Yampa River Basin Water Resources Planning Model Final Report

• Description: Yampa River Basin
• State: CO
• State: UT
• State: WY
• Basin: Yampa/White/Green
• Water Division: 6
• Date: 2/1/1997
• Author: Boyle Engineering Coporation, Riverside Technology, Inc.
• Title: Yampa River Basin Water Resources Planning Model Final Report
• Water Supply Pro - Doc Type: Report/Study

4.3.21 Estimation of Annual Net Evaporation
The annual net reservoir evaporation was estimated by subtracting the weighted average effective
monthly precipitation from the estimated gross monthly free water surface evaporation.
Annual estimates of gross free water surface evaporation were taken from the National Oceanic and
Atmospheric Administration (NOAA) Technical Report NWS 33. The annual estimates of
evaporation were distributed to monthly values based on elevation through the distributions listed in
Table 4.3.2a. These monthly distributions are those used by the State Engineer's Office.
TABLE 4.3.2A
Monthly Distribution of Evaporation as a Function of Elevation (percent)
Month
Greater than
6,500 ft
Less than
6,500 ft
Jan
3.0
1.0
Feb
3.5
3.0
Mar
5.5
6.0
Apr
9.0
9.0
May
12.0
12.5
Jun
14.5
15.5
Jul
15.0
16.0
Aug
13.5
13.0
Sep
10.0
11.0
Oct
7.0
7.5
Nov
4.0
4.0
Dec
3.0
1.5
Table 4.3.2b shows the net monthly free water surface evaporation estimates for the Yampa River
basin.
TABLE 4.3.2B
Net Monthly Free Water Surface Evaporation (inches)
Month
Oct
Nov
Dec
Jan
Feb
I May
Jun
Jul
IAug
Se
Yam a
.13
-.01
-.11
-.12
-.03
.06
.15
.28
.40
.39
.29
.25
The following precipitation stations were used in the calculation of annual net reservoir evaporation
for the Yampa basin.
• Steamboat Springs
• Yampa
The Phase IIIa enhancements did not impact the annual net evaporation file.
4.3.3 EOM Content File - yampaT.eom
The historical EOM reservoir contents for the water years 1975 -1991 for each reservoir modeled in
the Yampa River basin are used by the baseflow simulation component to simulate reservoir storage
Reservoirs 4 -13