WSPC01380

• File Number: 8200.700
• Description: Colorado River Basin General Publications - Augmentation-Weather Modification
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 4/18/1986
• Author: WBLA Inc
• Title: Uses of Increased Flows Originating on the Arapaho National Forest - Final Report
• Water Supply Pro - Doc Type: Report/Study

treatment

00312?

area for a range of possible ratios of annual flow to mean annual

Page 21

flow (Column I), and also gives the associated annuual runoff for the

treatment area (Column 3).

Table III-I: Arapaho National Forest Runoff Increase

Ratio
Annual Runoff to
Mean Annual Runoff

Predicted Annual
Precipitation
(Inches)

Predicted
Annual Runoff
(Inches)

.26
.37
.45
.56
1.0
1.18
1.5;;
1.80
2.0
2.2
2.3

14.4
16.3
17.7
18.7
27.5
30.7
37.3
41.8
45.4
48.9
50.7

1.4
1.7
1.9
2.2
3.0
3.2
3.7
3.9
4.1
4.2
4.25 _

~

(2) Annual per-acre runoff increase was predicted as a function df annual

~

precipitation using WET., the computerized version of WRENNS (Troendle and Leaf,

1980), for the average site characteristics of the treatment area, assuming a 50

percent removal of overs tory in clearcut strips. Model results were modified

based on professional judgment (Troendle, USDA Forest Service) to yield

estimates of annual runoff increase per-acre (Table III-I, Column 3). These

estimates refer to the watershed area, not to the 50 percent actually clearcut.

(3) Aggregate runoff increase was calculated by multiplying runoff

increase per acre times the acreage available for treatment, (Table 11-1). It

was assumed that all runoff increases were diverted to the east slope and

reached the Colorado mainstream or otherwise reached points of use without

carriage losses, and that all vegetation treatments occurred prior to the

beginning of the study period and were maintained throughout the study period.