WSP09829

• File Number: 8200.760
• Description: Yampa River General
• State: CO
• Basin: Yampa/White
• Water Division: 6
• Date: 1/1/1989
• Author: USGS
• Title: Simulation of Streamflow in Small Drainage Basins in the Southern Yampa River Basin - Colorado
• Water Supply Pro - Doc Type: Report/Study

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After optimizing SMAX, all other sensitive parameters were optimized
using the Gauss-Newton technique incorporated in the model (Leaves ley and
others,' 1983, p. 48). The objective function in this part of the optimization
was the sum of the squared differences between the observed and simulated
daily mean streamflow. As such, streamflow timing had a substantial effect
on the fitting of the included parameters. Optimized values for selected
parameters are listed in table 11 in the "Supplemental Data" section at the
back of the report.

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The observed and simulated annual streamflow volumes for each of the six
calibrated drainage basins after optimization are listed in table 4 for the
calibration period. The volumes of streamflow are not large for any of the
drainage basins, and the variability among water years in a specific drainage
basin can be substantial. For example, at streamflow-gaging station, Stokes
Gulch near Hayden (09244470), values of observed streamflow were 0 in. in 1977
and 2.10 in. in 1979. Small streamflow values and their variability make
calibration of the model difficult.

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RESULTS OF VERIFICATION

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An index of error is listed in table 4 by calculating the percent error
between observed and simulated streamflow volumes. Because of the small
values recorded, these percent errors can be extremely large and may not
indicate the actual differences observed; therefore, the absolute difference
between volumes of observed and simulated streamflow, in inches, also is
listed in table 4.

Values of observed and simulated annual streamflow volume. for each of
the six calibrated drainage basins for the verification period are listed in
table 5. Values of the absolute differences between observed and simulated
annual streamflow volume, in inches, are listed, and values of the percent
error between observed and simulated annual streamflow volume also are listed;
therefore, the calibration (table 4) and verification periods (table 5) can be
compared. The two Foidel Creek streamflow-gaging stations in region 1 had
values of absolute difference between observed and simulated annual streamflow
volume that ranged from 0.10 to 0.87 in., for the calibration period (table 4).
Values of absolute difference between observed and simulated annual streamflow
volume ranged from 0.20 to 1.22 in. for the verification period (table 5).

Values of absolute difference between observed and simulated annual
streamflow volume for Hubberson and Stokes Gulch streamflow-gaging stations
in region 2 ranged from 0 to 1.21 in. for the calibration period (table 4).
Values of the absolute difference between observed and simulated annual
streamflow volume ranged from 0.08 to 0.32 in. for the verification period
(table 5).

Values of absolute difference between observed and simulated annual
streamflow volume for Wilson and Jubb Creek streamflow-gaging stations in
region 3 ranged from 0 to 0.56 in. for the calibration period (table 4).
Values of absolute difference between observed and simulated annual stream-
flow volume ranged from 0.03 to 0.41 in. for the verification period
(table 5).

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