Shallow Groundwater Aquifers Research Articles

Potential Chemical Impacts of Subsurface CO2: An Integrated Experimental and Numerical Assessment for a Case Study of the Ogallala Aquifer

AbstractLeakage from geologic CO2sequestration (GCS) reservoirs to overlying underground sources of drinking water (USDW) is a tangible risk. This study is an integrated assessment that combines column experiments and reactive transport simulations of sediments sampled from the Ogallala aquifer above an active commercial‐scale GCS site (the Farnsworth Unit in northern Texas). Experimental and simulation results suggest that carbonate mineral (calcite and dolomite) dissolution is the most significant reaction following CO2intrusion, and is also the dominant source of trace metal release. Cation exchange is another key mechanism controlling trace metal release by cation interference. Most of the trace metals, including Ba, Sr, As, Pb, and Zn, show a short‐term release and quickly drop to the baseline values, suggesting low risk to the overlying USDW quality. Other trace metals, such as Mn and U, exhibit a tangible increase of their concentrations in the beginning, and drop to a higher level compared to the baseline, which may become a potential concern of long‐term USDW quality change with CO2introduction. This study provides a comprehensive example of combining laboratory experiments and simulations for assessment of CO2‐sediment interactions with combined release mechanisms in shallow groundwater aquifers. Data presented here provides useful insights for quantitative risk assessment and effective public education regarding CO2geological sequestration, and trace metal reactive transport studies in shallow groundwater aquifers.

Storage‐discharge characteristics of an active rock glacier catchment in the Innere Ölgrube, Austrian Alps

AbstractThe active rock glacier “Innere Ölgrube” and its catchment area (Ötztal Alps, Austria) are assessed using various hydro(geo)logical tools to provide a thorough catchment characterization and to quantify temporal variations in recharge and discharge components. During the period from June 2014 to July 2018, an average contribution derived from snowmelt, ice melt and rainfall of 35.8%, 27.6% and 36.6%, respectively, is modelled for the catchment using a rainfall‐runoff model. Discharge components of the rock glacier springs are distinguished using isotopic data as well as other natural and artificial tracer data, when considering the potential sources rainfall, snowmelt, ice melt and longer stored groundwater. Seasonal as well as diurnal variations in runoff are quantified and the importance of shallow groundwater within this rock glacier‐influenced catchment is emphasized. Water derived from ice melt is suggested to be provided mainly by melting of two small cirque glaciers within the catchment and subordinately by melting of permafrost ice of the rock glacier. The active rock glacier is characterized by a layered internal structure with an unfrozen base layer responsible for groundwater storage and retarded runoff, a main permafrost body contributing little to the discharge (at the moment) by permafrost thaw and an active layer responsible for fast lateral flow on top of the permafrost body. Snowmelt contributes at least 1/3rd of the annual recharge. During droughts, meltwater derived from two cirque glaciers provides runoff with diurnal runoff variations; however, this discharge pattern will change as these cirque glaciers will ultimately disappear in the future. The storage‐discharge characteristics of the investigated active rock glacier catchment are an example of a shallow groundwater aquifer in alpine catchments that ought to be considered when analysing (future) river runoff characteristics in alpine catchments as these provide retarded runoff during periods with little or no recharge.

An appraisal of Chott El Jerid brine encroachment in the Tozeur-south shallow aquifer: Geoelectrical and hydrochemical approach

Geoelectrical data were used in conjunction with hydrogeological information and hydrochemical measurements to investigate and conceptualize the Chott El Jerid saltwater encroachment into the Tozeur-south shallow aquifer, southern Tunisia. The hydrogeological investigation shows that the over-pumping of the unconfined aquifer groundwater has resulted in a localized water level decline, which enhanced the encroachment of the brines of the Chott El Jerid discharge area into the shallow water table. This transitional hydrodynamic state is further complicated by the upward vertical flow of relatively fresh-water from the underlying confined aquifer. The geoelectrical study has confirmed the brines encroachment through the predominance of relatively low resistivity values of the shallow aquifer groundwater close to the discharge area, which become progressively high as we move away towards the recharge zones. In fact, the toes shaped resistivity zones in the isoresistivity map bring insight to the mixing of shallow groundwater with Chott brines. However, the presence of a positive resistivity leakage plume confirmed the mixing with upward fresh-water leakages. Hydrochemically, the Chott brines encroachment is manifested by an evolution of hydrochemical facies from Na-Cl end-member towards a Ca-HCO3/SO4 end-member. The variation in groundwater hydrofacies between these two end-members, indicates a progressive evolution as we move along way from the Chott, by mix/Na-mix/SO4 and mix/Na-SO4. These findings are well illustrated in the conceptual model, which shows the impact of the stressed hydrodynamic regime on the behaviors of the electrical and the hydrochemical facies of the PQ aquifer and its groundwater, respectively.

Shallow groundwater environmental investigation at northeastern Cairo, Egypt: quality and photo-treatment evaluation.

Groundwater represents the primary source of freshwater for more than 35% of world people, and its contamination became a worldwide challenge. Egypt is suffering from water quantity and quality, especially in desert areas. El Obour city and environs Northeast Cairo face waterlogging owing to the elevated-shallow groundwater table. In the present research work, the water quality of the shallow groundwater aquifer was studied. The remediation efficiency of polluted water using photocatalytic treatment technique in the presence of modified nano-titania and solar radiation has also been investigated. Twenty-eight representative samples have been collected from different locations, and their microbial, physical, and chemical characteristics were determined. The average contents of Pb (214.96µg/L), As (1517µg/L), Cd (8.79µg/L), total bacterial count (2.22 × 105CFU/ml), and bacterial indicators (MPN-index/100ml): total coliform (497.4), fecal coliform (358.3), and fecal streptococci (115.9) were higher than WHO permissible limits for drinking water, possibly due to higher industrialization, agricultural, and urbanization rates. The organic pollutants reached critical concentrations (chemical oxygen demand up to 960.8mgO2/L). Most of the studied samples contained acceptable concentrations of the major ions, (e.g., K+, Mg2+, HCO3-), for drinking and irrigation purposes. The statistical analyses (e.g., principal component analysis and cluster analysis) pointed out the control of water-rock interaction and anthropogenic activities in water composition. The hydrochemical data show that most of the water samples (96.4%) are Na2SO4 and NaHCO3 type, indicating its meteoric origin. The contamination with human and animal fecal substances, NO3¯, and NH4+ was identified in all samples, which pointed out the control of anthropogenic activities in water pollution. The photocatalytic technique efficiently eliminated more than 82-95% of organic contents and microbial pollutants, respectively, but it was inefficient in reducing heavy metal levels. According to the current results, shallow groundwater injection into the deep aquifer must be constrained and reusable after treatment. Finally, more studies are imperative to disseminate the applied treatment techniques to elude bacteria and organic pollutants from water at a pilot scale.

Hydrogeological controls on the flow regime of an ephemeral temperate stream flowing across an alluvial fan

Alluvial fans often support ephemeral streams whose flow regimes and sediment dynamics are strongly controlled by fan sedimentary characteristics and interactions with shallow groundwater aquifers. The hydrogeology of such fans has most often been documented for large fans located within arid climate zones. This research focuses on a small (0.075 km2) alluvial fan situated in a temperate, high rainfall climate (the Lake District, North West England). An ephemeral stream flowing across this alluvial fan plays a key role in supplying water and sediment to the River Ehen, which is the focus of a habitat restoration initiative. This study combines high spatial resolution, near surface geophysics and outcrop data with hydrological data to characterise the hydrogeological properties of the alluvial fan. A conceptual hydrogeological model was developed to understand the hydrology across the alluvial fan and how that affects water and sediment supply to the River Ehen. The alluvial fan is composed predominantly of permeable debris flow deposits and numerous palaeochannels which may provide preferential groundwater flow paths. During streamflows, partial to full stream-aquifer connectivity occurs, especially in the distal fan where groundwater discharges back into the stream. Streamflows occur when the fan apex infiltration rate/capacity threshold of approx. 60 l/s−1 is exceeded, typically following rainfall events >9–11 mm. Understanding interactions between ephemeral streams and their underlying aquifers enables better predictions of the timing and magnitude of future flows, and in-turn, their likely impacts on the water courses into which they discharge.

Main Characteristics of Spring Water on the Territory of Belgrade (Serbia)

This paper presents main physicochemical and microbiological characteristics of the spring water on the territory of Belgrade city (Serbia) and estimates the possibility of their utilization for public water supply purposes. Analysis of 23 springs on the wider territory of Belgrade is done. The following physicochemical parameters were analyzed: turbidity, pH, TDS, EC, Cl–, $${\text{NO}}_{3}^{ - }$$ , Ca2+, Mg2+, $${\text{SO}}_{4}^{{2 - }}$$ , $${\text{HCO}}_{3}^{ - }$$ , K+ and Na+, Ca2+, Mg2+, Na+ and K+ ions, as well as $${\text{NH}}_{4}^{ + }$$ and Cl–, were determined by atomic absorption spectrophotometry (AAS). Total Fe was determined by atomic absorption spectroscopy. $${\text{HCO}}_{3}^{ - }$$ was determined by volumetric titration. $${\text{SO}}_{4}^{{2 - }}$$ was determined by gravimetric method, and $${\text{NO}}_{3}^{ - }$$ was determined by colorimetric method. Microbiological testing was done by Most Probable Number method. Water from 23 springs is defined as Ca–Mg–HCO3 type of water. The most common problem that was recorded is microbiological inappropriateness of water (analyzed: aerobic mesophilic bacteria, coliform bacteria, streptococcus, proteus species, clostridia, pseudomonas aeruginosa or isolated microorganisms presence in water above maximum allowed value), on the first place, and in some cases physicochemical deviations. Among the undesired physicochemical characteristics of several springs, elevated nitrate content due to anthropogenic impact on the shallow aquifer groundwater and elevated magnesium content due to the presence of dolomite, stand out as dominant. An increase in the nitrate content is evident at the area away from the city centre that belongs to the rural type of settlement with a larger number of septic tanks, individual agricultural production with the use of fertilizers as well as individual animal breeding. Other physicochemical parameters are mostly within the proposed limits for human use. Analyzed water would see far greater application if it was treated in order to correct their microbiological quality, as well as nitrate content.

Distribution and Community Composition of Anammox Bacteria in Shallow Groundwater of the Kathmandu Valley, Nepal.

The abundance and diversity of anaerobic ammonium oxidation (anammox) bacteria were assessed in 152 groundwater samples in the Kathmandu Valley, Nepal. Anammox bacterial 16S rRNA genes were detected in 54% (37/68) of samples collected in the dry season at 1.6×105–8.8×106 copies L–1, and in 60% (50/84) of samples collected in the wet season at 4.3×104–1.2×107 copies L–1. The 16S rRNA genes of “Candidatus Brocadia”, “Candidatus Anammoxoglobus”, and five new deduced anammox bacterial phylotypes were detected in the shallow groundwater samples. Diverse anammox bacteria were broadly distributed in the shallow groundwater aquifer of the Kathmandu Valley.

Optimizing Groundwater Aquifers Potential in The Development of Irrigation Wells for Agriculture Using Geo-Electrical Method

The identification of shallow groundwater aquifers is demanded to sustain the balance of utilization in agriculture and anticipate frictions that can occur due to the overlapping usage of groundwater resources. This study is aimed to identify the potential of groundwater resources based on the thickness and depth of the groundwater aquifer. Geoelectric resistivity methods have done with vertical electrical sounding (VES) and horizontal profiling techniques (2D mapping). The VES data acquisition was carried out with a Schlumberger array while 2D mapping by alpha Wenner array. Inversion results of vertical electrical sounding (VES) show that groundwater resistivity values in sedimentary rocks ranged from 1 to 100 ?m and in igneous rocks between 0.5 - 150 ?m. The results of 2D Resistivity Mapping also show that shallow aquifer depth ranged from 1 to 5 m with a thickness ranged from 15 m to more than 70 m. Meanwhile, bedrock depth ranged from 20 to 150 m with a pattern deeper to the west. Furthermore, the potential of groundwater aquifers in the development of irrigation wells for agriculture should be carried out in the western part of the study area.
 
 Keywords: Groundwater, Shallow Aquifer, Rock Resistivity, Irrigation Well, Geo-Electrical Sounding.

Spatial Assessment of Groundwater Quality and Health Risk of Nitrogen Pollution for Shallow Groundwater Aquifer around Fuyang City, China

Prolonged exposure to intensive and extensive agricultural and industrial activities is leading to an increased deterioration of groundwater quality, especially nitrogen pollution in shallow groundwater aquifers. This study was carried out using the fuzzy comprehensive method to assess the overall groundwater quality, and the noncarcinogenic risks were estimated using the human health risk assessment method recommended by the United States Environmental Protection Agency (USEPA) via drinking water intake pathways around Fuyang City, China. A total of 34 samples were collected from shallow groundwater private wells, and 16 parameters were analyzed for each groundwater sample. The evaluation results of groundwater quality show 14.7% of groundwater samples classified as poor and very poor quality, and NO3-N, TH, TDS, Fe3+, and Mn are of high potential to affect the quality of potable drinking water. These are mainly derived from anthropogenic pollutants, predominantly due to uncontrolled agricultural and industrial activities, as well as some natural processes. The noncarcinogenic risk of nitrate indicates that 8.82% of groundwater samples surpass the permissible limit recommended by the USEPA for both adults and children. This study may provide the local authority with insights into making scientific decisions for exploiting groundwater in a sustainable manner so as to protect public health.

Use of the geophysical approaches for studying the environmental impact assessment of the human burying techniques to the soil and groundwater: A case study of Geheina cemeteries, Sohag, Egypt

Electrical resistivity and self-potential are effective geophysical tools for monitoring the soil and groundwater pollution because they are accurate, rapid, costless and non-distractive techniques. Direct or indirect burying of the corpses into the soil is one of the main factors which pollute the soil and the groundwater after decomposition of the tissues and bones. Therefore, the main objective of this study are using these tools to evaluate the rate of soil and groundwater pollution due to burying the corpses in chipboard coffins at depths approximately 0.70–1.30 m (Christians burial method) and directly into the soil at depths about 1.5–1.8 m (Muslims burial method). Beside, assessing the contamination depths and flow paths of the groundwater investigated area. The study area was carefully chosen because of: 1- it contains two different burial methods, 2- presence of shallow groundwater aquifer, 3- the surface layer which contains the burial depth is porous and permeable, 4- the cemeteries are near enough to the population density and agricultural lands. The study area was divided to three main sites; site 1, site 2 and site 3 for Christian cemeteries, Muslims ones and control area that does not contains any cemeteries respectively. Five two-dimensional electrical resistivity tomography (ERT) profiles were surveyed and analyzed using RES2DINV software (two profiles on the site 1, two profiles on the site 2 and one profile on the site 3). 121 points of vertical electrical sounding (VES) at the same depth were collected and analyzed in 3D iso-resistivity map. Self-potential survey (SP) were performed on the same 121 points of VES stations for comparison where the data was contoured to build 3D iso-potential map. The geophysical results were correlated with the available borehole data. The results revealed presence of three resistivity zones of high resistivities (1000–3000 Ω m), moderate ones (50–1000 Ω m) and low ones (<50 Ω m). The main constituents of these three zones are clastic sedimentary rocks with different grain sizes. The rapid decreasing in the resistivity values in the site 2 than that in the site 1 is resulting from the rapid decomposition of the death bodies due to direct burying in the ground without coffins leading to more pollution rates of the soil and the groundwater than burying in coffins. Increasing of the burial depth causes increasing of the contamination rate of the shallow groundwater aquifer. Positive and negative values of potentials were recorded in 3D iso-potential contour map reflecting the flow direction from low to high potentials. The negative values were attributed to the leakage of more the putrefactive liquid resulting from decomposition of the death body. Positive potential values were caused due to the semi-fluid masses consisting of water and putrefied tissues which are mostly generated by the corpses buried in coffins with less amount of fluids and the putrefactive liquid evaporation and low humidity.

Groundwater recharge and water table response to changing conditions for aquifers at different physiography: The case of a semi-humid river catchment, northwestern highlands of Ethiopia

Groundwater recharge estimation, aquifer response to meteorological variables, and evapotranspiration calculations have been performed on a semi-humid catchment, in northwestern Ethiopian plateau. The Soil Moisture Balance (SMB), WetSpass water balance model, Water Table Fluctuation (WTF), and Chloride Mass Balance (CMB) methods are applied to estimate the groundwater recharge. Accordingly, 431 mm, 462 mm, and 477 mm recharge amounts are estimated as mean annual value, respectively, using SMB, WetSpass, and CMB methods. Based on the WTF method, the annual recharge rates of the volcanic aquifers range from 157 mm to 760 mm. The SMB and WetSpass methods are less effective for the flat physiographic area, where the recharge rate is storage controlled rather than precipitation amount. The calculated high recharge for maintain-front aquifers using WTF is attributed to extra rising due to lateral groundwater flow, which restricts the reliability of the method for such aquifer geometries. High groundwater level rising rate (121 mm/day) has been observed for the steeply sloping, low rates (11 mm/day) for the flat floodplain, and intermediate rate (52 mm/day) for the gently sloping volcanic aquifers. Similarly, receding rates of 3.18 mm/day were found for the steeply sloping, 0.40 mm/day for the floodplain, and 1.14 mm/day for the gentle sloping aquifers. The recession, in all of the topographies, is happening with second-order polynomial decay function. A strong connection between the shallow and deep groundwater aquifers is noted. Storage change in the relatively deeper volcanic aquifers is due to vertical groundwater flow from the overlying alluvial aquifer. This indicates that the recharge mechanism is local, and may be the reason for the low aquifer productivity of the Dangila wellfield. Diurnal water table fluctuation is detrended from the receding trend of the dry period, and evapotranspiration from the groundwater is estimated at 28% of total ET.

A multidisciplinary approach for delineating wastewater flow paths in shallow groundwater aquifers: A case study in the southeastern part of the Nile Delta, Egypt

Groundwater pollution is a global issue in highly populated areas, the Eastern Nile Delta region is a typical example; especially around artificial wastewater drains. In the present work, a multidisciplinary approach using hydrogeochemical, geostatistical, microbiological and geophysical data was applied to determine the vulnerability conditions and to identify potential pathways through which contaminants could potentially percolate to shallow aquifers in the southern boundary of the Eastern Nile Delta. An organized groundwater sampling was conducted for hydrogeochemical investigation in rural areas along the Belbies unlined drain. This drain is known of being heavily polluted by agricultural and municipal wastewater.The hydrogeochemical analysis reveals high pollution levels by Pb, Cd, and Cr for most of the collected shallow groundwater samples nearby the drain. Additionally, NO3−, fecal and total coliform bacteria were observed in many samples with high concentrations. Six factors were distinguished on the basis of principal component analysis and varimax rotation, with total variance more than 78%. These factors reflected sewage contamination, lithogenic and anthropogenic effects on the shallow groundwater. Hierarchical cluster analysis revealed two main clusters of groundwater groups. Accordingly, Electrical Resistivity Tomography (ERT) was carried out in the areas of the distinguished clusters to locate potential preferential flow paths and horizons of lateral flow around the drain. The obtained resistivity models illustrate breakthrough behavior in parts of the measured profiles due to the presence of permeable paths close to the drain.The applied integrative approach is valuable for understanding the ambiguities during the interpretation process and for characterizing water quality and the aquifer vulnerability conditions. Additionally, it may guide to understand the surface water-groundwater links in order to supply the growing population with safe water.

Hydrogeochemical assessment of spring water resources around Melamchi, Central Nepal

Abstract Groundwater in the hills and mountains is manifested as springs, the major water sources for people in Nepal's mountainous regions. The aim of this study was to investigate the seasonal variations of in-situ groundwater physicochemical parameters, evaluate groundwater hydrochemistry with respect to water types, and identify groundwater chemistry control mechanisms by analyzing spring water. The area's geology is dominated by schist and gneiss. Depression and fracture springs occur widely. The study involved observation of seasonal variations in in-situ physicochemical parameters, pH, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), and temperature, and major ion concentrations – Ca2+, Mg2+, Na+, K+, HCO3−, Cl−, SO42− – to describe the water's chemical characteristics. The seasonal variations in physicochemical parameters arose mainly from monsoonal precipitation and its interactions with host rocks. Chemical analysis showed that Ca-HCO3 type water dominated, indicating shallow aquifer groundwater processes. The relative abundance of cations was, in order, Ca2+ &amp;gt; Na+ &amp;gt; Mg2+ &amp;gt; K+ and of anions HCO3− &amp;gt; Cl− &amp;gt; SO42−. Lithological contributions from the interactions of rocks with water across spring flow networks were the major mechanisms controlling spring water chemistry.

Shallow aquifer groundwater dynamics due to land use/cover change in highly urbanized basin: The case of Kathmandu Valley

Study regionKathmandu Valley, Nepal. Study focusIn the context of rapid urbanization in Kathmandu Valley (KV), this study quantifies spatial distribution of recharge and changes in drawdown under pumping rate and land use/cover change scenarios. Both scenarios are incorporated in a groundwater flow model in MODFLOW. New hydrological insights for this regionCurrent groundwater recharge rate is spatially distributed across the basin in a range of 95.3–85.3 % of precipitation in dry season and 48−38% of precipitation in wet season as per recharge area distributions. This results in groundwater recharge of 1.052 MCM and 1.949 MCM in dry and wet seasons respectively. In the case of increase in both pumping rate and encroachment of recharge areas (due to land use/cover change) and only encroachment of recharge areas, drawdown is projected to change respectively by −5.25 m in dry season and −7.39 m in wet season and −1.09 m in dry season and -3.63 m in wet season in 2050. The central urban, northern foothills, and southern parts are projected to observe more draw down. Meanwhile, the boundary forest area has the potential to increase the water table in the future.

Susceptibility of shallow groundwater aquifers to water logging, case study Al Marashda area, West Nile Valley, Qena, Egypt

Attempts were carried out to delineate the areas where the aquifer is vulnerable to water logging, head drop and pollution in the new and old reclamation areas as well. All of the hydrological, geophysical and soil factors were incorporated in the DRASTIC model. Parameters included are; depth to water, net recharge, aquifer media, water salinity, thicknesses and resistivity of successive geoelectrical layers soil media, topography and impact of the vadose zone. Saturated soil hydraulic conductivity varies from 4.43 X10-4 to 243 X10-4 m/sec. Groundwater is supplied from the gravel sand saturated sediments belonging to the Quaternary aquifer. The aquifer thickness rangs from 60 to 120 m. Groundwater depths are gradually increased from 2 m in north to about 72 m in the southern area. Groundwater levels are ranging from 58 m a.s.l. to 74 m a.s.l. Transmissivity is ranging from 155 m2/day to 420 m2/day. Applying the DRASTIC model reveals that there are five vulnerable classes characterizing the study area. Very low and Low vulnerable areas characterize the southern area located near the table land area. Medium vulnerable area present at the pediment area just above the old cultivated lands and extends through the old cultivated lands East of Al Marashda area where groundwater depths are ranging from 5 m - 40 m and recharge is essentially from excess irrigation water. A very high and high vulnerable area is located in the old cultivated lands where groundwater is very shallow (< 5 m) and recharge is very high from excess irrigation water and percolation from surface water systems.

Geochemistry of groundwater and saltwater intrusion in a coastal region of an island in Malacca Strait, Indonesia

Most people in Bengkalis island use groundwater as their primary resource, but brackish water discovered in the wells located near the shore as well as in the distance. A hydrogeology study through geochemistry and isotope aspect conducted for the first time to identify the effect of saltwater intrusion (SWI) on groundwater. Na &gt; Mg &gt; K &gt; Ca were the most dominant cation sequence in groundwater, while Cl &gt; HCO3 &gt; SO4 was the most dominant for anion. NaCl is the main type of groundwater in shallow aquifer and NaCl &amp; NaHCO3 both became the most dominant type of groundwater in the deeper aquifer system. Most of the groundwater samples from dug wells indicating the weak acid exceeding strong acid. Meanwhile, the groundwater samples from bore wells dominated by alkalis exceeding alkaline earth. SWI analysis shows 36.4% of groundwater samples from dug wells and 40% of bore water samples experiencing the salinization process. From isotope analysis, the groundwater samples found to be originated from the higher elevation or distance source. Meanwhile, there are lighter 2H values in the samples that are indicating the groundwater flown in the deeper part of the aquifer.

Mapping the Groundwater Potentiality of West Qena Area, Egypt, Using Integrated Remote Sensing and Hydro-Geophysical Techniques

The integrated use of remote sensing imagery and hydro-geophysical field surveys is a well-established approach to map the hydrogeological framework, and thus explore and evaluate the groundwater potentiality of desert lands, where groundwater is considered as the main source of freshwater. This study uses such integrated approach to map the groundwater potentiality of the desert alluvial floodplain of the Nile Valley west of Qena, Egypt, as alternative water source to the River Nile. Typically ground gradient, faults and their stress field, lateral variation of rock permeability, drainage patterns, watersheds, rainfall, lithology, and soil types are the main factors believed to affect the groundwater recharge and storage from the infiltration of present-time and paleo-runoff. Following this generally accepted approach, different remote sensing data sets (SRTM DEM, Landsat-8, ALOS/PALSAR-1, Sentinel-1, and TRMM) as well as auxiliary maps (geological and soil maps) were used to identify and map these factors and prepare thematic maps portraying the different influences they exert on the groundwater recharge. These thematic maps were overlaid and integrated using weights in a GIS framework to generate the groundwater potentiality map which categorizes the different recharge capabilities into five zones. Moreover, the aeromagnetic data were processed to map the deep-seated structures and estimate the depth to basement rocks that may control the groundwater occurrence. In addition, the vertical electrical sounding (VES) measurements were applied and calibrated with the available borehole data to delineate the subsurface geological and hydrogeological setting as well as the groundwater aquifers. Different geoelectric cross-sections and hydro-geophysical maps were constructed using the borehole information and VES interpretation results to show the lateral extension of the different lithological units, groundwater-bearing zones, water table, and the saturated thickness of the aquifer. The GIS model and geophysical results show that the southwest part of Nag’a Hammadi-El-Ghoneimia stretch has very high recharge and storage potentiality and is characterized by the presence of two groundwater-bearing zones. The shallow groundwater aquifer is located at a depth of 30 m with a saturation thickness of more than 43 m. However, there are NW–SE faults crossing the study area and most likely serve as recharge conduits by connecting the shallow aquifer with the deeper ones. Such aquifers connection has been confirmed by investigating the chemical and isotopic composition of their groundwater.

Application of noble gas tracers to identify the retention mechanisms of CO2 migrated from a deep reservoir into shallow groundwater

Carbon Capture and Storage (CCS) is a valuable climate-mitigation technology, which offers the potential to cost-effectively reduce the emissions associated with the burning of fossil fuels. However, there is a potential risk of a small portion of the stored CO2 unintentionally migrating from a storage site to a shallow groundwater aquifer which is the final retaining zone for any migrated CO2 before it escapes to the atmosphere. Hence, it is imperative to identify the physical retention mechanisms of CO2 within a shallow aquifer. In this study 1.70 × 102 kg of CO2 and noble gas tracers (He, Ar and Kr) were continuously injected into a groundwater aquifer over 28 days with the aim of identifying the mechanisms and amount of CO2 retention. Among the tracers, Kr was found to be the earliest indicator of CO2 migration. The other tracers – He and Ar – arrived later and exhibited diluted signals. The diluted signals were attributed to degassing of the plume mass (1.6 % of CO2) during the early stages of CO2 migration. Diffusion accelerated the dilution of the lighter elements at the plume boundaries. Consequently, the clear relation of the noble gases with the CO2 proved that degassing and mixing primarily control the mass retention of CO2 in shallow groundwater, and the relative importance of these processes varies along the evolving path of migrating CO2.

Investigation of Groundwater Quality from Selected Wells in Paiko, Northcentral Nigeria

Groundwater from hand dug wells and boreholes in Paiko, northcentral Nigeria were subjected to physico-chemical as well as microbiological analysis to determine their suitability for drinking purpose. The water from the hand dug wells are predominantly calcium magnesium chloride (Ca-Mg-Cl) water while those from boreholes are calcium magnesium bicarbonate water (Ca-Mg-HCO3) facies. The results showed elevated cations and anions concentration in the hand dug wells in addition to the water being slightly acidic. Also, the nitrate concentration in the hand dug wells is above the maximum permissible limit of 50mg/l postulated by World Health Organization (WHO) and Nigerian Standard for Drinking Water Quality (NSDQ). Microbiological analysis revealed Total Coliform Count of 100cfu and 360cfu in the hand dug wells and borehole respectively signifying faecal contamination. The study revealed that improper sewage systems as well as poor waste disposal is responsible for the poor water quality as well as elevated concentration of nitrate in hand dug wells, and as such the shallow aquifer groundwater in the area are not safe for drinking purpose with respect to all the parameters taken together.

Groundwater Resources Management of the Shallow Groundwater Aquifer in the Desert Fringes of El Beheira Governorate, Egypt

Groundwater resources management is a master key for sustainable development of any region especially for agricultural, domestic, industrial and economic stability in the arid and semiarid regions. The study area is an important portion of the Egyptian desert fringes, where the groundwater in the shallow aquifer is started for exploitation since 30 years ago. Most of the groundwater wells were drilled randomly regardless of the hydrological rules such as well radius of influence and interference of cones of depressions, well losses and formation losses, which leads to the noteworthy drawdown of the water table and salinity enhancement. Hence, the main objective of this study is an attempt to draw a management road map of the shallow groundwater aquifer to avoid the depletion of water table and deterioration of water quality. In this study, all the hydrological parameters of the shallow confined to semi-confined aquifer were measured and calculated (~ 30 wells). The hydrological parameters (aquifer thickness, depth to water, water table and drawdown, transmissivity, hydraulic conductivity, well losses, formation losses and radius interference) between the pumping wells are based on the analyses of long duration and step-test pumping for 30 wells. The main findings in this study show that the drawdown ranges between 3.2 and 19.1 m, TDS ranges from 320 to 2970 mg/l, and the calculated radius interference between the drilled wells should not be less than about 350 m. In addition, efficiency of the wells ranges between 15.1 and 99%. Also, results show that 73% of the study wells are good to excellent efficiency, while about 27% of the wells have low values of efficiency which need a considerable management strategy.