Calibration (and more)Calibration (and more)

Hydrology is more of an art than a Hydrology is more of an art than a science!science!

CalibrationCalibration

Calibration process Calibration process Estimation of parameter values which will minimize Estimation of parameter values which will minimize

differences between observed and simulated differences between observed and simulated streamflowsstreamflows

Calibration problemsCalibration problems Parameter interactionParameter interaction Non-unique solutionsNon-unique solutions Time-consumingTime-consuming InaccuraciesInaccuracies Non-linearitiesNon-linearities Lack of understandingLack of understanding

CalibrationCalibration

Matching historical dataMatching historical data Accuracy vs. PrecisionAccuracy vs. Precision Calibration vs. Optimization Calibration vs. Optimization

Basic Thought ProcessBasic Thought Process

Set Init ial Set Init ial Parameter Parameter

ValuesValuesCompute Compute

HydrographHydrograph

Compute Compute Objective Objective FunctionFunction

New parameter New parameter estimationestimation

STOPSTOP

An Objective FunctionAn Objective Function

Some kind of measure….Some kind of measure…. Sum of absolute residualsSum of absolute residuals Sum of the squaresSum of the squares % Error in Peak% Error in Peak Peak-weighted Root mean square error – Peak-weighted Root mean square error –

RMS (default method).RMS (default method).

What data do you need?What data do you need?

What is the final goal – Apples to Apples!What is the final goal – Apples to Apples! What is the 100-year flow and rainfall?What is the 100-year flow and rainfall? Calibrate to a similar stormCalibrate to a similar storm Don’t calibrate to a 1-inch rainfall if the Don’t calibrate to a 1-inch rainfall if the

100-year rainfall is 7 inches! Remember 100-year rainfall is 7 inches! Remember how linear UHG theory is?how linear UHG theory is?

A real storm with real dataA real storm with real data QA/QC – missing data filled!QA/QC – missing data filled!

Calibration SystemCalibration System

Parameter estimation/optimization and watershed Parameter estimation/optimization and watershed simulationsimulation

InputInput Point or areal estimates of historical precipitation, Point or areal estimates of historical precipitation,

temperature, and potential evaporationtemperature, and potential evaporation Initial hydrologic conditionsInitial hydrologic conditions

OutputOutput Basin areal averages for point value inputsBasin areal averages for point value inputs Simulated hydrographs for historical analysis or use in Simulated hydrographs for historical analysis or use in

ESPESP Parameter values for models in operational forecast Parameter values for models in operational forecast

and ESP systemsand ESP systems

Calibration System Calibration System (continued)(continued)

CharacteristicsCharacteristics Performs computations for few forecast points for Performs computations for few forecast points for

many time stepsmany time steps Uses operations tableUses operations table Compatible with operational system and ESPCompatible with operational system and ESP Produces graphical output for manual calibrationProduces graphical output for manual calibration Includes algorithms for automatic optimizationIncludes algorithms for automatic optimization

ApplicationsApplications Historical watershed simulationHistorical watershed simulation Model calibrationModel calibration

Model CalibrationModel Calibration

StrategyStrategy Select river systemSelect river system Prepare dataPrepare data

MAP - Mean Areal PrecipitationMAP - Mean Areal Precipitation MAT - Mean Areal TemperatureMAT - Mean Areal Temperature PE - Potential EvaporationPE - Potential Evaporation QME - Mean Daily DischargeQME - Mean Daily Discharge QIN - Instantaneous DischargeQIN - Instantaneous Discharge

Model Calibration Model Calibration (continued)(continued)

Calibrate least complicated headwater basinsCalibrate least complicated headwater basins Select calibration periodSelect calibration period Estimate initial parameter - observed QsEstimate initial parameter - observed Qs Trial and error using MCPTrial and error using MCP

Statistics, observed versus simulated plotsStatistics, observed versus simulated plots Proper approach to parameter adjustmentProper approach to parameter adjustment

Automatic parameter optimization - OPTAutomatic parameter optimization - OPT Fine tuning - MCPFine tuning - MCP

Calibrate other headwater areasCalibrate other headwater areas Calibrate local areasCalibrate local areas

Model Calibration Model Calibration (continued)(continued)

Important considerationsImportant considerations Model structure, simulation processesModel structure, simulation processes Effects of parameter changesEffects of parameter changes Use of the forecast informationUse of the forecast information

Data PreparationData PreparationMAP Algori thms - Mean Areal PrecipitationMAP Algori thms - Mean Areal Precipitation

Techniques for converting point precipitat ion measurements into areal measurements Techniques for converting point precipitat ion measurements into areal measurements and distr ibuting them properly in t imeand distr ibuting them properly in t imeDaily and hourly dataDaily and hourly dataGrid point algorithmGrid point algorithmThiessen weightsThiessen weightsGrid point versus ThiessenGrid point versus ThiessenTwo-pass algorithm - distribute daily, then est imate missingTwo-pass algorithm - distribute daily, then est imate missingConsistency plotsConsistency plots

MAT Algorithms - Mean Areal TemperatureMAT Algorithms - Mean Areal TemperatureMax - min dataMax - min dataGrid point algorithm (1/D)Grid point algorithm (1/D)Elevation weighting factorElevation weighting factorCentroid (1/DCentroid (1/D PP ))Conversion to mean temperaturesConversion to mean temperaturesConsistency plotsConsistency plots

MAPE - Mean Areal Potent ial Evaporat ionMAPE - Mean Areal Potent ial Evaporat ionEvaporation pan dataEvaporation pan data

MAPE vs. Mean seasonal curveMAPE vs. Mean seasonal curve

Historical Data AnalysisHistorical Data AnalysisGeneral Information Needed

• Station data on Calibration files

• Station history infro - obs times, changes, location, moves

• Topog map of basin

MAP Specific Information

Non- Mountainous Mountains

--basin boundary --isohyetal map

--station weights

MAT Specific Information--mean max/min temperatures

Non-Mountainous Mountains

--basin boundary --areal-elev curve

MAPE Specific Information--Evaporation maps

--mean monthly evap

--station weights

MAP3

• (re)check consistency

• generate time series of MAP

PXPP

• check consistency

• compute normals

MAT3• generate time series of MAT

MAT3• check consistency

TAPLOT3• get mean max/min for mean zone elevation

MAPE• check consistency

• generate daily time series of MAPE

Precipitation Temperature Evaporation