WSP07539

• File Number: 8281.300
• Description: Colorado River Studies and Investigations - Colorado River Consumptive Uses and Losses Report
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 10/1/1991
• Title: Consumptive Uses and Losses in the Arizona Portion of the Upper Colorado River Basin for the Water Year 1990
• Water Supply Pro - Doc Type: Report/Study

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Consumptive Uses and Losses 18

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Although the water diverted for agricultural purposes is considered as
consumptive use in this report, a portion of the remaining surface water
on the Navajo Nation, excess to needs, does evaporate before reaching the
Colorado River. An attempt has not been made for this report to quantifY
these losses.

Uncertainties in estimating uses and losses exist, and the degree of variation
in the figures is presented. Fortunately, the areas with the highest degree
of uncertainty account for only a small percentage of the total consumptive
use. The largest component, industrial use of the NGS, is also the most
accurately monitored. The total annual value for estimated consumptive use
of water within the Arizona portion of the Upper Colorado River Basin for
1990 was 35,880 acre-feet, as shown in table 7.

Table 7.-Consumptive uee for
Arizona portion of Upper Colorado River Basin for 1990'

Total 1990 Uncertainty Percent
Consumptive Use Use (acre-feet)' of total
Industrial 20,720 620 68
Domestic and municipal 7,120 400 20
Livestock 1,600 460 4
Irrigation 3,620 1,450 10
Reservoir and stock
pond evaporation 2.920 --lli .J.
Total 36,880 1,860 100

, All numbers are rounded to the nearest ten (10). Values less than five (6) are rounded to
zero (0).
· The calculation ofthe total degree of uncertainty, represented as (rounded to acre-feet),
was computed by taking the square root of the sum of the individual uncertainties squared,
known as the quadratic sum. This method and nomenclature is used throughout this report.
This method was used because a simple sum does not account for the partial cancellation of
eITers occurring when calculating the total uncertainty derived from individual values that are
random and independent of each 'other. The individual uncertainties were set as a certain
percent of the value.