TEAM 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia I NTEREST OF DISTRIBUTED HYDROLOGICAL MODELS ( Mike SHE & HEC-HMS )

2 2 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-She comparison Conclusion HEC-HMS comparison 1) lumped = complete basin as single homogeneous element with average rainfall input 2) quasi-distributed = discretization of watershed into homogeneous sub-basins with single rainfall parameters based on topography 3) distributed = physically based, division into elementary unit areas as grid cells, solving equations in each cell Different types of models

3 much simpler than deterministic models obtained by aggregating or averaging the spatially variable processes usually not done in a formal mathematical manner rather, some simple assumptions are made which invariably start with continuity equation can’t be used for longer simulation periods considering groundwater infiltration and flow Model type - lumped 3 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-She comparison Conclusion HEC-HMS comparison

4 hydrological phenomena vary spatially and temporally in accordance with the conservation laws of mass, energy and momentum models based on conservation laws are physically- based laws expressed as partial differential equations (PDEs) solutions of PDEs on finite differences or finite element grid computationally demanding Model type - distributed 4 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-She comparison Conclusion HEC-HMS comparison

5 Loss MethodsCategorization Initial and constant rateEvent, lumped, empirical, fitted parameter SCS Curve Number (CN)Event, lumped, empirical, fitted parameter Gridded SCS CNEvent, distributed, empirical, fitted parameter Green and AmptEvent, distributed, empirical, fitted parameter Deficit and ConstantEvent, lumped, empirical, fitted parameter Transform MethodsCategorization User-specified unitEvent, lumped, empirical, fitted parameter Hydrograph (UH)Event, lumped, empirical, fitted parameter Clark’s UHEvent, lumped, empirical, fitted parameter ModClarkEvent, distributed, empirical, fitted parameter Kinematic WaveEvent, lumped, empirical, fitted parameter MethodsCategorization BaseflowLumped Channel Flow RoutingLumped HEC-HMS mainly lumped models Example of method’s categorization: 5 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-She comparison Conclusion HEC-HMS comparison

6 6 Fully Lumped Model based on mean value Quasi Distributed Example Using new Rainfall distribution based on Kriging method for each sub-catchments Distributed Model Inconvenient: Take time to build a model based on gridded file (.dss) Advantage: Good for long time computation window HEC-HMS 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-She comparison Conclusion HEC-HMS comparison

7 HEC-HMS Fully Lumped Model Vs Lumped Model Required parameters: 7 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-She comparison Conclusion HEC-HMS comparison

8 Fully Lumped Vs Lumped Model 8 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-She comparison Conclusion HEC-HMS comparison

Rainfall Distribution: Thiessen Polygons Lumped : assign 1 rainfall value for 1 polygon. Quasi distributed : Assign 2 rainfall values in 1 sub-basin. 9 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-She comparison Conclusion HEC-HMS comparison

Interpolation method : Best Linear Estimator Unbiased Could be interesting to apply with : More point of measurements, Taking into account the altitude, Taking into account the distance to the sea. Lack of data to built a variogram st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-She comparison Conclusion HEC-HMS comparison

Comparison In our case of study, the rainfall distribution method= Thiessen polygons 11 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-She comparison Conclusion HEC-HMS comparison

Fully distributed. The spatial and temporal variation of meteorological, hydrological, geological and hydrogeological data across the model area is described in gridded form for the input as well as the output from the model. Mike SHE model 12 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-SHE comparison Conclusion HEC-HMS comparison

Modelling Process Network : Manning MTopography Domain Thiessen Polygons and precipitation rates very complex and time consuming 13 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-SHE comparison Conclusion HEC-HMS comparison

Results 14 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-SHE comparison Conclusion HEC-HMS comparison

Results Mike SHE hydrograph doesn’t match observed/estimated discharge rates and peak time at Napoleon III - bridge although model is set up more precisely is doesn’t give more accurate results than lumped models Manning coefficients M can be adjusted, however no big influence is expected most likely destroyed sills/structures during the flood event responsible for “time-shifting” 15 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-SHE comparison Conclusion HEC-HMS comparison

CONCLUSION 16 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-SHE comparison Conclusion HEC-HMS comparison

CONCLUSION 17 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Are 5 rain gauges sufficient enough to distribute the rainfall well across the catchment? The observed/estimated discharge provided at Napoleon III Bridge is not accurate due to extrapolation of the rating curve. There is no justification in employing a complex, spatially distributed model when a simple one will suffice. Simpler models invariably have fewer parameters and are easy to calibrate. Definition Rainfall distribution methods Mike-SHE comparison Conclusion HEC-HMS comparison

Which model should we use? purpose (resolution of prediction) available data (spatially and temporal varying data – soil, landuse, precipitation, temp. and other forcing variables) time window (the more complex the more time needed) scale of the project (large – homogeneous / big – inhomogeneous catchment) budget (computational and engineering time are expensive 18 1 st Topic Presentation, Friday 18 th February 2011 Polytech’Nice - Sophia Definition Rainfall distribution methods Mike-SHE comparison Conclusion HEC-HMS comparison

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