WSP00392

• File Number: 8276.150
• Description: Grand Valley Unit-Colorado River Basin Salinity Control Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 4/1/1992
• Title: 1991 Annual Report: Grand Valley Salinity Control Project Monitoring and Evaluation Program
• Water Supply Pro - Doc Type: Annual Report

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A total of 166 irrigation events were monitored in 1991. The
results of these irrigation events from 23 sites are shown in Table
2 as the 1991 Annual summary. The Table provides the annual
summary of each monitored site. Irrigation data from individual
sites are presented as site summary data in Appendix D. site
summary data from each monitored site is compiled and presented in
Table 2. The annual irrigation summary for the 23 sites in Table 2
as well as other tables also include data from surge and
comparative conventional sites to estimate an overall average for
the Grand Valley. Data from comparison sites are discussed in
detail under the section, "Surge and conventional irrigation
comparison".

The 1991 irrigation monitoring site data presented in Table 2 as an
Annual Summary indicate the following:

1. The average amount of water applied to the field was 56.4 acre
inches per acre for the 23 sites. When separated by surface and
sprinkler systems, water application was 58.3 acre inches for the
surface systems and 45.8 acre inches for the sprinkler systems.

2. Average water application for different crops varied from a high
of 70.3 inches per acre for alfalfa to a low of 39.8 acre inches
for grapes.

3. The actual evapotranspiration varied for different sites
on crops, time of planting and harvest date. Table 2 shows
average actual ET to be about 26.6 inches for the 23 sites.
broken down by surface and sprinkler systems, actual ET was
and 31.1 inches respectively.

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4. The average deep percolation was 15.9 inches for all 23 sites;
17.3 inches for the 20 surface sites, and 7.1 inches for
sprinklers. When the 20 surface sites are separated by surge and
conventional systems, the deep percolation is 14.0 and 19.9 inches
respectively. Deep percolation for different crops varied
considerably from 19.8 inches for alfalfa to 6.8 inches for grapes.
There is not much difference in deep percolation between annuals
and perennials; 15.2 inches versus 16.4 inches.

5. The seasonal application efficiency ranged from a low of 27% for
a fall grain site to a high of 76% for an orchard site. This
orchard site was the only site without any deep percolation. The
average efficiency for all monitoring sites was 45.4 percent.

6. Surface runoff from sites varied considerably ranging from a low
of 4.1 inches to a high of 39.5 inches. On the average, 14.9
inches of water coming to the field was lost to surface runoff, or
26% of the total water applied to the field.

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