WSP04021

• File Number: 8062
• Description: Federal Reserved Water Rights
• State: CO
• Basin: Statewide
• Date: 9/1/1979
• Author: R Barry Nehring
• Title: Evaluation of Instream Flow Methods and Determination of Water Quantity Needs for Streams in the State of Colorado - September 1979
• Water Supply Pro - Doc Type: Report/Study

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27

Comparison of Predictive Capabilities of the Multiple
R-2 Cross and Incremental (IFG4) Methods

In addition to evaluating stream flow values, the capability
of the R-2 Cross and the IFG4 models for predicting average depth
and average velocity was evaluated. Predicted average velocity
varied considerably between model outputs. Variations in average
depth for a given transect were much less. In only five out of
fourteen stream reaches (the IFG4 Me~hod was not used on the South
Platte and East Rivers) did the average depth output between the
R-2 Cross and the IFG4 vary more than 0.1 fee~ and in 50 percent
of the cases the variation was 0.05 feet or less (Table 11).

Table 11. Comparison of multiple R-2 Cross and IFG4 methodologies
for average depth and average velocity predictions.
Av. Av. velo-
Number depth(ft) city(ft/sec)
of cross R-2 R-2
Stream name sections Cross IFG4 Cross IFG4
Cache la Poudre River, 4 0.65 0.63 1.18 0.67
Little South Fork
Carnero Creek, 8 0.33 0.33 1. 21 0.81
South Fork
Cucharas River 8 0.31 0.31 1.28 1.03
Cunningham River 7 0.24 0.52 2.09 0.43
Fryingpan River I 4 0.79 0.78 1.41 0.93
(Taylor Creek)
Fryingpan River II 3 0.70 0.75 1.09 0.80
(Castle View)
Fryingpan River, 6 0.38 0.49 0.83 0.60
North Fork
Fryingpan River, 5 0.40 0.53 0.66 0.67
South Fork
Gunnison River, 6 0.68 0.73 1.69 1.25
Lake Fork
Huerfano River 8 0.40 0.46 1.14 0.79
Rio Grande River, 6 0.58 0.63 1.27 0.93
South Fork
Sangre de Cristo Creek 8 0.25 0.34 0.92 0.65
St. Louis Creek 7 0.50 0.46 1.11 0.75
Williams Fork River 8 0.54 0.73 1.51 1.09
I & II