Phreatic Aquifer Research Articles

Groundwater vulnerability assessment of an urban coastal phreatic aquifer in India using GIS-based DRASTIC model

The groundwater pollution in shallow aquifers is usually an outcome of urbanisation resulting from the discharge of industrial and domestic effluents. Maps of aquifer vulnerability to pollution are becoming more in demand because it addresses the degree of sensitivity of the groundwater system towards changes in intrinsic and extrinsic factors. With this aim, the DRASTIC method was adopted to address the vulnerable groundwater zones for shallow aquifers of Greater Cochin and the surrounding region. Seven hydrogeological parameters either measured in-situ for 98 dug wells or derived from secondary sources and satellite data were integrated into a GIS platform and modelled using DRASTIC. Rating for the DRASTIC factors was derived based on weights assigned to each parameter. The resultant map depicted vulnerability index values ranging 79 to 174 reclassified as very high (>144), high (144–131), medium (<131 to 115) and low (<115). About 68% of the total study area, characterised by porous and permeable aquifer media with shallow groundwater levels, displayed a very high to high vulnerability index value. The majority of the highly vulnerable area falls in the urban centre with high population density within the lowland region. Sensitivity analysis shows that aquifer media has the biggest effect on vulnerability assessment. Water quality analysis was carried out for groundwater samples collected from 41 dug wells. The degree of contamination was calculated by adding the concentration of metals. The susceptible zones based on the degree of contamination (Cd) cross verified with vulnerability index depicted a significant correlation between vulnerability zones. The study indicates that contamination and vulnerability to contamination is a main cause of concern for more than 3.82 million people living in the region. The study suggests that DRASTIC model can be used as an efficient tool to manage water-sensitive urban development and groundwater sustainability.

Ecological Impact Prediction of Groundwater Change in Phreatic Aquifer under Multi-Mining Conditions

In aeolian sandy grass shoal catchment areas that rely heavily on groundwater, mining-induced geological deformation and aquifer drainage are likely to cause irreversible damage to natural groundwater systems and affect the original circulation of groundwater, thus threatening the ecological environment. This study aimed to predict the impact of groundwater level decline on vegetation growth in the Hailiutu River Basin (HRB), which is a coal-field area. Based on remote-sensing data, the land use/cover change was interpreted and analyzed, and the central areas of greensward land in the basin were determined. Subsequently, the correlation between groundwater depth and grassland distribution was analyzed. Then, the groundwater system under natural conditions was modeled using MODFLOW, and the groundwater flow field in 2029 was predicted by loading the generalized treatment of coal mine drainage water to the model. The change in groundwater depth caused by coal mining and its influence on the grassland were obtained. The results show that coal mining will decrease the groundwater depth, which would induce degradation risks in 4 of the original 34 aggregation centers of greensward land that originally depended on groundwater for growth in HRB because they exceeded the groundwater threshold. The prediction results show that the maximum settlement of groundwater level can reach 5 m in the northern (Yinpanhao), 6 m in the eastern (Dahaize), and 10 m in the southern (Balasu) region of HRB. Attention should be paid to vegetation degradation in areas where groundwater depth exceeds the minimum threshold for plant growth.

The Ajuricaba Basin Creek chemical signature of water resources: Geological sources and anthropogenic contributions

The Ajuricaba Basin Creek is located west of the Parana State, it is part of the Parana 3 Hydrographic Basin and it is located at southwest of the Marechal Candido Rondon county. Its area of around 18 km2 is manly used for agricultural purposes. The basin is part of the Serra Geral Aquifer System (SGAS), which comprises basic volcanic rocks of the Serra Geral Group. The main objectives of this study are the characterization of the hydrogeochemical environments and the understanding of the dissolved elements sources, both geological and human, in order to create a water circulation model of the basin. Two field campaigns, in August and November 2019, were done to collect water samples from surface waters (SW), phreatic aquifer (PA) and fractured aquifer (FA). During the 2019 field campaigns, the temperature, pH, total dissolved solids (TDS) and electrical conductivity (EC) were measured on site. Physicochemical parameters (SiO2, HCO3−, CO3−2, Cl−, F−, PO4−3, SO4−2, NO3−, NO2−, Ca+2, Mg+2, Na+, K+, Fe total, Mn+2, Nb, S, V, Zn, Al, Sr, Ba, P, Ti) of the collected samples were analysed. Preexisting data from December 2010 was also used to observe historical changes in water quality through time. Based on this data, statistical (univariate and correlation) and hydrochemical analysis were conducted in order to characterize the hydrogeochemical environments and surface and groundwater flows in the basin. Historical analysis revealed that SW and PA samples have the most significant impacts on water quality with double the median concentration of NO3− and three to nine times the concentration of Cl−. Hydrochemical analysis showed that SW have higher concentrations of HCO3−, Cl−, NO3−, Ca+2, Mg+2, Al, Sr, Ba and Fe, high TDS and neutral to acid pH. PA has the lowest TDS and acid pH and its main ions are HCO3−, NO3−, Ca+2 and Mg+2. In addition, FA was divided in: FA (Ca+2) with HCO3−, Ca+2 and Mg+2 as main ions, neutral pH and low TDS and FA (Na+) with CO3−2, HCO3−, SO4−2, Na+, V, Nb and P as main ions, basic pH and high TDS. SW has a similar pattern to PA and FA (Ca+2) indicating that the rivers are discharge zones for both aquifers. FA (Ca+2) has a similar hydrochemical signature to SGAS, confirming it origins. In opposition, the FA (Na+) aquifer hydrochemical signature differs from the SGAS and, in fact, is more similar to the one of the confined Guarani Aquifer System (GAS), suggesting a higher residence time. Fa (Na+) waters have higher TDS and basic pH, indicating a higher residence time and depth associated with the ascension of even deeper flows from GAS towards the basin. In addition to the hydrochemical model, this research also highlights the potential of the multielement-hydrochemistry to understand the relations between surface and groundwater resources contributing for the management of water resources in watersheds.

Geochemical and isotopic study of phreatic aquifer in an arid area, case study of El Golea region (Algerian Sahara)

Shallow groundwater is a major reservoir of water in arid areas. This water is characterized by strong mineralization which represents a major quality problem for human consumption and even for its use in agriculture. For this reason, geochemical, statistical and isotopic studies were conducted to obtain an overview of the processes that control water mineralization in the oasis of El Golea (Algerian Sahara). Spatial distributions of EC in this area show that the highest concentrations are situated close to the El Golea Lake formed by evaporitic rock. Geochemical and statistical analysis and data from 28 water points in the phreatic aquifer of the El Golea oasis show a strong correlation between electrical conductivity and the majority of chemical elements, indicating the influence of the interaction between fresh water and bed rock on this mineralization. The results obtained indicate that Carbonate minerals (calcite) are oversaturated in all groundwater samples. The ionic ratios demonstrate the role of weathering, dissolving, ion exchange, and evaporation procedures in mineralization acquisition. The scatter plot of that relates δ 2 H = f (δ 18 O) reveals that all of the samples were founds to be below both the GMWL of Craig (1961) and the Sfax local meteoric boundaries (South Tunisia) indicating that groundwater samples have an old origin. This isotopic composition depletion can be explained by the presence of mixes of phreatic groundwater and Continental Intercalaire (CI) (W2).

Irrigation Water Impact on Soil Properties in Arid Oued-Souf Region, Southeast Algeria

The perimeters of the Oued-Souf region are irrigated by salty water coming from the phreatic water and thus progressive salinization of the soil occurs. This study aims at a qualitative analysis of the evolution of the salinity in the soils irrigated by pivot irrigation for several years. For this, three plots were irrigated by pivots in each agricultural region. The choice of these 3 plots is justified by the number of years of their cultivation: plot 1 has been cultivated and irrigated for 2 years (2016–2017), plot 2 has been cultivated and irrigated for 5 years (2016–2020) were studied and compared to the controlled soil not irrigated. The irrigation is done by sprinkling with mineralized water from the phreatic water. The results obtained showed that the irrigation water is characterized by high salinity and low sodium adsorption ration (SAR). Sodium and chloride contents are excessive in sprinkler irrigation mode. The evolution of salinity in irrigated soils between 2 and 5 years was very significant compared to the control (non-irrigated). The salinity goes from 0.38 dS/m in the control site classified as low salinity to 1.54 dS/m in the cultivated site for the 5 years classified as high salinity soil. The geochemical facies at the three study regions after irrigation are sulfate-calcium. A significant correlation is observed between calcium and sulfate with electrical conductivity (EC), so the salinity of our soils is dominated by sulfate. These results are confirmed by statistical analysis of the data (PCA), which revealed that salinity is heavily influenced by Mg2+, Ca2+, SO42- in the topsoil. Keywords: Hydrochemical; Irrigation water; Oued-Souf area; Phreatic aquifer; Salinity; Soil; Statistical analysis.

Impacts of anthropogenic groundwater recharge (AGR) on nitrate dynamics in a phreatic aquifer revealed by hydrochemical and isotopic technologies

Although anthropogenic groundwater recharge (AGR) can either elevate or decline the concentration of nitrate in the phreatic aquifer with high hydraulic conductivity, the long-term impact of AGR on nitrate dynamics in the phreatic aquifer and its reason is seldom disclosed. In this study, the hydrogen and oxygen stable isotopes (δ2H-H2O and δ18O-H2O) combined with mixing stable isotope analysis in R (MixSIAR) were used to group the study area into the dominant area of AGR by surface water (AGRSW) and the dominant area of natural groundwater recharged by precipitation (NGRP). Hydrochemical parameters and multiple stable isotopes, including δ2H-H2O, δ18O-H2O, δ15N-NO3−, δ18O-NO3−, and δ13C-DIC, were applied to explore the impacts of AGR on the concentration, biogeochemical processes, and main sources of nitrate. The results showed that AGR by surface water with low nitrate content can reduce nitrate pollution in groundwater. The characteristic of δ18O-NO3− value revealed that nitrification was the primary biogeochemical process of nitrogen in groundwater. AGR may enhance nitrification as indicated by the δ18O-NO3− value closer to the nitrification theoretical line. Dual nitrate stable isotopes and MixSIAR revealed that chemical fertilizer (CF), soil nitrogen (SN), and surface water (SW) contributed 10.88%, 49.92%, and 27.64% to nitrate in AGRSW groundwater, respectively, which was significantly different from their contributions to NGRP groundwater (p < 0.05). Notably, AGR significantly increased the contribution of SW but decreased the contribution of CF and SN in groundwater. This study provided a basis and guidance for groundwater quality assessment and pollution control in the phreatic aquifer with high hydraulic conductivity.

Approximate analytical solution for seepage field of drained tunnel in vertically stratified phreatic aquifer

Approximate analytical solution for seepage field of drained tunnel in vertically stratified phreatic aquifer

Assessing and delineation of groundwater recharge areas in coastal arid area southern Tunisia

In Gabès region (southeastern Tunisia), given the semi-arid to arid climate conditions, groundwater is an essential resource to supply the growth needs of the socio-economic development. To ensure sustainable development and preserve water resources, a careful estimation of the present day recharge amount and the delineation of the potential zones of rainfall precipitation are of required for an accurate evaluation of regional water balance. In this context, this study aims to a preliminary assessment of groundwater recharge in Gabes basin in regard to the delineation of the potential recharge areas of phreatic aquifers. Thus, a geological and hydrogeological collected database coupled with remote sensing techniques (RST) were used for the determination of the lateral variation of recharging zone, Treatment by ArcGIS and Matlab softwares and Kohonen self-organizing maps (K-SOM) approaches. The obtained results indicate that five recharge potential areas have been identified and classified as 27% very low, 23% low, 40% moderate recharge, 7% good and 3% very good potential recharge located principally on southern part of the study region. This distribution is controlled principally by the geomorphological, geologic, and hydrogeologic features of the region. Reasonable management strategies based on a perennial exploitation of these low renewable resources are required to optimize the water dependent socio-economic development. The estimated groundwater potential recharge of Gabès aquifer system using K-SOM and RST is of 11.4 Mm3 y−1. This recharging rate is very low it present 7% of the total rain, thus it must be ameliorated. K-SOM and RST approach is a useful method for groundwater potential recharge mapping and is a helpful of wells establishment and groundwater sustainable management. an isotopic analyses is recommended to ameliorate the decision maker to establish the adequate strategy.

Quantifying lake–aquifer water exchange: the case of Lake Urmia, Iran

ABSTRACT This study investigated the lake–aquifer hydraulic interactions in Lake Urmia (LU) as the second largest hypersaline lake in the world. Due to the scarcity of hydrogeological data required for modelling, a method based on Darcy’s Law and lake water budget was used to quantify the lake–aquifer interaction. Long-term ground- and satellite-based hydrological datasets over the time frame 2001–2019 were used. Results indicate that the groundwater flux between LU and the aquifers controls 18.74 ± 1.67% of the lake’s water storage. While 10 out of 14 adjacent aquifers recharge LU at a rate of less than 180 m3/m.month, one phreatic aquifer recharges the LU up to 1400 m3/m.month. Two aquifers are recharged from the seawater of LU at a rate of 110–640 m3/m.month. The results of this study lead to a holistic understanding of the hydraulic interaction of LU–aquifers, which is essential for the sustainable management of both settings.

Multiscale and multifactor sea-groundwater interactions in southwestern Mauritania

Coastal aquifers in semi-arid zones are particularly exposed to environmental changes because of their low annual recharge and the increasing anthropogenic pressure. This is particularly the case in the Trarza phreatic aquifer (SW Mauritania), which is the uppermost northern part of the great Senegalese-Mauritanian sedimentary basin. The interactions between the Atlantic Ocean and the Tertiary-Quaternary aquifer have evolved considerably during the last millennia and these continuous changes concern the nature and location of processes at work, their intensity and their current consequences. In this vast region with a very flat topography, hydrodynamic and geochemical observations are still rare and currently allow only the main features of recent history to be reconstructed. The analysis of old and recent data reveals that eustatic variations and the annual flood of the Senegal River were in the past the most important factors of equilibrium between fresh water and sea water, even very far from the present coastline. Today, anthropization, in particular hydraulic developments and urbanisation, adds to the complexity of the system. At a more local scale, denser observations in the Nouakchott urban area or in the Diawling natural park provide a better understanding of current dynamics.

Short-Term Effects of the EU Nitrate Directive Reintroduction: Reduced N Loads to River from an Alluvial Aquifer in Northern Italy

The Po Plain (northern Italy) is one of the largest aquifers in Europe, and 67% of the utilized agricultural land in this area is classified as a nitrate vulnerable zone (NVZ). However, it hosts intensive agriculture and livestock farming. In a stretch of the Mincio River (a tributary of the Po River), hydraulic heads and physico-chemical parameters of river and groundwater were monitored for a hydrologic year (2020–2021), to evaluate the effects of manure fertilization and flooding irrigation on surface- and groundwater chemistry. From 2020 the Nitrate Directive’s fertilization limit was reintroduced and a comparison has been performed comparing surface- and groundwater data from the 2019 fertilization period (before limit reintroduction) and 2020 (after). Results suggest that in 2021 the phreatic aquifer displayed elevated nitrate (NO3−) concentrations, exceeding 50 mg L−1, although average values were lower than those of 2019. Nitrate loads in the Mincio River reached 6670 kg NO3− d−1 and resulted from the overfertilization in the surrounding area and the quick transfer of nitrogen from groundwater to the river. As compared to 2019, the river loads decreased by 59%, suggesting that the introduction of fertilization limits can produce measurable, short-term responses in alluvial aquifers.

Groundwater recharge in phreatic aquifers, a case study: modeling unsaturated zone and recharge rates of the Rio Claro Aquifer using Hydrus-1D

The hydrological process in which water infiltrates from the soil surface to the top of saturated zone of an aquifer is called groundwater recharge. A better understanding of this process is one of the keys for a proper management of an aquifer system, especially in places where water supply relies solely on groundwater. This study presents the applicability of the one-dimensional mathematical model HYDRUS-1D® to simulate the unsaturated zone of the Rio Claro Aquifer, southeastern Brazil, in order to interpret the behavior of the aquifer recharge over time and under different rainfall regimes. Deriving out of simulations, the influence of different precipitation rates, as well as the effect of different land use on the recharge zones was assessed. Results enabled us to observe the variation of distinct properties of the soil profile, such as the spatio-temporal changes in hydraulic conductivity and soil moisture content at different soil horizons and depths due to flow and rainfall dynamics. Moreover, the average infiltration time from the soil surface to the top of saturated zone was estimated to be between 85-90 days. The precipitation/recharge ratio was at 20-30% intervals, presenting higher values in periods of greater precipitation. Likewise, changes in land use such as the increase in paved areas led to a nearly virtual zero recharge emphasizing the importance of uncovered areas for natural aquifer recharge processes.

Qualitative assessment in river and phreatic aquifer water in a rural watershed in the Atlantic Forest biome

Watersheds have different water compartments (surface, subsurface, and underground) connected by the soil-water interface. In order to be able to relate these compartments, monitoring data are necessary, such as the case of the Ribeirão Concórdia watershed, in Lontras, Santa Catarina (SC). This study aimed to evaluate the behavior and the correlation between rainfall-runoff and phreatic surface levels with chemical species concentrations in surface and groundwaters in a rural watershed. Data of 3 piezometers installed in the hydrographic basin were used: PZ2127, PZ3, and PZMC. The piezometers are equipped with hydrostatic level sensors. A fluviometric station is located adjacent to PZ2127 (near the catchment outlet). Concentrations of anions and carbon forms were analyzed in water samples (river and piezometers) taken every 2-3 weeks, from January 14, 2012, to December 23, 2016, totaling 103 samples. Correlations between daily data were verified using Pearson’s correlation coefficient (ρ). The river presented a dilution effect, while the adjacent piezometer had the highest average concentrations of chemical species. Precipitation and chemical species concentration showed no seasonal pattern, with events/peaks throughout the year. Higher concentrations of carbon forms were found in the summer, while lower concentrations were observed in the winter. Positive correlations between concentrations of anions and carbon forms in surface and groundwaters were obtained.

Using Heat as a Tracer to Detect the Development of the Recharge Bulb in Managed Aquifer Recharge Schemes

Managed Aquifer Recharge (MAR), the intentional recharge of aquifers, has surged worldwide in the last 60 years as one of the options to preserve and increase water resources availability. However, estimating the extent of the area impacted by the recharge operations is not an obvious task. In this descriptive study, we monitored the spatiotemporal variation of the groundwater temperature in a phreatic aquifer before and during MAR operations, for 15 days, at the LIFE REWAT pilot infiltration basin using surface water as recharge source. The study was carried out in the winter season, taking advantage of the existing marked difference in temperature between the surface water (cold, between 8 and 13 °C, and in quasi-equilibrium with the air temperature) and the groundwater temperature, ranging between 10 and 18 °C. This difference in heat carried by groundwater was then used as a tracer. Results show that in the experiment the cold infiltrated surface water moved through the aquifer, allowing us to identify the development and extension in two dimensions of the recharge plume resulting from the MAR infiltration basin operations. Forced convection is the dominant heat transport mechanism. Further data, to be gathered at high frequency, and modeling analyses using the heat distribution at different depths are needed to identify the evolution of the recharge bulb in the three-dimensional space.

Influence of artificial recharge in a phreatic aquifer on deep excavation dewatering: a case study of Dongguantou Nan Station in Beijing, China

Influence of artificial recharge in a phreatic aquifer on deep excavation dewatering: a case study of Dongguantou Nan Station in Beijing, China

Geochemical Markers as a Tool for the Characterization of a Multi-Layer Urban Aquifer: The Case Study of Como (Northern Italy)

The analysis of geochemical markers is a known valid tool to explore the water sources and understand the main factors affecting natural water quality, which are known issues of interest in environmental science. This study reports the application of geochemical markers to characterize and understand the recharge areas of the multi-layer urban aquifer of Como city (northern Italy). This area presents a perfect case study to test geochemical markers: The hydrogeological setting is affected by a layered karst and fractured aquifer in bedrock, a phreatic aquifer hosted in Holocene sediments and connected with a large freshwater body (Lake Como); the aquifers recharge areas and the water geochemistry are unknown; the possible effect of the tectonic setting on water flow was overlooked. In total, 37 water samples were collected including water from two stacked aquifers and surface water to characterize hydrochemical features. Moreover, six sediment samples in the recent palustrine deposits of the Como subsurface were collected from cores and analyzed to understand the main geochemistry and mineralogy of the hosting material. The chemical analyses of water allow to observe a remarkable difference between the shallow and deep aquifers of the study area, highlighting different recharge areas, as well as a different permanence time in the aquifers. The sediment geochemistry, moreover, confirms the differences in trace elements derived from sediment-water interaction in the aquifers. Finally, an anomalous concentration of As in the Como deep aquifer was observed, suggesting the need of more detailed analyses to understand the origin of this element in water. This study confirms the potentials of geochemical markers to characterize main factors affecting natural water quality, as well as a tool for the reconstruction of recharge areas.

A new species of the troglobitic genus Spelaeogammarus da Silva Brum, 1975 (Amphipoda: Artesiidae) from a cave in the Brazilian semi-arid region, with new records of its congener, Spelaeogammarus spinilacertus Koenemann and Holsinger, 2000

We propose a new species of the troglobitic genus Spelaeogammarus da Silva Brum, 1975, with data on its distribution, ecology, aspects of behavior, and conservation status. Spelaeogammarus ginae sp. nov. occurs in a single cave in the Serra do Ramalho karst area, of the northeastern Brazilian semi-arid region. We also provide new data on the distribution and conservation status of its congener, Spelaeogammarus spinilacertus Koenemann and Holsinger, 2000 that occurs in the upper phreatic aquifer inside caves from Chapada Diamantina domain. Both species occur in caves in the state of Bahia, northeastern Brazil.

Hydrochemical characteristics, hydraulic connectivity and water quality assessment of multilayer aquifers in Western Suzhou City, Northern Anhui Province, China

Abstract The present study focuses on the shallow phreatic aquifer (SA) and the upper confined aquifer (CA) developed in Cenozoic loose strata, which are the major regional groundwater resources for drinking, irrigation, industry and other water-related activities. Seven samples from SA and seventeen samples from CA were analyzed to depict the hydrochemical characteristics, categorize the hydrochemical facies, evaluate the hydraulic connectivity, and appraise the drinking water and irrigation water quality. The abundance of cations is Na+ &amp;gt; Ca2+ &amp;gt; Mg2+ &amp;gt; K+ and the anions is HCO3− &amp;gt; SO42− &amp;gt; Cl− in both aquifers, respectively. Groundwater chemistry is controlled by water-rock interactions such as halite dissolution, ion exchange, reverse ion exchange, silicate weathering, and followed by the dissolution of Glauber's salt. The low connectivity and moderate connectivity between these two aquifers has engendered. The majority of the ion concentrations are within the limit for drinking, only one sample from the shallow aquifer was greater than the limit of 250 mg/L, a total of 29% from the shallow unconfined aquifer and 14% from the confined aquifer are not within the limit of 250 mg/L. The sodium absorption ratio (SAR), residual sodium carbonate (RSC) and soluble sodium percentage (%Na) values reveal that all the samples are appropriate for irrigation uses. The the US salinity laboratory (USSL) diagram shows that sixteen CA samples and all the SA samples fall in the C3S1 zone, implying high salinity hazard and low alkalinity hazard.

Improvement of the Theis unsteady well flow model with infiltration recharge in a phreatic aquifer

The recharge and discharge of groundwater are mainly vertical surface infiltration recharge, evaporation discharge (evaporation can be shown as negative value of infiltration) and lateral surface water recharge and discharge. One of the most basic problems in hydrogeology is the evaluation criteria of sustainable exploitation of groundwater, which involves the increment of recharge and the decrease of discharge. Therefore, the prediction model of groundwater exploitation must include the above two kinds of recharge and discharge factors, otherwise the evaluation of groundwater cannot meet the requirements. However, the classic Theis unsteady well flow model (1935) only involves the recharge and discharge of the side boundary, and does not considers the surface infiltration recharge of the upper boundary, even when groundwater is pumped near the river. In this way, the analytical model cannot be basically used for prediction, and can only be used for well flow test to obtain the aquifer parameters in dry season. Therefore, the goal of this paper is to develop the Theis unsteady well flow model with surface infiltration recharge. For the problem of phreatic flow, the equation of groundwater flow cannot be established by using head as the dependent variable in a confined aquifer. We use the potential function of the second linearization method to establish groundwater flow equation in the phreatic aquifer. For the solution of the generalized mathematical model of the complex hydrogeological problem with rainfall infiltration and a pumping well, we adopt the method of decomposing it into several simple sub-models and synthesizing them into the solution of the original complex mathematical model. Based on the principle of mass conservation and assuming that the seepage obeys the Darcy’s law and satisfies the Dupuit's assumptions, the differential equation of groundwater flow is established. Then, for the well flow problem with uniform and stable infiltration recharge in two parallel rivers and two kinds of strip regions formed by a river parallel to an impermeable boundary, the general equation of groundwater flow and several kinds of water table equations under specific conditions and their flux equations are obtained. In addition, the “boundary to boundary reflection method” is proposed and applied to solve the same problem in a strip of region between a river boundary in parallel to an impermeable boundary, which reduces many derivation processes. Finally, as a preliminary application of the above theoretical results, it is also an important application, that is, there is a pumping well near the river whose water quality cannot meet the requirements, and the critical flux equation of the pumping well is calculated on the premise of not absorbing the river water. The important and concise relation equation is obtained. The equation can also be used to calculate the critical pumping rate of pumping wells in coastal areas without seawater intrusion. In this paper, the groundwater flow network diagram at a certain time in the process of unstable well flow under the above conditions is given. Compared with the flow network of well flow near the river, which is commonly seen in the literature, the flow network has obvious characteristics.

Accessible Phreatic Groundwater Resources in the Central Shijiazhuang of North China Plain: Perspective From the Hydrogeochemical Constraints

Phreatic groundwater plays a significant role in the water supply for human communities, especially in water scarce regions. This research was conducted to investigate the hydrochemistry and contamination of phreatic groundwater and their constraints on drinking water supply in a semiarid region of the North China Plain. A total of 49 phreatic groundwaters were collected for the hydrochemical analysis. The results suggested the phreatic groundwater had a slightly alkaline nature. Although the groundwater had a large variation of salinity with the TDS of 172–1,875 mg/l, most groundwater was moderately-hard fresh and of HCO3-Ca type. Contaminants of NO3−, NO2−, NH4+, Fe, F−, Zn, Mn were detected, but only NO3−, NO2−, NH4+, and Fe were found exceeding the drinking water desirable limits at some sites. The nitrogen contaminants were from anthropogenic inputs (urban sewage effluents and agricultural fertilizers) and mainly distributed in the central study area. The anthropogenic inputs of nitrogen contaminants also elevated groundwater salinity. Among the exceeding contaminants, only NO3− would pose a potential health risk to water consumers. The existing health risks by NO3− ranged from medium risk (HQ of 1–4) to high risk (hazard quotient &amp;gt; 4) for all populations, and most risks were categorized into the medium risk rank. Groundwater F− was also found with health risk at some sporadic sites although it did not exceed, only approached, the desirable limit. Its health risk was only to infants and categorized into the medium risk with the maximum HQ of 1.55. Most phreatic groundwater (83.67%) in the study area had relatively good quality and was suitable for domestic usage with the EWQI value below 150. Others belonged to the poor (EWQI of 150–200) and extremely poor (EWQI &amp;gt; 200) quality categories, and mainly distributed in the urban Gaocheng. Thus, it is recommended to pay attentions to the anthropogenic contaminants inputs into phreatic aquifers in human activities areas.