Numerical modelling in the coastal aquifer between Burlamacca Canal and Bufalina Ditch, southern Versilia (Tuscany, Italy)

Groundwater numerical models are necessary instruments for management of water resources and for their protection, both in terms of quantity and quality. In this paper we present a study on an area located along the southern coastline of Versilia (Viareggio,LU) affected by marine intrusion. The main purpose of this work was to create a mathematical flow model based on a conceptual hydrogeological model defined by a multidisciplinary approach. For the realization of the numerical model the ModFlow code and the graphic interface Visual ModFlow was used. The procedure for defining the mathematical model involves a series of steps such as horizontal and vertical discretization of the space, the definition of the initial and boundary conditions, the assignment of the hydraulic properties of the cells and, finally, the definitions of external perturbations to the system (recharge, evapotranspiration, drainage and pumping wells). Implementation, development and calibration of the numerical flow model was performed both in steady and transient state. Both models were calibrated using the manual “trial and error adjustment” method using heads measurements. Moreover the model results gathered in transient state simulation were compared with the data continuously recorded by a piezometer of the monitoring network of the Regional Hydrological Service. There is a good correlation between the measured data and those calculated by the model which then turns out to be sufficiently representative and provides a solid basis for the development of a transport model that could be useful to control and manage the phenomenon of the salt water intrusion.

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Development of a THMC code for bentonites in COMSOL Multiphysics

E3S Web of Conferences ◽

10.1051/e3sconf/202019504002 ◽

2020 ◽

Vol 195 ◽

pp. 04002

Author(s):

Ángel Yustres ◽

Rubén López-Vizcaíno ◽

Virginia Cabrera ◽

Vicente Navarro

Keyword(s):

Reactive Transport ◽

Transport Model ◽

Numerical Models ◽

Swelling Pressure ◽

Double Porosity ◽

Comsol Multiphysics ◽

Chemical Potentials ◽

Definition Of ◽

High Degree ◽

First Time

The proposed use of active clays for the isolation of radioactive wastes in deep geological repositories has been followed by a deeper understanding of this type of soils. This increased knowledge has led to the need for both conceptual and numerical models capable of capturing the main trends in behaviour and the different couplings between different physical-chemical phenomena. In addition, the model must have a high degree of flexibility that enables it to accommodate future developments or new relevant phenomena. This work presents a numerical THMC code developed entirely on the COMSOL Multiphysics numerical implementation platform, which provides the required adaptability. This model includes, for the first time in this environment, a reactive transport model in unsaturated porous media for a relevant geochemical system (consistent with the MX-80 bentonite) together with a THM model based on a double porosity approach. The chemical potentials of water and solutes are used for the definition of thermodynamic equilibria between both porosity levels. Trends in the behaviour of a bentonite sample under oedometric conditions are satisfactorily simulated in response to a process of saturation and change in salinity conditions. Variations in swelling pressure, porosity distribution or dissolution/precipitation of the main accessory minerals are analysed and explained by means of the proposed conceptual model.

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Study of groundwater using visual MODFLOW in the Manas River Basin, China

Water Policy ◽

10.2166/wp.2016.180 ◽

2016 ◽

Vol 18 (5) ◽

pp. 1139-1154 ◽

Cited By ~ 2

Author(s):

Xiaolong Li ◽

Xinlin He ◽

Guang Yang ◽

Li Zhao ◽

Si Chen ◽

...

Keyword(s):

Groundwater Flow ◽

Flow Model ◽

Three Dimensional ◽

Transient State ◽

Normal Operation ◽

Groundwater Flow Model ◽

Visual Modflow ◽

Balance Study ◽

Groundwater Levels ◽

Groundwater Drawdown

For effective groundwater management of a basin, it is essential that a careful water balance study be carried out. A three-dimensional transient-state finite difference groundwater flow model is used to quantify the groundwater fluxes and analyze the dynamic changes of groundwater level. After monitoring groundwater levels for 43 typical observation wells through a simulation study of the groundwater flow model with a depth of 300 m, results reveal that the study area has a lateral recharge of about 3.57 × 109 m3, which makes up 79.08% of the total recharge; total evaporation is about 1.81 × 108 m3, which makes up 3.77% of the total discharge. The balance of groundwater is negative, with a recharge and discharge difference of −2.81 × 108 m3. The correlation coefficient between the observed head and the calculated head for the simulation period is greater than 0.81, indicating the simulation results are satisfactory. The maximum groundwater drawdown is 26.59 m and the rate of the groundwater drawdown is 0.15 m/d during normal operation of the pumping well.

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Chemical heterogeneities in the mantle: progress towards a general quantitative description

Solid Earth ◽

10.5194/se-10-1409-2019 ◽

2019 ◽

Vol 10 (4) ◽

pp. 1409-1428 ◽

Cited By ~ 1

Author(s):

Massimiliano Tirone

Keyword(s):

Mass Transfer ◽

Chemical Equilibrium ◽

Transport Model ◽

Numerical Models ◽

Quantitative Description ◽

Transient State ◽

Real Data ◽

Initial State ◽

Initial Size ◽

Chemical Equilibration

Abstract. Chemical equilibration between two different assemblages (peridotite type and gabbro–eclogite type) has been determined using basic thermodynamic principles and certain constraints and assumptions regarding mass and reaction exchange. When the whole system (defined by the sum of the two subsystems) is in chemical equilibrium the two assemblages will not be homogenized, but they will preserve distinctive chemical and mineralogical differences. Furthermore, the mass transfer between the two subsystems defines two petrological assemblages that separately are also in local thermodynamic equilibrium. In addition, when two assemblages previously equilibrated as a whole in a certain initial mass ratio are held together assuming a different proportion, no mass transfer occurs and the two subsystems remain unmodified. By modeling the chemical equilibration results of several systems of variable initial size and different initial composition it is possible to provide a quantitative framework to determine the chemical and petrological evolution of two assemblages from an initial state, in which the two are separately in chemical equilibrium, to a state of equilibration of the whole system. Assuming that the local Gibbs energy variation follows a simple transport model with an energy source at the interface, a complete petrological description of the two systems can be determined over time and space. Since there are no data to constrain the kinetics of the processes involved, the temporal and spatial scale is arbitrary. The evolution model should be considered only a semiempirical tool that shows how the initial assemblages evolve while preserving distinct chemical and petrological features. Nevertheless, despite the necessary simplification, a 1-D model illustrates how chemical equilibration is controlled by the size of the two subsystems. By increasing the initial size of the first assemblage (peridotite like), the compositional differences between the initial and the final equilibrated stage become smaller, while on the eclogite-type side the differences tend to be larger. A simplified 2-D dynamic model in which one of the two subsystems is allowed to move with a prescribed velocity shows that after an initial transient state, the moving subsystem tends to preserve its original composition defined at the influx side. The composition of the static subsystem instead progressively diverges from the composition defining the starting assemblage. The observation appears to be consistent for various initial proportions of the two assemblages, which somehow simplify the development of potential tools for predicting the chemical equilibration process from real data and geodynamic applications. Four animation files and the data files of three 1-D and two 2-D numerical models are available following the instructions in the Supplement.

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Assessing the Fresh–Saline Groundwater Distribution in the Nile Delta Aquifer Using a 3D Variable-Density Groundwater Flow Model

Water ◽

10.3390/w11091946 ◽

2019 ◽

Vol 11 (9) ◽

pp. 1946 ◽

Cited By ~ 2

Author(s):

Marmar Mabrouk ◽

Andreja Jonoski ◽

Gualbert H. P. Oude Essink ◽

Stefan Uhlenbrook

Keyword(s):

Groundwater Flow ◽

Flow Model ◽

Dynamic Equilibrium ◽

Nile Delta ◽

Salt Water ◽

Three Dimensional ◽

Variable Density ◽

Salt Water Intrusion ◽

Groundwater Flow Model ◽

Saline Groundwater

The Nile Delta Aquifer (NDA) is threatened by salt water intrusion (SWI). This article demonstrates an approach for identifying critical salinity concentration zones using a three-dimensional (3D) variable-density groundwater flow model in the NDA. An innovative procedure is presented for the delineation of salinity concentration in 2010 by testing different simulation periods. The results confirm the presence of saline groundwater caused by SWI in the north of the NDA. In addition, certain regions in the east and southwest of the NDA show increased salinity concentration levels, possibly due to excessive groundwater extraction and dissolution of marine fractured limestone and shale that form the bedrock underlying the aquifer. The research shows that the NDA is still not in a state of dynamic equilibrium. The modeling instrument can be used for simulating future scenarios of SWI to provide a sustainable adaptation plan for groundwater resource.

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STREAM 1D: Numerical model for predicting the salt-water intrusion in highly stratified estuaries

Common Foundations 2018 - uniSTem: 6th Congress of Young Researchers in the Field of Civil Engineering and Related Sciences ◽

10.31534/co/zt.2018.17 ◽

2018 ◽

Author(s):

Nino Krvavica ◽

Nevenka Ožanić

Keyword(s):

Numerical Model ◽

Salt Water ◽

Salt Water Intrusion ◽

Water Intrusion ◽

Stratified Estuaries

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Can one use Earth’s magnetic axial dipole field intensity to predict reversals?

Geophysical Journal International ◽

10.1093/gji/ggaa542 ◽

2020 ◽

Author(s):

K Gwirtz ◽

M Morzfeld ◽

A Fournier ◽

G Hulot

Keyword(s):

Magnetic Field ◽

Numerical Models ◽

Dipole Field ◽

Axial Dipole ◽

Intensity Threshold ◽

Magnetic Dipole Field ◽

Model Hierarchy ◽

Definition Of ◽

Virtual Axial Dipole Moment ◽

Prediction Strategy

Summary We study predictions of reversals of Earth’s axial magnetic dipole field that are based solely on the dipole’s intensity. The prediction strategy is, roughly, that once the dipole intensity drops below a threshold, then the field will continue to decrease and a reversal (or a major excursion) will occur. We first present a rigorous definition of an intensity threshold-based prediction strategy and then describe a mathematical and numerical framework to investigate its validity and robustness in view of the data being limited. We apply threshold-based predictions to a hierarchy of numerical models, ranging from simple scalar models to 3D geodynamos. We find that the skill of threshold-based predictions varies across the model hierarchy. The differences in skill can be explained by differences in how reversals occur: if the field decreases towards a reversal slowly (in a sense made precise in this paper), the skill is high, and if the field decreases quickly, the skill is low. Such a property could be used as an additional criterion to identify which models qualify as Earth-like. Applying threshold-based predictions to Virtual Axial Dipole Moment (VADM) paleomagnetic reconstructions (PADM2M and Sint-2000) covering the last two million years, reveals a moderate skill of threshold-based predictions for Earth’s dynamo. Besides all of their limitations, threshold-based predictions suggests that no reversal is to be expected within the next 10 kyr. Most importantly, however, we show that considering an intensity threshold for identifying upcoming reversals is intrinsically limited by the dynamic behavior of Earth’s magnetic field.

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Urban Air Quality Modeling Using Low-Cost Sensor Network and Data Assimilation in the Aburrá Valley, Colombia

Atmosphere ◽

10.3390/atmos12010091 ◽

2021 ◽

Vol 12 (1) ◽

pp. 91

Author(s):

Santiago Lopez-Restrepo ◽

Andres Yarce ◽

Nicolás Pinel ◽

O.L. Quintero ◽

Arjo Segers ◽

...

Keyword(s):

Air Quality ◽

Data Assimilation ◽

Transport Model ◽

Cost Model ◽

Low Cost ◽

Model Performance ◽

Monitoring Network ◽

Correlation Factor ◽

Chemical Transport Model ◽

High Quality

The use of low air quality networks has been increasing in recent years to study urban pollution dynamics. Here we show the evaluation of the operational Aburrá Valley’s low-cost network against the official monitoring network. The results show that the PM2.5 low-cost measurements are very close to those observed by the official network. Additionally, the low-cost allows a higher spatial representation of the concentrations across the valley. We integrate low-cost observations with the chemical transport model Long Term Ozone Simulation-European Operational Smog (LOTOS-EUROS) using data assimilation. Two different configurations of the low-cost network were assimilated: using the whole low-cost network (255 sensors), and a high-quality selection using just the sensors with a correlation factor greater than 0.8 with respect to the official network (115 sensors). The official stations were also assimilated to compare the more dense low-cost network’s impact on the model performance. Both simulations assimilating the low-cost model outperform the model without assimilation and assimilating the official network. The capability to issue warnings for pollution events is also improved by assimilating the low-cost network with respect to the other simulations. Finally, the simulation using the high-quality configuration has lower error values than using the complete low-cost network, showing that it is essential to consider the quality and location and not just the total number of sensors. Our results suggest that with the current advance in low-cost sensors, it is possible to improve model performance with low-cost network data assimilation.

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