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This paper aims to study the impacts of groundwater seepage on artificial freezing process of gravel strata, the temperature field characteristics of the strata, and the strata process, closure time and thickness evolution mechanism of the frozen wall.

In this paper several laboratory model tests were conducted, considering different groundwater seepage rate.

The results show that there is a significant coupling effect between the cold diffusion of artificial freezing pipes and groundwater seepage; when there is no seepage, temperature fields upstream and downstream of the gravel strata are symmetrically distributed, and the thickness of the frozen soil column/frozen wall is consistent during artificial freezing; groundwater seepage causes significant asymmetry in the temperature fields upstream and downstream of the gravel strata, and the greater the seepage rate, the more obvious the asymmetry; the frozen wall closure time increases linearly with the increase in the groundwater seepage rate, and specifically, the time length under seepage rate of 5.00 m d⁻¹ is 3.2 times longer than that under no seepage; due to the erosion from groundwater seepage, the thickness of the upstream frozen wall decreases linearly with the seepage velocity, while that of the downstream frozen wall increases linearly, resulting in a saddle-shaped frozen wall.

The research results are beneficial to the optimum design and risk control of artificial freezing process in gravel strata.

The purpose of this paper is to emphasize the importance of groundwater‐surface water interaction when studying, modeling and assessing climate change impacts on river water management.

The investigations were focused on River Vantaa and its tributaries in southern Finland. The main methods used involved aerial infrared photography, thermal profiling of river sediments, water quality measurements, isotopic composition of oxygen and hydrogen δ¹⁸O, δ²H and river water temperature measurements. The authors present the first results of the field measurements targeted to identify the groundwater recharge and discharge zones within the river system.

Groundwater discharge zones were found to have a significant impact on water quality and volume in River Vantaa and its tributaries. In the drainage basin, the aerial infrared photography seemed to be a feasible and cost‐effective method to identify areas of groundwater discharge across the entire river basin. Around 350 groundwater/surface water interaction sites along the 220 km river system could be identified.

The interaction sites identified during the season of low flow rate should be considered as potential risk areas because during flood periods groundwater quality might be at risk due to bank infiltration. This should be considered in river basin management within predicted changing climatic conditions.

This is the first attempt in Finland to map systematically groundwater and river water interactions. The focus of the paper is relevant, because according to the existing climate scenarios, flooding of the main rivers in Finland will be more frequent in future, increasing the probability of groundwater‐surface water interaction.

The contamination of groundwater by natural arsenic is currently a worldwide epidemic. Arsenic-contaminated groundwater has been reported in Argentina, Chile, Mexico, China, Hungary, West Bengal in India, Bangladesh, and Vietnam. Of these regions, Bangladesh and West Bengal are the most seriously affected in terms of the size of the population at risk and magnitude of health problems. Hence, chronic exposure to arsenic >50′′μg/L in drinking water can result in serious health problems. Common symptoms of arsenic-related ailments are skin, cardiovascular, renal, hematological, and respiratory disorders. Therefore, this chapter focuses on nature, origin, and extent of groundwater arsenic contamination, probable causes, and its impacts on food, drinking water, and social coverage. It further discloses mitigation approaches proposed and practiced by the different research groups to combat this problem and finally concludes.

The purpose of this paper is to indicate the limitations of the studies that address the impact of climate change on groundwater resources and to suggest an improved approach.

A general review, both from a groundwater hydrological and a climatological viewpoint, is given, oriented on the impact of climate change on groundwater resources.

The impact of climate change on groundwater resources is not the subject of many studies in the scientific literature. Only rarely sophisticated downscaling techniques are applied to downscale estimated global circulation model (GCM) future precipitation series for a point or region of interest. Often it is not taken into account that different climate models calculate considerably different precipitation amounts (conceptual uncertainty). The joint downscaling of the meteorological variables that govern potential evapotranspiration (ET) is never done in the context of a study that assessed the impact of climate change on groundwater resources. It is desirable that actual ET is calculated in (groundwater) hydrological models on a physical basis, i.e. by coupling the energy and water balance at the Earth's surface.

This review signalises a number of problems with published studies on the impact of climate change on groundwater resources. In many studies the method to downscale meteorological variables from a climate model to a hydrological model is not adequate. ET is often calculated in a strongly simplified manner and not all hydrological processes are modelled in a fully coupled fashion. More sophisticated downscaling approaches, physically based schemes to calculate ET and well‐calibrated, integrative hydrological models are needed.

Major land use changes can have a significant impact on the environment, e.g. increased leaching and run‐off losses of nutrients and water contamination. Nitrate (NO₃^–) can be easily leached and, when present at high concentrations in drinking water, can be a health hazard. This paper seeks to report an easy‐to‐use computer model designed to provide predictions of possible impacts on groundwater NO₃^– concentration on a regional scale.

The model takes into account NO₃^–‐N concentrations from various land use activities, land surface recharge rates (as affected by soil water retention capacity, land management, irrigation and rainfall), and mixing of surface recharge and river recharge. Spatial information on land use and groundwater recharge sources are lumped into groundwater management zones (100‐500 km²), and vertical concentration profiles of NO₃^– in groundwater are estimated from a one‐dimensional dispersion model. The model is applied to the 2,300 km² Central Canterbury Plains of New Zealand.

A scenario analysis for the Bankside groundwater management zone showed that the NO₃^–‐N concentration at the groundwater surface could increase from 7.8 mg N L^‐1 to 11.3 mg N L^‐1 if all the land used for sheep farming is replaced by dairy farming (increasing dairy land from 21 per cent to 64 per cent of the total land area). However, the impact of such land use changes on the NO₃^–‐N concentration 50 m below the groundwater surface was relatively small, resulting in an increase of NO₃^–‐N concentration from 0.4 to 0.5 mg N L^‐1. This is because of the significant mixing of surface recharge with river recharge at this depth.

The model can serve as a useful tool for first‐order estimation of possible trends of NO₃^–‐N concentration profiles in aquifers as a result of land use changes.

The elevated level of nitrate in groundwater is a serious problem in Texas aquifers. To control and manage groundwater quality, the characterization of groundwater contamination and identification of the factors affecting the nitrate concentration of groundwater are significant. The purpose of this paper is to determine factors which have significant impacts on the elevated groundwater nitrate concentrations of the Southern High-Plains and the Edwards-Trinity aquifers.

The characterization of groundwater nitrate contamination was undertaken by analyzing the hydrochemical data of groundwater within a statistical framework. The multivariate statistical analysis (ordinary least square) and geographically weighted regression (GWR) models were used to study the relationship between groundwater nitrate contamination and land use of the study areas.

Results show groundwater nitrate contamination is typically due to an overapplication of N fertilizers to cotton in the Southern High-Plains aquifer and to grassland in the Edwards-Trinity aquifer. Adjusted R² (0.45) explains variations of nitrate concentration by well-depth, cotton production, shrubland and grassland in the Edwards-Trinity aquifer. The results of an analysis of variations in N concentration with well depth for all 192 wells indicate that nitrate concentrations in water from wells in the Southern High-Plains and Edwards-Trinity aquifers tend to decrease with increasing well-depth.

In this study, the GWR model was built to identify nitrate concentration within a geographic framework to ensure sustainable use of groundwater, which is important for local management purposes. The analysis should include local spatial variations of elements such as hydrologic characteristics and the land use activities if groundwater nitrate contamination causes adverse effects on human and ecosystem health.

Urban groundwater is an important and valuable resource for Shijadran City, China. With the impact of rapid urban growth Shijadran is at risk of severe aquifer depletion, regional water table decline and supply facilities refurbishment. This paper presents a multi‐plan management of urban groundwater with two optimisation scenarios in order to alleviate and improve the environmental, social and economic situations caused by over‐exploitation of groundwater. It was developed based on the analysis of regional hydrogeology, water use and land use. A calibrated groundwater flow model was incorporated into the optimisation models through a water head response matrix of the Quaternary aquifer. The current supply optimisation not only met the increasingly growing need of water demand but also controlled and eliminated the various hazards caused by groundwater over‐pumping. Artificial recharge management, with conjunctive use of surface water and groundwater, provided a practical solution to the overall groundwater exhaustion and led to a solution for water table recovery, aquifer protection and sustainable water use. A comprehensive water management strategy for decision making was developed to reduce the negative impacts of urban growth on water use.

Groundwater plays a critical part in both natural and human existence. When surface water is scarce in arid climates, groundwater becomes an immensely valuable resource. Dak Lak is an area that frequently lacks water resources for everyday living and production, and the scarcity of water resources is exacerbated during the dry season. As a result, it is critical to do study and understand about groundwater to meet the region's water demand. This study aims to extend the use of the MODFLOW model for groundwater simulation and assess the overall groundwater reserves and water demand in the highland province Dak Lak.

The MODFLOW model is used in this work to compute and analyze the flow, prospective reserves of groundwater from which to plan extraction and estimate groundwater variation in the future.

The application of the MODFLOW model to Dak Lak province demonstrates that, despite limited data, particularly drilling hole data for subterranean water research, the model's calculation results have demonstrated its reliability and great potential for use in other similar places. The use of the model in conjunction with other data extraction modules is a useful input for creating underground flow module maps for various time periods. The large impact of recharge and evaporation on groundwater supplies and water balance in the research area is demonstrated by simulations of climate change scenarios RCP4.5 and RCP8.5.

None of the studies has been done previously to analyze water resources of Dak Lak and the scarcity of water resources is exacerbated during the dry season. Therefore, this study will provide useful insights in the water resource management and the conservation of Dak Lak. The groundwater in Dak Lak can meet the area's water demand, according to the results obtained and water balance in the study area. However, the management of water resources and rigorous monitoring of groundwater extraction activities in the area should receive more attention.

The quality of groundwater in the vicinity of petroleum products retailing stations in Ile-Ife, Nigeria was investigated with a view to providing valuable information on the organic and other physico-chemical parameters associated with the contamination of the groundwaters by petroleum products. The paper aims to discuss these issues.

Three sets of samples were collected per season from artesian wells within petroleum products retailing stations for polycyclic aromatic hydrocarbons (PAHs), trace metals and other physico-chemical parameters analysis. Extraction, cleaned-up and concentration of the PAHs were done using certified analytical methods. Levels of the PAHs and metals were determined using gas chromatography coupled with flame ionization detector and bulk scientific atomic absorption spectrophotometer, respectively, while other pollution indicators were measured using standard analytical procedures.

The groundwaters contained elevated levels of PAHs, Cu, Zn, Mn, Pb, Cr, V, Ni, Fe and total dissolved solids than their maximum allowable limits for drinking water. Analysis of variance (ANOVA) results confirmed that both seasonal variation and location had much influence on the levels of most of the analyzed parameters. Some of the parameters showed strong positive correlation with each other, while Cr/Pb and Na/Pb displayed strong negative correlation with each other, indicating similar source(s) and/or chemical affinity and vice versa, respectively. Cross-plot analysis results using metals and PAHs concentrations as variables showed significant positive correlations (R2=0.99) and (R2=0.60), respectively, suggesting similar source(s) of contamination of the two sets of samples.

The level of the groundwater contamination was an indication of indiscriminate discharge of petroleum products and/or underground tank leakage within the study areas.

This paper aims to define the current and potential extent of seawater intrusion in Manukan Island under different scenarios of varying recharge and pumping rates. The calibrated model was also used to predict the extent of seawater intrusion in low lying area of Manukan Island for two years with all conditions assumed to remain the same as those in December 2009.

Different scenarios of varying recharge and pumping rates based on threats received by Manukan Island were investigated. El‐Nino events and overpumping are represented by varying recharge and pumping rates. Simulation was done using SEAWAT‐2000, the latest modeling software available in groundwater modeling that couples flow and transport together.

The seawater‐freshwater mixing ratio moves landwards after two years of simulation in Scenario 1. In order to control overpumping in this study area, Scenario 2 has resulted in backward movement of the 1.4 percent seawater‐freshwater mixing ratio toward the coast after two years of prediction. The current contamination of the coastal aquifers by seawater intrusion will be more severe with an impact of El‐Nino events on groundwater resources depletion in Scenario 3. Reductions of pumping and recharge rates in Scenario 4 have worsened the seawater intrusion problem. With the aid of artificial recharge in Scenario 5, highest hydraulic heads and lowest chloride concentration were observed.

The sustainable groundwater management selected for Manukan Island's current situation will be Scenario 2. In view of the effects of El‐Nino events in the future, Scenario 5 can be implemented to restore groundwater resources. The numerical model has showed the groundwater condition during El‐Nino events and overpumping illustrated that simulation modeling is an excellent tool to understand the behavior and management of an aquifer system. The output of simulation modeling via numerical model provides a framework toward groundwater management. Thus, current study output with similar approach which will restore groundwater (artificial recharge and reduction of pumping rate) can be applied in other small islands of similar hydrogeological condition and stresses for the purpose of groundwater resource protection.

Briefly, these findings will effectively contribute to water policy analysis, planning and management in the study area to combat current as well as future seawater intrusion problem.