MOHICAN. MOdèle Hydrologique Intégré pour le calcul des Crues et l Amplitude des Niveaux d eau

Transcription

1 MOHICAN MOdèle Hydrologique Intégré pour le calcul des Crues et l Amplitude des Niveaux d eau Integrated hydrological Model for the calculation of floods and water levels FSAGx HA Prof. Mme Dautrebande ULG LGIH Prof. Monjoie ULG HYD Prof. Lejeune, Prof. Pirotton ULG CEME J. Smitz 1 st Meeting on Hydrology MET Namur (B) - June 27, 2000

2 MOHICAN : OBJECTIVES to obtain a deterministic representation of the dynamics of the watershed and of the hydrographic network under high flow conditions (floods) to improve the knowledge and simulation of floods and inundation processes to develop a decision-making tool, planning-oriented : - management of watersheds - management of hydrographic network (summer beds / winter beds)

3 MOHICAN : APPROACH integrated description of the water cycle. «soil» compartment. «groundwater» compartment. «hydrographic network» compartment for each compartment :. specific time scales / length scales / discretizations. deterministic, physically-based representations floods = waves => need to explicitly represent : propagation, transfer times, time lags,

4 Mohican : approach (cont.) spatial scales : basins from 100 km² to km² time scales : flows, water levels : hourly general structure of the model :. 1 module «soil». 1 module «groundwater». 1 module «hydrographic network». 1 module "supervisor"

5 «SOIL» MODULE (FSAGx HA) grid cell : 1 km x 1 km grid cell subdivided into non-georeferenced homogeneous elements (/ land use, soil type, slope, ) for each element of a grid cell : hydrological processes represented by the model hourly EPIC-grid computed variables : - vertical profile of humidity in the soil - runoff flux (hourly) - rapid hypodermic flux (daily) - slow hypodermic flux (daily) - flux to the groundwater (daily)

6 Fonctionnement général du modèle EPIC Précipitations Evaporation du sol Transpiration Couche 1 Couche 2 Couche n Infiltration Percolation 1 Percolation 2 Stock1 Stock2 Stock n Ruissellement Ecoulement latéral 1 Ecoulement latéral 2 Ecoulement latéral n Couche 10 Percolation n Percolation 10 Stock 10 Ecoulement latéral 10 Faculté Univer sitaire des Sciences Agr onomique s de Gemblou x Unité d Hydr au lique Agricole (Gén ie Ru ral) Prof. Mme S. Dautrebande

7 «GROUNDWATER» MODULE (ULG-LGIH) identification and delineation of hydrogeological basins and groundwater systems détermination of hydrogeological characteristics water pumping détermination of the transfer function of the groundwater (= response to a unitary pulse of percolated flux) :. utilisation of a deterministic model of the groundwater. deconvolution of the baseflow b(t) by the input function k(t) of the percolated flux determination of the outlets of the groundwater systems

8 Limons sur sables du Bruxellien Calcaires du Givétien, Frasnien et Viséen Limons sur craie (Crétacé),sur sables fins (Landenien) et sur sables argileux (Tongrien) Silurien altéré et limons sur Silurien altéré

9 «HYDROGRAPHIC NETWORK» MODULE (ULG HYD) spatial discretization : - level 1 : selection of rivers (explicitly described) - level 2 : longitudinal subdivision of the river (nodes) - level 3 : transverse sections : topography of summer and winter beds flow with active summer- and winter beds propagation of flood waves coexistence of various hydraulic regimes calculation of river flows, water elevation and extension of flooded areas

10 MOHICAN : COMPUTER CODE integrated code : 3 modules + supervisor module transfer of information and commands : MPI technique run on workstation option : run on multi-processors machine (IBM SP/2) utilisation of the model to reproduce past situations : - warm-up period - simulation period

11 "SUPERVISOR" MODULE (ULG-CEME) CALCULATION OF TRANSFERTS : SOIL-GRW-RIVERS Soils rivers runoff rapid hypodermic flux slow hypodermic flux Soils groundwater percolated water fluxes Groundwater rivers baseflow

12 Infiltration efficace Gestion des FLUX de MOHICAN Maille 1Km² Hypodermique Rapide Ruissellement Imp Directement Connecté Ecoulement MAILLE-RIVIERE Temps de transfert Réseau des Rivières explicitement décrites Hypodermique Lent Urbain Egoutté GROUND Nappe BV BV Urb

13 MOHICAN : RESULTS Tests on 5 representative watersheds : - Amblève 1071 km² - Lesse 303 km² - Méhaigne 340 km² - Hoyoux (Néblon) 216 km² - Semois 1324 km² + test on the Meuse basin in Wallonia + tests on the Geule (B/NL) and the Chiers (B/F) watersheds SIMULATION PERIODS : Tests warm up period : years 1989 and 1990 simulations : years (5 years)

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18 Bassin de la Chiers Comparaison des débits à Athus 21 Janvier au 1 Février 1995 Q Cal Athus Q Mes Athus Bassin de la Chiers Comparaison des débits à Athus 21 Janvier au 1 Février 1995 Prise en compte des zones d'égouttage Q Cal Athus Q Mes Athus

19 MOHICAN : CONCLUSIONS Innovative aspects : conception of the model integrated approach possibilities to test extended types of scenarios The first results show : the important role of the basin the role of the slow hypodermic flux significant effects of sewage systems (to be confirmed) positive effect of flooding areas