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Sainte-Foy-lès-Lyon, France

Jean-Baptiste N.,IRSTEA | Malaterre P.-O.,IRSTEA | Doree C.,Compagnie Nationale du Rhone | Sau J.,CNRS Fluid Mechanics and Acoustics Laboratory
Mathematics and Computers in Simulation | Year: 2011

Water 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 Manning-Strickler 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. © 2010 IMACS.

Guertault L.,IRSTEA | Camenen B.,IRSTEA | Peteuil C.,Compagnie Nationale du Rhone | Paquier A.,IRSTEA
Advances in Geosciences | Year: 2014

An analysis of the long term morphological evolution of the Génissiat reservoir (France) is provided. First, a methodology for bathymetric data processing and reservoir sediment volume budget calculation is described. An estimation of global uncertainties in volume calculation is proposed. The reservoir bathymetric budget for several dam flushing events and interflush periods is presented, showing the global decrease of deposited sediment volume with time. The spatial dynamics of the reservoir subreaches is highlighted and typical patterns in flush and interflush periods are identified. © 2014 Author (s).

Marty R.,Grenoble Institute of Technology | Zin I.,Grenoble Institute of Technology | Obled C.,Grenoble Institute of Technology | Bontron G.,Compagnie Nationale du Rhone | Djerboua A.,RHEA
Journal of Applied Meteorology and Climatology | Year: 2012

Heavy-rainfall events are common in southern France and frequently result in devastating flash floods. Thus, an appropriate anticipation of future rainfall is required: for early flood warning, at least 12-24 h in advance; for alerting operational services, at least 2-3 days ahead. Precipitation forecasts are generally provided by numerical weather prediction models (NWP), and their associated uncertainty is generally estimated through an ensemble approach. Precipitation forecasts also have to be adapted to hydrological scales. This study describes an alternative approach to commonly used limited-area models. Probabilistic quantitative precipitation forecasts (PQPFs) are provided through an analog sorting technique, which directly links synoptic-scale NWPoutput to catchment-scale rainfall probability distributions. One issue concerns the latest developments in implementing a daily version of this technique into operational conditions. It is shown that the obtained PQPFs depend on the meteorological forecasts used for selecting analogous days and that the method has to be reoptimized when changing the source of synoptic forecasts, because of the NWP output uncertainties. Second, an evaluation of the PQPFs demonstrates that the analog technique performs well for early warning of heavy-rainfall events and provides useful information as potential input to a hydrological ensemble prediction system. It is shown that the obtained daily rainfall distributions can be unreliable. A statistical correction of the observed bias is proposed as a function of the no-rain frequency values, leading to a significant improvement in PQPF sharpness. © 2012 American Meteorological Society.

Le Coz J.,IRSTEA | Hauet A.,Electricite de France | Pierrefeu G.,Compagnie Nationale du Rhone | Dramais G.,IRSTEA | Camenen B.,IRSTEA
Journal of Hydrology | Year: 2010

Flash-floods that occur in Mediterranean regions result in significant casualties and economic impacts. Remote image-based techniques such as Large-Scale Particle Image Velocimetry (LSPIV) offer an opportunity to improve the accuracy of flow rate measurements during such events, by measuring the surface flow velocities. During recent floods of the Ardèche river, LSPIV performance tests were conducted at the Sauze-Saint Martin gauging station without adding tracers. The rating curve is well documented, with gauged discharge ranging from 4.8m 3s -1 to 2700m 3s -1, i.e., mean velocity from 0.02ms -1 to 2.9ms -1. Mobile LSPIV measurements were carried out using a telescopic mast with a remotely-controlled platform equipped with a video camera. Also, LSPIV measurements were performed using the images recorded by a fixed camera. A specific attention was paid to the hydraulic assumptions made for computing the river discharge from the LSPIV surface velocity measurements. Simple solutions for interpolating and extrapolating missing or poor-quality velocity measurements, especially in the image far-field, were applied. Theoretical considerations on the depth-average velocity to surface velocity ratio (or velocity coefficient) variability supported the analysis of velocity profiles established from available gauging datasets, from which a velocity coefficient value of 0.90 (standard deviation 0.05) was derived. For a discharge of 300m 3s -1, LSPIV velocities throughout the river cross-section were found to be in good agreement (±10%) with concurrent measurements by Doppler profiler (ADCP). For discharges ranging from 300 to 2500m 3s -1, LSPIV discharges usually were in acceptable agreement (<20%) with the rating curve. Detrimental image conditions or flow unsteadiness during the image sampling period led to larger deviations ranging 30-80%. The compared performances of the fixed and mobile LSPIV systems evidenced that for LSPIV stations, sampling images in isolated series (or bursts) is a better strategy than in pairs evenly distributed in time. © 2010 Elsevier B.V.

This paper summarizes the main techniques for measuring and controlling river flows. Most of technological advances have been made in the course of the last twenty years with the development of ultrasound, radar and video technical. The limits of use of these equipments and/or precautions that the user must implement will be highlighted. It will be reminded the context and challenges of river flow measurements that are very different in the laboratory. Indeed, in situ measurements are dependent on natural inputs or hydraulic structures operations as well as the morphological evolution of the river, including deepening of the bed or further aggradation following the floods. It's easier to plan laboratory tests in terms of repetition tests of measuring range or the shape of the flow sections to represent. Some of these measurement techniques will be illustrated by CNR experience for its concession or through experience shared with other agencies. The range of methods can be divided in the following areas: gauging method according to volume (weighing, dilution) or discretization the field velocity (exploration of the velocity field with current meter or profiler) and transfer law (rating curve for weir in river or hydraulic structure, index velocity with its ultrasound sensors immersed or non intrusive sensors like radar and LSPIV). All these methods have advantages and disadvantages. It is suitable for each of them, especially for innovative technologies to test and compare them with proven methods. Most of the time, validation will occur after a period of observation. After this adjustment phase, the equipment will provide data which reliability has been controlled. In fact, it often takes time to be able to scan the full range of use of equipment in situ and to detect its limitations of uses in order to validate them. In the field of hydrometry, improving the measurement process goes often, if not always, through the sharing of experience between different organizations. Indeed, the issues and the types of rivers are so different that it is desirable to gather the knowledge to move forward efficiently. © 2014 Société Hydrotechnique de France .

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