# Presentation: 265845

## Calibration (and more)

- Hydrology is more of an art than a science!

## 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

- Matching historical data
- Accuracy vs. Precision
- Calibration vs. Optimization

## Basic Thought Process

**Set Initial Parameter Values**

**Compute Hydrograph**

**Compute Objective Function**

**New parameter estimation**

**STOP**

## An Objective Function

- Some kind of measure....
- Sum of absolute residuals
- Sum of the squares
- % Error in Peak
- Peak-weighted Root mean square error – RMS (default method).

## What data do you need?

- What is the final goal – Apples to Apples!
- What is the 100-year flow and rainfall?
- Calibrate to a similar storm
- Don’t calibrate to a 1-inch rainfall if the 100-year rainfall is 7 inches! Remember how linear UHG theory is?
- A real storm with real data
- QA/QC – missing data filled!

## 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)

- 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

- 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)

- 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 (continued)

- Important considerations
- Model structure, simulation processes
- Effects of parameter changes
- Use of the forecast information

## 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**
**	****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/D****P****)**
**	****Conversion to mean temperatures**
**	****Consistency plots**
**MAPE - Mean Areal Potential Evaporation**
**	****Evaporation pan data**
**MAPE vs. Mean seasonal curve**

## 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

- 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