Crystalline Aquifer System Research Articles

Groundwater apparent ages and isotopic composition in Crystalline, Diabase and Tubarão aquifers contact area in Campinas, Southeastern Brazil

This study refines the hydrogeological conceptual model of an area with three interconnected aquifers, namely the Crystalline Aquifer System (CAS - igneous and metamorphic rocks), which is in contact with the Tubarão Aquifer System (TAS - sedimentary rocks) and the Diabase Aquifer System (DAS – diabase rocks). The detailed investigation involved geophysical logging and hydraulic and hydrodynamic characterization with straddle packers in a local tubular well, in which groundwater presents high uranium concentrations. Hydrogeochemical and isotope (δ2H, δ18O, 3H, δ13C, 14C) analysis in this well and in other three neighboring wells, with lower U concentrations, showed that ancient and modern waters (3H from <0.8 to 1.12 TU, 14C from 69.43 to 78.72 pMC) mix within the aquifer. During groundwater pumping, vertical fractures in the diabase aquifer possibly induce water mixing and recharge of the deeper levels of the aquifers from shallow layers. The high [U] are related to ancient waters from a confined aquifer hosted in CAS that reaches the wells through hydraulically active fractures located deeper than 159 m depth. Groundwater apparent ages do not increase systematically with depth, revealing a complex circulation model for CAS. The results obtained from the other wells, which are all located on drainage lineaments, reveal that one extracts modern water from DAS and TAS, another one extracts modern and ancient water from DAS and CAS, and the third extracts only ancient water from CAS, confirming the complexity of the local hydrogeology. Regarding regional groundwater management, the study revealed the need to characterize the sources of groundwater in each well, in order to protect modern waters from anthropogenic contamination and to protect ancient groundwater from overexploitation, as CAS hosts groundwaters recharged thousands of years ago or more.

Hydrogeochemical processes and causative pollution sources in the highly urbanized crystalline aquifer system in Southern India

Groundwater contamination due to the disposal of untreated or partially treated domestic and industrial sewage is posing a severe threat to urban groundwater reserves in many parts of the world. The efforts made for the modelling of contaminant transport to understand these pollution transport and hydrogeochemical processes in urban areas are often challenging due to the difficulty in selecting source boundary condition locations mainly in the presence of Multiple Point Sources (MPS). The present research used Multivariate Statistical analysis (MSA) to classify the major pollution sources and to demarcate its area in the highly urbanized Hussain Sagar (HS) lake catchment situated in Hyderabad, South India. The observed monitoring data of groundwater levels and groundwater quality (pH, TDS, Ca2+, Mg2+, Na+, K+, HCO32−, Cl−, SO42−, NO3-N, total hardness) at 108 locations for eight different seasons over four years have been used for modelling. The MSA has revealed that the first component is associated with industrial pollution loads that are restricted to Kukatpally and Dulapally streams and HS lake with a total variance of up to 46% to the total pollution load. Component 2 and component 3 are associated with domestic pollution loads (HCO32−, Na+, and NO3-N) that spread across the lake catchment with a total variance of up to 37%. The approach used in this study can be applied to any local to regional scale river basins for understanding hydrogeochemical processes and to provide inputs to simulate contaminant transport.

18O, 2H, and ³H isotopic data for understanding groundwater recharge and circulation systems in crystalline rocks terrain of Southeastern Brazil

The 18O, 2H and ³H isotopes have been used to identify recharge and circulation patterns in aquifer systems by determining the relationships between isotopic signatures of meteoric, ground, and surface waters. This research investigates a Crystalline Aquifer System in Southeastern Brazil, where the isotopic fractionation results from the effects of precipitation, altitude, and continentality, while the Local Meteoric Water Line (LMWL) is expressed as δ2H = 8.49 δ18O + 18.97. The isotopic signature of groundwater follows that of rain, varying according to the climate conditions of each sector of the basin. The groundwater in the upper sector of the basin have a renewal time of up to 25.75 years and low mineralization, being an important recharge zone for the Crystalline Aquifer System. However, in the lower and hotter sector of the basin, the evaporative processes influence the recharge and, therefore, the groundwater is more mineralized with a renewal time of up to 85 years, indicating an infiltrated water source upstream. Surface water is enriched with heavy isotopes resulting from evaporation due to sun exposure, with isotopic data plotting above the LMWL during the rainy season and similar to groundwater during the dry season, showing the effluent character of the main drainage channels. We propose a conceptual model where the isotopic signature and mineralization of groundwater are influenced by the relief, climate conditions, and lithological diversity.

Entropy-weighted water quality index (EWQI) modeling of groundwater quality and spatial mapping in Uppar Odai Sub-Basin, South India

Groundwater is the primary source of water supply in Uppar Odai Sub-basin in the Amaravati River basin in South India. In this crystalline aquifer system, groundwater occurs in joints fissures, fractures at shallow depth in the partially weathered rocks. An integrated approach of hydrochemical analysis of 32 samples with numerical indexing Entropy-weighted water quality index(EWQI) model was proposed for the study area. General hydrochemical data showed that the Na–Cl and Ca–Mg–Cl–SO4 types dominated, with most of the samples are alkaline nature. More than 50% of the samples exceeded the permissible limit of TDS, and a high concentration of Cl and NO3 showed the influence of anthropogenic influences, such as industrial effluents and agricultural fertilizers. Groundwater chemistry was found to be varying along the groundwater flow paths. Geogenic contaminant F¯ was exceeding the WHO permissible limit of 1.5 mg/L. Entropy-weighted Water Quality Index (EWQI) model showed that 53% of the samples were medium, and 22% were of poor quality. Na–Cl and mixed Ca–Mg–Cl types of water were reported with high EWQI values. A high correlation for EWQI with TDS, TH, Mg, Cl, SO4, and NO3 is an indication of the human activities on the groundwater quality. GIS-based spatial variation maps of water quality parameters and EWQI specify that northern, northwestern, and central regions are poor water quality. In those regions where water quality has deteriorated, proper treatment of water is suggested before consumption to avoid health risks.

Geo-spatial distribution of arsenic contamination of groundwater resources in intricate crystalline aquifer system of Central India: Arsenic toxicity manifestation and health risk assessment

The behavior of As in aqueous media in the complex crystalline aquifers like that of the present study area is not yet understood properly. To that end, groundwater and river water samples from two different seasons are analyzed for As and physicochemical parameters. The groundwater in the area is evolved by simple dissolution or mixing of two or more different facies (Ca2+–Mg2+–Na+–SO4 2–). However, the majority of samples with the base-exchange indices (85%) and meteoric genesis indices (77%) value less than unitary (<1) divulges that Na+– SO4 2– type water and deeper meteoric percolation. The estimation of As in groundwater (<0.1–202 ppb) shows the spatial and temporal inconsistency with 17.31% (pre-monsoon) and 11.67% (post-monsoon) of the samples surpassed the permissible limit of 10 ppb. Furthermore, health risk associated with As in terms of hazard quotient (HQ) values > 1 (pre-monsoon: 21.15% and post-monsoon: 20%) for children and carcinogenic risk values >1.00 × 10−6 for different seasons (44.25% and 33.33% of samples) represents a serious health risk. Furthermore, the different stages of Keratosis and Melanosis diseases reported in the study area establish the severity of As toxicity on the local populace. The study concludes geogenic arsenic contamination in the study area is primarily associated with Rhyolite and its comagmatically formed Dongargarh granite batholith emplacements.

Using specific capacity for assessing of the factors controlling borehole productivity in crystalline bedrock aquifers of N’Zi, Iffou and Moronou regions in the eastern area of côte d’Ivoire

Hard rock aquifers are characterized by high heterogeneity which leads to difficulties in boreholes implementation in the eastern region of Côte d’Ivoire. This is due to the combination of many factors including poor knowledge of hydrogeological environment. The thrust of this study is to highlight the influence of borehole depth, lithotypes, weathering thickness and electrical resistivity of the geological structures on borehole productivity that exploit the crystalline aquifer systems in N’Zi, Iffou and Moronou regions. Bivariate analysis was used to determine the relationships between these factors and specific capacity values for measuring borehole productivity. The values ranged from 0.02 to 4.09 m3 h−1.m−1. The analysis shows that there is no correlation between productivity and weathering thickness. However, weathering depths between 10 and 69 m provide the highest specific capacity values. Schist is more productive than granite. For hydrogeological discontinuities interest, boreholes located in H and KH anomaly curve types were the most productive. As productivity diminishes with depth, a deeper borehole can be more productive if it reaches a geological structure that is favorable for groundwater flow. Those geological and hydrogeological parameters are extremely important in borehole productivity in the above-mentioned regions.

Borehole Productivity Controlling Factors in Crystalline Bedrock Aquifer of Gk&amp;amp;#234;k&amp;amp;#234; Region, Center of C&amp;amp;#244;te d’Ivoire

The presence of both weathered rocks and fractured crystalline bedrock aquifers makes Hydrogeology in Gbeke region of Cote d’Ivoire. Access to water in this region is not easy. This study focuses on the influence of borehole depth, weathering thickness and electrical resistivity of the geological structures on borehole productivity that exploit the crystalline aquifer system. Bivariate analysis was used to determine the relationships between these factors and specific capacity for measuring borehole productivity. The values ranged from 0.0088 to 2.20 m3∙h−1∙m−1. The analysis shows that there is no correlation between productivity and weathering thickness. However, weathering depths between 15 and 35 m provide the highest specific capacity values (Qs ≥ 1 m3∙h−1∙m−1). For hydrogeological discontinuities interest, boreholes located in KH, QH and H anomaly curve types were the most productive. As productivity diminishes with depth, a deeper borehole can be more productive if it reaches a geological structure that is favorable for groundwater flow. Those hydrogeological parameters are extremely important in borehole productivity in Gbeke region.

Integrated multi-parameter approach for delineating groundwater potential zones in a crystalline aquifer of southern India

Groundwater resources in the semi-arid regions of southern India are under immense pressure due to large-scale groundwater abstraction vis-a-vis meager rainfall recharge. Therefore, understanding and evaluating the spatial distribution of groundwater is essential for viable utilization of the resource. Here, we assess groundwater potential at the watershed scale, in a semi-arid environment with crystalline aquifer system without a perennial surface water source using remote sensing, geophysical, and GIS-based integrated multi-parameter approach. GIS-based weighed overlay analysis is performed with input parameters, viz., geology, geomorphology, lineament density, land use, soil, drainage density, slope, and aquifer thickness. The watershed is categorized into four zones, namely, “very good” (GWP4), “good” (GWP3), “moderate” (GWP2), and “low” (GWP1) in terms of groundwater potential. Overall, ~ 70% of the study area falls under moderate to low groundwater potential, indicating a serious threat to the future availability of the resource. Therefore, serious measures are required for maintaining aquifer resilience in this over-exploited aquifer (e.g., restricting groundwater withdrawal from GWP1 and GWP2 zones). Further, as the aquifer is under tremendous anthropogenic pressure, rainwater harvesting and artificial recharge during monsoon are advocated for sustainable aquifer management. Due to the direct dependence of crop production vis-a-vis farmer economy on groundwater, this study is an important step towards sustainable groundwater management and can be applied in diverse hydrological terrains.

2D TEM Modeling for a Hydrogeological Study in the Paran&amp;#225; Sedimentary Basin, Brazil

This work uses 2D TEM (Transient Electromagnetic) modeling for a hydrogeological study in the Paraná sedimentary basin. The study area is located at the northern region of the state of São Paulo, Brazil, where groundwater is exploited from two aquifer systems: one sedimentary, shallow, and the other crystalline, deep. The interest in applying the TEM method in this area owes to the high exploitation rates of groundwater from the crystalline aquifer system for irrigation, which is triggering considerable seismic activity locally. This aquifer system is composed of fractured basalt within the Serra Geral Formation and is about 120 m deep. Eighty-six TEM soundings were acquired at this location, but in nine cases the data did not fit the modelled curve for 1D geoelectrical models due to the geological complexity of the area. This paper shows 2D geoelectrical modeling results based on the FDTD (Finite Differences in Time Domain) method to explain the lateral resistivity variation within the geological setting. A 2D model was generated for each sounding and compared with 1D inversion models as well as with direct information from wells. The results show some vertical variations of about 10 to 30 meters on the upper interface of the basalt layer from Serra Geral Formation. They are located at approximately 60 meters from the center of the soundings. The existence of these 2D structures in the subsurface can be related to the drainage system in the study area. The presence of these structures may indicate a connection between the shallow and deep aquifer systems, acting like a conduit that may contribute to the seismic activity reported.

Numerical analysis of groundwater flow and potential in parts of a crystalline aquifer system in Northern Ghana

The groundwater flow system in a crystalline aquifer system in parts of Northern Ghana was simulated and calibrated under steady-state conditions. The objective was to estimate the regional distribution of a key aquifer hydraulic parameter (the hydraulic conductivity) and recharge and also to predict possible effects of different abstraction and groundwater recharge scenarios on the sustainability of groundwater resources in the area. The study finds that the hydraulic conductivity field is quite homogeneous and has values ranging between 1.70 and 2.24 m/day. There is an apparent dominance of regional groundwater flow systems compared to local flow systems. This is probably attributed to the homogeneity in the hydraulic conductivity field and the absence of complex local relief. Estimated groundwater recharge ranges between 0.036 and 0.164 m/yr representing 3.6 and 16.4 % of the local annual precipitation, respectively. Substantial subsurface inflows and outflows have also been simulated through general head boundaries. The simulation suggests that under the current conditions of groundwater recharge estimated at calibration, the system can sustain increment in groundwater abstraction by up to 50 % without any significant changes in the groundwater flow geometry and drawdowns in the hydraulic heads. However, significant drawdowns will be expected in the wake of 100 % increment in groundwater abstraction and a reduction in recharge by 10 % during the 20-year period. Under such conditions, the flow geometry will significantly be altered and a reversal in groundwater flow will be observed.

A preliminary analysis of the hydrogeological conditions and groundwater flow in some parts of a crystalline aquifer system: Afigya Sekyere South District, Ghana

A steady state groundwater flow model was calibrated to simulate the complex groundwater flow pattern in some crystalline aquifer systems in north-central Ghana. The objective was to develop the general geometry of the groundwater system and also estimate spatial variations in the hydraulic conductivity field as part of efforts to thoroughly investigate the general hydrogeology and groundwater conditions of aquifers in the area. The calibrated model was used in a limited fashion to simulate some scenarios of groundwater development in the terrain. The results suggest the dominance of local groundwater flow systems resulting from local variabilities in the hydraulic conductivity field and the topography. Estimated horizontal hydraulic conductivities range between 1.04m/d and 15.25m/d, although most of the areas consist of hydraulic conductivities in the range of 1.04m/d and 5.5m/d. Groundwater flow is apparently controlled by discrete entities with limited spatial interconnectivities. Recharge rates estimated at calibration range between 4.3% and 13% of the annual rainfall in the terrain. The analysis suggests that under the current recharge rates, the system can sustain increasing groundwater abstraction rates by up to 50% with minimal drawdown in the hydraulic head for the entire terrain. However, with decreasing groundwater recharge as would be expected in the wake of climate change/variability in the area, increased groundwater abstraction by up to 50% can lead to drastic drawdowns by more than 25% if recharge reduces by up to 50% of the current levels. This study strongly recommend the protection of some of the local groundwater recharge areas identified in this study and the promotion of local recharge through the development of dugouts and other conduits to encourage recharge.

Hydrogeological characterization of a tropical crystalline aquifer system

This research used a numerical groundwater flow model, calibrated under steady-state conditions to develop the groundwater flow system in the West Mamprusi District of Northern Ghana. It was aimed at conceptualizing the flow system to initiate a thorough hydrogeological study of the rocks in the area. Stable isotopes were used to relate groundwater recharge in the area to recent meteoric water that had been evaporated in transit down the surficial material. On this basis, direct vertical groundwater recharge from precipitation was applied in the numerical modeling. This study suggests that the prospects of commercial development of the aquifers are high as the estimated recharge ranges between 3.3% and 29% of the annual precipitation. Estimated horizontal hydraulic conductivity ranges between 3.2 and 48 m/d in the area. The variability in the horizontal hydraulic conductivity has led to the development of four prominent groundwater flowpaths in the area. However, a prominent NE–SW flow has been observed and is in consonance with the reported structural grain of the country. A groundwater flow divide noted in the southern part of the study area has been attributed to the structural heterogeneity rather than topographical complexities as the area is largely flat.

CARACTERIZAÇÃO HIDROGEOLÓGICA DOS SISTEMAS AQÜÍFEROS CRISTALINO E

The Jundiai River Catchment is located mainly on the Crystalline Aquifer System, where groundwater flow depends on rock discontinuities, and other part of this catchment is on the Tubarao Aquifer System, which behavior is also heterogeneous and anisotropic. The productivity of these aquifers is not so different: the wells that exploit the Tubarao Aquifer System have median specific capacity equal to 0,09 m 3 /h/m, and the ones that exploit the Crystalline Aquifer System, as well as the mixed wells (which exploit both aquifer systems), have specific capacity equal to 0,07 m 3 /h/m. The distribution of values is greatly variable, since the productivity depends on the location of wells in relation to the geological structures witch characteristics (opening and conectivity) favour groundwater flow. They are brittle structures with NW-SE and E-W directions that occur mainly along the regional shear and fault zones. The main groundwater flow in the basin is from southeast to northwest and the main recharge area is in highlands. From highlands, groundwater is led to the Parana Sedimentary Basin, passing by the geological structures cited above.

Well productivity controlling factors in crystalline terrains of southeastern Brazil

Over the last decades, increasing water demands have fostered research to obtain high well yields in crystalline terrains where, besides the intrinsic properties of rocks, the groundwater flow depends on several factors. The depth of the wells, the lithotypes, the presence and thickness of sedimentary coverings and weathered layers, the landforms, the geological structures, and the effects of tectonic stresses are among the most investigated factors considered as determinant of well productivity. The influence of these factors on productivity of wells that exploit the Crystalline Aquifer System in the Jundiai River Catchment, southeastern Brazil, is investigated in this work. The largest region of the studied area is located on the Precambrian Basement, partially covered by sedimentary deposits. The results show that the sedimentary deposits and the weathered layer are important for high well yield, but it also depends on the existence of a net of open fractures, in order to maintain high productivity. The sites that have more possibility of occurrence of such structures are the regional shear and fault zones and other minor structures with NW–SE and E–W directions, which characterize areas subjected to transtensional stress related to the neotectonics.