A numerical analysis of dimensionality and heterogeneity effects on advective dispersive seawater intrusion processes

Two-dimensional (2D) and 3D numerical simulations of the dispersive Henry problem show that heterogeneity affects seawater intrusion differently in 2D and 3D. When the variance of a multi-Gaussian isotropic hydraulic conductivity field increases, the penetration of the saltwater wedge decreases in 2D while it increases in 3D. This is due to the combined influence of advective and dispersive processes which are affected differently by heterogeneity and problem dimensionality. First, the equivalent hydraulic conductivity controls the mean head gradient and therefore the position of the wedge. For an isotropic medium, increasing the variance increases the equivalent conductivity in 3D but not in 2D. Second, the macrodispersion controls the rotation of the saltwater wedge by affecting the magnitude of the density contrasts along the saltwater wedge. An increased dispersion due to heterogeneity leads to a decreasing density contrast and therefore a smaller penetration of the wedge. The relative magnitude of these two opposite effects depends on the degree of heterogeneity, anisotropy of the medium, and dimension. Investigating these effects in 3D is very heavy numerically; as an alternative, one can simulate 2D heterogeneous media that approximate the behaviour of the 3D ones, provided that their statistical distribution is rescale

Status of the Korba groundwater resources (Tunisia): observations and three-dimensional modelling of seawater intrusion

The Korba aquifer is located in the east of the Cape Bon peninsula in Tunisia. A large groundwater depression has been created in the central part of the aquifer since the 1980s, due to intense groundwater pumping for irrigation. The data collected show that the situation continues to deteriorate. Consequently, seawater is continuing to invade a large part of the aquifer. To better understand the situation and try to forecast its evolution, a three-dimensional (3D) transient density-dependent groundwater model has been developed. The model building process was difficult because of data required on groundwater discharge from thousands of unmonitored private wells. To circumvent that difficulty, indirect exhaustive information including remote sensing data and the physical parameters of the aquifer have been used in a multi-linear regression framework. The resulting 3D model shows that the aquifer is over-exploited. It also shows that after 50 years of exploitation, the time needed to turn back to the natural situation would be about 150 years if the authorities would ban all exploitation now. Such an asymmetry in the time scales required to contaminate or remediate an aquifer is an important characteristic of coastal aquifers that must be taken into account in their managemen

Stochastic forecasts of seawater intrusion towards sustainable groundwater management: application to the Korba aquifer (Tunisia)

A stochastic study of long-term forecasts of seawater intrusion with an application to the Korba aquifer (Tunisia) is presented. Firstly, a geostatistical model of the exploitation rates was constructed, based on a multi-linear regression model combining incomplete direct data and exhaustive secondary information. Then, a new method was designed and used to construct a geostatistical model of the hydraulic conductivity field by combining lithological information and data from hydraulic tests. Secondly, the effects of the uncertainties associated with the pumping rates and the hydraulic conductivity field on the 3D density-dependent transient model were analysed separately and then jointly. The forecasts of the impacts of two different management scenarios on seawater intrusion in the year 2048 were performed by means of Monte Carlo simulations, accounting for uncertainties in the input parameters as well as possible changes of the boundary conditions. Combining primary and secondary data allowed maps of pumping rates and the hydraulic conductivity field to be constructed, despite a lack of direct data. The results of the stochastic long-term forecasts showed that, most probably, the Korba aquifer will be subject to important losses in terms of regional groundwater resource

The EU’s Democracy, Human Rights and Resilience Discourse and Its Contestation

MEDRESET Work Package 4 (WP4) aims at evaluating the effectiveness of EU policies on democracy promotion and human rights in the Southern and Eastern Mediterranean (SEM) region from the perspective of bottom-up actors’ interests, needs, perceptions and expectations, both at the local and the EU level, with the purpose of identifying inclusive, responsive and flexible policy actions to reinvigorate Euro-Mediterranean relations. This paper will firstly provide a background analysis for WP4, based on a critical review of the discourses of the EU and other key international and regional players, discursive positions of civil society actors (including at this stage only documents produced by civil society networks which span the Mediterranean) and the academic discourse. The second part will give an introductory overview on the central role played by civil society in the Arab uprisings and beyond, while the third part will outline the analytical and methodological indications that will inform research and fieldwork in this WP

High-resolution truncated plurigaussian simulations for the characterization of heterogeneous formations

Integrating geological concepts, such as relative positions and proportions of the different lithofacies, is of highest importance in order to render realistic geological patterns. The truncated plurigaussian simulation method provides a way of using both local and conceptual geological information to infer the distributions of the facies and then those of hydraulic parameters. The method (Le Loc'h and Galli 1994) is based on the idea of truncating at least two underlying multi-Gaussian simulations in order to create maps of categorical variable. In this manuscript we show how this technique can be used to assess contaminant migration in highly heterogeneous media. We illustrate its application on the biggest contaminated site of Switzerland. It consists of a contaminant plume located in the lower fresh water Molasse on the western Swiss Plateau. The highly heterogeneous character of this formation calls for efficient stochastic methods in order to characterize transport processes.Comment: 12 pages, 9 figure

GIM (Groundwater Integrated Modelling). The hydrogeological compiler

Complex problems in Earth Sciences demand the use of numerical models. To this end, a large number of codes have been developed during the last two decades. In spite of their power, as displayed in their many applications, these codes are sparse and, most often, used in the academic framework. To make things worse, they are aimed at solving a given set of physical phenomena (e.g. most codes solve groundwater flow and contaminant transport, but they do not take into account material defor- mation, others include deformation but not heat transfer, etc.) and most often they do not integrate stochastic techniques. GIM (Groundwater Integrated Modelling) is aimed at providing a platform to fill this gap. The objective is to integrate the existing codes in an overall fully-parallel object oriented FORTRAN 95 structure. Thus, the capabilities of GIM are numerous (differ- ent solvers of direct and inverse problem, of groundwater flow, contaminant (conservative or not) or heat transport, etc.) as it takes profit of those of the codes embedded in its structure. The use of GIM is illustrated with a simple example consisting of a Monte Carlo analysis of flow and transport problem: 1. Read data common to most of the existing \u201chost\u201d codes (finite elements or finite differences mesh, geostatistical model, state variable measurements, etc.) in an XML fashion. \u201cHost\u201d code particular variables (options, tolerances, convergence criteria, etc.) are supplied separately. 2. The data are used to pre-process the initial hydraulic conductivity fields on the basis of the geostatistical model. These fields will be calibrated in step 4.3. Write data in the appropriate format for the \u201chost\u201d code. 4. Execute \u201chost\u201d code(s). In this example, an inversion code is used. However, many codes can be used at step 4 (e.g. for solving the inherent direct problem, modeller can use a flow simulator to calculate the velocity field driving the con- taminant transport, which will be simulated using a \u201craw\u201d transport simulator). 5. Collect results (the calibrated fields). 6. Post-process the output (e.g. histogram of hydraulic conductivity). Including \u201chost\u201d codes in the overall structure of GIM is easy. One needs to add a routine for writing data at step 3 and a routine for reading the output at step 5. This confers versatility and an ample room for future developments

Trastuzumab and pertuzumab without chemotherapy in early-stage HER2+ breast cancer: a plain language summary of the PHERGain study

This is a summary of a publication about the PHERGain study, which was published in The Lancet Oncology in May 2021. The study includes 376 women with a type of breast cancer called HER2-positive breast cancer that can be removed by surgery. In the study, researchers wanted to learn if participants could be treated with two medicines called trastuzumab and pertuzumab without the need for chemotherapy. To identify HER2-positive tumors with more sensitivity to anti-HER2 therapies, the researchers used a type of imaging called a FDG-PET scan to check how well the treatments were working.Participants took a treatment before surgery, consisting of either chemotherapy (docetaxel and carboplatin) plus trastuzumab and pertuzumab (group A) or trastuzumab and pertuzumab alone (plus hormone therapy if the tumor was hormone receptor-positive; group B). After two cycles of treatment, participants underwent a FDG-PET scan. Participants assigned to group A completed 6 cycles of treatment regardless of 18F-FDG-PET results. Participants in group B continued the same treatment until surgery if their FDG-PET scan showed the treatment was working. While participants who did not show a response started treatment with chemotherapy in addition to trastuzumab and pertuzumab. All participants then had surgery.The results revealed that, of the participants in group B who showed a response using FDG-PET scan, 37.9% achieved a disappearance of all invasive cancer in the breast and axillary lymph nodes. This rate appears to be higher than those reported in previous studies evaluating the same treatment. These participants also had less side effects and improved overall quality of life compared with participants taking chemotherapy plus trastuzumab and pertuzumab.Early monitoring of how well participants respond to treatment by FDG-PET scan seems to identify participants with operable HER2-positive breast cancer who were more likely to benefit from trastuzumab and pertuzumab without the need to have chemotherapy. The PHERGain study is still ongoing and results on long-term survival are expected to be released in 2023. Clinical Trial Registration: NCT03161353 (ClinicalTrials.gov)