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Jiu Jimmy Jiao - One of the best experts on this subject based on the ideXlab platform.
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occurrence and geochemical behavior of arsenic in a Coastal Aquifer aquitard system of the pearl river delta china
Science of The Total Environment, 2012Co-Authors: Ya Wang, Jiu Jimmy Jiao, John A CherryAbstract:Abstract Elevated concentrations of arsenic, up to 161 μg/L, have been identified in groundwater samples from the confined basal Aquifer underlying the aquitard of the Pearl River Delta (PRD). Both aquatic arsenic in pore water and solid arsenic in the sediments in the basal Aquifer and aquitard were identified. Arsenic speciation of groundwater in the basal Aquifer was elucidated on a pH-Eh diagram. In the PRD, arsenic is enriched in groundwater having both low and high salinity, and arsenic enriched groundwater is devoid of dissolved oxygen, has negative Eh values, is slightly alkaline, and has abnormally high concentrations of ammonium and dissolved organic carbon, but low concentrations of nitrate and nitrite. Results of geochemical and hydrochemical analyses and sequential extraction analysis suggest that reductive dissolution of iron oxyhydroxide could be one of the important processes that mobilized solid arsenic. We speculate that mineralization of sedimentary organic matter could also contribute to aquatic arsenic. Scanning electron microscope analysis confirms that abundant authigenic pyrite is present in the sediments. Sulphate derived from paleo-seawater served as the important sulfur source for authigenic pyrite formation. Co-precipitation of arsenic with authigenic pyrite significantly controlled concentrations of aquatic arsenic in the Coastal Aquifer–aquitard system.
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abnormally high ammonium of natural origin in a Coastal Aquifer aquitard system in the pearl river delta china
Environmental Science & Technology, 2010Co-Authors: Jiu Jimmy Jiao, Ya Wang, John A Cherry, Xusheng Wang, Haiyan DuAbstract:High-nitrogen loadings of rivers and Aquifers systems are a major concern because of potential effects on human health and water quality impacts such as eutrophication of lakes and Coastal zones. This nitrogen enrichment is commonly attributed to anthropogenic sources such as sewage and agricultural and industrial wastes. The aims of this study were to delineate spatial distribution of groundwater ammonium in the Coastal Aquifer system in Pearl River Delta (PRD), China and to identify the origin of the abnormally high ammonium. A total of 40 boreholes were drilled to collect core samples of the aquitard and groundwater samples in the basal Aquifer. The core samples were used for extraction of pore water for centrifugation and bulk chemical analyses in laboratory. Unlike previous studies which focused mainly on the Aquifer, this study treated the Aquifer-aquitard system as a hydrogeochemical continuum. The results show that the Aquifer-aquitard system contains an exceptionally large total ammonium mass. Am...
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influence of the tide on the mean watertable in an unconfined anisotropic inhomogeneous Coastal Aquifer
Advances in Water Resources, 2003Co-Authors: Jiu Jimmy JiaoAbstract:For an isotropic, homogeneous Coastal Aquifer, previous studies [Aust J Phys 26 (1973) 513; Water Resour Res 17 (4) (1981) 1222] have found that the mean watertable is influenced by the sea tide and will stand considerably above the mean sea level even in the absence of net inland recharge. This paper investigates the influence of the tide on the mean watertable for the case that the unconfined Coastal Aquifer is inhomogeneous and anisotropic. A two-dimensional free surface model is considered under the following assumptions: (a) the principle directions of the hydraulic conductivities are horizontal and vertical; (b) the horizontal hydraulic conductivity KxðyÞ depends on the depth of the Aquifer only and the vertical hydraulic conductivity Kyðx; yÞ is arbitrary; (c) the water–land boundary is vertical and there is no seepage face; (d) the specific storage is constant wherever the free surfaces are located; and (e) there is no net inland recharge. An integral equation satisfied by the asymptotic watertable as the landward distance approaches infinity is derived for multi-sinusoidal-component sea tide. This equation suggests that the asymptotic watertable is independent of Kyðx; yÞ and higher than mean sea level for arbitrary KxðyÞ. The asymptotic watertable is solved explicitly from the integral equation for three common patterns of KxðyÞ: constant, piecewise constant and linearly decreasing with the depth. Compared with the first two patterns, the third pattern has significant enhancing effect on the asymptotic watertable. Several previously published analytical solutions and the experiment data are in line with the analytical solution of this paper. 2002 Elsevier Science Ltd. All rights reserved.
Bithin Datta - One of the best experts on this subject based on the ideXlab platform.
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modelling saltwater intrusion processes and development of a multi objective strategy for management of Coastal Aquifers utilizing planned artificial freshwater recharge
Modeling Earth Systems and Environment, 2018Co-Authors: Alvin Lal, Bithin DattaAbstract:The need for freshwater is emerging as the utmost critical resource issue facing humanity. In several arid and semi-arid parts of the world, groundwater resources are being used as an alternative source of freshwater. Excessive and/or unplanned groundwater withdrawals have a negative impact on the Aquifer. Groundwater withdrawn from Coastal Aquifers are susceptible to contamination by saltwater intrusion. This study investigates the efficiency and viability of using artificial freshwater recharge (AFR) to increase fresh groundwater pumping from production wells for beneficial use. A three dimensional (3D), transient, density dependent, finite element based flow and transport model of an illustrative Coastal Aquifer is implemented using FEMWATER code. First, the effect of AFR on inland encroachment of saline water is quantified for existing scenarios. Specifically, groundwater head and salinity concentration differences at monitoring locations before and after artificial recharge is presented. Second, a multi-objective management model incorporating groundwater pumping and AFR is implemented to control groundwater salinization in an illustrative Coastal Aquifer system. To avoid computational burden and ensure computational feasibility, the numerical flow and transport simulation model is substituted by the new support vector regression (SVR) predictive models as approximate simulators in the simulation–optimization framework for developing optimal management strategies. The performance evaluation results indicated that the SVR models were adequately trained and were capable of approximating saltwater intrusion processes in the Aquifer. Multi-objective genetic algorithm (MOGA) is used to solve the multi-objective optimization problem. The Pareto-optimal front obtained as solution from the SVR–MOGA optimization model presented a set of optimal solutions needed for the sustainable management of the Coastal Aquifer. The pumping strategies obtained as Pareto optimal solutions with and without freshwater recharge wells showed that saltwater intrusion is sensitive to the AFR. Also, the hydraulic head lenses created by AFR can be used as one practical option to control saltwater intrusion in Coastal Aquifers. The developed 3D saltwater intrusion model, predictive capability of the developed SVR models and the feasibility of using the proposed linked multi-objective SVR–MOGA optimization model makes the proposed methodology potentially attractive in solving large scale regional saltwater intrusion management problems.
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Genetic Programming and Gaussian Process Regression Models for Groundwater Salinity Prediction: Machine Learning for Sustainable Water Resources Management
2018 IEEE Conference on Technologies for Sustainability (SusTech), 2018Co-Authors: Alvin Lal, Bithin DattaAbstract:Degradation of the quality of groundwater due to saltwater intrusion is considered as a major constraint limiting the use of water resources in Coastal areas. Groundwater salinity prediction models can be used as surrogate models in a linked simulation-optimization methodology needed for developing and solving computationally feasible sustainable Coastal Aquifer management models. The present study utilizes two machine learning algorithms, namely, Genetic Programming (GP) and Gaussian Process Regression (GPR) models to approximate density dependent saltwater intrusion processes and predict salinity concentrations in an illustrative Coastal Aquifer system. Specifically, the GP and GPR models are trained and validated using pumping and resulting salinity concentration datasets obtained by solving a numerical 3D transient density dependent finite element based Coastal Aquifer flow and transport model. Prediction capabilities of the developed GP and GPR models are quantified using standard statistical parameters such as root mean squared error, coefficient of correlation and the Nash-Sutcliffe coefficient calculations. The results suggest that once trained and tested, both the GP and GPR models can be used to predict salinity concentration at selected monitoring locations in the modelled Aquifer under variable groundwater pumping conditions. The performance evaluation results for the illustrative Aquifer study area also show that the predictive capability of the GPR models are superior to those of the GP models. Therefore, GPR prediction models can be used as a substitute for the complex numerical simulation model in a linked simulation-optimization approach requiring numerous solutions of the simulation model to develop computationally feasible regional scale sustainable Coastal Aquifer management strategies.
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coupled simulation optimization model for Coastal Aquifer management using genetic programming based ensemble surrogate models and multiple realization optimization
Water Resources Research, 2011Co-Authors: J Sreekanth, Bithin DattaAbstract:Approximation surrogates are used to substitute the numerical simulation model within optimization algorithms in order to reduce the computational burden on the coupled simulation-optimization methodology. Practical utility of the surrogate-based simulation-optimization have been limited mainly due to the uncertainty in surrogate model simulations. We develop a surrogate-based coupled simulation-optimization methodology for deriving optimal extraction strategies for Coastal Aquifer management considering the predictive uncertainty of the surrogate model. Optimization models considering two conflicting objectives are solved using a multiobjective genetic algorithm. Objectives of maximizing the pumping from production wells and minimizing the barrier well pumping for hydraulic control of saltwater intrusion are considered. Density-dependent flow and transport simulation model FEMWATER is used to generate input-output patterns of groundwater extraction rates and resulting salinity levels. The nonparametric bootstrap method is used to generate different realizations of this data set. These realizations are used to train different surrogate models using genetic programming for predicting the salinity intrusion in Coastal Aquifers. The predictive uncertainty of these surrogate models is quantified and ensemble of surrogate models is used in the multiple-realization optimization model to derive the optimal extraction strategies. The multiple realizations refer to the salinity predictions using different surrogate models in the ensemble. Optimal solutions are obtained for different reliability levels of the surrogate models. The solutions are compared against the solutions obtained using a chance-constrained optimization formulation and single-surrogate-based model. The ensemble-based approach is found to provide reliable solutions for Coastal Aquifer management while retaining the advantage of surrogate models in reducing computational burden.
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artificial neural networks approximation of density dependent saltwater intrusion process in Coastal Aquifers
Journal of Hydrologic Engineering, 2007Co-Authors: Bithin Datta, Rajib Kumar Bhattacharjya, Mysore G SatishAbstract:The flow and transport processes in a Coastal Aquifer are highly nonlinear, where both the flow and transport processes become density dependent. Therefore, numerical simulation of the saltwater intrusion process in such an Aquifer is complex and time consuming. An approximate simulation of those complex flow and transport processes may be very useful, if sufficiently accurate, especially where repetitive simulations of these processes are necessary. A simulation methodology using a trained artificial neural network model (ANN) is developed to approximate the three-dimensional density dependent flow and transport processes in a Coastal Aquifer. The data required for initially training the ANN model is generated by using a numerical simulation model (FEMWATER). The simulated data consisting of corresponding sets of input and output patterns are used to train a multilayer perceptron using the back-propagation algorithm. The trained ANN predicts the concentration at specified observation locations at differe...
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development of multiobjective management models for Coastal Aquifers
Journal of Water Resources Planning and Management, 1999Co-Authors: Amlan Das, Bithin DattaAbstract:Optimal management of the Coastal Aquifers focuses mainly on the evolution of good operational strategies to contain the Aquifer salinity within a mandated limit, while simultaneously meeting the demand for water supply and/or recharge. The development of any such feasible operational policy requires evolution of management models that incorporate the simulation of the seawater intrusion process. In this study management models are developed and solved that are based on the advective-dispersive density-dependent miscible flow and transport processes in the Aquifer. Various conflicting objectives of Aquifer management are considered. The density-dependent miscible flow and salt transport process in Coastal Aquifers is simulated within the management model. Two optimization models incorporating multiple objectives of Coastal Aquifer management are formulated. The miscible seawater intrusion process is simulated within the management model. These models are solved for a hypothetical three-dimensional Aquifer system for transient flow and transport conditions. The obtained solution results demonstrate potential feasibility of using the embedding technique for the development of multiple-objective Coastal Aquifer management models, considering the density-dependent miscible three-dimensional flow and transport processes of seawater intrusion. In general, a planned, spatially and temporally varying pumping strategy, obtained as solutions of an embedded optimization model, is shown to be a viable management method for beneficial exploitation and salinity control of a Coastal Aquifer. The potential feasibility of these management models for evolving a transient spatially dependent pumping strategy to facilitate beneficial exploitation of the Aquifer and to control or remediate contamination due to seawater intrusion is also demonstrated.
John A Cherry - One of the best experts on this subject based on the ideXlab platform.
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occurrence and geochemical behavior of arsenic in a Coastal Aquifer aquitard system of the pearl river delta china
Science of The Total Environment, 2012Co-Authors: Ya Wang, Jiu Jimmy Jiao, John A CherryAbstract:Abstract Elevated concentrations of arsenic, up to 161 μg/L, have been identified in groundwater samples from the confined basal Aquifer underlying the aquitard of the Pearl River Delta (PRD). Both aquatic arsenic in pore water and solid arsenic in the sediments in the basal Aquifer and aquitard were identified. Arsenic speciation of groundwater in the basal Aquifer was elucidated on a pH-Eh diagram. In the PRD, arsenic is enriched in groundwater having both low and high salinity, and arsenic enriched groundwater is devoid of dissolved oxygen, has negative Eh values, is slightly alkaline, and has abnormally high concentrations of ammonium and dissolved organic carbon, but low concentrations of nitrate and nitrite. Results of geochemical and hydrochemical analyses and sequential extraction analysis suggest that reductive dissolution of iron oxyhydroxide could be one of the important processes that mobilized solid arsenic. We speculate that mineralization of sedimentary organic matter could also contribute to aquatic arsenic. Scanning electron microscope analysis confirms that abundant authigenic pyrite is present in the sediments. Sulphate derived from paleo-seawater served as the important sulfur source for authigenic pyrite formation. Co-precipitation of arsenic with authigenic pyrite significantly controlled concentrations of aquatic arsenic in the Coastal Aquifer–aquitard system.
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abnormally high ammonium of natural origin in a Coastal Aquifer aquitard system in the pearl river delta china
Environmental Science & Technology, 2010Co-Authors: Jiu Jimmy Jiao, Ya Wang, John A Cherry, Xusheng Wang, Haiyan DuAbstract:High-nitrogen loadings of rivers and Aquifers systems are a major concern because of potential effects on human health and water quality impacts such as eutrophication of lakes and Coastal zones. This nitrogen enrichment is commonly attributed to anthropogenic sources such as sewage and agricultural and industrial wastes. The aims of this study were to delineate spatial distribution of groundwater ammonium in the Coastal Aquifer system in Pearl River Delta (PRD), China and to identify the origin of the abnormally high ammonium. A total of 40 boreholes were drilled to collect core samples of the aquitard and groundwater samples in the basal Aquifer. The core samples were used for extraction of pore water for centrifugation and bulk chemical analyses in laboratory. Unlike previous studies which focused mainly on the Aquifer, this study treated the Aquifer-aquitard system as a hydrogeochemical continuum. The results show that the Aquifer-aquitard system contains an exceptionally large total ammonium mass. Am...
Jian Luo - One of the best experts on this subject based on the ideXlab platform.
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assessment of the impact of sea level rise on steady state seawater intrusion in a layered Coastal Aquifer
Journal of Hydrology, 2018Co-Authors: Wenlong Shi, Jian LuoAbstract:Abstract Previous studies on the impact of sea-level rise (SLR) on seawater intrusion (SWI) are mostly based on the assumption of a homogeneous Coastal Aquifer. In this study, we extend those studies by investigating SLR-induced SWI in a layered Coastal Aquifer using the analytical method developed by Strack and Ausk (2015). We provide analytical solutions for steady-state SWI in confined and unconfined Coastal Aquifers, where both constant-head and constant-flux inland boundary conditions are considered. The analysis based on a three-layer Aquifer indicates that in general Aquifer stratification affects either or both the initial location and response distance of the interface toe. Specifically, for flux-controlled unconfined Coastal systems, the toe response distance driven by SLR is a linear function of the hydraulic conductivity of the top layer and independent of hydraulic conductivities of lower layers. Using an equivalent homogeneous hydraulic conductivity (derived based on the initial interface toe location before SLR) would result in overestimation or underestimation of the toe response distance, depending on the hydraulic conductivities and thicknesses of the layers. For flux-controlled confined layered Coastal systems, by contrast, SLR can not cause variation of the steady-state interface toe location, which is consistent with previous findings for homogeneous Coastal Aquifers. The interface toe location in head-controlled layered Coastal systems is only a function of relative hydraulic conductivities between the layers. Moreover, the effect of the layer thickness on the interface toe location and response distance in the head-controlled system exhibits a more complicated pattern than in the flux-controlled Coastal system, as changing the layer thickness changes both the overall Aquifer transmissivity and inland freshwater flux. The results obtained enhance the understanding of the impact of SLR on SWI, which could provide a first-order assessment tool for relevant practitioners.
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seawater intrusion in response to sea level rise in a Coastal Aquifer with a general head inland boundary
Journal of Hydrology, 2015Co-Authors: Pei Xin, Jian LuoAbstract:Seawater intrusion in response to sea-level rise has been studied extensively in recent years by assuming largely a constant-head or constant-flux inland boundary condition. However, these two types of boundary conditions are not sufficient when the inland edge of the model domain is neither natural groundwater nor known hydraulic boundaries. Under these circumstances, a general-head inland boundary condition capable of characterizing the hydraulic response of model boundaries is needed. Previous studies adopting the general-head inland boundary condition to assess Coastal Aquifer vulnerability to sea-level rise are limited and all based on numerical modeling. In this study, we derive analytical solutions of the interface toe location in both confined and unconfined Coastal systems with a general-head inland boundary condition. Comparison among the performances of the three different types of inland boundary conditions in evaluating the sea-level rise impact on Aquifer salinization is carried out by assuming the same initial system condition. It is found that the displacement of the interface toe predicted using a general-head inland boundary is between those of using a constant-head (upper bound) and constant-flux (lower bound) inland boundary, depending on the values of two general-head boundary parameters (i.e., hydraulic conductance and reference head). More importantly, analytical solutions developed could serve as a tool for calibrating the two boundary parameters defined in the general-head boundary condition for site-specific assessments.
Mohammad N Almasri - One of the best experts on this subject based on the ideXlab platform.
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seawater intrusion into the Coastal Aquifer in the gaza strip a computer modelling study
The Lancet, 2013Co-Authors: Reem Sarsak, Mohammad N AlmasriAbstract:Background Climate change is transforming life on earth, as seasons shift, rainfall decreases, and temperatures increase. Rising sea levels and overpumping are causing seawater intrusion into the Coastal Aquifer. This problem acutely affects people living in the occupied Palestinian territory (oPt), and is worst in the Gaza Strip, where the Coastal Aquifer is the region's only freshwater resource and is therefore insufficient for the needs of the population. This Aquifer has already been degraded by over extraction, infiltration of sewage, and seawater intrusion, contributing to high rates of waterborne diseases in the Gaza Strip. The Israeli authorities tightly control the quantity of water from the Aquifer that Palestinians in the Gaza Strip can extract. Palestinians in the oPt receive less than the WHO recommendation of 100 L/day per person. An Israeli citizen uses 250 L/day, whereas a Palestinian citizen uses 66 L/day. Seawater intrusion into the Gaza Strip's northern Coastal Aquifer was predicted with computer modelling to show the potential effects of climate change and human overuse on the region's only freshwater source. Methods A simulation of seawater intrusion into the Coastal Aquifer into the northern part of the Gaza Strip was done with SEAWAT, a computer program developed by the US Geological Survey for simulating the three-dimensional variable density groundwater flow in porous media with multispecies solute transport. This program was used to analyse the groundwater flow and transport, water replenishment rates, and extraction quantities with projected rises in the sea level. The simulation enables prediction of inland seawater intrusion rates and chloride concentrations in the abstraction wells for the next 35 years. Findings Various scenarios were simulated to study the effects of climate change on seawater intrusion due to rises in the sea level, and variations in replenishment and pumping rates at the study area. The current rate of seawater intrusion into the Coastal Aquifer is 65 m/year. Computer-modelled scenarios with SEAWAT of future low replenishment rates predict worst-case-scenario intrusion rates of about 80 m/year by the end of the study in 2035. The best computer-modelled prediction of 35 m/year intrusion was obtained with solutions proposed in the management scenario by the local water authorities to reduce the water deficit and remove water salinity in the Aquifer. Interpretation Seawater intrusion can jeopardise the groundwater resources for Coastal communities such as those living in the Gaza Strip, putting them at risk of waterborne diseases. The best management of seawater intrusion would be to apply desalination technology and improve the efficiency of existing waste-water treatment plants for water recycling and subsequent reuse. These methods will become increasingly important as climate change negatively affects the Aquifer and population demand increases. Funding None.
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assessment of intrinsic vulnerability to contamination for gaza Coastal Aquifer palestine
Journal of Environmental Management, 2008Co-Authors: Mohammad N AlmasriAbstract:Gaza Coastal Aquifer (GCA) is the major source of fresh water for the 1.5 million residents of Gaza Strip, Palestine. The Aquifer is under deteriorating quality conditions mainly due to the excessive application of fertilizers. The intrinsic vulnerability of GCA to contamination was assessed using the well-known DRASTIC method. Detailed analysis of the intrinsic vulnerability map of GCA was carried out and did consider different relationships between the vulnerability indices and the on-ground nitrogen loadings and land use classes. In addition, correlation between vulnerability values and the nitrate concentrations in GCA was studied. Based on the vulnerability analysis, it was found that 10% and 13% of Gaza Strip area is under low and high vulnerability of groundwater contamination, respectively, while more than 77% of the area of Gaza Strip can be designated as an area of moderate vulnerability of groundwater contamination. It was found that the density of groundwater sampling wells for nitrate concentration is high for the moderate and high vulnerability zones. The highest first quartile, median, mean, and third quartile of nitrate concentrations are reported in the high vulnerability zones. Results of sensitivity analysis show a high sensitivity of the high vulnerability index to the depth to water table.