A Variational Data Assimilation Algorithm to Estimate Salinity in the Berre Lagoon with TELEMAC-3D

Numerical Aspect

Estimation Of Offtake Discharge And Cross-Device Parameters Using Data Assimilation For The Automatic Control Of An Irrigation Canal

The automatic control of open surface hydraulic systems such as Rivers (with dams and/or hydropower plants) or irrigation canals (with gated cross-devices) almost always use hydraulic models. These models can be used in different manners, either just to test and validate controllers prior to implementation, to tune the controller parameters off-line, or used on-line in real-time. The control algorithm calculates the control action variables u, using measured variables z obtained from the real system, in order to achieve some objectives for some controlled variables y. These models have always limited precision due to unknown or wrong: parameters, input variables and internal states. Among the parameters we find cross-device discharge and bed friction coefficients. Among input variables we find the inflow or outflow discharges entering into the river, or taken by users from the canal. Indeed, they are rarely measured, or in the best cases with a limited precision. This is a problem since the tuning of the control parameters of the feedback loops depends a lot on the dynamics of the system and therefore on the previous listed parameters. A feedforward control component, very useful for this class of delayed systems, could benefit from the knowledge of the input variables. In this paper we will show how data assimilation technics can reconstruct these unknown parameters and variables. We will also focus on the required number and locations of the measurements, to be able to reconstruct this correctly. We will study the best or required configurations allowing to use this information, detect and isolate some problems, correct the model, and reconstruct the wrong or unknown variables, inputs or parameters of the model. The framework we will use for this study is the Kalman filtering one. We will see that this framework is very powerful to solve the above described problems

Asimilacija računskog modela Dunava od Novog Sada do HE "Đerdap 1" u približno realnom vremenu - rezultati testiranja

In this paper, a novel data assimilation method for operational reservoir management on the Danube river section between Novi Sad and Iron Gate I is presented. The proposed data assimilation method allows discharges of river flow simulation model to be updated in near real time according to results of continuous water surface levels measurements. The model discharges are adjusted according to difference between measured and calculated water surface elevations using so-called PI controllers at locations where water levels measurements take place. The effect of different number of PI controllers on method effectiveness and stability are studied for different scenarios. The recommendations for method improvement are given at the end of the paper.U radu se predstavlja jedna od mogućih metoda asimilacije, korišćenja kontinualnih merenja nivoa vode duž Dunava za ažuriranje numeričkog modela tečenja Dunavom od Novog Sada do HE "Đerdap 1", napravljenog za potrebe HIS "Đerdap". Opisana metoda omogućava kontinualno, u realnom vremenu, usaglašavanje stanja računskog modela i stvarnog sistema, putem postepene korekcije nivoa promenom nepouzdanih dotoka u modelu. Korekcije se izračunavaju korišćenjem PI (eng. Proportional Integral) kontrolera koji su postavljeni na mestima gde postoje pouzdana merenja nivoa. U radu se prikazuju dobijeni rezultati testiranja primenjene metode za asimilaciju podataka pri različitim scenarijima promene protoka (odnosno, nepoznatog dotoka) na delu Dunava od Novog Sada do hidroelektrane "Đerdap". Testiranja su sprovedena sa različitim brojem kontrolera, kako bi se jasno video njihov efekat, stabilnost i efikasnost asimilacije. Na kraju rada se daju preporuke za dalja poboljšanja metodologije

Asimilacija računskog modela Dunava od Novog Sada do HE "Đerdap 1" u približno realnom vremenu - rezultati testiranja

In this paper, a novel data assimilation method for operational reservoir management on the Danube river section between Novi Sad and Iron Gate I is presented. The proposed data assimilation method allows discharges of river flow simulation model to be updated in near real time according to results of continuous water surface levels measurements. The model discharges are adjusted according to difference between measured and calculated water surface elevations using so-called PI controllers at locations where water levels measurements take place. The effect of different number of PI controllers on method effectiveness and stability are studied for different scenarios. The recommendations for method improvement are given at the end of the paper.U radu se predstavlja jedna od mogućih metoda asimilacije, korišćenja kontinualnih merenja nivoa vode duž Dunava za ažuriranje numeričkog modela tečenja Dunavom od Novog Sada do HE "Đerdap 1", napravljenog za potrebe HIS "Đerdap". Opisana metoda omogućava kontinualno, u realnom vremenu, usaglašavanje stanja računskog modela i stvarnog sistema, putem postepene korekcije nivoa promenom nepouzdanih dotoka u modelu. Korekcije se izračunavaju korišćenjem PI (eng. Proportional Integral) kontrolera koji su postavljeni na mestima gde postoje pouzdana merenja nivoa. U radu se prikazuju dobijeni rezultati testiranja primenjene metode za asimilaciju podataka pri različitim scenarijima promene protoka (odnosno, nepoznatog dotoka) na delu Dunava od Novog Sada do hidroelektrane "Đerdap". Testiranja su sprovedena sa različitim brojem kontrolera, kako bi se jasno video njihov efekat, stabilnost i efikasnost asimilacije. Na kraju rada se daju preporuke za dalja poboljšanja metodologije

Data assimilation for real-time estimation of hydraulic states and unmeasured perturbations in a 1D hydrodynamic model

International audienceWater management, in a variety of contexts and objectives, is a very important issue gaining increasing attention worldwide. In some places and during some periods, this is due to the scarcity of the water resource, and increasing competition for its use. In some others, it can be risk reduction due to flood events, or optimization of hydropower production along rivers. Hydraulic modeling, system analysis and automatic control are now parts of most water management projects. In order to operate hydraulic devices on irrigation canals or rivers, detailed information on the hydraulic state of the system must be available. This is particularly true when the control algorithms are based on Linear Quadratic Gaussian or Predictive Control approaches, using full state space models. Usually, the only known quantities are water levels, measured at limited locations. Sometimes, the discharge is known at specific locations (cross devices with gates, weirs, or hydropower turbines). The design of an observer is a very useful tool for reconstructing unmeasured data, such as discharges or water levels at other locations, unknown perturbations, such as inflows or outflows, and model parameters such as ManningStrickler or hydraulic device discharge coefficients. Several approaches are able to provide such observers. The paper illustrates and compares the use of sequential Kalman Filter and sequential Particle Filter State Observer on these water management problems. Four scenarios have been selected to test the filters, based on twin experiences or using real field data. Both approaches proved to be efficient and robust. The Kalman Filter is very fast in terms of calculation time and convergence. The Particle Filter can handle the non-linear features of the model

Modelling the Eddy Pattern in the harbour of Zeebrugge

Hydrodynamic

Metodologija za brzu asimilaciju podataka u modelima otvorenih tokova

Upravljanje vodnim resursima (vodosnabdevanje, odbrana od poplava, hidroenergetika) zahteva prognoze dostupne količine vode kao pomoć u donošenju upravljačkih odluka. Najčešće se te prognoze zasnivaju na upotrebi različitih fizički zasnovanih modela. Tako dobijeni rezultati su često veoma nepouzdani zbog prisustva različitih tipova neodređenosti. Kod primene linijskih (1D) modela tečenja u otvorenim tokovima neki od dominantnijh izvora neodređenosti su nedovoljno dobro poznavanje graničnih uslova (hidrogrami dotoka, krive protoka) i nepouzdani početni uslovi koji su osnova od koje se započinje prognoza. Kontinulana merenja na sistemu (npr. merenja nivoa na reci) predstavljaju relativno pouzdan reprezent njegovog stanja ali pokrivaju samo jedan mali deo domena koji se razmatra. Zbog toga se pribegava postupku asimilacije podataka kojom se usaglašavaju rezultati modela i merenja. Ova usaglašavanja se sprovode za već prikupljene podatke, u vremenskom periodu neposredno pre trenutka od koga se želi izvršiti prognoza. Taj period usaglašavanja naziva se asimilacioni period. Na kraju asimilacionog perioda model bolje oslikava trenutno stanje na celom domenu i može se iskoristiti za prognozu. U ovom istraživanju prikazana je nova asimilaciona metoda za modele otvorenih tokova korišćenjem indirektnog, fizički zasnovanog pristupa za usaglašavanje nivoa pomoću korektivnih dotoka. Korektivni dotoci se računaju koristeći teoriju Proporcionalno-Integrativno-Derivativnih (PID) kontrolera iz oblasti teorije upravljanja (eng. control theory). Metoda je razvijena u cilju primene jednostavnijeg i bržeg postupka asimilacije podataka u realnim sistemima otvorenih tokova. Nova asimilaciona metoda poredi se sa standardnom metodom asimilacije podataka (Ensemble Kalman Filter - EnKF) koja se najčešće koristi u sličnim istraživanjima. Poređenjem na hipotetičkim test primerima pokazano je da se primenom nove asimilacione metode dolazi do značajnog ubrzanja proračuna bez smanjenja kvaliteta asimilacije podataka. Primena ove metode na realne sisteme zahteva rešavanje problema određivanja optimalne konfiguracije (forme, strukture) i optimalnog podešavanja parametara PID kontrolera. Na primeru Hidroenergetskog sistema Đerdap sprovedeno je detaljno ispitivanje optimalne konfiguracije na osnovu definisanih indikatora kvaliteta asimilacije podataka. Utvrđeno je da jednostavnija konfiguracija kontrolera, sastavljena od proporcionalnog i integrativnog faktora (PI kontroler) daje najbolje rezultate asimilacije. Optimalno podešavanje parametara kontrolera rešeno je višekriterijumskom optimizacijom pomoću genetskog algoritma sa nedominantnim sortiranjem (eng. Nondominated Sorting Genetic Algorithm II – NSGA-II). Utvrđeno je da se podešavanje kontrolera višekriterijumskom optimizacijom može uraditi koristeći neku od kombinacija sa 2 suprotstavljene kriterijumske funkcije. Dodatna ispitivanja pokazala su potencijal ove asimilacione metode za rekonstrukciju stvarnih hidrograma na osnovu zabeleženih nivograma, kao alata za rekonstrukciju poplavnih talasa i smanjivanje neodređenosti krivih protoka

Quantitative and Qualitative Modelling for the Management and the Monitoring of Irrigation Canals: the Canale Emiliano Romagnolo Case Study

La presente tesi di dottorato è focalizzata sull’analisi quanti-qualitativa del Canale Emiliano Romagnolo (CER), una delle principali infrastrutture irrigue nazionali. La modellazione quantitativa è stata utilizzata per stimare le portate idriche non misurate dei prelievi e lungo l’asta. Sono stati testati due software: HEC-RAS e SIC2. Quest’ultimo si è rivelato il più efficace e, combinato con un opportuno DSS, ha permesso l’elaborazione di un “approccio multi-disciplinare”, sviluppato su un Segmento Pilota (PS) e applicato su un Segmento Esteso (ES). I valori delle variabili idrauliche sono risultati da processi di ottimizzazione. L’analisi qualitativa si è focalizzata sul parametro E.coli e si è basata sul modello ottimizzato di ES. Sono state elaborate due metodologie per l’imposizione delle condizioni al contorno e la validazione dei risultati. Quindi, si determinato il valore del coefficiente di decadimento. L’approccio è stato sviluppato su un segmento (PS) caratterizzato da una semplice geometria e una disponibilità significativa di misure idrometriche riportando ottimi risultati. Successivamente, è stato testato su una realtà più complessa (ES) ricostruendo con successo i dati per anni dalle condizioni meteo-climatiche standard. È stato riscontrato come l’accuratezza e il posizionamento degli strumenti di misura siano fattori chiave per la modellazione. Considerando l’analisi qualitativa, la mancata disponibilità di una serie continua di valori di E.coli ha portato alla necessità di considerare un database particolarmente esteso a livello temporale di misure discrete. Gli sviluppi futuri del presente lavoro sono essenzialmente due. Il primo prevede l’estensione della modellazione alla rete di consegna a valle delle derivazioni irrigue insistenti sul CER costituita da canali in terra di cui si devono considerare le perdite idriche. Il secondo consiste nell’approfondimento della relazione tra i parametri E.coli e TSS.The present PhD thesis is focused on the quantitative and qualitative analysis of the open-canal Canale Emiliano Romagnolo (CER), which is one of the major irrigation infrastructures in Italy. The quantitative modelling was used for the unmeasured offtake and flowing discharge estimation. Two software were tested: HEC-RAS and SIC2; the latter resulted the more effective one. It was combined with DSS in order to obtained a “multi-disciplinary approach” that was developed on a Pilot Segment (PS) and applied on an Extended Segment (ES). Hydraulic variables were determined after optimisation processes. The ES optimised model represented the basis for the qualitative analysis focused on E.coli. Two methodologies were elaborated for the reconstruction of the boundary conditions and the results validation. Therefore, the decay rate of E.coli was estimated. The work was developed on a segment (PS) characterized by a quite simple geometry and full availability of water levels, and it gave good results. Its application on a more complex segment (ES) with a poor data availability and accuracy, underlined that the approach can be successfully used to reconstruct data for years with standard meteo-climatic conditions, while years with extreme climatic conditions are more difficult to be simulated. It was found that the measuring point and consequently instrument accuracy are key factors for obtaining a model that can well represent the reality. Considering the qualitative analysis, the lack of an ongoing collection of parameters values involved the use of large historic discrete database for the modelling results validation. The main further development are two. The work considers a lined concrete canal; for widening its application on secondary channels often on earth, the analysis will introduce variables for the infiltration losses. In literature, the values of E.Coli are often related with those of TSS; this could be verified on the present case study

Assimilation de données ensembliste et couplage de modèles hydrauliques 1D-2D pour la prévision des crues en temps réel. Application au réseau hydraulique "Adour maritime"

Les inondations sont un risque naturel majeur pour les biens et les personnes. Prévoir celles-ci, informer le grand public et les autorités sont de la responsabilité des services de prévision des crues. Pour ce faire ils disposent d'observations in situ et de modèles numériques. Néanmoins les modèles numériques sont une représentation simplifiée et donc entachée d'erreur de la réalité. Les observations quant à elle fournissent une information localisée et peuvent être également entachées d'erreur. Les méthodes d'assimilation de données consistent à combiner ces deux sources d'information et sont utilisées pour réduire l'incertitude sur la description de l'état hydraulique des cours d'eau et améliorer les prévisisons. Ces dernières décennies l'assimilation de données a été appliquée avec succès à l'hydraulique fluviale pour l'amélioration des modèles et pour la prévision des crues. Cependant le développement de méthodes d'assimilation pour la prévision en temps réel est contraint par le temps de calcul disponible et par la conception de la chaîne opérationnelle. Les méthodes en question doivent donc être performantes, simples à implémenter et peu coûteuses. Un autre défi réside dans la combinaison des modèles hydrauliques de dimensions différentes développés pour décrire les réseaux hydrauliques. Un modèle 1D est peu coûteux mais ne permet pas de décrire des écoulement complexes, contrairement à un modèle 2D. Le simple chainage des modèles 1D et 2D avec échange des conditions aux limites n'assure pas la continuité de l'état hydraulique. Il convient alors de coupler les modèles, tout en limitant le coût de calcul. Cette thèse a été financée par la région Midi-Pyrénées et le SCHAPI (Service Central d'Hydrométéorolgie et d'Appui à la Prévisions des Inondations) et a pour objectif d'étudier l'apport de l'assimilation de données et du couplage de modèles pour la prévision des crues. Elle se décompose en deux axes : Un axe sur l'assimilation de données. On s'intéresse à l'émulation du filtre de Kalman d'Ensemble (EnKF) sur le modèle d'onde de crue. On montre, sous certaines hypothèses, qu'on peut émuler l'EnKF avec un filtre de Kalman invariant pour un coût de calcul réduit. Dans un second temps nous nous intéressons à l'application de l'EnKF sur l'Adour maritime avec un modèle Saint-Venant. Nous en montrons les limitations dans sa version classique et montrons les avantages apportés par des méthodes complémentaires d'inflation et d'estimation des covariances d'erreur d'observation. L'apport de l'assimilation des données in situ de hauteurs d'eau sur des cas synthétiques et sur des crues réelles a été démontré et permet une correction spatialisée des hauteurs d'eau et des débits. En conséquence, on constate que les prévisions à court terme sont améliorées. Nous montrons enfin qu'un système de prévisions probabilistes sur l'Adour dépend de la connaissance que l'on a des forçages amonts ; un axe sur le couplage de modèles hydrauliques. Sur l'Adour 2 modèles co-existent : un modèle 1D et un modèle 2D au niveau de Bayonne. Deux méthodes de couplage ont été implémentées. Une première méthode, dite de "couplage à interfaces", combine le 1D décomposé en sous-modèles couplés au 2D au niveau frontières liquides de ce dernier. Une deuxième méthode superpose le 1D avec le 2D sur la zone de recouvrement ; le 1D force le 2D qui, quand il est en crue, calcule les termes d'apports latéraux pour le 1D, modélisant les échanges entre lit mineur et lit majeur. Le coût de calcul de la méthode par interfaces est significativement plus élevé que celui associé à la méthode de couplage par superposition, mais assure une meilleure continuité des variables. En revanche, la méthode de superposition est immédiatement compatible avec l'approche d'assimilation de données sur la zone 1D. L'apport, sur la zone 2D, de l'assimilation des observations in situ des hauteurs d'eau sur la zone 1D a été mis en évidence pour un fort événement de crue de la Nive en Janvier 2014. ABSTRACT : Floods represent a major threat for people and society. Flood forecasting agencies are in charge of floods forecasting, risk assessment and alert to governmental authorities and population. To do so, flood forecasting agencies rely on observations and numerical models. However numerical models and observations provide an incomplete and inexact description of reality as they suffer from various sources of uncertianties. Data assimilation methods consists in optimally combining observations with models in order to reduce both uncertainties in the models and in the observations, thus improving simulation and forecast. Over the last decades, the merits of data assimilation has been greatly demonstrated in the field of hydraulics and hydrology, partly in the context of model calibration or flood forecasting. Yet, the implementation of such methods for real application, under computational cost constraints as well as technical constraints remains a challenge. An other challenge arises when the combining multidimensional models developed over partial domains of catchment. For instance, 1D models describe the mono-dimensional flow in a river while 2D model locally describe more complex flows. Simply chaining 1D and 2D with boundary conditions exchange does not suffice to guarantee the coherence and the continuity of both water level and discharge variables between 1D and 2D domains. The solution lies in dynamical coupling of 1D and 2D models, yet an other challenge when computational cost must be limited. This PhD thesis was funded by Midi-Pyrénées region and the french national agency for flood forecasting SCHAPI. It aims at demonstrating the merits of data assimilation and coupling methods for floof forecasting in the framework of operational application. This thesis is composed of two parts : A first part dealing with data assimilation. It was shown that, under some simplifying assumptions, the Ensemble Kalman filter algorithm (EnKF) can be emulated with a cheaper algorithm : the invariant Kalman filter. The EnKF was then implemented ovr the "Adour maritime" hydraulic network on top of the MASCARET model describing the shallow water equations. It was found that a variance inflation algorithm can further improve data assimlation results with the EnKF. It was shown on synthetical and real cases experiments that data assimilation provides an hydraulic state that is in great agreement with water level observations. As a consequence of the sequential correction of the hydraulic state over time, the forecasts were also greatly improved by data assimilation over the entire hydraulic network for both assimilated and nonassimilated variables, especially for short term forecasts. It was also shown that a probabilistic prediction system relies on the knowledge on the upstream forcings ; A second part focusses on hydraulic models coupling. While the 1D model has a great spatial extension and describes the mono-dimensional flow, the 2D model gives a focus on the Adour-Nive confluence in the Bayonne area. Two coupling methods have been implemented in this study : a first one based on the exchange of the state variables at the liquid boundaries of the models and a second one where the models are superposed. While simple 1D or chained 1D-2D solutions provide an incomplete or discontinuous description of the hydraulic state, both coupling methods provide a full and dynamically coherent description of water level and discharge over the entire 1D-2D domain. On the one hand, the interface coupling method presents a much higher computational cost than the superposition methods but the continuity is better preserved. On the other hand, the superposition methods allows to combine data assimilation of the 1D model and 1D-2D coupling. The positive impact of water level in-situ observations in the 1D domain was illustrated over the 2D domain for a flood event in 2014