Rademacher Department Water Balance, Forecasting and Predictions Federal Institute of Hydrology (Bfg) Koblenz

Operational low flow forecasts

Silke Rademacher Department Water Balance, Forecasting and Predictions Federal Institute of Hydrology (BfG) Koblenz

KHR-CHR Workshop Low flows and droughts 25 & 26 September 2007, Würzburg

Operational low flow forecasts Page 1 Responsibility in Germany

• Navigability of ships and maintenance of large rivers: Federal Waterway and Navigation Administration (WSV)

• Flood defence, flood warning and forecasting service German Federal States

Operational low flow forecasts Page 2 Water Level Forecasting System WAVOS

Operational low water forecast Bundesanstalt für Hochwasser- Gewässerkunde, Vorhersagezentrale Koblenz Frankfurt (Oder)

Vorhersagezentrale Hochwassermeldezentrum Elbe, Magdeburg Rhein, Mainz

WAVOS Saar Hochwassermeldezentrum Hochwasser- Saarland, Saarbrücken Vorhersagezentrale Main, Hof

Operational low flow forecasts Page 3 Low flow forecasting along the Rhine

> 7 gauging stations: Oestrich, Kaub, Koblenz, Köln, Düsseldorf, Duisburg-Ruhrort, Emmerich

> Forecasting horizon: 48 hours

> Forecasting time: 7:00

> Daily Forecast: Water level at gauge Ruhrort ≤ 400cm

Operational low flow forecasts Page 4 WAVOS Rhine

> 1D hydrodynamic model >Rhine and Moselle (685 km)

Operational low flow forecasts Page 5 WAVOS Rhine

> Tributaries Rhine model > Maxau/Oberrhein > Rockenau/Neckar > Neubrück/Erft > Raunheim/Main > Hattingen/Ruhr >Grolsheim/Nahe > Schermbeck/Lippe > Kalkofen/Lahn > Trier u. Cochem/Mosel > Friedrichstal/Wied > Altenahr/Ahr > Menden/Sieg > Opladen/Wupper

Operational low flow forecasts Page 6 WAVOS Rhine

> 1D hydrodynamic model >Rhine and Moselle (685 km)

Operational low flow forecasts Page 7 WAVOS Rhine

> 1D hydrodynamic model >Rhine and Moselle (685 km) >Main (380 km)

Operational low flow forecasts Page 8 WAVOS Rhine

> 1D hydrodynamic model >Rhine and Moselle (685 km) >Main (380 km) >Moselle-Saar-Sauer (425 km)

Operational low flow forecasts Page 9 WAVOS Rhine

> 1D hydrodynamic model >Rhine and Moselle (685 km) >Main (380 km) >Moselle-Saar-Sauer (425 km) > Statistical model >Maxau/Rhein >Rockenau/Neckar >Fremersdorf/Saar

Operational low flow forecasts Page 10 WAVOS Rhine

> 1D hydrodynamic model >Rhine and Moselle (685 km) >Main (380 km) >Moselle-Saar-Sauer (425 km) > Statistical model >Maxau/Rhein >Rockenau/Neckar >Fremersdorf/Saar > External forecasts

Operational low flow forecasts Page 11 WAVOS Rhine

> 1D hydrodynamic model >Rhine and Moselle (685 km) >Main (380 km) >Moselle-Saar-Sauer (425 km) > Statistical model >Maxau/Rhein >Rockenau/Neckar >Fremersdorf/Saar > External forecasts > Forecaster’s estimate

Operational low flow forecasts Page 12 WAVOS Rhine

Operational low flow forecasts Page 13 WAVOS Rhine - Results

100 20

80 16

60 12

40 8 kleiner 10cm [%]

6 [cm] Standardabweichung

1-Tages-Vorhersage 20 4 Anteil der Vorhersagen mit einer Differenz einer mit Vorhersagen der Anteil 2-Tages-Vorhersage

Standardabweichung (1-Tages-VHS) 2 Standardabweichung (2-Tages-VHS) 0 0 Oestrich Kaub Koblenz Köln D`dorf Ruhrort Emmerich Vorhersagepegel Operational low flow forecasts Page 14 WAVOS Rhine - Results

100

80 fferenz zwischen

60 sagen mit einer Di einer mit sagen Pegel Oestrich 50 Pegel Kaub Pegel Koblenz Pegel Köln Vorhersage- und Messwert kleiner 10 cm [%] kleiner 10 cm und Messwert Vorhersage- 40 Pegel Düsseldorf

Anteil der Vorher Anteil Pegel Ruhrort Pegel Emmerich Auswertezeitraum: 01.07.2005 - 30.06.2007 30 12 24 36 48

Operational low flow forecasts Vorhersagedauer [h] Page 15 WAVOS Rhine

> 1D hydrodynamic model >Rhine and Moselle (685 km) 48h-Forecast ☺ >Main (380 km) >Moselle-Saar-Sauer (425 km) > Statistical model >Maxau/Rhein >Rockenau/Neckar >Fremersdorf/Saar > External forecasts > Forecaster’s estimate

Operational low flow forecasts Page 16 Low flow forecasting along the Rhine

> 7 gauging stations: Oestrich, Kaub, Koblenz, Köln, Düsseldorf, Duisburg-Ruhrort, Emmerich

> Forecasting horizon: 48 hours 96 hours > Forecasting time: 7:00

> Daily Forecast: Water level at gauge Ruhrort ≤ 400cm

> Dissemination via email to river headquarter and Internet (ELWIS)

Operational low flow forecasts Page 17 WAVOS Rhine

> 1D hydrodynamic model >Rhine and Moselle (685 km) 96h-Forecast >Main (380 km) / >Moselle-Saar-Sauer (425 km) > Statistical model Forecasting Range to short >Maxau/Rhein >Rockenau/Neckar >Fremersdorf/Saar > External forecasts Only for 2 tributaries available > Forecaster’s estimate ....

Operational low flow forecasts Page 18 WAVOS Rhine

> 1D hydrodynamic model >Rhine and Moselle (685 km) >Main (380 km) >Moselle-Saar-Sauer (425 km) > Statistical model >Maxau/Rhein >Rockenau/Neckar To obtain >Fremersdorf/Saar > a consistent forecast > External forecasts > with a adequate leadtime > Precipitation runoff model for all tributaries

Operational low flow forecasts Page 19 NL HBV Rhine D Precipitation runoff model

L > Catchment upstream of Lobith ( more than 160.000 km²) > 134 subbasins (each between 500 and 2.000 km²)

> time step: 1 hour F

CH Operational low flow forecasts Page 20 NL HBV Rhine D Development in cooperation with RIZA:

L > Flood forecast RIZA > case studies >Transnational effects of extreme floods at the Lower Rhine > Climate change

CH Operational low flow forecasts Page 21 WAVOS Rhine – FEWS DE

Operational low flow forecasts Page 22 WAVOS Rhine – FEWS DE Meteo Meteo Hydro forecasts External forecasts measurements measurements Hydro measurements FEWS – DE WAVOS Rhine forecast for tributaries

Rhine forecast

Operational low flow forecasts Page 23 FEWS DE Precipitation runoff model - input data

Phase Data Parameter Spatial Timestep Leadtime Resolution

Measured P, T 45 stations 1 h

TTRR station data Measured P, T 204 stations 6 h / 12 h synop station data

Initialisation Measured W 47 gauges ≤ 1 h water level

DWD weather forecast P, T ~ 7 km 1 h 78 h Local Model (LM) DWD weather forecast P, T ~ 40 km 3 h 174 h Global Model (GME) Forecast Forecast BAFU W gauge 1 h 67 h external forecast Rheinfelden

Operational low flow forecasts Page 24 WAVOS Rhine – FEWS DE Results

Pegel Köln (10 cm – Schwelle)

100

70 Pegel Köln (20 cm – Schwelle) 100 Pegel Köln 60 2-Tages-VHS (operat. 2007) 90 GME + manuelle Anpassungen 50 GME automatisch LM + manuelle Anpassungen 80 LM automatisch 40 HVZ + LM WAVOS + LM 70 Anteil der Vorhersagen mit einer Differenz kleiner 10 cm 10 kleiner Differenz einer mit Vorhersagen der Anteil HVZ + WAVOS + LM 30 Pegel Köln 12 24 36 4860 60 72 84 96 2-Tages-VHS (operat. 2007) Vorhersagedauer [h] GME + manuelle Anpassungen 50 GME automatisch LM + manuelle Anpassungen LM automatisch 40 HVZ + LM WAVOS + LM Anteil der Vorhersagen mit einer Differenz kleiner 20 cm kleiner Differenz einer mit Vorhersagen der Anteil HVZ + WAVOS + LM

30 12 24 36 48 60 72 84 96 Operational low flow forecasts Vorhersagedauer [h] Page 25 FEWS DE

One of the main sources for the increasing of uncertainty is the uncertainty in the weather forecast ⇒ Ensemble weather predictions ⇒ Project “Verification of Ensemble forecasting in the Rhine basin” ⇒ RIZA – BfG Cooperation /CHR -Project ⇒ WL | Delft hydraulics

Operational low flow forecasts Page 26 Verification of Ensemble forecasting in the Rhine basin • ECMWF-EPS ensemble (re-sampled as used in FEWS-NL) • 50 ensemble members + 1 control run • timestep 12h 07 6/20 • leadtime 240h 08/0 04 - • Spatial resolution ~ 80km 6/20 07/0 • COSMO-LEPS ensemble • 16 ensemble members •timestep3h • leadtime 5 1/2d 07 • Spatial resolution ~ 10km 5/20 21/0 07 - 1/20 09/0

Operational low flow forecasts Page 27 FEWS DE – Ensemble

Operational low flow forecasts Page 28 FEWS DE - Ensemble

Lahn Catchment Area

Operational low flow forecasts Page 29 FEWS DE - Ensemble

Operational low flow forecasts Page 30 FEWS DE - Ensemble

Operational low flow forecasts Page 31 FEWS DE - Ensemble

Operational low flow forecasts Page 32 FEWS DE - Ensemble

Operational low flow forecasts Page 33 Verification of Ensemble forecasting in the Rhine basin •What is the skill, reliability and potential utility of the ensemble in predicting events at different lead times? •What are the effects of scale on the skill of the ensemble predictions? •Do the high resolution ensembles available through COSMO-LEPS indicate a higher skill than the low resolution ECMWF-EPS ensemble where the scale issue becomes apparent?

Operational low flow forecasts Page 34 Verification of Ensemble forecasting in the Rhine basin •Several statistics commonly applied in verification of probabilistic forecasts were used • the Brier (Skill) Score, • the Ranked Probability • (Skill) Score • verification diagrams • Relative Operating Characteristic • Attributes diagram.

Operational low flow forecasts Page 35 Verification of Ensemble forecasting in the Rhine basin - Results •At low flows it is shown that the ensemble forecasts are a reliable indicator, with a high forecast skill for long lead times. •For the smaller catchments the skill of the ensemble forecast was clearly shown to deteriorate faster than in the larger catchments. •In all cases the ensemble forecast were demonstrated to have positive skill, meaning that there is utility in using ensemble in forecasting for the Rhine basin.

Operational low flow forecasts Page 36 Verification of Ensemble forecasting in the Rhine basin - Results • The period over which the ensembles have been verified is limited, with few events of significance occurring in the Rhine basin. As a result the skill in predicting rare events for which the forecasting system has been constructed has not been assessed, but can only be inferred on the results found for the evaluation period. • Relatively short period for which the COSMO-LEPS ensemble is currently available => Repeat the analysis in 1 to 1½ years when a more substantial set of ensembles is available, and if available a larger number of (extreme) events Operational low flow forecasts Page 37 Thank you for your attention !

Silke Rademacher Referat Wasserhaushalt, Vorhersagen und Prognosen Bundesanstalt für Gewässerkunde Am Mainzer Tor 1 56068 Koblenz

Tel.: 0261/1306-5858, Fax: 0261/1306-5280 E-Mail: [email protected] www.bafg.de

Operational low flow forecasts Page 38