Groundwater flow modeling in the basaltic hard rock area of Maharashtra, India

The ecological sustainable development and planning of groundwater resources is an excessive challenge for many countries currently facing water insufficiency. The main focus of this work was to determine the direction of groundwater flow, head value, and water level using the steady-state finite difference model (MODFLOW software) in basaltic formations in Maharashtra, India. The MODFLOW model was integrated with ground data using Geographic Information System (GIS) for sustainable groundwater resource management in the hard rock terrain. The MODFLOW-2005 model simulated the interaction between heads and time in 2014–18 by steady-state conditions. In this present study, four observation wells were selected. During the field survey, four observation wells have been monitored regularly as per the Central Groundwater Board guidelines. MODFLOW software has been conceptualized as a double-layered rigid and fractured aquifer area feast over 18,312 m × 11,265 m area. This research demonstrates that the integration of GIS, conventional fieldwork, and mathematical model can support to understand groundwater demand and supply in a better way.

Evaluation of transmissivity in a fractured aquifer—the Nyanzari wellfield, Burundi

Due to population growth, the city of Gitega in the central part of Burundi is lacking drinking water. Therefore, the national urban water supply company decided to expand the Nyanzari wellfield by drilling additional wells.Two additional wells were drilled to 80 m (F7.2) and 85 m (F8bis) depths. Step tests followed by 72-hours aquifer tests were performed in each well. Results indicate bilinear flow followed by linear flow and radial flow in F7.2. No reaction was observed in observation wells. Fracture-matrix transmissivity was estimated at 3 · 10−4 m2/s. In the case of F8bis, linear flow in an infinite flow fracture followed by radial flow was visible. Reaction was measured in observation wells. Transmissivity was estimated at 3.3 · 10−3 m2/s.Both wells lie no more than 300 m apart, but no evidence of interference between them was depicted during the tests. It appears that two independent fracture systems prevail in the wellfield.

Hydrochemical Characteristics, Quality Assessment and Solute Source Identification of Coal Bearing Fractured Aquifer in Dingji Coal Mine, Huainan Coalfield, China

Coal-bearing fractured aquifer is regarded as one of the most dynamic mine water inrush sources, and after pumping and treating, it can be used as a water supply for coal mine production, coal preparation plant, rural irrigation, and even reserved drinking water source. Hence, this study focuses on the hydrochemical characteristics, ion source, and water quality evaluation with respect to drinking and irrigation of the coal-bearing fractured aquifer in Dingji coal mine, Huainan coalfield, China. Descriptive statistics and hydrochemical classification diagrams including the Piper diagram and Chadha rectangular diagram were carried out to depict the hydrochemical characteristics and facies. The water quality of the aquifer was assessed for irrigation and drinking purposes using the WHO threshold value, water quality index (WQI), SAR, % Na and RSC. Hydrochemical formation mechanism and solute origin of major ions were explained by Gibbs diagram, bivariate diagrams, and multivariate statistical analysis. The results show that the dominant hydrochemical facies are the Cl-Na type and the HCO3-Na type. The sequence of ions is Na+ > Ca2+ > Mg2+ for cations, and HCO3? > Cl- > SO42- > CO32- for anions. The main solute sources are controlled by various factors including the dissolution of halite, sulfate, and carbonate rocks, the weathering of silicate, and cation exchange. Water quality assessment based on WQI suggests that none of the samples fall under the excellent category, even 32.5% is not suitable for direct drinking. Meanwhile, the samples of the aquifer are generally unsuitable for irrigation. Before utilization for irrigation and even drinking, appropriate water treatment should be applied to guarantee its security during usage.

Geohydraulic and vulnerability assessment of tropically weathered and fractured gneissic aquifers using combined electrical resistivity and geostatistical methods

Sustainable potable groundwater supplied by aquifers depends on the protective capacity of the strata overlying the aquifer zones and their thicknesses, as well as the nature of the aquifers and the conduit systems. The poor overburden development of the Araromi area of Akungba-Akoko, in the crystalline basement of southwestern Nigeria, restricts most aquifers to shallow depths. Hence, there is a need to investigate the groundwater quality of the tropically weathered and fractured gneissic aquifers in the area. A combined electrical resistivity tomography (ERT) and Schlumberger vertical electrical sounding (VES) technique were employed to assess the groundwater-yielding potential and vulnerability of the aquifer units. The measured geoelectric parameters (i.e., resistivity and thickness values) at the respective VES surveyed stations were used to compute the geohydraulic parameters, such as aquifer resistivity (\({\rho }_{o}\)), hydraulic conductivity (K), transmissivity (T), porosity (\(\phi\)), permeability (\({\Psi }\)), hydraulic resistance (\({\text{K}}_{R}\)), and longitudinal conductance (S). In addition, regression analysis was employed to establish the correlations between the K and other geohydraulic parameters to achieve the objectives of this study. The subsurface lithostratigraphic units of the studied site were delineated as the motley topsoil, weathered layers, partially weathered/fractured bedrock units, and the fresh bedrock, based on the ERT and the A, H, AK, HA, and KQ curve models. The K model regression-assisted analysis showed that the \({\rho }_{o}\), T, \(\phi\), \({\Psi }\), and S contributed about 81.7%, 3.31%. 96.6%, 100%, and 11.63%, respectively, of the determined K values for the study area. The results, except T and S, have strong high positive correlations with the K of the aquifer units; hence, accounted for the recorded high percentages. The aquifer units in the area were classified as low to moderate groundwater-yielding potential due to the thin overburden, with an average depth of <4 m. However, the deep-weathered and fractured aquifer zones with depths ranging from about 39–55 m could supply high groundwater yield for sustainable exploitation. The estimated S values, i.e., 0.0226–0.1926 mho, for aquifer protective capacity ratings rated the aquifer units in the area as poor/weak to moderately high with extremely high to high aquifer vulnerability index, based on the estimated low Log \({\text{K}}_{R}\) of about 0.01–1.77 years. Hence, intended wells/boreholes in the study area and its environs, as well as any environments with similar geohydraulic and vulnerability characteristics, should be properly constructed to adequately prevent surface and subsurface infiltrating contaminants.

Geohydraulic and vulnerability assessment of tropically weathered and fractured gneissic aquifers using combined electrical resistivity and geostatistical methods

Sustainable potable groundwater supplied by aquifers depends on the protective capacity of the strata overlying the aquifer zones and their thicknesses, as well as the nature of the aquifers and the conduit systems. The poor overburden development of the Araromi area of Akungba-Akoko, in the crystalline basement of southwestern Nigeria, restricts most aquifers to shallow depths. Hence, there is a need to investigate the groundwater quality of the tropically weathered and fractured gneissic aquifers in the area. A combined electrical resistivity tomography (ERT) and Schlumberger vertical electrical sounding (VES) technique were employed to assess the groundwater-yielding potential and vulnerability of the aquifer units. The measured geoelectric parameters (i.e., resistivity and thickness values) at the respective VES surveyed stations were used to compute the geohydraulic parameters, such as aquifer resistivity (\({\rho }_{o}\)), hydraulic conductivity (K), transmissivity (T), porosity (\(\phi\)), permeability (\({\Psi }\)), hydraulic resistance (\({\text{K}}_{R}\)), and longitudinal conductance (S). In addition, regression analysis was employed to establish the correlations between the K and other geohydraulic parameters to achieve the objectives of this study. The subsurface lithostratigraphic units of the studied site were delineated as the motley topsoil, weathered layers, partially weathered/fractured bedrock units, and the fresh bedrock, based on the ERT and the A, H, AK, HA, and KQ curve models. The K model regression-assisted analysis showed that the \({\rho }_{o}\), T, \(\phi\), \({\Psi }\), and S contributed about 81.7%, 3.31%. 96.6%, 100%, and 11.63%, respectively, of the determined K values for the study area. The results, except T and S, have strong high positive correlations with the K of the aquifer units; hence, accounted for the recorded high percentages. The aquifer units in the area were classified as low to moderate groundwater-yielding potential due to the thin overburden, with an average depth of <4 m. However, the deep-weathered and fractured aquifer zones with depths ranging from about 39–55 m could supply high groundwater yield for sustainable exploitation. The estimated S values, i.e., 0.0226–0.1926 mho, for aquifer protective capacity ratings rated the aquifer units in the area as poor/weak to moderately high with extremely high to high aquifer vulnerability index, based on the estimated low Log \({\text{K}}_{R}\) of about 0.01–1.77 years. Hence, intended wells/boreholes in the study area and its environs, as well as any environments with similar geohydraulic and vulnerability characteristics, should be properly constructed to adequately prevent surface and subsurface infiltrating contaminants.