Presentation by Jan Verkade, Deltares, at the wflow - User Day (Developments in distributed hydrological modelling), during Delft Software Days - Edition 2019. Friday, 08 November 2019, Delft.

1. wflow and the River Suir operational flood
forecasting system, Republic of Ireland
Dr Jan Verkade, Bob van Rongen, Deltares
Delft, November 8, 2019

2. wflow and the Suir forecasting system – summary
• A wflow-HBV model was developed as an alternative to the existing semi-lumped models
• … continuous soil-moisture accounting rather than event-based model
• … allowing for future use of data-assimilation
• Streamflow data assimilation results in an increase of forecast quality
• Projected developments include
• … data-assimilation of satellite estimates of soil moisture
• … more appropriate rainfall interpolation technique

3. Brief introduction: Jan Verkade
• Hydrologist; expert in real-time hydrological forecasting
• Member of the Rijkswaterstaat River Forecasting Service
• Author of PhD dissertation “Estimating real-time predictive hydrological
uncertainty” (2015)
• Research interests:
• real-time hydrological forecasting
• uncertainty analyses; probabilistic forecasting
• forecast verification
• forecast use
http://bit.ly/verkade2015dissertation

5. Clonmel, Co Tipperary, Ireland
Clonmel town

6. Clonmel, Co Tipperary, Ireland, early September 2015

7. Clonmel, Co Tipperary, Ireland, October 2011

8. December 2015 precipitation events (Storms Desmond, Frank)

9. … these were required to protect the town from flooding
Photo credit: Joseph O’Dwyer, Tipperary Co Council
… but they take some time to be mounted
(‘some time’ >> concentration time of the basin)

10. Clonmel, Co Tipperary, Ireland, late December 2015
Photo credit: Joseph O’Dwyer, Tipperary Co Council

11. Forecast – warning – response chain
Source: Verkade, J. S. ‘Estimating Real-Time Predictive Hydrological Uncertainty’. Ph.D. dissertation, Delft University of Technology, 2015. http://dx.doi.org/10.4233/uuid:a7e8ac36-4bdb-4231-a11e-
d46778b2ae4a
Suir AFFS

12. How is a hydrological forecast produced?

13. 14 gauged sub-basins
Thurles
(16004)
Athlummon
(16001)
Beakstown
(16002)
New Bridge
(16008)
Rathkennan
(16003)
Aughnagross
(16005)
Ballinaclogh
(16006)
Caher Park
(16009)
Killardry
(16007)
Tar (@Tar Br,
16012)
Newcastle Bridge
(16137)
Nire
(@Fourmilewater,
16013)
Suir (@Clonmel,
16011)
Knocklofty
(16139)

14. wflow case: the Suir catchment
• semi-lumped catchment models in place: the “14-split URBS model”
• very reasonable results.
• Challenges:
• transitioning from dry to wet period.
• limited ability to apply data assimilation techniques
Ongoing research project:
• Set up a distributed hydrological model: wflow – HBV
• Allows for ingesting of remotely senses data, e.g. catchment wetness

15. the wflow Suir model
Fully-distributed HBV conceptual rainfall-runoff model:
• wflow framework (wflow-HBV)
• Grid size of 500x500 m
• Distribution of topography, land cover, soil types & input forcing data

16. Calibration and validation data
Data for HBV model:
• Precipitation (P)
• Temperature (T)
• Potential evapotranspiration (PET)
→ Direct shortwave radiation → Makkink equation
MÉRA (Met Éireann Re-Analysis):
• High resolution regional climate reanalysis for Ireland using
HARMONIE-AROME
• From 1981 to present
• Hourly timestep

17. Calibration approach: “Lumped to distributed”
• Use single parameter values across any of the sub-basins as starting point for parameter
optimization

18. https://doi.org/10.1016/j.jhydrol.2009.02.021

20. “Unsatisfactory” results for Fourmilewater basin
• Prompted student to look further
• Found: Streamflow @ Fourmilewater > (2 x Precip @ Fourmilewater’s catchment)
• Root cause: rainfall interpolation
• Inverse Distance based spatial interpolation
• Does NOT take into account presence of Knockmealdown mountain range
• Which DOES have an effect on the spatial distribution of precip
• We drafted a student research project to apply a more physics-based approach: genRE
Intermezzo – on precipitation estimates

21. Intermezzo – on precipitation estimates

22. Intermezzo – on precipitation estimates

23. Student assignment
• “Application of the genRE approach to spatial interpolation of precipitation gauge data”
• Assignment has been drafted and distributed to various Dutch, Irish universities
• Applications to
• Suir basin, using OPW telemetry network
• ROI, using Met Éireann’s telemetry network
• In both cases, develop ‘background grid’ using MÉRA
Intermezzo – on precipitation estimates

30. Data assimilation: the principles
Observations available up to
~now
Last update run ran at
midnight; note the model drift
Forecast run starts at end of update run
However: this means that some model
drift is present at t0 also:
• doesn’t look great
• Possible solution: data assimilation

31. Data assimilation
• Real-time forecasting: recent/current data may be available
• Q: how to effectively use this in the forecasting process
• A: data assimilation techniques
• Input updating
• State updating
• Parameter updating
• Output updating = error correction
www.openda.org

35. Suir AFFS / wflow – projected developments
• Include data-assimilation procedures in operational system
• Explore assimilation of satellite observations of soil moisture

36. wflow and the Suir forecasting system – summary
• A wflow-HBV model was developed as an alternative to the existing semi-lumped models
• … continuous soil-moisture accounting rather than event-based model
• … allowing for future use of data-assimilation
• Streamflow data assimilation results in an increase of forecast quality
• Projected developments include
• … data-assimilation of satellite estimates of soil moisture
• … more appropriate rainfall interpolation technique

37. Jan Verkade
jan.verkade@deltares.nl, +31 6 5161 6107
Thank you for your attention!