WSP10689

• File Number: 8273.600
• Description: Colorado River Basin Salinity Control - Federal Agencies - USDA
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1994
• Author: USDA
• Title: Grand Valley Salinity Project - 1993 Annual Monitoring and Evaluation Report
• Water Supply Pro - Doc Type: Annual Report

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irrigation, the application efficiency will be very high and may
not necessarily be an indication of good irrigation. The seasonal
application for all sites (sl,lrface and sprinkler) is. provided in
Table 2. The table shows application efficiency to be 47% for
surface irrigation sites (20 sites) and 76% for sprinklers (2
sites). When surge/conventional sites and annual/perennial crops
are taken into account, the efficiency is 67%, 39%, 3$%, .and.51t
respectively. Application efficiency for .individualirrigation.
events are shown. under site summaries in Appendix D.

The overall seasonal irrigation application efficiency was 45t in
1991/1992 and 48% in 1993, which-are less than 1988 and 1989
figures (Table 4). This is considerably better than 1985, which
had an efficiency of 30%. A comparison of irrigation monitoring
data from 1985 to 1989.shows.that during this period irrigation. .
efficiency increased progressively from year to year, resulting in
less water application, reduced runoff, and deep percolation (Table
4). Nine years of monitoring data indicate the average application'
efficiency to be about 44t (Table 4). Appendix H provqides Annual
SUllllUary data for sites monitored between 1986 through 1992'.' '.:

Of the 20 surface' irrigated sites monitored in 1993, thirteen sites
(65%) had an irrigation efficiency of 50% or more, considerably
more than 1989 and 1988 where half the sites had more than 50t
efficiency. Efficiency at sites 16 and 31 decreased in 1993
compared to 1992 because of crop changes' from alfalfa to corn and
at site 54' because of land leveling.

In 1993 the variation in efficiencies for individual irrigations
ranged from 5.6% to 92.7% for surface irrigation and from 50.0t to
about 8l.lt for sprinklers (refer to Appendix D for more .details on
individual irrigations). The sites with poor irrigation
efficiencies generally were irrigated sooner and longer than
needed. Improper scheduling and long set times caused excessive
deep percolation on some of the sites. Irrigation1efficiencies can
.be improved at some sites with better irrigation scheduling and
adjustment of set times or inflow rates.

d.Surge and Conventional Irrigation Comparison: .

In 1993, initially, on three different fields, surge and
conventional sites were iocated side-by-side (separate acreages)
for comparison. However, one field with sites 15 (conventional)
and 41 (surge) had to be dropped because of equipment andhdata
collection problems. On the remaining two fields, 15 surge
irrigation events were monitored on about 14.6 acres; 15 I
conventional irrigation events on 21.9 acres were also monitored
(Table 5). Comparison of surge and conventional irrigation on the
same field with similar solIs indicated that with the use pf surge
systems there is a potential for reductions in water application;
reSUlting in tailwater and deep percolation reductions.

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