Flow Measurements Instruments and Techniques Technical and metrological

Flow Measurements Instruments and Techniques Technical and metrological needs and efforts: The case of France Ouvèze River – Vaison-la-Romaine, South-East France – 22 th September 1992 WMO – Exploratory Meeting Assessment of the Performance of Flow Measurements Instruments and Techniques WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Summary 1. River flow measurements in France 1. floods, rivers and uses 2. hydrometric services 3. needs for methodology and metrology 2. Assessment of the instruments and techniques performance 1. uncertainties associated with various gauging methods 2. field tests and a. Dcp regattas 3. rating curves: uncertainty assessment and extension 3. Research on innovating methods 1. acoustic Doppler current profilers (a. Dcp, Groupe Doppler) 2. discharge monitoring systems 3. projects for video-based field measurements (LS-PIV) WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Flow Measurements Instruments and Techniques 1. River flow measurements in France 1. floods, rivers and uses 2. hydrometric services 3. needs for methodology and metrology WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Floods, rivers and uses in France • Floods = the most damaging natural hazard in France • River habitats: min. flow rates and max. water temperature (EU WFD 2000) • Most of the large rivers are regulated (excepted the Allier. Loire rivers) Lyon flooded by the Saône river in 1856 • Uses: water supply, industry, agriculture (irrigation), power generation (hydropower, cooling of nuclear power plants), navigation, tourism. . . WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Floods, rivers and uses in France Gard River, St-Nicolas Bridge, September 2002 • Specific technical challenges: • Influenced reaches (tides, shipping. . . ) • Flash floods: • Mediterranean belt • French tropical islands (Martinique, Guadeloupe, La Réunion…) Borne river (Ardèche catchment) WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ 27 m

The French galaxy of flow measurement • National hydrometric network Regional Environment Agencies (DIREN), Flood Forecast Services (SPC and SCHAPI), Ministry of Environment (MEDD), Météo. France • Hydropower industry Electricité de France (EDF), Compagnie Nationale du Rhône (CNR) • Waterways office Voies Navigables de France (VNF), Ministry of Infrastructure • Research institutes and laboratories Cemagref, IRD (Brazil, Africa. . . ), LTHE, CEREGE, universities. . . WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ Source: MEDD/DE/SCHAPI 2006

The French galaxy of flow measurement Real-Time Flood Forecast (SPC/SCHAPI/MEDD) www. vigicrues. ecologie. gouv. fr 4 warning levels Source: MEDD/DE/SCHAPI 2007 WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Needs for methodology and metrology • Accurate river flow measurements are requested for • hydrological research and studies • human uses (water supply, power plants, agriculture, …) • river management (flood risk, habitats…) • Technical and metrological difficulties • field deployment conditions (floods, night…) • rating curves: uncertainty assessment and extension • uncertainties associated with various gauging methods Source Cemagref Lyon • Innovating methods bring new solutions… and new problems! • need for standard procedures (field operations and data processing) • comparison with classical methods (and subsidiarity) • performance, limitations and uncertainty assessment WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Flow Measurements Instruments and Techniques 2. Assessment of the instruments and techniques performance 1. uncertainties associated with various gauging methods 2. field tests and a. Dcp regattas 3. rating curves: uncertainty assessment and extension WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Uncertainties associated with various gauging methods • U(Q)=5 -7% for current-meter discharges (ISO 748 & NF ENV 13005 “GUM”) • Current-meter and a. Dcp gauging comparison (CNR/Cetiat) Olivier et al. 2006, CNR/Cetiat Estimation des incertitude sur les débits des écoulements à surface libre déterminés par jaugeage à l'ADCP ou au moulinet 13ème Congrès International de Métrologie (Lille, France) WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Uncertainties associated with various gauging methods • QADCP uncertainty from comparison with current-meter (QCM ) (CNR/Cetiat, NF ENV 13005) (k=2) UADCP / QADCP U = bias + k * reproducibility = 7. 9 % UADCP = 4 -6 % UCM / QCM Olivier et al. 2006, CNR/Cetiat Estimation des incertitude sur les débits des écoulements à surface libre déterminés par jaugeage à l'ADCP ou au moulinet 13ème Congrès International de Métrologie (Lille, France) WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Field tests and a. Dcp regattas • Comparison tests performed by the different services (EDF/CNR/MEDD…) • Results for a. Dcp’s are being collected by the Groupe Doppler • Wide and open diffusion of the results (Internet? ) • Source EDF-DTG Grenoble Need for accepted protocols and comparison standards • suitable site (gauging requirements, logistics, safety…) • reference discharge values and hydrodynamical conditions • parameter configuration and deployment procedures (Ntransect = 6) • interpretation of the results Vignon 2006, EDF-DTG Comparaison des mesures avec divers ADCP: Broad-Band, Rio-Grande, Streampro (rapport technique) WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Rating curves: uncertainty assessment Uncertainty assessment based on standard NF ENV 13005 "Guide for the expression of the Uncertainty of Measurement" (1999) Rhône at Beaucaire (1994 -2003, 54 gauging values) U(Q) = 8 -10% Olivier et al. 2006, CNR Incertitude sur les débits calculés à partir des courbes de transformation hauteur/débit WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Rating curves: extension • A review of a set of 327 rating curves (Cemagref/MEDD, 2005 -2006) T < 1 yr (53%) 1 < T < 2 yr (7%) 2 < T < 10 yr (31%) 10 < T < 100 yr (8%) T > 100 yr (1%) Lang et al. 2006, Cemagref Review on the rating curves of the national French database (HYDRO) for flood discharge – 5 th FRIEND World Conference WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Rating curves: extension High-discharge extension based on hydraulic modelling (1 D/2 D) Hérault river at Ganges-Laroque Relative error : d. Q/Q=20 to 30% Lang et al. 2006, Cemagref Review on the rating curves of the national French database (HYDRO) for flood discharge – 5 th FRIEND World Conf. WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Flow Measurements Instruments and Techniques 3. Research on innovating methods 1. acoustic Doppler current profilers (a. Dcp, Groupe Doppler) 2. discharge monitoring systems 3. projects for video-based field measurements (LS-PIV) WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

The “Groupe Doppler” • A forum for French a. Dcp users (2005, CNR/MEDD/EDF) • Technical solutions, mobile bed! • Metrological tests and comparisons • a. Dcp methodological guide (2007? ) Photos: DIREN RA & CNR Le Coz et al. 2007, Cemagref Uses of a. Dcp in rivers: a review (in French) – La Houille Blanche ADcp river discharge measurement: sharing experience (in French) – La Houille Blanche WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Discharge monitoring systems From continuous velocity sampling to discharge time series: VLSPIV • Transit time ultrasonic systems • Doppler flow-meters (small streams) • Horizontal a. Dcp (H-a. Dcp) • Radar Bragg diffraction • Video-based velocimetry (LS-PIV) Water level Quality of velocity estimates Assumptions on the velocity field structure WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ Bathymetry profile

Doppler flow-meters (small streams) Birgand, Benoist et al. 2005, Cemagref Mesure des débits à l’aide de débitmètres ultrasoniques Doppler - Cas des petits cours d’eau ruraux, Ingénieries – EAT, 41, 23 -38 Correlation between the mean velocity (Vm=Q/S) and the flow-meter velocity (Vc) WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Uncertainty u(S) in % Doppler flow-meters (small streams) Water depth h [metres] Estimation of the section area uncertainty for sections with different batter slopes: <23° (A&B) WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ vs. 40° (C&D)

Doppler flow-meters (small streams) Relative discharge error (%) at 4 Doppler flowmeter stations (against standard stream discharge measurements) WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

St-Georges H-a. Dcp (CNR, Saône river, Lyon) Width 75 m Streamwise velocity Influence of downstream dam (backwater) 3 beam H-a. Dcp 300 k. Hz (TRDI) Q computed from point velocity measurements through a theoretical vertical profile Parameters : z 0 and A 1 (VISEA-H; Van Rijn, 1986) 24 h (time step = 1 min) WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

z/h 0 St-Georges H-a. Dcp: a. Dcp dataset postprocessing u/<uref> Experimental unit profile ( z 0 , A 1 ) Surface coefficient (α=0. 91± 0, 04) H-a. Dcp vs. a. Dcp: DQ/Q <3% Le Coz et al. 2007, Cemagref/CNR Mean vertical velocity profiles from a. Dcp river discharge measurement datasets – 32 nd Congress of IAHR (Venice, Italy) WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

ua. H-a. Dcp/ua. Dcp St-Georges H-a. Dcp: performance evaluation Distance from H-a. Dcp [m] Problems: far-field, low flows… Empirical regressions (index velocity) Metrological analysis in progress Le Coz et al. 2007, Cemagref/CNR Experimental evaluation of a horizontal Doppler profiler (H-a. Dcp) – HMEM 07 (Lake Placid, USA) WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Projects for video-based field measurements (LS-PIV) • Principle of operation: tracking surface movements by image analysis • Geometric correction of images: surface velocities from [pixels/s] to [m/s] • Discharge computation from bathymetry profile and hydrodynamical assumptions on the velocity field structure • Performance assessment and potential error sources • Non-contact discharge monitoring (flash-floods!) • Collaboration: IIHR (Iowa City), LTHE (Grenoble) and Cemagref (Lyon) • Iowa City LS-PIV station (IIHR, M. Muste, A. Hauet. . . ) • Tests in 2005 -2006 (LTHE/Cemagref) : Arc river • The Ardèche river project 2007 -2008 (LTHE/Cemagref/CNR/SPC-GD) • Other application opportunities in France: Ain river, Guadeloupe Island, etc. WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

LS-PIV : tests during a dam release (Arc 2006) 10 -m high mast & remotely controlled video camera LS-PIV surface velocities & gauging transect Artificial tracers (cornstarch chips) WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

LS-PIV : tests during a dam release (Arc 2006) 77 m 3/s 113 m 3/s LS-PIV and simulated (Rubar 20 code) velocities Q_currentmeter (blue dots) Q_LSPIV (red dots) Q_rating curve (solid line) Jodeau, Hauet et al. 2007, Cemagref/LTHE/IIHR LSPIV technique to measure surface flow velocities during a reservoir flushing – HMEM 07 (Lake Placid, USA) WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Flow Measurements Instruments and Techniques Thanks for your attention. WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ

Flow Measurements Instruments and Techniques WMO CHy – Flow Measurements – Geneva, 2007/04/25 – J. LE COZ