B-3-17
3.4.2 Validation Results
Validation involves using the calibrated model to generate the data for comparison with a second
independent set of information consisting of field measurements of the same type as the data output from
the model. If the test results lie within an acceptable limit, the calibrated model is considered valid.
Generally, the calibrated Little Wabash River HSPF model was validated by comparing simulated flows
with observed flow from four stations at Effingham, Clay, Wayne, and Carmi from 1993 to 1994. Table
B.3-5 summarizes the validation statistics. It shows that the calibrated HSPF model predicted flows with
an overall accuracy of 15 to 25 percent. This performance is comparable to that of the calibration.
TABLE B-3-5. SUMMARY OF FLOW VALIDATION FOR LITTLE WABASH RIVER
FROM 1993 TO 1994
Total Runoff Volume
(inches)
50% Lowest Flow
(inches)
10% Highest Flow
(inches)
Outlet Location
USGS
Gauge
No.
HSPF
Sub-basin
Code Observed Simulated Observed Simulated Observed Simulated
Little Wabash River at
Effingham Station 03378635 8 38.20 30.70 1.10 0.96 26.40 24.40
Little Wabash River at
Clay Station 03379500 11 34.00 32.50 1.30 1.60 19.50 21.10
Skillet Creek at
Wayne Station 03380500 5 37.70 31.20 0.66 1.03 27.30 22.28
Little Wabash River at
Carmi Station 03381500 17 36.30 30.10 1.81 2.41 13.80 18.00
3.5 Modeled Fox River Flow Data Results
The calibrated model was used to generate flow data for the Fox River. Figure B.3-6 shows the simulated
flow at the mouth of the Fox River (RCH3) and at the mouth of Sub-basin No. 1 (RCH1) (see Figure
B.3-2). No flow data are available to further validate the simulated flow in Fox River. The simulated
flow reflects actual flow conditions and seasonal variations given that the Fox River is a first-order
tributary to the Little Wabash River. The upstream segment in Sub-basin No. 1 has a flow close to zero in
October and November 1999. It was confirmed that the upstream portion of the Fox River is ephemeral
during Tetra Tech’s site visit. The downstream segment (RCH3) experienced low flow when there was
no rainfall in the watershed for a long time. At such times, the Onley STP contributes the primary flow.
The model results replicate a low flow close to the Olney STP average discharge rate of 3 cubic feet per
second.
