Presentation on theme: "Modelling the rainfall-runoff process"— Presentation transcript:
1Modelling the rainfall-runoff process Available Rainfall Runoff (RR) models:UHMNAMSMAPURBAN
2Modelling the rainfall-runoff process (NAM) POTENTIAL EVAPORATIONMODELPARAMETERSRUNOFF COMPONENTSEVAPORATIONRECHARGE
3NAM : “nedbør-afstrømnings model” Describes the land phase of the hydrological cycleThe NAM is a lumped, conceptual model:lumped catchment regarded as one unit.parameters are average valuesconceptual based on considerations of thephysical processesSimilar models: Stanford, SSARR, HBV, SMAR,..
4Types of Application General hydrological analysis - runoff distribution- estimates of infiltration / evaporationFlood Forecasting- subcatchment inflow to river model- links to meteorological modelsExtension of streamflow records- advanced gap-filling- improved basis for extreme value analysis etc.Prediction of low flow- for irrigation management- for water quality control
6NAM, Initial conditions Data to be specified:Initial Water Content of Surface and Root zone storagesInitial values for Overland flow and InterflowInitial Groundwater DepthRecommended to disregard the first half year or so of the results to eliminate erroneous Initial Conditions!
7NAM, Model CalibrationMost NAM Parameters of empirical nature => values must be determined by Calibration:Water balance in systemRunoff hydrographs, peak and shapeComparison of Runoff results with observationsGenerally recommended to change only one parameter between each run !
8NAM, Model Calibration1. Manual Step-by-step procedure (changing one variable at a time)2. Autocalibration Automatic optimisation routine using multi-objective optimisation strategy objectives: 1) Overall Volume error (= water balance) 2) Overall root mean square error (= hydrograph shape) 3) average root mean square error of peak flow events 4) average root mean square error of low flow eventsEasy to use - BUT EVALUATION OF VARIABLE VALUESREQUIRED TO JUDGE HYDROLOGICAL SENSIBILITY
12RR Input to HD Simulation Inclusion of Runoff results in River model:1) RR-simulation (produce RR Result-file)2) Specify Catchment definitions in Network Editor (input to single points or distributed along reach)3) Specify RR Result-filename in Simulation Editor