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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2480

FAD Radiation

The FAD Radiation method is an adaptation of earlier work by G. F.

Makkink i/. Air temperature, sunshine, and cloudiness or

radiation data are required along with general levels of

humidity and wind. The recommended relationship is: .

ETp = c (W x Rs) (16)

in which:

ETp is grass based reference crop ET in mm/day,

Rs is solar radiation in equivalent evaporation in mm/day,

W is a weighting factor depending on temperature and
altitude, and

c is an adjustment factor depending on mean relative humidity
and daytime wind.

Tables and graphical solutions are presented in the original

document

to

determine

recently,

adjustment

factors. More

polynomial equations have been developed to speed calculation of

coefficients for all FAD methods using hand calculators or

programmable computers 12/. Equations are given in Appendix A-l.2

for each method.

1.3.5 Combination MethOds

The Penman equation is by far the most commonly used of the

combination methods.

.Combination" ~efers to the two components,

net radiation and advective energy.

It has the most extensive data

requirements of all the methods, but is capable of the most accurate

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