WSP05706

• File Number: 8272.500
• Description: Colorado River Basin Salinity Control - Colo Dept of Public Health - WQCC and WQCD
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 7/21/1980
• Author: Kenneth Rennard
• Title: Estimating Erosion and Sediment Yield from Rangeland
• Water Supply Pro - Doc Type: Report/Study

170

WATERSHED MANAGEMENT

TABLE 2.--'-CHARACTERISTICS OF STOCK TANKS AT WALNUT GULCH AND OF T1iE
CONTRIBUTING WATERSHEDS

Tank Ora; nage Record Soil Measured annual
no. area 1 en9th associ at; anI Vegetation sediment
mi2 accumulation
ac-ft/mi2
2012 0.170 1960-70 Ri 11 ito-Karro Brush 0.49
1971-79 Gras s 0.13
207 D.42B i962-77 Rilli,to-Cave- Brush 0.11
Tortugas
20B 0.356 1973-77 Hathaway- Grass 0.13
Bernardi no
Cave-Ri 11 ito-
212 1.316 1964-77 laveen, and Brush 0.11
Tortugas
213 0.616 1962-79 Graham-House Brush/Grass 0.09
Mounta; n
214 0.581 1957-77 HathaWay- Grass 0.37
Bernardi no
215 0.136 1966-?7 . Hathaway- Brush 0.70
Nickel
216 0.325 1962-77 Hathaway- Grass 0.51
Bernardino
223 0.169 1962-77 Rillito- Brush 0.30
laveen
1
2 From GeIdennan (1970) root plowed and reseeded in 1971
The tank drainage was
DISCUSSION OF RESULTS

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Tables 3, 4, and 5 sunrnarize the results of the investigation.
The values assigned to each of the nine factors used in the PSIAC method
(Table 3) were made usin9 some interpolation between the three yield
levels defined in the manual. This was consistent both with ~ know-
ledge of the watersheds and IllY familiarity with the method (I partici-
pated in its development). Several watershed estimates agree with the
observed data.

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ESTIMATING EROSION

171

TABLE 3.-SUMMARY OF THE VACTOR VALUES USED 10 ESTIMATE SEDIMENT YIELD
WITH THE PACIFIC SOUTHWEST INTERAGENCY COMMITTEE METHOD

Factor valuesl/ Computed annual
Tank sediment yield
number A B C 0 E F G H Total ac-ft/mi2
2 2 1 "5 0 10 10 36 0.28
201 B 5 5 B
G 5 5 B I.' 1 0 -10 5 10 25 0.19
207 2 2 B 2 B -8 - 5 10 5 24 0.18
20B 5 3 B 2 I -5 2 5 0 21 0.16
212 3 5 B 1 I 0 0 10 10 3B 0.30
213 2 2 B 2 5 -5 0 5 5 24 0.18
214 5 5 B 2 2 0 2 5 15 44 0.38
215 5 3 B 2 1 -2 0 15 15 47 0.42
216 5 5 8 1 2 0 0 10 5 36 0.28
223 5 2 B 2 0 -5 - 5 10 20 37 0.29
lThe factors are defined on p. 3 of the text. defi ned in the manual
2Some interpolation between the three yield levels
(9) was used.

TABLE 4.--PREDICTION OF SEDIMENT YIELD FROM WATERSHEDS AT WALNUT GULCH
USING HAXMANMETHOD (EQUATION 4)

Tank
number

Factor valuesl
X2 X3

Annual sediment yield
Y
X4 ac-ft/mi2

X12

-O.lBO
0.049
0.313
0.142
0.375
0.154
0.249
0.341
0.085

201 0.192 5.3 72 0
207 0.206 6.9 55 0
20B 0.179 8.6 47 0
212 0.206 5.B 41 0
213 0.206 11.0 46 0
214 0.216 B.6 52 0
215 0.216 8.7 44 0
216 0.216 12.0 52 0
223 0.206 9.4 65 0
IFactor values are defined on p. 5 for useo in Eq. 4. .
2Average temperature at Tont>stone is 63.1 F. Some adJustment was made
based on elevation differences between the !ont.stone weather station
and the pond (30F increase per 1000 ft elevat,on decrease).

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