WSP04649

• File Number: 8276.150
• Description: Grand Valley Unit-Colorado River Basin Salinity Control Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 2/1/1990
• Title: Draft 1989 Annual Report: Grand Valley Salinity Control Project Monitoring and Evaluation Program
• Water Supply Pro - Doc Type: Annual Report

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Smal I qrain: Two fields were monitored in 1989. Of the 2 fields,
site 29 was in small grain in 1988 and site 37 was in beans. A total
of 56 acres in small grain was monitored, or less than 1% of the 7,500
acres in the Grand Va I I ey <Tab I e 7).

The average deep percolation for the 2 smal I grain sites was 25.9
inches (Table 8), or about 200% of the average deep percolation for
a II 19 sites <12.3 inches). The average deep perco I at i on losses for
smal I grain was 9 times more than the acceptable deep percolation
requ i red for leach i ng purposes <Tab Ie 4).

Sites 29 and 37 had excessive deep percolation and was 35% over the
plant water requirements for small grains <Table 4). Site 29
increased deep percolation from 6.6 inches to 30.0 inches and reduced
application efficiency from 42 to 25% in 1989 compared to 1988. At
site 29, approximately 45% of deep percolation occurred by the end of
the second irrigation <Table 8).

Site 37 was in beans in 1988 and fa II gra i n in 1989. There was not
much change in seasonal efficiency and deep percolation between 1988
and 1989, although there was a change in crop. This site had
approximately 60% of deep percolation losses by the end of second
irrigation <Table 8).

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With small grain, the general trend in the Valley is to "black over"
the field during the first irrigation in the fall. Consequently, on
the average, about 50% of deep percolation losses occurred by the end
of the second irrigation at these 2 sites <Table 8). Both operators
,-eceived irrigation monitoring data and soil moisture deficit ^'
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information during the irrigation season to help them with their water "
management decisions. The operator at site 29 irrigated approximately,~'
every 2 weeks when 40 to 50% of the ava i I ab I e so i I mo i sture had been '\
depleted. However, his i,-rigation set times were much too long which \
increased deep percolation and reduced irrigation efficiency.

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Orchard: Three sites covering about 19 acres were monitored in 1989,
the same as 1988. There are over 3200 acres of orchard within the
Grand Va II ey <Tab Ie 7) and the mon i tored sites represent I ess than 1%
of the total orchard acreage.

The 3 monitored sites include 2 apple orchards and 1 peach orchard.
The average deep percolation for these sites was 4.3 inches (Table 8)
in 1989, down from 12.1 inches in 1988 <Tab I e 6). The average deep
percolation was close to the acceptable deep percolation (Table 4)
necessary to keep salts below the root zone. This is a substantial
improvement from 1988 where the average deep percolation was about 3
times more than the acceptable deep percolation.

Sites 14 and 18 had no deep percolation
and 0. 1 i n c h e s de e p per C 0 I at ion i n 1988,

in 1989 <Tab I e 8) but had 18.0
respectively. Site 18

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