Assignment of groundwater level at the wastewater collecting pipe for a landfill groundwater simulation: utilization of the two-dimensional saturated–unsaturated groundwater numerical model

In order to understand the effects of a landfill operation on groundwater flow behavior, a 2D horizontal groundwater simulation model was carried out. The model saved the memory of computer and time consumption, comparing it with the 3D groundwater flow model. However, the greatest difficulty is the assignment of the collecting pipe boundary at the study site. Therefore, a 2D vertical model was applied to calculate the change of the groundwater table above the collecting pipe. This paper focuses on examining the validation of the assignment of the collecting pipe boundary by applying the results of the 2D vertical model. The 2D horizontal model was coupled with the recharge model to solve the partial differential equation of groundwater flow. The finite difference method and iterative successive over relaxation were applied. The drainage volume of leachate collection was summed up in the whole landfill site and compared with the average volume of treated wastewater. The study demonstrated that the results of the 2D vertical model validated and can be applied to the 2D horizontal groundwater flow simulation.     

Quantification of groundwater–seawater interaction in a coastal sandy aquifer system: a study from Panama,Sri Lanka

The Panama coastal aquifer system is an important water resource in the southeast coast of Sri Lanka that provides adequate supplies of water for agriculture and domestic uses. One of the biggest threats to these fragile aquifers is the sea water intrusion. In this study, recharging mechanism and geochemical evaluation of groundwater in the coastal sandy aquifer of Panama were evaluated using chemical and stable isotope techniques. Thirty groundwater samples were collected and analyzed for their major ion concentrations and stable isotope ratios of oxygen (¹⁸O/¹⁶O) and hydrogen (D/H). All studied samples showed a ranking of major anions in the order Cl^? > HCO ₃ ^?  > SO ₄ ^2?  > N-NO₃ ^? while cations showed a decreasing order of abundance with Na⁺ > Ca²⁺ > Mg²⁺ > K⁺. Dominant groundwater hydrogeochemical types were Na–Cl and mixed Ca–Mg–Cl. Results of saturation index calculations indicate that the investigated groundwater body was mostly saturated with respect to calcite, dolomite and gypsum. In addition, stable isotope and geochemical data suggest that fresh groundwater in the aquifer is recharged mainly by local precipitation with slight modification from evaporation and saline water intrusions. Isotope data suggest that mixing of salt water with freshwater occurs in aquifers which are located towards the lagoon. Since the communities in the study area depend entirely on groundwater, an understanding of the hydrogeochemical characteristics of the aquifer system is extremely important for the better water resource management in the region.     

Geostatistical analysis of spatiotemporal variability of groundwater level fluctuations in Amman–Zarqa basin,Jordan: a case study

The main objective of this study was to assess the spatial and temporal variability of groundwater level fluctuations in the Amman–Zarqa basin, during the period 2001–2005. In the year 2003, as a consequence of war, there was a sudden increase in the population in this basin. Knowing that the basin is already heavily populated and witnesses most of the human and industrial activities in Jordan, this study was prompted to help make wise water resources management decisions to cope with the new situation. Data from 31 fairly distributed wells in the upper aquifer of the basin were subjected to geostatistical treatment. Kriging interpolation techniques have indicated that the groundwater flow directions remained almost constant over the years. The two main directions are SW–NE and E–W. Kriging mapped fluctuations have also showed that drop and rise events are localized in the basin. Forecasting possibilities for management purposes were tackled using autocorrelation analysis. The constructed autocorrelograms indicated, in general, the temporal dependence of seasonal water level fluctuations, and that forecasting can be carried out within a period of 3–21 months. Several suggestions were made to mitigate the drop and rise hazards in the detected sites.     

Effects of terrigenic He components on tritium–helium dating: A case study of shallow groundwater in the Saijo Basin

Dating using a combination of ³H and ³He is believed to be the most practical method for estimating the short residence time of shallow groundwater. However, this method must estimate tritiogenic ³He alone and tends to overestimate the residence time of groundwater, if terrigenic ³He from the mantle cannot be excluded from the total dissolved ³He. We demonstrate the exclusion of terrigenic ³He in the Saijo Basin, where mantle He is easily released along the major active fault, Median Tectonic Line. The ³He/⁴He ratios suggest that the west bank of the Kamo River, which lies within the basin, has experienced greater emanations of mantle He than the east bank. We estimate the residence times to be 1.1–96 years by the proposed exclusion method.     

Comments on ‘A comparative study of ANN and neuro-fuzzy for the prediction of dynamic constant of rockmass’

Singh et al (2005) examined the potential of the ANN and neuro-fuzzy systems application for the prediction of dynamic constant of rockmass. However, the model proposed by them has some drawbacks according to fuzzy logic principles. This discussion will focus on the main fuzzy logic principles which authors and potential readers should take into consideration.     

Numerical simulation of groundwater under complex karst conditions and the prediction of roadway gushing in a coal mine: a case study in the Guang’an Longtan Reservoir in Sichuan Province,China

Numerical simulation of groundwater in karst areas has long been restricted by the difficulty of generalizing the hydrogeological conditions of reservoirs and of determining the relevant parameters due to the anisotropy and discontinuity of the karst water-bearing media in these areas. In this study, we used the Guang’an Longtan Coal mine in Sichuan as an example, and generalized the complex hydrogeological conditions in the reservoir area. A finite element numerical flow model was used to simulate current and future scenarios of roadway gushing at the bottom of the coal mine at pile number 1 + 700 m. The results show that the roadway section corresponding to valleys has a gushing quantity of 4323.8–4551.25 m³/d before impoundment. Modeled water inflow after impoundment increased to 1.6 times the water inflow before impoundment, which threatens the impoundment as well as the roadway’s normal operation. Therefore, roadway processing measures are needed to guarantee the safety of the impoundment and of the mining operation.     

A numerical simulation of landslide-prone slope in Himalayan region—a case study

Stability of slope will always a problem due to its geodynamic nature of Himalayan region. The area investigated belongs to the Lower Siwalik formation, which is prone to failure due to presence of various weak planes or structures present in the rock mass. Frequent landslides causing loss of life, property, disturbance of morphological, surface and subsurface water flow pattern. A huge landslide in the Amiyan area occurred in 1999 and blocked the Gaula River which caused loss of agricultural land and other properties as well as waterlogged upstream side. The debris of Amiyan slope contains soil and sandstones of various types. This article deals with instability analysis of slopes of the Amiyan area, near Kathgodam, Nainital, Uttarakhand. This area experiences a number of local as well as regional slides. Extensive field surveys have been carried out to understand the geological detail. Laboratory experiments have been conducted to determine the various physicomechanical properties of rock mass. These properties have been used as input parameters for the numerical simulation. A number of researchers have used two-dimensional numerical models to simulate the slide area. Three-dimensional slope stability studies provide a better understanding of the mechanism of failure as well as zone of influence. The computed deformations and stress distribution, along the failure surface, have been compared with the field measurements and found to be in good agreement with field observations. In this case, finite difference method has been applied on the stability analysis of Amiyan slope. The study indicates that the slope is vulnerable and needs proper protection.     

Is 222Rn a suitable tracer of stream–groundwater interactions? A case study in central Italy

River water infiltration into an unconfined porous aquifer (∼73% gravels, ∼12% sands, ∼15% silts and clays) in the Petrignano d’Assisi plain, central Italy, was traced combining isotopic techniques (²²²Rn) with hydrochemical and hydrogeologic techniques in order to characterize the system under study. The ²²²Rn gave information about the river water residence times within the aquifer and hydrochemical data, in a two-component mixing model, which allowed estimating the extent of mixing between surface waters and groundwater in wells at increasing distances from the river. The mixing measured in the well closer to the riverbank indicated a higher contribution of river water (up to 99%) during the groundwater recession phase and a moderate contribution (up to 64%) during the recharge phase. A model describing ²²²Rn concentrations in groundwater as the result of both parent/daughter nuclide equilibrium and mixing process (²²²Rn mixing/saturation model) was used to describe observed Rn concentrations and mixing index trends with the aim of evaluating water mean infiltration velocities along the transect. The stream bank infiltration velocities obtained by the model ranged from 1 m day⁻¹ during groundwater recharge periods, when river water infiltration is lower, to 39 m day⁻¹ during recession phases, when river water infiltration is larger.     

Hydrochemistry of groundwater in a coastal region and its repercussion on quality,a case study—Thoothukudi district,Tamil Nadu,India

A hydrogeochemical study was conducted in Thoothukudi district situated in the southeast coast of Tamil Nadu, India to identify the influence of saltwater intrusion and suitability of groundwater for domestic and agricultural purposes. Scattered studies of this coastal region have reported signs of seawater intrusion, salt pan and industrial activity together with natural weathering process. To have a holistic picture of geochemical processes in the entire district, a total of 135 groundwater samples were collected and analyzed for major cations and anions. The geochemical parameters were compared with world and Indian standards and it was found that most samples are unsuitable for drinking purpose. The geochemical facies of the groundwater showed Na–Cl as the dominant water type indicating the saline nature of the groundwater. Chadda’s plots show that most of the samples fall in the Na–Cl type of water due to seawater intrusion. The samples were classified with parameters like sodium absorption ratio, residual sodium carbonate, total hardness, chloride, index to base exchange, electrical conductivity and facies to determine their suitability for irrigation purpose. It was inferred that the samples falling along the coast are not suitable for the irrigation purpose. The seawater-mixing percentage indicates that strong mixing was observed in the near shore and at the proximity of the salt pan. The permanent hardness was predominant in all the samples compared to the carbonate hardness reducing its domestic usability.     

Validity evaluation of a groundwater dam in Oshipcheon River,eastern Korea using a SWAT–MODFLOW model

It is assumed that the groundwater dam under consideration is located in the lower Oshipcheon River along Yeongdeok-gun County, Gyeongsangbuk-do Province, eastern Korea. In this study, changes in groundwater level and construction effects of the groundwater dam were analyzed using a SWAT–MODFLOW model designed for integration of surface water and groundwater, and validity analysis before and after construction of the groundwater dam was evaluated. There are an average increase of 0.46 m and a maximum increase of 1.16 m, respectively, at the upstream region due to the groundwater dam. Groundwater levels at the upstream region show an average increase of 0.42 m by the groundwater dam when the water quantity of demand (10,080 m³/day) is pumped. The groundwater dam has potential as an alternative for the surface water dam to secure water resources in the study area.     

A case-study of complex gas–water–rock–pollutants interactions in shallow groundwater: Šalek Valley (Slovenia)

The complex geochemical interactions in the groundwater of the industrial area of Šalek Valley (Slovenia) between natural and anthropogenic fluids were studied by means of major (Ca, Mg, Na, K, HCO₃ ⁻, Cl⁻ and SO₄ ²⁻) and trace elements’ (As , Cd, Cu, Pb, Zn, Hg, Se and V) abundances, geochemical classification and statistical analysis of data. Cation abundances indicate mixing between a dolomitic end-member and an evaporitic or geothermal end-member. Anion abundances indicate mixing between bicarbonate waters and either sulphate-enriched waters (suggesting hydrothermalism) or chlorine-rich waters. Principal component analysis (PCA) allowed the extraction of seven factors, which describe, respectively: water–rock interaction mainly on dolomitic rocks; redox conditions of water; Cd–Zn enrichment in chlorine-rich waters (probably from industrial wastes); hydrothermal conditions in waters close to major faults; Pb and Cu pollution; V and K enrichments, indicating their common organic source; the role of partial pressure of CO₂ dissolved in water, which is highest in three wells with bubbling gases. Average underground discharge rates of solutes from the Valley range between 0.09 t/a (V) and 1.8 × 104 t/a (HCO₃ ⁻) and indicate how natural fluids can significantly contribute to the levels of elements in the environment, in addition to the amount of elements released by human activities.     

A study of outburst activity of Z and in 2000–2010

We present the results of our study of the classical symbiotic star Z And during its period of activity in 2000–2010. In this period, the system experienced a series of six outbursts, for three of which high-resolution spectra were obtained and analyzed. These observations provided information about the system’s behavior during the entire activity period, rather than during an individual outburst. In particular, we found a fundamental difference between the first outburst, which initiated the activity period, and subsequent outbursts, namely, the presence of bipolar collimated optical outflows for some of the outbursts. We propose a model that can explain all the spectroscopic phenomena observed during this series of outbursts, as well as previous series of outbursts of Z And, and suggest that similar scenarios may be valid for other classical symbiotic stars.     

Hydrochemical evolution of groundwater in a riparian zone affected by acid mine drainage (AMD), South China: the role of river–groundwater interactions and groundwater residence time

Investigations were undertaken in the riparian zone near Shangba village, an AMD area, in southern China to determine the effects that river–groundwater interactions and groundwater residence time have had on environmental quality and geochemical evolution of groundwater. Based on the Darcy’s law and ionic mass balances as well as the method of isotopic tracer, the results showed that there were active interactions between AMD-contaminated river water and groundwater in the riparian zone in the study area. River water was found to be the main source of groundwater recharge in the northwestern part of the study area, whereas groundwater was found to be discharging into the river in the southeastern part of the study area throughout the year. End-member mixing analysis quantified that the contributions of river water to groundwater decreased gradually from 35.9% to negligible levels along the flow path. The calculated mixing concentrations of major ions indicated that water–rock reactions were the most important influence on groundwater quality. The wide range of Ca²⁺?+?Mg²⁺ and HCO₃^? ratios and the change of groundwater type from Ca²⁺–SO₄^2? type to a chemical composition dominated by Ca²⁺–HCO₃^? type indicated a change of the major water–rock reaction process from the influence of H₂SO₄ (AMD) to that of CO₂ (soil respiration) along a groundwater flow path. Furthermore, the kinetics interpretation of SO₄^2? and HCO₃^? concentrations suggested that the overlapping time of their kinetics triggered the hydrochemical evolution and the change of major weathering agent. This process might take approximately 8 years and this kinetic time will be continued when a steady source of contamination enter the aquifer.     

A three-dimensional hydrogeological–geophysical model of a multi-layered aquifer in the coastal alluvial plain of Sarno River (southern Italy)

The coastal alluvial plain of Sarno River (Campania Region, southern Italy) is a very rich environment that has experienced a long history of changes due to both natural phenomena such as eustatic sea-level variations and deposition of volcanoclastic sediments, and human civilizations who populated this area since historical times. As a result, it is characterized by complex stratigraphic sequences and groundwater flow systems. The architecture of the multi-layered aquifer system in a sample area, located in a densely urbanized sector at the mouth of Sarno River, was reconstructed. Starting from the analysis of stratigraphic log data and laboratory geotechnical measurements, the lithostratigraphical-unit sequence was retrieved and a realistic three-dimensional (3D) model of the hydrogeological heterogeneity was obtained. The results of a detailed 2D electrical resistivity tomography survey were used to support the analysis of the spatial heterogeneity of the aquifer system in a sector characterized by lack of log data. The integration of hydrogeological and geophysical data allowed for the reconstruction of a 3D hydrogeophysical model of the multi-layered system, which electrically characterizes and geometrically identifies two aquifers. Finally, piezometric-level measurements validated the hydrogeological–geophysical model and showed the effectiveness of the methodology.     

Hydrogeochemistry and quality of groundwater of coastal unconfined aquifer in Amol–Ghaemshahr plain,Mazandaran Province,Northern Iran

Groundwater of the unconfined aquifer (1,100 sq. km) of a two-tier coastal aquifer located in the Amol–Ghaemshahr plain, Mazandaran Province, Northern Iran, is classified into fresh and brackish water types. Fresh groundwater (FGW) samples (n = 36) are characterized by Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ and HCO₃ ^? > Cl^? > SO₄ ^2? > NO₃ ^?. Spearman’s rank correlation coefficient matrices, factor analysis data, values of the C-ratio (av. = 0.89) and CAI and values of the molar ratios of Ca²⁺/HCO₃ ^?, Ca²⁺/SO₄ ^2?, Mg²⁺/HCO₃ ^? and Mg²⁺/SO₄ ^2? indicate that the ionic load in the FGW is derived essentially from carbonic acid-aided weathering of carbonates and aluminosilicates, saline/sea water trapped in the aquifer sediments (now admixed with the groundwater) and ion exchange reactions. Values of the CAI and Na⁺/Cl^? molar ratio suggest that the part of the Ca²⁺ (±Mg²⁺) content in 23 FGW samples is derived from clay minerals of the aquifer matrix, and part of the Na⁺ content in 20, 12, and 3 FGW samples is derived, respectively, from alkali feldspar weathering, clay minerals of the aquifer matrix and rain water and/or halite. Brackish groundwater (BGW) samples (n = 4) contain Cl^? as the dominant anion and their average total ionic concentration (38.65 meq/L) is 1.79 times higher than that of the FGW samples (21.50 meq/L). BGW pockets were generated by non-conservative mixing of FGW with the upconed saline water from the underlying saline groundwater zone of the semi-confined aquifer along bore wells involved in excessive extraction of groundwater from the unconfined aquifer. Groundwater belongs essentially to “high salinity, low sodium” irrigation water class.     

Impact assessment of a saline waste lagoon on groundwater pollution near a coastal aquifer in India—synthesis of geoelectrical and hydrochemical studies

The present study is an attempt to assess the impact of a saline waste lagoon on the near subsurface through electrical resistivity tomography (ERT). Resistivity and IP imaging data have been collected on profiles close to the lagoon and at a far off location (control location). Water samples have been collected from the lagoon and a municipality drinking well close to it and analysed for the water chemistry. The geoelectrical sections indicate very low resistivity formations in the near subsurface in the vicinity of the lagoon as compared to the control profile. The water chemistry data from the monitoring well close to the profile also indicates very high total dissolved solids (8658 mg/L) and qualitatively supports the contamination of the near subsurface. The conductive formations in the vicinity of the lagoon can be attributed to the overflow from the lagoon or the seepage.     

Thirty years(1984–2014) of groundwater science teaching and research in China: A dissertation-based bibliometric survey

In order to track the footprint of groundwater science teaching and research in China during the past years, a bibliometric analysis was conducted based on the database of China National Knowledge Infrastructure (CNKI), which covered the time span from 1984 to present and included more than 2.6 million master and doctoral dissertations from hundreds of institutions of Mainland China. The bibliometric analysis summarized output, geographical, and institutional patterns, as well as research directions and hotspots in groundwater studies in China in the period of 1984-2014. A total of 1 396 groundwater-related dissertations including 1 161 master dissertations and 235 doctoral dissertations, contributed by 128 institutions distributed in 53 cities nationwide, were searched out in the database. It can be seen obviously that, the groundwater science teaching and research in China has experienced a notable growth in the past three decades especially during 2000-2014. Groundwater modeling, resource, and exploitation were the top three major subject categories; China University of Geosciences (Beijing), Jilin University and Chang’an University were the top three productive institutions together accounting for more than one third of the total dissertations and 50% of the doctoral dissertations, which further prompted the cities (Beijing, Changchun, and Xi’an) to become the top three productive cities. The dissertations generally covered all the international research topics, which indicated that hydrogeologists in China have tracked the international frontier closely during the past decades. The keywords analysis revealed that, (1) numerical modeling was still the hottest topic and PHREEQC, MODFLOW, GMS, and FEFLOW were the four most used softwares; (2) the topics related with groundwater pollution and quality developed steadily and rapidly; (3) environmental isotopes and GIS were frequently used tools for hydrogeological condition analysis, and spatial data processing respectively; and (4) the unsaturated zone as an integral part of aquifers attracted more and more attentions from hydrogeologists focus on saturated zone.