Title: | Model performance sensitivity to objective function during automated calibrations |
Authors: | Muleta, M.K. |
Year: | 2011 |
Journal: | Journal of Hydrologic Engineering |
Volume (Issue): | 17(6) |
Pages: | 1-27 |
Article ID: | |
DOI: | 10.1061/(ASCE)HE.1943-5584.0000497 |
URL (non-DOI journals): | |
Model: | SWAT |
Broad Application Category: | hydrologic only |
Primary Application Category: | calibration, sensitivity, and/or uncertainty analysis |
Secondary Application Category: | hydrologic assessment |
Watershed Description: | 116 km^2 upper subwatershed of the Little River Experimental Watershed in south central Georgia, U.S. |
Calibration Summary: | |
Validation Summary: | |
General Comments: | |
Abstract: | Previous studies have reported limitations of the efficiency criteria commonly used in hydrology
to describe goodness of model simulations. This study examined sensitivity of model
performance to the objective function used during automated calibrations. Nine widely used
efficiency criteria were evaluated for their effectiveness as objective function, and goodness of
the model predictions were examined using thirteen criteria. Two cases (Case I: using observed
streamflow data and Case II: using simulated streamflow) were considered to accomplish
objectives of the study using a widely used watershed model (SWAT) and good-quality field
data from a well-monitored experimental watershed. Major findings of the study include: (1)
Automated calibration results are sensitive to the objective function group, group that work
based on minimization of the absolute deviations (Group I), group that work based on
minimization of square of the residuals (Group II) and groups that use log of the observed and
simulated streamflow values (Group III), but not to objective functions within the group. 2)
Efficiency criteria that belong to Group I were the most effective when used as objective
function for accurate simulation of both low flows and high flows. (3) Group I and Group II
objective functions complement each other’s performance. (4) With regard to the capability to
describe goodness of model simulations, efficiency criteria that belong to Group I showed
superior robustness. 5) For the study watershed, use of the long-term inter-annual calendar day
mean as baseline model did not improve capability of an efficiency criterion to describe model
performance. (6) Even for ideal conditions where uncertainty in input data and model structure
are fully accounted for, identifying the so-called "global" parameters values through calibration
could be daunting as parameter values that were significantly divergent from predetermined
values produced model simulations that can be considered near perfect even when judged using
multiple efficiency criteria. |
Language: | English |
Keywords: | Efficiency Criteria, Calibration, Model Evaluation, Goodness-of-fit Criteria, Sensitivity Analysis, Objective Function |