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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Fort Coil ins, Colorado. The measured data parameters included wind
run, solar radiation, maximum and minimum temperatures, relative
humidity, and precipitation. The calculated ETp results were
ca Ii brated with ETp resu I ts gathered by the ARS on the Co I orado State
University Experimental Fa,-m in the Grand Valley.

Soil Water Deficit: The soil water deficit is calculated using the ETp
times a crop coefficient based on type of crop and stage of
development and an adjustment factor based on days since precipitation
or irrigation to simulate plant stress. The crop coefficient and
stress adjustments were supp lied by the ARS in Grand Junct i on and Fort
Co I I ins.

Deep percolation m.p.): Deep percolation equals the infiltrated water
depth minus the soil water deficit in inches at the time of each
irrigation. The deep percolation is calculated using a computerized
water budget program.

Seasonal IrriQation Efficiencv: The seasonal
expressed as a percentage, equals the volume
volume of outflow minus the deep percolation
divided by the volume of inflow.

irrigation efficiency
of inflow minus the
times one hundred,

IRRIG^TION MONITORING SITES

Table 1 shows the sites that have been monitored since 1985. Some of
these sites were also monitored in 1984. However, 1984 was the year
the monitoring program started and a ful I season of data was not
obtained at that time. Between 1985 to 1989, 27 different sites were
monitored. Since 1986, a few sites have been dropped and new ones
added each year so that at least 16 active sites are maintained
annu<llly.

Of the 16 sites installed in 1985, at least 8 of them were sti II being
mon i tored through 1989 <Tab I e 1>. The rema in i ng 8 sites have been
dropped because of various problems with maintaining these sites. Of
the 27 different sites monitored so far, 3 sites have 1 year of data,
8 sites have 2 years, 6 sites have 3 years, 2 sites have 4 years and
8 sites have 5 years of data <Table 1>.

Site 31 was partially monitored in 1987: a full season of data could
not be obtained at that time and also could not be monitored in 1988
since the land was put under the ASCS set-aside program. This site
was fully monitored in 1989.

In 1988,19 sites were initially established. Three sites from 1987
were dropped and 6 new ones added. However, one new site, #34 was
later dropped because only partial data could be obtained. This site
had a sideroll sprinkler system on small grain. The producer intended
to sell the land and therefore stopped irrigating after the first 2
irrigations. Site 10 was dropped in 1988 because the operator
i nd i cated that the i nf I ow

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