Hard Rock Aquifer System Research Articles

Assessment to locate potential deep aquifer systems using lithological logs, pumping tests and electromagnetic surveys in hard rock terrain of Dodoma urban area, Tanzania

The Dodoma region located in Central Tanzania is a semi-arid area characterised by scarce surface water resources. Because of climate change and dependence on groundwater resources in the Dodoma urban area, there is currently an increased demand for water due to low groundwater recharge and high groundwater withdrawals due to the growing population. There is therefore a need to explore potential deep aquifer systems around the Dodoma urban area to meet the increasing water demand. This study uses lithological logs, pumping tests, and electromagnetic survey data to delineate the subsurface lithologies to locate potential deep aquifer system in the area. Results show that the shallow aquifer system is unconfined in some areas with resistivity values ranging from 11 to 28 Ωm and semi-confined in other areas with resistivity values ranging from 19 to 27 Ωm. The unconfined aquifer extends up to 60 m, while the semi-confined aquifer extends between 50–55 m and 65–120 m. The study found a potential deep aquifer system at a depth of between 200 and 290 m, with resistivity values ranging from 11 to 20 Ωm. Currently, this deep aquifer system has not been exploited as most boreholes in the area are only up to 150 m deep. The main lithology in the study area is weathered and fractured granite, with different degrees of weathering and fracturing, indicating a hard-rock aquifer system. This study adds valuable knowledge on the location of potential deep aquifer systems in the area for proper groundwater utilisation and management.

Piezometric Modelling of a Hard Rock Aquifer System in An Intertropical Zone: The Case of the Batouri Mining District (South-East Cameroon)

Piezometric Modelling of a Hard Rock Aquifer System in An Intertropical Zone: The Case of the Batouri Mining District (South-East Cameroon)

Contribution of Piezometry and Hydro-Geochemistry to a Better Understanding of the Adamawa-Yadé Hard Rock Aquifer System in Ngaoundéré

Contribution of Piezometry and Hydro-Geochemistry to a Better Understanding of the Adamawa-Yadé Hard Rock Aquifer System in Ngaoundéré

Uranium anomaly in groundwater of the hard rock aquifer system in southeast Brazil

This study presents a hydrogeological characterization that fills knowledge gaps in an area where a complex geological scenario connects two fractured (granite/metamorphic rocks and diabase) and one porous (sedimentary rocks) aquifer systems. Previous groundwater studies from the four local deep supply wells suggested the sedimentary aquifer as the source of uranium (∼60 μg/L) in one of the wells. Despite the water extraction interruption from this well, this finding needed to be supported by evidence provided by the geological and structural characteristics of the aquifers. Data collected through video inspection, caliper, optical (OPTV), and acoustic borehole televiewers (ATV) revealed the predominance of the crystalline aquifer in the area. As recorded by video inspection, the well's borehole with high U intersects the crystalline rocks at several open fractures and presents the highest gamma radiation values. Therefore, we infer that the origin of dissolved U is the weathering of primary minerals locally occurring in those rocks. The U leaching and complexation as calcium-uranyl-carbonates favors its solubility in that specific aqueous medium, as shown by hydrogeochemical modeling using PHREEQC. Additionally, the major ions and trace elements concentrations allow the division of the wells into two groups: a) two with higher U concentrations, influenced by the granite/metamorphic aquifer and possibly longer residence times, and b) the other two wells with lower U concentrations, higher nitrate concentrations, influenced by the diabase aquifer, possibly have younger residence times.

Three-dimensional electric-field vector resistivity imaging for deep subsurface fractures network in heterogeneous crystalline rocks

SUMMARY Crystalline rocks, exposed in different parts of the world and over about one-third of India, have complex aquifer systems, which pose a challenge to mapping groundwater dynamics. Electrical resistivity tomography in quasi-3-D and electrical logging of some borewells carried out in an experimental ‘hydrogeological park’ in southern India, which has numerous boreholes and other geophysical information for validation, were unable to map the existence of deeper bedrock fractures and their connectivity. We have attempted electric-field vector resistivity imaging (EVRI), a new tool, to resolve the possible fracture-induced deep interconnectivity in a hard rock aquifer system. In the experiment, multiple two-orthonormal-channels independent receiver nodes for potential measurements are deployed and illuminated with several current injections between ∼ 0.9–3.7 A in full 3-D fashion, which allowed for improved mapping of resistivity variation than earlier approaches. The EVRI-derived full 3-D model shows the presence of fractures for depths between 20 and 70 m with substantial resistivity variations, supported by some borewells hydraulic investigations. It has also enhanced lateral resolution for depths > 30 m and almost doubled the depth of investigation than earlier electrical models. EVRI results revealed unweathered/unfractured granitic rock with no significant signature of fractures beyond 70 m depth that corroborates with existing borehole logs and hydrogeological conceptual model. Therefore, this study demonstrates the potential of EVRI for 3-D mapping of heterogeneous crystalline rocks, which would greatly help in groundwater management.

Groundwater quality analysis using different water quality indices in the hard rock aquifer region in semi-arid environment

AbstractThe present study aimed to assess the groundwater quality in the hard rock aquifer system of the Nand Samand catchment for irrigation use by employing distinct water quality indices (sodium adsorption ratio, per cent sodium, electrical conductivity, residual sodium carbonate, soluble sodium per cent, Kelly's ratio, and permeability index) and also, using graphical illustration techniques (United States Salinity Laboratory (USSL) diagram, Piper, Gibbs, Wilcox, and Chadha diagram, Rajasthan, India. Groundwater samples were collected in two seasons, i.e., pre-monsoon and post-monsoon seasons (for the years 2019 and 2020). Ninety-five samples were collected and analyzed to assess overall groundwater quality for irrigation use. The USSL diagram indicated that the maximum groundwater samples were classified under categories C3S1 and C4S1 during the pre-monsoon season, indicating groundwater suitable for irrigation. The major facies observed in groundwater are mixed Ca–Mg–Cl, CaHCO3, and Ca–Mg–Cl type. Gibbs's diagram depicts that the maximum groundwater samples belonged to the evaporation–crystallization zone, which raises salinity by raising sodium and chloride concerning the increase of total dissolved solids. The results showed that the majority of the samples are suitable for irrigation, and the suitability improves during the post-monsoon season.

Components of urban ground water recharge in Bengaluru, India

ABSTRACT This study investigates the various components of groundwater recharge in an urban hard-rock aquifer system of Bengaluru, India. Groundwater meets more than fifty percent of the water demand in the city. This has led to an endangered situation of groundwater. Urbanization changes the source and path of groundwater recharge. Understanding the components of groundwater recharge is the foremost important step in groundwater management in an urban environment. Rotated empirical orthogonal function (REOF) analysis of ground water level data was used to identify the significant components of ground water level variation in the study area. Rainfall and pipeline leakage were identified as the major components of groundwater recharge in the study area. The stochastic interpolation method of ordinary kriging was used to regionalise the identified significant empirical orthogonal functions.

Appraisal of the Quality Parameters of the Groundwater used for Domestic and Irrigation Purposes in the Hard Rock Aquifer System of the Vasishta sub- basin of the Vellar River, Tamil Nadu


 
 
 
 This article presents an appraisal of the quality of groundwater in the hard Received in revised form: 15.07.2021 rock aquifer system of the Vasishta sub basin, of the Vellar River Basin. Seventy nine representative groundwater samples were collected from dug and bore wells which are intensively used for domestic and irrigational purposes. The physical parameters viz. PH, EC and TDS were estimated in the field using a portable multiparameter meter. The groundwater samples were transported to the laboratory for measuring major ionic concentrations viz, Ca, Mg, Na, K, CO3, HCO3, Cl, SO4, F and NO3. The hydrochemical data were graphically projected and spatial temporal thematic maps generated with reference to the World Health Organization (WHO) and Bureau of Indian (BIS) Standards. The peoples living in the sub basin engage in agricultural activities where the groundwater availability is sufficient. The groundwater is a major source for meeting their basic needs, such as for domestic, irrigational and industrial purposes. Good correlation is exhibited between EC and TDS Cl, SO4.Cl exhibits good correlation with Mg and Ca (0.817), (0.751) indicating leaching of secondary salts. TDS and EC showed strong correlation with Cl, SO4. Clustering groundwater samples based on their similarity is known as Q-mode type clustering method. Spatial and temporal maps of the water quality index reveal that the majority of the groundwater samples fall under the categories excellent to good.
 
 
 

Morphometric characterization of sub-basins in a hard-rock aquifer system of Maharashtra, India, using geospatial and geostatistical tools

Morphometric characterization of sub-basins in a hard-rock aquifer system of Maharashtra, India, using geospatial and geostatistical tools

Joint geophysical prospecting for groundwater exploration in weathered terrains of South Guangdong, China.

Groundwater occurrence in a hard rock terrain is strongly controlled by the weathered/fractured zones. However, delineation of such zones is a challenging task given their structural heterogeneity. Traditionally, large numbers of well tests are conducted to assess the subsurface formation. But, such tests suffer from efficiency in terms of cost, time, and data coverage. Non-invasive geophysical methods can be the best alternative of expensive drilling methods. However, a geophysical method alone is ambiguous to interpret the highly heterogeneous subsurface formation. In this study, joint application of electrical resistivity tomography (ERT), magnetic method, and joint profile method (JPM) was conducted for groundwater exploitation in a weathered terrain of South Guangdong, China. ERT, magnetic, and JPM data were acquired along different geophysical profiles via a variety of survey parameters. The interpreted 2D models of electrical resistivity and magnetic data coupled with the local accessible boreholes and hydrogeological information constrain the subsurface geologic formation into four discrete layers with specific electrical resistivity range, i.e., topsoil cover, highly weathered saturated layer, semi-weathered saturated layer, and un-weathered substratum. Incorporation of JPM (ER, SP, and IP methods) with ERT and magnetic models reveal three faults (F1, F2, and F3) and several saturated intense fractures/discontinuities. The groundwater reserves associated with the weathered/fractured rock were estimated via hydraulic parameters, namely hydraulic conductivity and transmissivity. The results suggest that high-yield groundwater resources are found within the weathered/fractured zones. Geophysical results of this joint application fit pretty well to the local hydrogeological data of the study area. Our novel approach reduces any ambiguity caused in the geophysical interpretation and provides clearer insight of the subsurface formation with more confident solutions to the most challenging problems of the hard rock sites. This hydrogeophysical study provides important contributions to groundwater exploration in areas where weathering has significant effects on the hard rock aquifer system. Compared with traditional methods, this approach is more advantageous for assessment of groundwater resources in hard rock terrains.

Geogenic groundwater arsenic in high altitude bedrock aquifers of upper Indus river basin (UIRB), Ladakh

Many sedimentary aquifers across the globe are contaminated with As, a known toxicant and carcinogen, thereby making millions of people vulnerable to a health hazard. Although the source of As enrichment is being linked to the provenance of the sediments (i.e. hard rocks), there are limited studies of groundwater As enrichment in hard rock areas. In this study, we collected the groundwater samples from complex hard rock aquifer system across the Himalayan collision zone in Upper Indus River Basin (UIRB) to understand the source and to evaluate the hydrogeochemical processes responsible for groundwater As mobilization. The study suggests that groundwater As enrichment comes from volcanic rocks and ophiolitic mélange. Such, As contaminated aquifers are widely used for groundwater exploitation for drinking and other purposes in Ladakh (UIRB). The results indicated that As enrichment occurs with an increase in temperature and depth. The results also indicated that the groundwater in Ladakh is described by multiple hydrochemical facies with pH circum-neutral to alkaline in nature. Higher pH, Fe2+ and Mn and lower ORP, NO3−, and SO42− in groundwater are found to be associated with high As groundwater indicating metal oxides/hydroxides under reducing conditions are predominantly controlling the groundwater As mobilization.

Long-term geochemical assessment of groundwater in a hardrock aquifer system

Long-term geochemical assessment of groundwater in a hardrock aquifer system

Groundwater vulnerability and contamination risk assessment using GIS-based modified DRASTIC-LU model in hard rock aquifer system in India

Groundwater vulnerability and risk assessment is an essential step for preventing and controlling contamination in any area. DRASTIC model with modification incorporating land use (LU) widely used for assessing groundwater vulnerability worldwide. The present study used this modified model termed as DRASTIC-LU considering LU as a significant parameter in addition to other conventional DRASTIC parameters. Geographic information system employed to prepare and integrate different parameter maps led to demarcate the risk zones in a catchment of Damodar River, Jharkhand, India. Final DRASTIC-LU map was categorized as low (19.50%), moderate (34.02%), high (29.90%) and very high (16.58%) risk zones of groundwater contamination. Validation of models done through Spearman’s rank correlation coefficient (ρ) and receiver operating characteristic curve using nitrate concentration in groundwater, which indicated DRASTIC-LU (ρ = 0.893; AUC = 71.65%) had a better agreement than DRASTIC model (ρ = 0.7818; AUC = 67.36%). Thus, such modification in DRASTIC improves the performance of the model.

Comprehensive risk assessment of groundwater contamination in a weathered hard-rock aquifer system of India

Risk assessment is indispensable for the efficient monitoring and management of groundwater contamination. This study presents the first application of comprehensive risk assessment in a weathered hard-rock aquifer of India at a macro-scale by integrating aquifer vulnerability with the sources and consequences of groundwater contamination. Aquifer vulnerability was evaluated using a modified DRASTIC model, contaminant sources were identified using hazard inventory, and the consequences of groundwater contamination were estimated based on the significance of groundwater. Finally, these three components were integrated in the GIS environment to determine the risk of groundwater contamination. The results were validated using two approaches based on the concentration of groundwater-quality parameters that pose threat to groundwater contamination. The results of aquifer vulnerability reveal that 70% of the study area has ‘High’ to ‘Very High’ vulnerability and the hazard map indicates that about 44% of the area has ‘Rare’ likelihood of hazard incidence. On the other hand, the consequence map reveals that 83% of the study area may experience ‘Maximum’ to ‘Extreme’ consequences due to groundwater contamination. The developed risk map shows that 37% of the study area has ‘Major’ risk of groundwater contamination, whereas 10% has ‘Catastrophic’ risk. Further, both the validation approaches confirmed that the developed risk map is reliable. It is emphasized that the higher vulnerability does not necessarily indicate higher risk of groundwater pollution, rather the occurrence of hazard determines the actual risk of groundwater contamination in any region. Hence, the assessment of risk is imperative for exploring current status of groundwater quality and for formulating efficient strategies to minimize or avoid groundwater contamination.

Estimation of specific yield using water table fluctuations and cropped area in a hardrock aquifer system of Rajasthan, India

Assessment of specific yields is important for effective groundwater management in semi-arid hardrock aquifers, especially in India with its unsustainable groundwater usage rates. The Dharta watershed in the Udaipur district of Rajasthan is one such hardrock area in India where the groundwater extraction rate is a concern. In this study, we use groundwater balance analysis to estimate the specific yield (Sy) based on crop irrigation water use and changes in water table depths, during the irrigation season, to develop an understanding of the volume of groundwater recharge from pre and post monsoon water table depths and an understanding of the spatial and temporal changes in estimates of specific yield in the study area. The analysis used here estimates values at village scale (average area 3.65 km2) and is a technique compatible with the farmers monitoring of groundwater levels to facilitate local cooperative groundwater management. Five villages in the Dharta watershed in Rajasthan were selected and 50 wells per village were monitored for water table depth, at weekly intervals, over a two-year period. This resulted in a total of 250 wells in the study area and the monitoring was carried out by local farmer volunteers − called Bhujal Jankaars (BJs), a Hindi word meaning ‘groundwater informed.’ Crop area coverage (with a total of 40 crops) was examined for two years in the study area. Estimates of Sy in the five villages were between 1.4 and 8%, resulting in values comparable with previous studies. The watershed area-weighted average Sy was 3.8%. The method used in this study enabled estimates of recharge without needing a calibrated groundwater model in an area with sparse information on aquifer hydraulic characteristics and unreliable digital elevation maps.

‘Lineaments’ the Potential Groundwater Zones in Hard Rock Area: A Case Study of Basaltic Terrain of WGKKC-2 Watershed from Kalmeswar Tehsil of Nagpur District, Central India

Hard rock aquifer system, as it lacks in primary porosity, is complex because of heterogeneity, and hence its performance solely depends on secondary factors such as weathering, fractures, joints and lineaments, etc. As a result, there is no uniformity in behavior of such aquifer system which varies with the intensity of factors causing secondary porosity. In view of this aquifer system of hard rock, particularly multilayered aquifer system such as basalt, the targeting of deeper aquifer system becomes uncertain. Under this situation, mapping of lineament assumes great importance particularly for targeting the deeper aquifer. In view of this, a small watershed WGKKC-2 falling in Nagpur District of Central India has been studied in detail to understand the significance of lineaments on governing deeper aquifer system. The study has been carried out by deploying remote sensing technique for delineation of hydro geomorphology and lineaments vis-a-vis performance of bore wells. The results are encouraging which mainly emphasize the role of lineament mapping in hard rock aquifer system for identification of groundwater potential zones.

Delineation of groundwater potential zone in hard rock terrain in Gangajalghati block, Bankura district, India using remote sensing and GIS techniques

This study employed with the integration of remote sensing (RS) and geographical information system (GIS) techniques to delineate ground water potential zones for ground water management of Gangajalghati block, Bankura district, West Bengal and is located on the eastern slope of Chotanagpur plateau and area belongs to predominantly Precambrian gneissic terrain, and small area belongs to Gondwana deposits and quaternary sediments. The groundwater in this region is confined within the weathered residuum and fracture zones in pediment region. Survey of India topographical maps and satellite imageries along with other data and field observation data have been utilized to prepare various thematic layers viz. drainage, slope, lineament, geology, hydrogeomorphic units, land-use/land cover, soil, and depth to water level map of this hard rock terrain. All the thematic map that influence ground water occurrences have been analyzed and integrated through GIS analysis based on weights assignment. The weighted index overlay method has been followed to delineate ground water potential zones. The result revealed that the study area can be categorized into four different ground water potential zones viz., very good, good, moderate, and poor zones. The bore well yield data reveals that medium yielding wells (50–100 L per min) are in and around the moderate to high lineament density zone and buried pediment medium region. Afterward validation with well yield data revealed a good correlation with respect to the observed ground water potential zonation. This study is useful for better planning and management of ground water resources as well as providing quick prospective guides for ground water exploration in hard rock aquifer system.

Hydrogeology of Hard Rock Aquifer System - A Case Study from Turinjahalli Watershed, Dharmapuri District, Tamilnadu, India

Hydrogeology of Hard Rock Aquifer System - A Case Study from Turinjahalli Watershed, Dharmapuri District, Tamilnadu, India

Estimating aquifer properties and distributed groundwater recharge in a hard-rock catchment of Udaipur, India

The present study determined aquifer parameters in hard-rock aquifer system of Ahar River catchment, Udaipur, India by conducting 19 pumping tests in large-diameter wells. Spreadsheet programs were developed for analyzing pumping test data, and their accuracy was evaluated by root mean square error (RMSE) and correlation coefficient (R). Histograms and Shapiro–Wilk test indicated non-normality (p value <0.01) of pre- and post-monsoon groundwater levels at 50 sites for years 2006–2008, and hence, logarithmic transformations were done. Furthermore, recharge was estimated using GIS-based water table fluctuation method. The groundwater levels were found to be influenced by the topography, presence of structural hills, density of pumping wells, and seasonal recharge. The results of the pumping tests revealed that the transmissivity (T) ranges from 68–2239 m2/day, and the specific yield (Sy) varies from 0.211 to 0.51 × 10−5. The T and Sy values were found reasonable for the hard-rock formations in the area, and the spreadsheet programs were found reliable (RMSE ~0.017–0.339 m; R > 0.95). Distribution of the aquifer parameters and recharge indicated that the northern portion with high ground elevations (575–700 m MSL), and high Sy (0.08–0.25) and T (>600 m2/day) values may act as recharge zone. The T and Sy values revealed significant spatial variability, which suggests strong heterogeneity of the hard-rock aquifer system. Overall, the findings of this study are useful to formulate appropriate strategies for managing water resources in the area. Also, the developed spreadsheet programs may be used to analyze the pumping test data of large-diameter wells in other hard-rock regions of the world.

Identifying source and evaluation of hydrogeochemical processes in the hard rock aquifer system: geostatistical analysis and geochemical modeling techniques

In order to quantify spatio-temporal changes in the hydrogeochemistry of Swarnamukhi river basin, Andhra Pradesh, India, a total of 239 groundwater samples have been collected for pre- and post-monsoon seasons of 2014 and 2015. The geology of the study area is comprised of granite, granitic gneisses, shales, quartzites, laterites and recent alluvium along the river course. Based on the study of geochemical processes of different seasons, it is found that the occurrence of Na and HCO3 in 2014 shifted toward Ca and HCO3 in 2015 due to cation exchange process. Fe shows the higher concentration value than safe limit due to dissolution of ferruginous minerals and domestic sewage discharges. Bivariate plots of various ions and ratios depict the predominance of silicate weathering over carbonate and evaporite dissolution apart from anthropogenic activities in the enrichment of groundwater constituents. High nitrate concentration was observed in the urbanized regions of the basin followed by intense agricultural areas. Geochemical modeling was carried out using mineral saturation index and thermodynamic stability plots to deduce major weathered products. Most of the groundwater samples in the study area are saturated with carbonate minerals but are undersaturated with silicate minerals. Thermodynamic stability plots suggest the formation of kaolinite secondary mineral and presence of aluminosilicate minerals. Fuzzy calculation is applied to determine the water quality index, which categorizes a majority of the samples as excellent to good category for human use. Factor analysis points toward the mixed source identification of ionic constituents. Saline water mixing index model calculation suggests the effect of salinization in coastal areas due to heavy withdrawal of the fresh groundwater resources for various uses, whereas in the mainland it is due to agricultural runoff and domestic waste water.