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National Weather Service River Forecast System Model Calibration. COMET Hydromet 00-2 7 March 2000 2290 East Prospect Road, Suite 1 Fort Collins, Colorado 80525. Calibration. Calibration process

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national weather service river forecast system model calibration

National Weather ServiceRiver Forecast SystemModel Calibration

COMETHydromet 00-27 March 2000

2290 East Prospect Road, Suite 1

Fort Collins, Colorado 80525

calibration
Calibration
  • Calibration process
    • Estimation of parameter values which will minimize differences between observed and simulated streamflows
  • Calibration problems
    • Parameter interaction
    • Non-unique solutions
    • Time-consuming
    • Inaccuracies
    • Non-linearities
    • Lack of understanding
calibration system
Calibration System

Parameter estimation/optimization and watershed simulation

  • Input
    • Point or areal estimates of historical precipitation, temperature, and potential evaporation
    • Initial hydrologic conditions
  • Output
    • Basin areal averages for point value inputs
    • Simulated hydrographs for historical analysis or use in ESP
    • Parameter values for models in operational forecast and ESP systems
calibration system continued
Calibration System (continued)
  • Characteristics
    • Performs computations for few forecast points for many time steps
    • Uses operations table
    • Compatible with operational system and ESP
    • Produces graphical output for manual calibration
    • Includes algorithms for automatic optimization
  • Applications
    • Historical watershed simulation
    • Model calibration
model calibration
Model Calibration
  • Strategy
    • Select river system
    • Prepare data
      • MAP - Mean Areal Precipitation
      • MAT - Mean Areal Temperature
      • PE - Potential Evaporation
      • QME - Mean Daily Discharge
      • QIN - Instantaneous Discharge
model calibration continued
Model Calibration (continued)
  • Calibrate least complicated headwater basins
    • Select calibration period
    • Estimate initial parameter - observed Qs
    • Trial and error using MCP
      • Statistics, observed versus simulated plots
      • Proper approach to parameter adjustment
    • Automatic parameter optimization - OPT
    • Fine tuning - MCP
  • Calibrate other headwater areas
  • Calibrate local areas
model calibration continued1
Model Calibration (continued)
  • Important considerations
    • Model structure, simulation processes
    • Effects of parameter changes
    • Use of the forecast information
data preparation
Data Preparation

MAP Algorithms - Mean Areal Precipitation

Techniques for converting point precipitation measurements into areal measurements and distributing them properly in time

Daily and hourly data

Grid point algorithm

  • Estimating precipitation at a point (1/D2)
  • Estimate: >least, <greatest
  • 100-150 points within basin
  • Normalize at each grid point, then renormalize

Thiessen weights

Grid point versus Thiessen

Two-pass algorithm - distribute daily, then estimate missing

Consistency plots

MAT Algorithms - Mean Areal Temperature

Max - min data

Grid point algorithm (1/D)

Elevation weighting factor

Centroid (1/DP)

Conversion to mean temperatures

Consistency plots

MAPE - Mean Areal Potential Evaporation

Evaporation pan data

MAPE vs. Mean seasonal curve

QME

QIN

historical data analysis
Historical Data Analysis
  • General 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

  • PXPP
  • check consistency
  • compute normals
  • MAT3
  • check consistency
  • MAPE
  • check consistency
  • generate daily time
  • series of MAPE
  • TAPLOT3
  • get mean max/min for
  • mean zone elevation
  • MAP3
  • (re)check consistency
  • generate time series
  • of MAP
  • MAT3
  • generate time
  • series of MAT

Temperature

Evaporation

Precipitation

sacramento model structure

E T Demand

Precipitation Input

Px

Impervious

Area

E T

Direct Runoff

PCTIM

ADIMP

Pervious Area

Impervious Area

Upper Zone

Surface Runoff

EXCESS

Tension Water

UZTW Free Water

UZFW

E T

UZK

Interflow

E T

Percolation

Zperc. Rexp

Total Channel Inflow

Distribution Function

E T

RIVA

Streamflow

1-PFREE

PFREE

Lower Zone

Free Water

Tension Water P S

LZTWLZFP LZFS

RSERV

Supplemental

Base flow

LZSK

E T

LZPK

Total Baseflow

Primary

Baseflow

Side

Subsurface Discharge

Sacramento Model Structure
hydrograph decomposition

Impervious and Direct Runoff

Surface Runoff

Interflow

Discharge

Supplemental Baseflow

Primary Baseflow

Time

Hydrograph Decomposition
sacramento soil moisture components

SAC-SMA Model

Precipitation

Impervious and Direct Runoff

Pervious

Impervious

Surface Runoff

Evaporation

Upper

Zone

Interflow

Supplemental Baseflow

Lower

Zone

Primary Baseflow

Sacramento Soil Moisture Components
initial soil moisture parameter estimates by hydrograph analysis continued
Initial Soil-moisture Parameter Estimates By Hydrograph Analysis (continued)

LZSK - Supplemental baseflow recession (always > LZPK)

Flow that typically persists anywhere from 15 days to 3 or 4 months

automatic optimization
Automatic Optimization
  • Program OPT3
    • Uses operations table
    • Compatible with MCP, OFS, ESP
    • Objective functions
      • Daily RMS error
      • Monthly volume RMS error
      • | S - O |**Exp.
      • | log S - log O | **Exp.
      • Correlation coefficient
      • Maximum Likelihood Estimator
automatic optimization continued
Automatic Optimization (continued)
  • Program OPT3 (continued)
    • Optimization schemes
      • Pattern search
      • Adaptive random search
      • Shuffled complex evolution
    • Buffer
    • Exclusion periods
    • Low flows
    • Convergence criteria
    • Optimize SAC-SMA, SNOW-17, UG, API-SLC, XIN-SMA