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

I

2477

SCS Modified Blaney-Criddle

I

General form of the consumptive use equation

is:

I

ET crop = Kc x Kt x t x P x .01
in which:

(ll )

I

ET crop is monthly crop consumptive use or ET in inches,

Kc is a monthly crop growth stage coefficient,

I

Kt is a climatic coefficient related to the mean air
temperature (Kt = 0.0173 t - .314),

I

t is mean monthly air temperature in degrees F, and

P is monthly percentage of daylight hours in the year.

I

Crop ET is computed directly wi thout the use of a reference ET or crop

coefficients.

Crop factors influencing ET are incorporated in Kc,

I

Crop growth stage coefficients for a numbe'i' of crops are presented in

I

graphical form in ]j. These coefficients are not universally

adaptable, however, they represent a starting point when other data

I

are not available.

I

FAa Modified Blaney-Criddle

Reference crop ET is calculated by the equation:

I

ETp = c

[p (.46T + 8)]

(12 )

in which:

I

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

I

T is mean daily temperature in degrees C over the
month considered,

I

P is mean daily percent of total annual daytime
hours for a given month and latitude, and

I

c is an adjustment factor relating to minimum
relative humidity, sunshine hours, and daytime
wind,

I

1-14

I

I