Tracer Test Data Assimilation for the Assessment of Local Hydraulic Properties in Heterogeneous Aquifers

The hydraulic conductivity distribution in a natural porous media is characterized by a great heterogeneity that makes its spatial assessment problematic and expensive. At the same time, a detailed knowledge of the hydraulic properties, as porosity, storativity, transmissivity and hydraulic conductivity K, is fundamental for the prediction of groundwater flow and solute transport in natural formations. Among the hydraulic properties, being the subsurface transport phenomena in natural formations mainly controlled by the Darcy's law, the proper definition of the K spatial distribution at different scales plays a fundamental role to evaluate the evolution of a contaminant plume, to define the well-catchment areas or to monitor a landfill site. To estimate aquifer hydraulic properties, inverse models have long been studied and, beyond the traditional hydraulic conductivity and head measurements, tracer test analyses have been widely adopted in the past and their use have increased in the recent years thanks to a great improvement of geophysical techniques. Among others, the Electrical Resistivity Tomography (ERT) allows to monitor a tracer test injection, providing time-lapse informations about the plume evolution with limited cost. Assuming that time-lapse spatially distributed data deduced from a tracer test are available, the present work investigates different approaches aimed to the estimation of the local K distribution. At this purpose, Kalman filter based data assimilation techniques are coupled with the Lagrangian transport model and applied in different synthetic context

Ensemble Kalman Filter Assimilation of ERT Data for Numerical Modeling of Seawater Intrusion in a Laboratory Experiment

Seawater intrusion in coastal aquifers is a worldwide problem exacerbated by aquifer overexploitation and climate changes. To limit the deterioration of water quality caused by saline intrusion, research studies are needed to identify and assess the performance of possible countermeasures, e.g., underground barriers. Within this context, numerical models are fundamental to fully understand the process and for evaluating the effectiveness of the proposed solutions to contain the saltwater wedge; on the other hand, they are typically affected by uncertainty on hydrogeological parameters, as well as initial and boundary conditions. Data assimilation methods such as the ensemble Kalman filter (EnKF) represent promising tools that can reduce such uncertainties. Here, we present an application of the EnKF to the numerical modeling of a laboratory experiment where seawater intrusion was reproduced in a specifically designed sandbox and continuously monitored with electrical resistivity tomography (ERT). Combining EnKF and the SUTRA model for the simulation of density-dependent flow and transport in porous media, we assimilated the collected ERT data by means of joint and sequential assimilation approaches. In the joint approach, raw ERT data (electrical resistances) are assimilated to update both salt concentration and soil parameters, without the need for an electrical inversion. In the sequential approach, we assimilated electrical conductivities computed from a previously performed electrical inversion. Within both approaches, we suggest dual-step update strategies to minimize the effects of spurious correlations in parameter estimation. The results show that, in both cases, ERT data assimilation can reduce the uncertainty not only on the system state in terms of salt concentration, but also on the most relevant soil parameters, i.e., saturated hydraulic conductivity and longitudinal dispersivity. However, the sequential approach is more prone to filter inbreeding due to the large number of observations assimilated compared to the ensemble size

Benefici dell\u2019idrovia Padova-Venezia sulla riduzione della pericolosit\ue0 idraulica nel bacino Brenta-Bacchiglione

-La gestione del nodo di Voltabarozzo (Padova) non pu\uf2 prescindere dalle condizioni del fiume Brenta -L\u2019idrovia Padova-Venezia per ridurre la pericolosit\ue0 idraulica nel Bacchiglione-Brenta -L\u2019idrovia per ridare flessibilit\ue0 di manovra al nodo idraulico di Voltabarozz

Minimization, equivalence and fate of the hydrogeological hazard: a new criterion to manage the flood threats applied to the Padova hydraulic node

Until two centuries ago, the Bacchiglione river crossed the city of Padova and the entire neighborhoods were threatened by its floods. In order to solve this problem, in 1830 the Austrian Government established the construction of a new channel, the Scaricatore channel, diverting the Bacchiglione river outside Padova, up to the Roncajette river at Voltabarozzo. However, this artificial channel was not able to convey the maximum flow rates of the Bacchiglione. Therefore, in the 1930s, according to the project of Luigi Gasparini, the Scaricatore was enlarged and the new San Gregorio channel was digged with the aim of diverting the water from the Voltabarozzo node toward the Piovego channel and then to the Brenta river, in order to reduce the hydraulic threat in the Roncajette. The water discharged through both the San Gregorio and the Roncajette is controlled by two different systems of sluice gates, located at the Voltabarozzo node. The management of these gates is actually manual, based on the water level gauged in some sections of the Bacchiglione and the Brenta. In the present study we first estimated the flow capacity of the San Gregorio channel, depending on the water level both at Voltabarozzo and in the Brenta. The target of this work is to develop an automatic procedure to define the optimal maneuvers at the gates, according to a criterion that consists in the "minimization, equivalence and fate" of the hydraulic hazard. Five hazard classes have been identified, related to the water level in the Scaricatore and to the flow rates both in the Brenta and in the Roncajette, as result of the regulations at the gates. The definition of these classes has been strongly related to the knowledge of the geomorphological and hydrogeological features of the territory: the key elements we considered are the spatial and temporal propagation mechanisms of the flood waves, the characterization of overflow-collapse triggering mechanisms of the banks and the assessment of the threat to infrastructure and private buildings. The procedure has been tested over several events, by means of a 2-D shallow water numerical model, based on a finite-element technique where the domain is discretized with triangular elements. Results show that the automatic procedure can be a powerful tool to manage the Padova node during the floods of the Bacchiglione river. Moreover, this procedure allows to reproduce the regulations at the gates carried out in the past floods events, when the regulations have not been recorded yet. Finally, the procedure has been used to evaluate the effects of some hydraulic interventions, such as the rise of the levees at some locations and the construction of the waterway "Idrovia Padova - Venezia", which should divert part of the flow rates of the Brenta toward the Venice lagoon, just downstream the confluence with the San Gregorio - Piovego system. Criteria and strategies implemented here for the Voltabarozzo node can be applied to other regulation structures, in order to improve the hydraulic hazard mitigation and decision making process

Sistema integrato di previsione delle piene in tempo reale nel bacino idrografico Brenta-Bacchiglione

-Modello idrologico-idrodinamico per la previsione delle piene in tempo reale nel Brenta-Bacchiglione. -Interfaccia grafica GIS funzionale alla gestione delle emergenze in corso di evento. -Limitazione dell\u2019incertezza delle condizioni iniziali forzando il modello con misure di precipitazione e di livello. -Buona precisione e affidabilit\ue0 del sistema confermate dalle simulazioni di eventi passati

Heterozygous FOXN1 Variants Cause Low TRECs and Severe T Cell Lymphopenia, Revealing a Crucial Role of FOXN1 in Supporting Early Thymopoiesis

FOXN1 is the master regulatory gene of thymic epithelium development. FOXN1 deficiency leads to thymic aplasia, alopecia, and nail dystrophy, accounting for the nude/severe combined immunodeficiency (nu/SCID) phenotype in humans and mice. We identified several newborns with low levels of T cell receptor excision circles (TRECs) and T cell lymphopenia at birth, who carried heterozygous loss-of-function FOXN1 variants. Longitudinal analysis showed persistent T cell lymphopenia during infancy, often associated with nail dystrophy. Adult individuals with heterozygous FOXN1 variants had in most cases normal CD4+ but lower than normal CD8+ cell counts. We hypothesized a FOXN1 gene dosage effect on the function of thymic epithelial cells (TECs) and thymopoiesis and postulated that these effects would be more prominent early in life. To test this hypothesis, we analyzed TEC subset frequency and phenotype, early thymic progenitor (ETP) cell count, and expression of FOXN1 target genes (Ccl25, Cxcl12, Dll4, Scf, Psmb11, Prss16, and Cd83) in Foxn1nu/+ (nu/+) mice and age-matched wild-type (+/+) littermate controls. Both the frequency and the absolute count of ETP were significantly reduced in nu/+ mice up to 3 weeks of age. Analysis of the TEC compartment showed reduced expression of FOXN1 target genes and delayed maturation of the medullary TEC compartment in nu/+ mice. These observations establish a FOXN1 gene dosage effect on thymic function and identify FOXN1 haploinsufficiency as an important genetic determinant of T cell lymphopenia at birth

Tracer Test Data Assimilation for the Assessment of Local Hydraulic Properties in Heterogeneous Aquifers

The hydraulic conductivity distribution in a natural porous media is characterized by a great heterogeneity that makes its spatial assessment problematic and expensive. At the same time, a detailed knowledge of the hydraulic properties, as porosity, storativity, transmissivity and hydraulic conductivity K, is fundamental for the prediction of groundwater flow and solute transport in natural formations. Among the hydraulic properties, being the subsurface transport phenomena in natural formations mainly controlled by the Darcy's law, the proper definition of the K spatial distribution at different scales plays a fundamental role to evaluate the evolution of a contaminant plume, to define the well-catchment areas or to monitor a landfill site. To estimate aquifer hydraulic properties, inverse models have long been studied and, beyond the traditional hydraulic conductivity and head measurements, tracer test analyses have been widely adopted in the past and their use have increased in the recent years thanks to a great improvement of geophysical techniques. Among others, the Electrical Resistivity Tomography (ERT) allows to monitor a tracer test injection, providing time-lapse informations about the plume evolution with limited cost. Assuming that time-lapse spatially distributed data deduced from a tracer test are available, the present work investigates different approaches aimed to the estimation of the local K distribution. At this purpose, Kalman filter based data assimilation techniques are coupled with the Lagrangian transport model and applied in different synthetic contextsLa distribuzione di conducibilità idraulica in un mezzo poroso naturale è caratterizzata da grande eterogeneità, che rende la sua determinazione problematica e costosa. Allo stesso tempo, una approfondita conoscenza delle proprietà idrauliche, quali la porosità, l'immagazzinamento specifico e la conducibilità idraulica K, è di fondamentale importanza per poter predire e analizzare il flusso sotterraneo e il trasporto di soluti in formazioni naturali. Poichè i fenomeni di trasporto sotterraneo che si realizzano negli acquiferi sono principalmente controllati dalla legge di Darcy, tra le diverse proprietà idrauliche sopraccitate, un'opportuna definizione della distribuzione spaziale di K gioca un ruolo fondamentale nella predizione del plume di inquinanti, e quindi assume particolare rilevanza in molte attività di pratico interesse, quali la definizione delle aree di salvaguardia dei pozzi o il monitoraggio di discariche. Le proprietà idrauliche degli acquiferi sono di norma stimate con l'ausilio di modelli inversi utilizzando, oltre le tradizionali misure di conducibilità idraulica e piezometria, quelle derivanti da analisi di iniezioni controllate (test con traccianti o tracer test nella comune dizione anglosassone). I test con traccianti sono stati in diverse occasioni adottati nel passato ma il loro uso è aumentato negli anni recenti grazie agli sviluppi delle tecniche geofisiche che semplificano il monitoraggio delle prove in situ. Fra queste, la Tomografia Elettrica Resistiva (ERT) sembra essere la più appropriata per misurare le quantità di interesse nel caso di iniezioni di traccianti, essendo possibile acquisire un grande numero di informazioni sull'evoluzione spazio-temporale dell'evoluzione del plume, a costi relativamente limitati. Partendo dal presupposto che siano disponibili misure derivanti da una iniezione controllata in pozzo, il presente lavoro suggerisce alcuni approcci che, sulla base dei dati deducibili dalle misure ERT, permettono di stimare la distribuzione spaziale di K e verifica la loro effettiva capacità predittiva. Tali modelli risultano dall'accoppiamento di tecniche basate sul filtro di Kalman con modelli di trasporto Lagrangiano: l'applicazione ad una estesa serie di casi sintetici ha permesso inoltre di ottenere utili indicazioni in relazione a vantaggi e svantaggi di ciascuna delle metodologie propost

Definizione delle propriet\ue0 idrauliche locali di un acquifero dall'analisi di test con traccianti

Scopo del presente lavoro \ue8 fornire uno strumento in grado di individuare le propriet\ue0 idrauliche degli acquiferi naturali dall\u2019analisi delle informazioni provenienti da test su traccianti. A tal fine, alcune tecniche geofisiche, come ad esempio la tomografia elettrica resistiva (ERT), sembrano adatte a descrivere l\u2019evoluzione spazio-temporale di un soluto che si muove in un acquifero naturalmente eterogeneo. La distribuzione spaziale delle propriet\ue0 idrauliche, quali la conducibilit\ue0 idraulica e la porosit\ue0, controlla direttamente il trasporto del soluto: si pu\uf2 quindi ragionevolmente cercare di dedurre tale distribuzione a partire dalla conoscenza dell\u2019evoluzione della concentrazione a prefissati intervalli di tempo. A tale scopo, un modello basato sulla formulazione Lagrangiana del trasporto \ue8 stato accoppiato ad una tecnica di assimilazione dati. Al fine di analizzare le potenzialit\ue0 del metodo proposto, sono stati condotti alcuni test in un dominio tridimensionale, simulando una prova con tracciante in un acquifero eterogeneo. I risultati ottenuti dimostrano che il modello proposto, nonostante una qualche sensibilit\ue0 ai valori che inizializzano la procedura, pu\uf2 rappresentare uno strumento efficace per la descrizione della distribuzione locale della conducibilit\ue0 idraulica