WSP08883

• File Number: 8273.600.20
• Description: Colorado River Basin Salinity Control - Federal Agencies - USDA
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 4/1/1996
• Title: Grand Valley Salinity Project 1995 Annual Monitoring and Evaluation Report
• Water Supply Pro - Doc Type: Annual Report

N TABLE ..
1":1 GRAND VALLEY SALINITY CONTROL PROJECT
~ AVERAGE IRRIGATION WATER MANAGEMENT DATA
O'J BY CROPS, 1985-1995
Crop Years Irrig. Inflow Outflow Infil. SMD D.P. Irrig.
Monitored No. (in.) (in.) (in. ) (in.) (in.) Eff. (%)
ALFALFA 11 8 64.0 17.1 46.9 30.1 16.8 48
CORN 11 7 52.3 17.1 35.3 19.4 15.9 38
SMALL GRAIN 10 6 55.5 16.3 39.2 15.4 23.8 32
ORCllARD 10 6 50.1 12.6 38.9 30.3 8.6 60
GRAPES 7 14 33.4 2.6 30.8 24.5 6.3 74
BEANS 6 10 48.0 11.8 36.2 17.0 19.2 36
SOYBEANS 3 8 89.9 28.3 61.6 23.8 37.8 26

Infiltration Estimates:

'Application infiltration rates for each site were determined from
individual site summaries. The infiltrated depth was divided by the
number of hours per set to determine an application infiltration rate in
inches per hour. The average infiltration rates for the different soils
monitored on surface irrigation sites were determined and provided in
Figure 2. The infiltration.rates ranged from, 0.17 inches to 0.38 inches
per hour.

In the infiltration rate calculation, the wetted perimeter was not taken
into consideration and the data shown in Figure 2 is based on 100%
wetted acreage. Our field observations have shown that the wetted
perimeter on furrow irrigated fields is actually less than 50%. This
means that the application infiltration rates shown in Figure 2 could be
doubled for sites with every row irrigation to get an estimate ,of
average soil intake rate (a conservative estimate based upon having only
50% of the soil surface actually wetted). Alternate row irrigation is
also fairly common in the Valley. with this method, the wetted
perimeter may be assumed to be about 25%. In alternate row irrigation,
the application infiltration rates may be multiplied by a factor of four
in order to estimate soil intake rate.

Infiltration rate for the first irrigation is generally higher for
annual row crops, but not necessarily so for perennial crops. The
monitoring data indicates that for most soils, the infiltration rates
may be higher than previously thought. Irrigation M&E data from 1985 to
1989 also verifies this. Therefore, for salinity IWM planning purposes
"infiltration rate planning ranges" based on 1986 to 1990 M&E data have
been provided to the field office planners. These infiltration rate
ranges seem to provide a better estimate of projected deep percolation,
flow rate and irrigation efficiency. The planning infiltration ranges
and average infiltration rates from 1986 to 1990 are provided below.

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