scholarly journals Simulating seawater intrusion in a complex coastal karst aquifer using an improved variable-density flow and solute transport–conduit flow process model

2019 ◽  
Vol 27 (4) ◽  
pp. 1277-1289 ◽  
Author(s):  
Zhongyuan Xu ◽  
Bill X. Hu ◽  
Zexuan Xu ◽  
Xiujie Wu
Keyword(s):  
Solute Transport ◽  
Seawater Intrusion ◽  
Process Model ◽  
Karst Aquifer ◽  
Variable Density ◽  
Flow Process ◽  
Conduit Flow ◽  
Variable Density Flow ◽  
Density Flow ◽  
Coastal Karst

Prediction of seawater intrusion to coastal aquifers based on non-dimensional diagrams

2020 ◽  
Author(s):  
Charalampos Doulgeris ◽  
Evangelos Tziritis ◽  
Vassilios Pisinaras ◽  
Andreas Panagopoulos ◽  
Christoph Külls
Keyword(s):  
Hydraulic Conductivity ◽  
Case Studies ◽  
Seawater Intrusion ◽  
Coastal Aquifers ◽  
Variable Density ◽  
Real Case ◽  
Constant Thickness ◽  
Variable Density Flow ◽  
Density Flow ◽  
Dimensional Parameters

<p>A numerical analysis of the groundwater flow and contaminant transport equations, based on the variable density flow approach, is used for the construction of non-dimensional diagrams to predict seawater intrusion to confined coastal aquifers. The classical Henry’s seawater intrusion problem is analysed by using a finite element model. The model’s equations are written in non-dimensional form and the numerical solutions depend solely on three non-dimensional parameters:</p><p>α=q΄/Κ<sup>0</sup>, β=(bΚ<sup>0</sup>)/(nD<sub>m</sub>), α΄=bS<sup>0</sup>/n                                                                                           (eq. 1 a,b,c)</p><p>where q’ is the freshwater recharge rate (m/d), K<sup>0</sup> the freshwater hydraulic conductivity (m/d), b the aquifer thickness, n the porosity (-), D<sub>m</sub> the molecular diffusion coefficient (m<sup>2</sup>/d) and S<sup>0</sup> the freshwater specific storage (1/m). Please note that hydraulic conductivity appears in two of the non-dimensional parameters, α and β.</p><p>The non-dimensional formulation has led to the construction of non-dimensional diagrams of salt distribution for a homogeneous and isotropic confined aquifer with horizontal base and constant thickness that is uniformly recharged with freshwater. These diagrams illustrate the influence of the key hydrological and hydraulic parameters, and furthermore, can be used to predict the evolution of seawater intrusion in real case studies.</p><p>The numerical simulations were carried out up to the equilibrium state for different values of the non-dimensional parameters of equation 1. By decreasing the value of parameter α=q΄/Κ<sup>0</sup>, seawater intrusion is advancing inland and the width of dispersion zone is increasing. By increasing the parameter β=(bΚ<sup>0</sup>)/(nD<sub>m</sub>), the seawater-freshwater transition zone is narrowing and shifted to the seaside at the upper part of the aquifer, while the intrusion of saltwater is advancing inland at the lower part of the aquifer. The distribution of the salts in the aquifer was found essentially identical for different values of the parameter α΄=bS<sup>0</sup>/n; hence this parameter exhibits very low sensitivity, which makes it of low importance, especially for real case studies.</p><p>Overall, the non-dimensional diagrams – constructed by following the variable density flow approach and under specific assumptions – can be used for a quick and direct prediction of seawater intrusion in real aquifers. These diagrams would be useful for an initial prediction at the case studies of the PRIMA MEDSAL project (www.medsal.net), namely the coastal aquifers in Rhodope (Greece), Samos island (Greece), Bouficha (Tunisia), Bouteldja (Algeria), Tarsus (Turkey) and under specific assumptions to the karstic aquifer in Salento (Italy).</p>

scholarly journals Prolonged river water pollution due to variable‐density flow and solute transport in the riverbed

2015 ◽  
Vol 51 (4) ◽  
pp. 1898-1915 ◽  
Author(s):  
Guangqiu Jin ◽  
Hongwu Tang ◽  
Ling Li ◽  
D. A. Barry
Keyword(s):  
Water Pollution ◽  
Solute Transport ◽  
River Water ◽  
Variable Density ◽  
Variable Density Flow ◽  
Density Flow ◽  
River Water Pollution

scholarly journals Efficient Stochastic Simulation of Seawater Intrusion, With Mixing, in Confined Coastal Aquifers

2021 ◽  
Vol 3 ◽  
Author(s):  
Evangelos Rozos ◽  
Katerina Mazi ◽  
Antonis D. Koussis
Keyword(s):  
Seawater Intrusion ◽  
Coastal Aquifers ◽  
High Efficiency ◽  
Flow Region ◽  
Variable Density ◽  
Tracer Transport ◽  
Advection Dispersion ◽  
Variable Density Flow ◽  
Density Flow ◽  
Principal Directions

We present a high-efficiency method for simulating seawater intrusion (SWI), with mixing, in confined coastal aquifers based on uncoupled equations in the through-flow region of the aquifer. The flow field is calculated analytically and the tracer transport numerically, via spatial splitting along the principal directions (PD) of transport. Advection-dispersion processes along streamlines are simulated with the very efficient matched artificial dispersivity (MAD) method of Syriopoulou and Koussis and the system of discretized transverse-dispersion equations is solved with the Thomas algorithm. These concepts are embedded in the 2D-MADPD-SWI model, yielding comparable solutions to those of the uncoupled SWI equations with the state-of-the-art FEFLOW code, but faster, while 2D-MADPD-SWI achieves an at least hundredfold faster solution than a variable-density flow model. We demonstrate the utility of the 2D-MADPD-SWI model in stochastic Monte Carlo simulations by assessing the uncertainty on the advance of the 1,500 ppm TDS line (limit of tolerable salinity for irrigation) due to randomly variable hydraulic conductivity and freshwater flow rate.

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