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International audience; It has been well established in several experimental and modeling studies that leak areas are often not fixed, but vary as linear functions of pressure. Replacing this linear equation into the orifice equation results in a two-part modified orifice leakage equation with head exponents of 0.5 and 1.5 respectively. The purpose of this study was to incorporate the modified orifice equation into the hydraulic network formulation and evaluate its impact on model performance. The conventional and modified software were applied to 600 instances of stochastic leakage distributions in three different pipe networks. It was found that the conventional power leakage equation results in significant leakage volume and flow rate errors under certain conditions. In addition, a problem of non-convergence of the conventional global gradient algorithm for leakage exponents greater than two was observed and is discussed.

CCWI 2017 – Computing and Control for the Water Industry, Sheffield, , 05-/09/2017 - 07/09/2017; International audience; Water supply networks (WSNs) represent an important part of urban technical infrastructure. Recently, the resilience of water distribution networks facing different physical and cyber threats has gained increasing attention. In order to improve the operation of complex water distribution systems under both, extreme and normal hydraulic conditions, mathematical simulation models are indispensable tools for engineers, network planners, network operators and decision makers. Especially, in the case of extremely disruptive events that might be caused by natural hazards or deliberate malevolent attacks by humans, the proper operation of the system for maintaining the supply of drinking water to at least parts of the population is a very challenging task. Resilient behaviour can be reached only by adaptive system operation including isolation of parts of the network and control of pressure and flows in the system. For that purpose, different kinds of control devices are used that may be remotely controlled or which are operated in the field. Existing hydraulic simulation software often fails to calculate reliable results for systems under control and pressure insufficiency. A mathematical framework for the simulation of the steady-state flow in reticulation water supply networks with special consideration of feedback control devices and pressure dependent demands is proposed in this paper. First, the importance of the steady-state calculation in the face of disruptive events is stressed and a brief review of synthetic and analytical methods for the hydraulic steady- state calculation is given. In this paper, the well-known content model is extended by the content of pressure dependent outflows. The nonlinear consumption functions in combination with linear inequality constraints (box constraints) replace the constant demands of demand driven analysis. It is also shown that the range of solvable problems in combination with flow control devices is enlarged by the relaxation of fixed demands.

Ce numéro comprend les articles issus du colloque de restitution Ecophyto Recherche « Des outils et des dispositifs pour éclairer les décisions, explorer les possibles et accompagner la transition vers des systèmes économes et multi-performants », qui s’est tenu à Saint-Malo, du 22 au 24 mars 2017.; National audience; Assessment and comparison of the impacts on the environment and on humanhealth of pesticides used in conventional and innovative cropping systems: main results of theECoPESt projectIn the context of the French Ecophyto programme which aims at reducing the use of pesticides, theobjectives of the ECoPESt project were (1) to assess and to compare the environmental and healthperformances of innovative cropping systems designed to reduce pesticides use, (2) to relateagricultural practices, pesticides pressure and impacts, (3) to identify the cropping systems allowing todecrease the impacts on the environment and on human health, and to preserve the ecosystemservices of regulating and provisioning, and (4) to develop a new approach, based on modelling, to apriori assess the performances of cropping systems. The assessment of the impacts of the pesticideson the environment (i.e. observed, and MACRO, PEARL, PRZM and STICS-MACRO simulatedgroundwater concentrations) and on human health (assessed with the BROWSE model) showed,independently of the considered conventional reference cropping system, that systems based onreduced tillage (or no-till) would tend to increase the potential impacts on human health because of anincrease in pesticide applications, and that they also lead to the highest risks of groundwatercontamination by pesticides. On the contrary, innovative cropping systems such as those targeting a50% decrease in the TFI (treatment frequency index) compared to the reference systems, and thesystems based on mechanical weeding (i.e. no herbicide systems) allowed to reduce the impacts onhuman health and on the environment. This project confirmed the relationship between pesticides use(i.e. agricultural practices and associated pesticides pressure) and impacts on environment and humanhealth.; Dans le contexte Ecophyto de la diminution du recours aux produits phytosanitaires, le projet ECoPESta pour objectifs (1) d’évaluer et de comparer les performances environnementales et sanitaires desystèmes de culture conçus avec l’objectif de réduire l’usage des pesticides, (2) d’établir un lien entrepratiques, pression et impacts des pesticides, (3) d’identifier les systèmes permettant de réduire lesimpacts liés à l’utilisation des pesticides et de préserver les services écosystémiques (notammentservices d’approvisionnement et de régulation) et (4) d’élaborer une démarche d’évaluation a priori desperformances des systèmes, basée sur des approches de modélisation. L’évaluation des impacts despesticides sur l’environnement (i.e. concentrations dans les eaux souterraines observées et simuléesavec les modèles MACRO, PEARL, PRZM et STICS-MACRO) et sur la santé humaine (estimés avec lemodèle BROWSE) a montré qu’indépendamment du système de culture conventionnel de référenceconsidéré, les systèmes basés sur les techniques culturales sans labour tendraient à augmenter lesimpacts potentiels sur la santé en raison de la multiplication du nombre de traitements herbicides etqu’ils présentent aussi les risques les plus élevés de contamination des eaux souterraines par lespesticides. En revanche, les systèmes innovants tels que les systèmes visant une réduction de 50 % del’IFT (indicateur de fréquence de traitements) par rapport aux systèmes conventionnels correspondants,basés notamment sur des rotations et non sur des monocultures, et les systèmes de culture privilégiantles techniques de désherbage mécanique permettraient de réduire de façon significative les impacts surla santé et sur l’environnement. Ce projet a par ailleurs confirmé le lien direct entre usage despesticides (i.e. pratiques et pression associée) et impacts sur l’environnement et la santé.

Dans le contexte Ecophyto de la diminution du recours aux produits phytosanitaires, le projet ECoPESt a pour objectifs (1) d’évaluer et de comparer les performances environnementales et sanitaires de systèmes de culture conçus avec l’objectif de réduire l’usage des pesticides, (2) d’établir un lien entre pratiques, pression et impacts des pesticides, (3) d’identifier les systèmes permettant de réduire les impacts liés à l’utilisation des pesticides et de préserver les services écosystémiques (notamment services d’approvisionnement et de régulation) et (4) d’élaborer une démarche d’évaluation a priori des performances des systèmes, basée sur des approches de modélisation. L’évaluation des impacts des pesticides sur l’environnement (i.e. concentrations dans les eaux souterraines observées et simulées avec les modèles MACRO, PEARL, PRZM et STICS-MACRO) et sur la santé humaine (estimés avec le modèle BROWSE) a montré qu’indépendamment du système de culture conventionnel de référence considéré, les systèmes basés sur les techniques culturales sans labour tendraient à augmenter les impacts potentiels sur la santé en raison de la multiplication du nombre de traitements herbicides et qu’ils présentent aussi les risques les plus élevés de contamination des eaux souterraines par les pesticides. En revanche, les systèmes innovants tels que les systèmes visant une réduction de 50 % de l’IFT (indicateur de fréquence de traitements) par rapport aux systèmes conventionnels correspondants, basés notamment sur des rotations et non sur des monocultures, et les systèmes de culture privilégiant les techniques de désherbage mécanique permettraient de réduire de façon significative les impacts sur la santé et sur l’environnement. Ce projet a par ailleurs confirmé le lien direct entre usage des pesticides (i.e. pratiques et pression associée) et impacts sur l’environnement et la santé., Assessment and comparison of the impacts on the environment and on human health of pesticides used in conventional and innovative cropping systems: main results of the ECoPESt project In the context of the French Ecophyto programme which aims at reducing the use of pesticides, the objectives of the ECoPESt project were (1) to assess and to compare the environmental and health performances of innovative cropping systems designed to reduce pesticides use, (2) to relate agricultural practices, pesticides pressure and impacts, (3) to identify the cropping systems allowing to decrease the impacts on the environment and on human health, and to preserve the ecosystem services of regulating and provisioning, and (4) to develop a new approach, based on modelling, to a priori assess the performances of cropping systems. The assessment of the impacts of the pesticides on the environment (i.e. observed, and MACRO, PEARL, PRZM and STICS-MACRO simulated groundwater concentrations) and on human health (assessed with the BROWSE model) showed, independently of the considered conventional reference cropping system, that systems based on reduced tillage (or no-till) would tend to increase the potential impacts on human health because of an increase in pesticide applications, and that they also lead to the highest risks of groundwater contamination by pesticides. On the contrary, innovative cropping systems such as those targeting a 50% decrease in the TFI (treatment frequency index) compared to the reference systems, and the systems based on mechanical weeding (i.e. no herbicide systems) allowed to reduce the impacts on human health and on the environment. This project confirmed the relationship between pesticides use (i.e. agricultural practices and associated pesticides pressure) and impacts on environment and human health.

International audience; Temperate eels are three panmictic catadromous species with a long period of oceanic passive larval drift and large distribution areas in contrasting environments. Spatial patterns of life history traits have been observed, and are correlated with environmental gradients, and may arise from both adaptive phenotypic plasticity and genetic polymorphism. This raises the question of the effect of spatially heterogeneous anthropogenic pressures on these populations. In this context, we used Geneveel, an individual-based optimization model that includes both phenotypic plasticity and genetic polymorphism, to explore the effects of different kinds of anthropogenic pressures: glass eel and silver eel fisheries, obstacles to upstream migration, and turbine mortality. More specifically, we analyzed the effects of these pressures on five output variables: the number of escapees, the proportion of females, the proportion of slow growers, the mean length-at-silvering and the resulting egg production. Our results suggest that phenotypic plasticity could act as a compensatory mechanism that mitigates the effects of some pressures (glass eel fishery and obstacles to upstream migration) and could be a source of resilience for the population, while other pressures did not show any compensatory effect (silver eel fishery and turbine mortality). Therefore, global impacts are very hard to assess, and the pressure that kills the most individuals does not necessarily have the biggest impact on the spawning biomass.

14th CCWI international conference, Computing and Control in Water Industry, Amsterdam, NLD, 07-/11/2016 - 07/11/2016; International audience; Research has shown that area of leak openings varies linearly with pressure under both elastic and viscoelastic conditions. However, hydraulic modelling of water distribution systems currently uses a power function that does not explicitly take into account leak area variation with pressure. This function is commonly known as the N1 power equation. This paper investigates the possibility of explicitly incorporating leak area variation into hydraulic modelling of water distribution systems. The FAVAD (Fixed And Variable Area Discharges) equation, which takes into account leak area variation with pressure, was incorporated into the widely used Global Gradient Algorithm (GGA) in EPANET. A stochastic model was developed to generate and distribute leaks in a standard water distribution system. It was based on existing theories about leakage in water distribution systems, taking into account physical properties of the system. Thereafter, hydraulic simulations were run using both FAVAD and N1 equations. The results show that the N1 power equation estimates the total system leakage with an error of up to 20%. On a specific junction, the leakage estimation error was found to be as high as 60%.

The pressure sensor described here is an hybrid association of a capacitive sensing cell in Silicium/Pyrex technology, and a capacitance/frequency transducer based on the charge and the discharge of a capacitor with constant current. The modelling response of each part allows us to explicit the transfer function of the sensor. Accurate evaluation of different parameters is achieve by both numerical simulation and experimental characterisation of the sensing cell and the electronic circuit. Studies on a simple and a ratiometric architecture show the feasibility of pressure sensor which is able to mainly self-compensate nonlinearity and drifts. In the range of ten percent of the offset frequency, the demonstrator nonlinearity is less than one percent and its thermal coefficient is about twenty parts of million by Celsius degree. Numerical simulations show that to optimise ratiometric sensor performances, it is necessary to use identical ways of measuring both signals : the reference one and the measure one. These optimal performances can be obtained by integrating both converters on the same silicon substrate. Experimental results also point out several problems of interference between oscillators through grid-to-channel capacitances. One way to minimise these coupling effects is to add a decoupling capacitance. All the results obtained allow us to conclude that measurement principles and the associated technologies used are adequate to develop a new family of miniature pressure sensor which can be relatively accurate (about 1% of the full scale), cheap and easily connected with numeric communication networks.; Le capteur de pression étudié résulte de l'assemblage hybride d'une cellule sensible capacitive en technologie Silicium/Pyrex et d'un convertisseur capacité/fréquence basé sur le principe de la charge et de la décharge d'une capacité à courant constant. La modélisation de la réponse de chacune des deux parties permet d'établir la fonction de transfert du capteur. La détermination précise des différents paramètres s'effectue à partir d'une approche mixte fondée sur la simulation numérique et sur la caractérisation expérimentale de la cellule et du circuit. L'étude des comportements d'un montage inverseur et d'une architecture ratiométrique montre la faisabilité d'un capteur dans lequel la nonlinéarité et les dérives thermiques s'autocompensent en grande partie. Dans une plage de fréquence de l'ordre de dix pour-cent de la fréquence à pression nulle, le démonstrateur de capteur présente une nonlinéarité inférieure à 1 % et une dérive thermique par degré Celsius égale à deux cents millièmes. La simulation numérique indique que pour optimiser les performances du capteur ratiométrique, il faut que les deux voies de référence et de mesure soient identiques. Cet optimum peut être quasiment atteint en intégrant sur un substrat commun de silicium les deux convertisseurs. Les essais expérimentaux révèlent également des phénomènes d'interférences entre les oscillateurs véhiculés au travers des capacités de recouvrement des transistors MOS. La minimisation de ce problème peut s'obtenir en ajoutant une capacité de découplage suffisamment grande entre les oscillateurs. L'ensemble de ces résultats obtenus permet de conclure que les principes et les technologies utilisées sont adéquats pour développer une nouvelle famille de capteurs de pression miniatures relativement précis (de l'ordre de 1 % de l'étendue de mesure), peu coûteux et facilement interfaçables avec des réseaux de communication numériques.

1st International WDSA / CCWI 2018 Joint Conference, Kingston, CAN, 23-/07/2018 - 25/07/2018; International audience; In this manuscript, we consider the problem of optimally scheduling the restoration of a water distribution network with multiple failures after a disaster. The decisions made are the sequence of burst/broken pipes and leaks that need to be replaced or repaired, respectively, subject to constraints on workforce availability and physical hydraulic conditions. In order to sufficiently capture the objectives of the utility (\eg service levels, resilience loss and customer minutes lost without service), which are all pressure dependent, pressure driven leakage and demand models (PDM) are employed. The restoration decisions are modelled as time-dependent closure and opening of links and are simulated using a PDM in EPANET, propagating decisions as pressure-driven hydraulic constraints and computing a posteriori their impact on the multiple desired restoration objectives, some of which have trade-offs. The combination of discrete decisions with time-dependent couplings, and the presence of objectives that are conditional functions of demands met and time indices make it difficult to pose this optimal task scheduling problem as a standard numerically tractable mixed-integer programming problem. To make the problem tractable for the given large-scale water distribution system, we propose greedy heuristics that use a hierarchical decomposition of the decision space using structural properties of the network graph and hydraulics. Firstly, PDM simulations are used to sort the breaks and leaks from the biggest losses to the smallest, or determine visibility of the damages. In addition to solving the multi-criteria scheduling problem, we also use engineering principles to derive metaheuristic that can prioritise water loss reductions. The greedy algorithm is employed to iteratively schedule isolation and repairs by first stabilizing the system with the isolation of the biggest breaks; an alternative approach considers all objectives `equally'. With these we explore the trade-offs in response between water loss and resilience indicators. To enable the scheduling, we use graph decomposition techniques to identify the valves that need to be closed to isolate a hydraulic segment (\ie set of links sharing same closing valves) for replacement; this gives us a map (or look up table) that will be used in the scheduling. The map also includes information about the number of nodes isolated, unsatisfied demand when isolating each segment and the total pipe length of the segments. We also analyse the system flows, network pressures and how the depletion of tanks affects service levels. Using these, we make recommendations for improving the capacity of the system, including the improvement of pumping stations, installation of control valves and some pipe re-enforcement. The same greedy task scheduling algorithm is then used under these alternative network improvements, to show a much better response in all criteria.