WSPC04421

• File Number: 8064.100
• Description: Ute Tribes
• State: CO
• Basin: San Juan/Dolores
• Water Division: 7
• Date: 9/1/1986
• Author: Boyle Engineering
• Title: Agricultural Engineering Study - Southern Ute and Ute Mountain - Ute Indian Reservations - Task A Report - On-Farm Water Requirements
• Water Supply Pro - Doc Type: Report/Study

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2478

Estimates of ETp made with the above equation should be increased 10

percent for each 1000 meters altitude above sea level in arid and

semi-arid areas.

Crop coefficients must be based upon grass

reference crops.

1.3.4 Radiation Methods

Several solar radiation-based methods have been developed.

The

Jensen-Haise and FAO modified radiation methods, however, are the

most commonly used.

They are popular because they are generally

more reliable than the temperature methods without having the

complexity or data requirements of the combination methods.

Jensen-Haise

M. E. Jensen and H. R. Haise 9/ evaluated 3000
observations of ET as determined by soil sampling
procedures over a 35-year period. From these data they
developed the following linear equation for potential
ET:

ETp = Ct (T-Tx)Rs X 0.000673 lQ/

( 13)

in which:

ETp is potential evapotranspiration for a well
watered crop of alfalfa with 30-50 cm of top
growth in in/day,

T is average daily temperature, degrees F,

Tx is the intercept of the temperature axis
(Tx = 2.5 -0.14 (e2-el) - elev/550), with
elevation in meters, and

Rs is global solar radiation in langleys/day
(multiplied by .000673 to obtain in/day).

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