HydrologyWellAugmentationInSP

• File Number: 8420.500
• Description: South Platte River Basin Task Force
• State: CO
• Basin: South Platte
• Date: 8/1/2007
• Author: Charles F. Leaf
• Title: Review Draft Report Submitted to SPTF
• Water Supply Pro - Doc Type: Report/Study

ApPENDIX I

The ASCE Task committee on Definition of Criteria for
Evaluation of Watershed Models of the Watershed Manage-
ment Committee, Irrigation and Drainage Division (ASCE
Task Committee, 1993) has recommended the use of several
goodness-of-fit criterion for evaluating model performance.
The deviation of runoff volumes Dv, is one of the more simple
tests and is computed as follows:

D (%) = V-V' x 100
v V

[IA]

where V = the measured annual or seasonal runoffvolume,
and
V' = the model computed annual or seasonal runoff
volume.

The second basic goodness-of-fit criterion is the Nash-
Sutcliffe coefficient, R2, expressed as:

R2 = 1 -

n

L (Q.-Q'l
1 1
1=1

[2A]

n

L (Q. _ Q)2
1
1=1

In equations [IA] and [2A] above, Dv = 0 and R2 = 1, would
indicate a perfect fit respectively.

In equation [2A], ifR2 = 0, the model is doing no better than
using the average of the observed runoff. R2 = 1 denotes
perfect agreement between observed and simulated values.

Table 1 (A) summarizes computations of Dv and R2 for the
South Platte River at Julesburg for the 1947-1970 calibra-
tion period. Calculations ofDv for the 1975-1994 validation
period are summarized in Table 2 (A).

Table 1 (A)
Computation of: (1) Deviation to Runoff Volume, Dv and
(2) Nash.Sutcliffe Coefficient for Simulated 1975. 1994 Annual Water Yield at Julesburg, CO

Year V V' V-V' (V-V') 2 (V-V) (V-V) 2 Dv (%)
1975 255.4 255.1 0.3 .09 -205.66 42296.04 0.12
76 161.8 140.3 21.5 462.25 -299.26 89556.55 13.29
77 110.2 83.2 27.0 729.00 -350.86 123102.74 24.50
78 72.4 144.7 -72.3 5227.29 -388.66 151056.60 -99.86
79 474.5 634.3 -219.8 48312.04 13.44 180.14 -46.32
1980 1369.8 1472.5 -102.7 10547.29 908.74 825808.39 -7.50
81 232.7 64.2 168.5 28392.25 2378.19 5655787.68 72.41
82 138.6 86.0 52.6 2766.76 -322.46 103980.45 37.95
83 1433.1 1478.1 -45.0 2025.00 972.04 944861.76 -3.14
84 832.7 1292.7 -460.0 211600.00 371.64 138116.29 -55.24
1985 802.6 797.0 5.6 31.36 341.54 116649.57 .70
86 496.0 588.5 -92.5 8556.25 34.94 1220.80 -18.65
87 740.7 601.6 139.1 19348.81 279.64 78198.53 18.78
88 392.8 239.0 153.8 23654.44 -68.26 4659.43 39.15
89 211.9 102.1 109.8 12056.04 -249.16 62080.70 51.82
1990 266.6 192.1 74.5 5550.25 -194.46 37814.69 27.94
91 264.3 83.3 181.0 32761.00 -196.76 38714.50 68.48
92 370.9 295.1 75.8 5745.64 -90.16 8128.82 20.44
93 359.4 181.5 177.9 31648.41 -101.66 2033.20 49.50
94 234.8 120.8 114.0 12996.00 -226.26 51193.59 48.55
Total 462410.17 8475440.97
Mean 461.06 12.15
Std. Dev. 389.34 43.14

R2 = 1 - 462410.17 = 1 - .0546
8475440.97
R2= .9454
R =.9723

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