WSP03457

• File Number: 8276.100
• Description: Grand Valley Unit - Colorado River Basin Salinity Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 4/1/1992
• Title: Grand Valley Salinity Project Monitoring and Evaluation Program -- 1990 Annual Report
• Water Supply Pro - Doc Type: Annual Report

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In cont~ast, the diffe~ences between sites 16 and 37 can be att~ibuted
to diffe~ences in soi I type and management p~actic:es. The i~~igation
system and c~ops a~e simi la~ but the~e is a vast diffe~ence in deep
pe~colation between the two sites, 0 inches at site 16 and 39.2 inches
at site 37. The data to date indicate that Hanksvi lie soi I is ha~de~
to manage because of uneven wate~ dist~ibution due to shaley soi I.

Eight of the monito~ed sites had deep pe~colation losses g~eate~ than
the ave~age fo~ 1990, 17 inches pe~ ac~e. Of the 16 sites also
monito~ed in 1989, only six sites had less deep pe~colation in 1990.
Sp~inkle~ sites, 33 and 36 showed some fai~ly high deep pe~colation in
1990 compa~ed to 1989. A field test of sp~inkle~ appl ication ~ates at
these sites indicated that the inflow mete~s we~e unde~estimating the
amount of flow to the sp~inkle~s. Adjustment of data showed wate~
appl ication to be highe~ than p~eviously estimated and this ~esulted
in showing la~ge~ deep pe~colation than befo~e. Data fo~ 1988 and
1989 wi I I need to be adjusted to ~eflect the inc~eased flow.

The ~esults in Table 6 show that fo~ most sites and c~ops, the actual
deep pe~colation is conside~ably mo~e than the acceptable deep
pe~colatjon fo~ leaching based on 15% of ETa value. O~cha~ds had deep
pe~colation less than 15% of ETa. Deep pe~colation of a~ound 5% of
ETa is adequate to keep excessive salts below the ~oot zone. A ta~get
of 15% deep pe~colation is used as being p~actical and achievable.
With the amount of data co II ected 50 fa~ on deep pe~co I at i on and 50 i I
sal inity levels, it is difficult to dete~mine any t~end. The amount
of deep pe~colation ~equi~ed in the G~and Valley to leach salts below
the ~oot zone can only be ~ecommended following seve~al yea~s of
i~~igation monito~ing. Refe~ to Pa~t 2 fo~ mo~e detai Is on soi I
sal inity monito~ing.

Detai led deep pe~colation values fo~ each site ar'e p~ovided in Table
7. These a~e shown in two fo~mats, as ac~e inches pe~ ac~e and as a
pe~centage fo~ each individual i~~igation event.

The ~esults fo~ each c~op a~e discussed below:

Alfalfa: Seven sites we~e monito~ed in 1990, of which sites five we~e
ur(de~ su~face i~~igation and two unde~ side~oll sp~inkle~ system
<Table 2}. All the seven sites monito~ed in 1990 we~e the same as
1989. Sixty nine i~~igation events we~e monito~"d on 175 ac~es of
alfalfa.

In 1990, the~e was an ave~age of 17.9 inches of deep pe~colation f~om
the seven alfalfa sites (Table 2) which was conside~ably mo~e than in
1989 (9.9 inches). It was also slightly highe~ than the 17.0 inches
ave~age deep pe~colation fo~ all 25 sites monito~ed. When only
su~face i~~igated sites a~e taken into conside~ation, the ave~age deep
pe~colation is 20.2 inches <Table 7}.

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