WSP07375

• File Number: 8210.140.20
• Description: Colorado River Basin Organizations and Entities - Colorado River Basin States Forum - California
• State: CA
• Basin: Western Slope
• Date: 7/2/2003
• Author: Robert W Johnson
• Title: Part 417 Determinations and Recommendations Imperial Irrigation District Calendar Year 2003
• Water Supply Pro - Doc Type: Report/Study

3367

Within lID, the climate (including low rainfall conditions) varies little from year to year,
as indicated by the total reference evapotranspiration (ETo) for the time period /987 to
2002, shown below in Figure 2 (Jensen/Walter Supplement 2003, p, 2),

Annual Reference ET and Annual Rainfall

_____,___________,__________,__u,_________'__ 20
18

100
90
80
~
~ 70
.c
~
,S 60
>-'
w 50
"
~ 40
c
"
"
..!! 30
~
0: 20
10
0

.

16 U'l
~
14 "5
c
12 ~
"
10 "E
.~
8

"
6 ~
c
4 "

2
o

1987 1988 1989 1990 1991 1992 1993 1994 1995 19961997 1998 19992000 2001 2002

1- Annual Rainfall · Ref-ET - Avg-Ref-ET I

Figure 2,

Total annual reference ET (ETo) and rainfall in the Imperial
Irrigation District (Source: Jensen/Walter Supplement 2003, p, 2)

This figure identifies an overall average reference ET of 76,2 inches for the period with a
standard deviation ofanJluaJ reference ET of3,2 inches, and a coefficient of variability of
4,1% (a small amount of variation in statistical terms), This figure supports the
conclusion that there are stable climatic conditions in the Imperial Valley, as evidenced
by the small amount of variation around the mean, For purposes of this determination It
is appropriate Reclamation concludes that 2003 climatic conditions within lID will
continue the historical pattem of recent years and will remain stable,

FACTOR 3. LAND CLASSIFICATION

Part 417,3 identifies land classification as a factor to be analyzed, The primary source of
sorls infonnation data for the Imperial Valley area is from the United States Department
of Agriculture's Soil Conservation Service (SCS): "Soil Survey of Imperial County,
California", ZImmerman, USDA, SCS, 1981. Several of the teclulical consultants
providing information and data to Reclamation discussed this factor and reviewed the

July 2, 2003

16

Determinations and Recommendation<;
For liD - Calendar Year 2003