifer in this area, the paleo-channel is heterogeneous and anisotropic, and the two-dimensional hydraulic conductivity in each horizontal direction cannot be obtained from aquifer tests. Therefore, this study adopts a chemical kinetics method to calculate the ionic activity and mineral saturation indices of shallow groundwater, determine the groundwater chemical potential field, and construct a horizontal two-dimensional groundwater chemical kinetics model. This model is used to calculate the hydraulic conductivity, flow rate and retention time of groundwater in areas of different chemical kinetics, as well as evaluate horizontal heterogeneity of the Quaternary paleo-channel aquifer. The results indicate that the groundwater chemical potential field can reflect the characteristics of the groundwater seepage field in each horizontal direction. The paleo-channel is the main channel of groundwater circulation, which shows the statistical difference of its permeability. Alluvial and lacustrine strata affect groundwater circulation due to their different hydrogeological structures and permeability. The groundwater chemical kinetics results of hydraulic conductivity along the paleo-channel are approximately consistent with traditional hydrogeological calculation results derived from aquifer test data. Hydraulic conductivity is higher in the extension direction of the paleo-channel, and lower if the path crosscuts multiple paleo-channels. This feature can be used to build a hydrogeological structure model combined with drilling data. Furthermore, excessive groundwater exploitation will change the actual flow rate and retention time of groundwater, thereby affecting the groundwater circulation conditions. This study of groundwater circulation in Xiong’an New Area by means of chemical kinetics makes up for the deficiency in the study of the unconsolidated sedimentary aquifer anisotropy within the paleo-channel.

Mixed-Unit-Model-Based and Quantitative Studies on Groundwater Recharging and Discharging between Aquifers of Aksu River

The confined aquifer in the Aksu River Basin is the main aquifer for drinking water within the area. In this study, the unconfined aquifer and the confined aquifer in the Aksu River Basin were divided into different water circulation units through analysis of their flow field. After the hydrochemistry and isotope characteristics of each unit were analyzed, these data were used as water volume quantitative information of the aquifer according to the mixed-unit model. With this quantitative information, the transformation relationship between the unconfined aquifer and the confined aquifer, the recharging source, recharging amount, recharging proportion, and discharging amount of the confined aquifer were revealed. The results showed that the confined aquifer receives a recharge of 21.48 × 106 m3/a from the unconfined aquifer. The recharging sources of the confined aquifer in the middle and upper stream of the Aksu River mainly included side recharging and leakage recharging from the unconfined aquifer, while the confined aquifer received little recharging from unconfined aquifer downstream of the Aksu River and did not receive recharging from the unconfined aquifer in the southeast of the basin. Additionally, drainage methods of the confined aquifer were mainly lateral flowing and artificial well-group pumping. The side discharging volume through the whole area was 15.67 × 106 m3/a, and the artificial pumping volume was 21.20 × 106 m3/a. The confined aquifer was in a negative balance state from the middle-upper stream to the downstream. The downstream confined aquifer and its unconfined aquifer had a plane laminar flow movement, and the unconfined aquifer provided very little recharging to the confined one, which was further enhanced by the artificial well pumping and caused an accumulating negative balance state of the downstream aquifer.

Assessment of the Hydrogeochemical Characteristics of Groundwater Resources at some Wadis in the East of El Minia Governorate, Eastern Desert, Egypt

AbstractThe El Minia governorate lies within the Nile Valley, surrounded by calcareous plateaus to the east and west. The present study focuses on the hydrogeochemistry of the Eocene limestone aquifer at some wadis in the east El Minia governorate, Eastern Desert, Egypt. Hydrogeologically, two main aquifers are encountered in the study area, namely the Maghagha marly limestone and the Samalut chalky limestone aquifers. The Maghagha aquifer is composed of alternating layers of marly limestone and shale with thicknesses ranging from 3.49 m to 177.05 m and a groundwater depth ranging from 8.5 m to 59.27 m which reflects low groundwater potentiality. The groundwater salinity representing this aquifer ranges from 603.5 mg/L to 978.5 mg/L, reflecting fresh water type. Samalut aquifer is made up of chalky, cavernous and fractured limestone with thickness ranging from 30 m to 205 m and groundwater depth ranging from 9 m to 86.77 m, which indicates good groundwater potential. The groundwater salinity of the concerned aquifer ranges from 349.7 mg/L to 2043.9 mg/L, reflecting fresh to possibly brackish water types. Groundwater in the study area is of meteoric water origin; recent recharge is mainly controlled through the presence of fractures and their densities. The majority of groundwater samples in the study area are suitable for drinking and irrigation purposes.

Review: Assessment of the aquifers in South Sudan with a focus on Lakes State

The current state of knowledge on groundwater in South Sudan (a data-scarce country) is presented, based on extensive field surveys in Lakes State in the central part of the country, limited published literature, and unpublished consultancy reports. The Basement Complex and the unconsolidated sediments of the Umm Ruwaba Formation are the most extensive geological formations and are the most exploited for groundwater. The water-resource potential properties of the main Umm Ruwaba aquifer (the ‘second’ aquifer, mostly confined) in Lakes State are generally fair to good, with a shallow piezometric surface (<25 m deep), favourable transmissivity (median 8.4, mean 21.5 m2/day), and low salinity and nitrate content. However, some areas have poor groundwater potential due to deep piezometric levels (up to 80 m deep), low transmissivity (mean <5 m2/day) and/or brackish salinity. The estimated recharge is modest (1–8 mm/year) due to predominantly confined aquifer conditions. Aquifer recharge mainly occurs along the geological boundary with the Basement Complex and from the Bahr el Jebel River. Published literature shows saline groundwater and a groundwater trough in northeast South Sudan that was interpreted as being related to a buried saline lake. Additional data on groundwater levels indicate that the extent of the trough may be less than originally sketched. In the Basement Complex, the groundwater potential varies over short distances and depends on the thickness and sand content of the weathered top layer and/or the presence of fractures; the transmissivity is generally low (median for Lakes State is 4.2 m2/day).

Contribution of isotopic techniques to the knowledge of the aquiferous system of the great Sebkha of Oran

In the Great Sebkha Basin of Oran, water flows, both surface and subterranean, originate on the slopes and converge toward the discharging area of the salt Lake Great Sebkha of Oran (≈ 80 m above sea level). Isotopic water tracing of 2H, 18O, 14C, and 13C was carried out on the main aquifer formations to clarify the phenomena of evaporation, dissolution, mixing of different water bodies, and their residence time in the aquifer system. The data concern: the salt Lake of the Great Sebkha of Oran, the Quaternary alluvial water table of the periphery, the limestone Miocene, the Brédéah pumping station (whose waters are polluted by brackish water intrusions), deepwater tabler table of the Mio-Pliocene complex of the Plain of Maflak, the Pliocene of the Plain of Tameira, and the Thermal Complex of Hammam Bou Hadjar. The d18O levels range from −9.61 to + 4.8 ‰ V-SMOW at the salt Lake of Great Sebkha of Oran. The 2H contents range from −70 to 20. Minimum values characterize run off from the northern slopes of the Tessala. The 13C contents of dissolved total inorganic carbon (TDI) measured ranged from −10.92 to −3.9 ‰ vs PDB. The activities of the 14C are divided between 2 and 51 PMC. The highest activity in 14C (≈50 PMC) is measured on samples taken from the Miocene limestones of Djebel Murdjadjo.

Multidisciplinary investigations of a karst reservoir for managed aquifer recharge applications on the island of Vis (Croatia)

Managed aquifer recharge (MAR) refers to a suite of methods by which excess surface water or non-conventional water is stored underground for subsequent recovery or environmental purposes. MAR solutions have been largely used in unconsolidated aquifers, while their application in karst aquifers is rare. This research presents the first results of a MAR viability study on the island of Vis, a small karstic island in the Adriatic Sea. Favorable geological and hydrogeological conditions enable the formation of karst aquifers, making the island autonomous in terms of water supply. The island’s main aquifer, exploited in the Korita well field, is protected from seawater intrusion by several hydrogeological barriers. However, climate change and high seasonal pressures related to tourism pose a threat to the future availability of freshwater. Multidisciplinary field and laboratory investigations were carried out to detail the geological and hydrogeological setting of the island and its groundwater resource. Field analyses consisted of groundwater monitoring and sampling, geophysical investigations (i.e., electrical resistivity tomography), and structural measurements. Laboratory analyses included measurements of principal cations and anions and tritium activity. Despite low precipitation during the observation period (September 2019 - December 2020), the groundwater resource at the Korita site showed stable trends of physico-chemical parameters with a good storage potential and a long-term reserve. Geophysical investigations evidenced a relatively homogeneous sequence of the rock mass at a larger scale, while structural analyses indicated the occurrence of E-W karstified and open fractures that could represent a preferential flow path in the carbonate aquifer. A MAR solution for the Vis island was proposed combining an infiltration pond scheme with the direct injection of the accumulated waters into the aquifer using available wells. The potential water source could be represented by the runoff collected in an old artificial channel and the associated pond system in Korita.

Characterization of Valley-Fill Alluvial Aquifers in Plutonic and Volcanic Semi-arid Andes Using Electromagnetic Methods: The Case of the Limarí Catchment (Chile)

Many areas of the world are facing sustained periods of water resource stress during which the enhanced exploitation of groundwater is key to maintaining irrigation and drinking water supplies. A good knowledge about groundwater resources is therefore essential to develop sustainable water management strategies. In this study, we aimed to characterize a mountainous watershed in the semi-arid Chilean Andes. The area of interest is distinguished by a high topographic gradient and narrow valleys filled with sedimentary deposits of various origins and surrounded by plutonic and volcano-sedimentary rocks. To characterize the hydrostratigraphy of this complex sedimentary system and to estimate the volume of groundwater stored, we implemented a multidisciplinary approach integrating geophysical data from transient electromagnetic sounding (TEM), hydrogeological, geological, geomorphological and groundwater quality information. The results indicate the presence of two aquifer layers in the majority of the investigated area: a superficial unconfined aquifer and a deeper confined (or semi confined) aquifer. We found that the width and depth of the sedimentary deposits increase with decreasing topography, while the proportion of fine material increases, in coherence with the sedimentation processes. Finally, we quantified the groundwater contribution of the different areas of the catchment and identified the main aquifer potential area in the pediplanes of the coastal mountain range (storing approximately 67% of the water available for extraction). The main contributions to the total uncertainties on the groundwater storage (ranging between 30 and 80% of the estimated volumes) are due to the propagation of the uncertainty on the thickness and porosity/specific yield of the modeled hydrostratigraphic layers. Due to the large spacing between TEM soundings and the limited number of stratigraphic bore logs in part of the studied area, the obtained characterization should be integrated with additional data for precise borehole sittings. Nevertheless, the implementation of TEM allowed to cover an extensive area and to reach large depth of exploration, so that it was possible to extract general information about the hydrostratigraphy of the different areas of the catchment.

Estimation of spatiotemporal groundwater recharge distribution in humid regions with tropical climate

The precise determination of groundwater recharge variation is a fundamental task for the sustainable planning of groundwater resources, particularly in heavily pressured aquifers. In order to determine the spatial and temporal variability of groundwater recharge in an urban aquifer with a humid climate, such as the San Salvador aquifer, two Mass Balance methods were used (one in the subsurface zone, Soil Water Balance (SWB) and another in the saturated zone, Chloride Mass Balance (CMB)). The SWB was calculated on a daily scale for four years (2012-2015) through the modified Thornthwaite and Mather method, using a set of daily climatic data grids and physical data from the study area. The CMB was used to determine the groundwater recharge in drilled wells and springs samples taken during 2009 and 2016, in the upper part of the basin, where various studies suggest that the main aquifer recharge occurs. The results of the SWB indicate a strong temporal and spatial variation of the recharge in the study area, which can vary between 326 and 561 mm year-1, in dry and wet years, respectively. The CMB results showed consistency with the SWB, groundwater recharge values ranged between 313 and 693 mm year-1. In both methods the mean annual recharge is similar and represents between 20% and 30% of the precipitation. The application of both methods could be used in similar areas, the selection of the method will depend on the objectives of the study.

State of the Practice Worldwide: HCA‐PCA‐EWM Discrimination Model of Water Inrush Source in Mines

AbstractThe hydrogeological conditions in the North China type coal mine area are complex and diverse, and water gushing accidents are frequent. Quickly and accurately identifying the source of water in these incidents is necessary to reduce the harmful effects of mine floods. Taking the Pingdingshan mining area as an example, what chemical composition data from each of the main aquifers was collected and a mine gushing water source model, based on Hierarchical Cluster Analysis—Principle Component Analysis—Entropy Weighted Membership (HCA‐PCA‐EWM), was established. First, typical water sample data from an aquifer were selected by systematic cluster analysis. Then, the remaining water samples were randomly divided into training and prediction samples. Principal component analysis was used to reduce the dimension of water chemical components in training samples. Finally, the discriminant model of the water gushing source was established on the basis of the entropy weight‐membership degree principle. The accuracy of the HCA‐PCA‐EWM discriminant model approached 100%, while those of traditional PCA‐Fisher and PCA‐EWM discriminant models were 62.5 and 87.5%, respectively. From the above, the HCA‐PCA‐EWM discriminant model can effectively select typical aquifer water samples, significantly improve the accuracy of the model, and provide a theoretical basis for the effective identification of mine water gushing sources.

3D geophysical mapping of the subsurface to support urban water planning: a case study from Simawa, Nigeria

ABSTRACT Simawa town, Ogun state, lacks the required water infrastructure for rapid urban development. This study seeks to use the geoelectric method – taking into account the geology and hydrogeology of the study area – to determine the groundwater potential of the town. Fifteen Vertical Electrical Sounding (VES) stations were spread across the town to characterise the subsurface layers. Interpretation of the VES data yielded five geoelectric layers. A lithology log from a prior borehole was used as a geologic control to confirm the validity of the VES results. The five geoelectric layers correspond to the topsoil (layer 1), Akinbo clay (layer 2), Akinbo shale (Layer 3), Ewekoro limestone (Layer 4), and Abeokuta sandstone (layer 5). The Abeokuta sandstone represents the main aquifer unit, a confined aquifer that can serve as a suitable source of potable water. Boreholes drilled in Simawa town should target the confined sandstone aquifer at a minimum depth of 80 m.

Conceptual Modelling of Two Large-Scale Mine Water Geothermal Energy Schemes: Felling, Gateshead, UK.

A conceptual model is presented of two MW-scale low enthalpy mine water geothermal heat pump schemes that are being developed in Tyneside, UK. The Abbotsford Road scheme (54.955° N 1.556° W) is operating (as of May 2021) at 20–30 L/s, abstracting groundwater (and heat) from an unmined Coal Measures Upper Aquifer System (UAS) and reinjecting to the deeper High Main Aquifer System (HMAS), associated with the High Main (E) coal workings and the overlying High Main Post sandstone. A similar scheme, 700 m away at Nest Road (54.959° N 1.564° W), abstracts at 40 L/s from the HMAS, recovers heat from the mine water and reinjects the thermally spent water to deeper workings associated with the Hutton (L), Harvey-Beaumont (N) (and possibly other) coal seams, termed the Deep Mined Aquifer System (DMAS). The three aquifer systems are vertically discontinuous and possess different hydraulic (storage, transmissivity and continuity) properties that would have been near-impossible to predict in advance of drilling. At the sites, 10 boreholes were drilled to obtain five usable production/reinjection boreholes. Development of mine water geothermal energy schemes thus carries a significant project risk, and also a potential ongoing maintenance burden related to iron hydroxide scaling. These do not preclude mine water geothermal as a useful low carbon heating and cooling technology, but the involvement of skilled hydrogeologists, hydrochemists, mining and groundwater engineers is a pre-requisite.

Multifrequency electromagnetic method for the hydrogeophysical characterization of hard-rock aquifers: the case of the upstream watershed of White Bandama (northern Ivory Coast)

In West Africa, the drinking water supply relies on the hard-rock aquifers. In Ivory Coast, the population growth along with the climate changes make drinking water resources highly vulnerable. The White Bandama upstream watershed in northern Ivory Coast is located on a fissured hard-rock aquifer and is poorly known, both in the geometry of the reservoirs and in the hydrogeological potential of the reserves it contains. Indeed, the heterogeneous subsurface in this region shows high variability in the hydraulic conductivity inducing difficulties in the hydrogeological exploration. The determination of the geometry and hydrodynamic properties of the aquifer are required for a sustainable management of this water resource and for a better choice of future well locations. This study presents a hydrogeophysical approach using the multifrequency electromagnetic device PROMIS®, as well as lithology logs and geological information of a 30 × 30 km zone in the northwestern part of the White Bandama catchment. Our geophysical data are interpreted with 1D multi-layer models consistent with the discontinuities observed in lithology logs and the geology of the site. Results allow to precise the local thicknesses of the 3 main units of our study area down to 50 m, being from top to down, saprolite (which is often indured close to the surface), fissured-rock zone and rock substratum. Between the saprolite and the fissured zone, the main aquifer unit constitutes the interesting target for productive water wells. Its thickness ranges from 15 to 30 m. A detailed knowledge of the local aquifer geometry constitutes the first and crucial step before going further into a complete hydrogeological study.

Assessment of Groundwater Yield Potentials Zones of Idi-Ayunre using Vertical Electrical Sounding and Geographic Information System (GIS)

To fully harness the increasing number of observations and variant data sets available and put them to efficient use in geological studies aimed at solving earth science-related problems, GIS technique is a veritable tool. The dynamic techniques and the complex nature of earth sciences is a serious cause for worry for geologists. In this work vertical electrical sounding (VES) was integrated with geographic information system (GIS) to delineate subsurface characteristics and evaluate groundwater potential zones in Idi Ayunre, Oluyole Local Government Area, Oyo State. The results of the VES curves obtained from the partial curve matching were used to constrain the interpretation by the computer using iteration software known as WINRESIST® and extended analysis on the data set was done using geostatistical analysis tool on archGIS 10.0®. The Root Mean Square (RMS) errors for the analysis were found to be very low with an average of 2.96% . This underscores the reliability of the analysis tool for this type of work. The area is dominated predominantly by Type-H curves which amassed twenty (20) out of the twenty-one (21) VES and one (1) VES producing a type-K curve. The VES results revealed a maximum of three geo-electric layers, viz: topsoil, weathered layer, bedrock respectively. The yields of wells dug in most of these locations may be insufficient, even for domestic use because of its relatively small thicknesses. However, at a depth of 7.8 m, a fractured zone occurs in VES 10 with resistivity value of 21.2 Ωm suggesting the presence of groundwater, which may be considered the main aquifer units suitable for groundwater exploration.