WSP04560

• File Number: 8271.300
• Description: Colorado River Basin Salinity Control Program - General Information and Publications - Reports
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 2/9/1994
• Author: John Hedlund
• Title: Salt Primer - Water and Salt Budgets
• Water Supply Pro - Doc Type: Report/Study

22

Ditch seepage

5.06 tons/acre foot for the east side and 2.04 tons/acre foot for
the west side. ..A~ ;<:,1-

USDA Program in Lower Gunnison: ~.

SALT LOAD ~~~UCTTnN )
1981 Report 1 computations
tons/vr ac ft/vr tons/vr
------------- ~
125, 0-60) .1~_,J.9..Q.._ \~V

35,000 5,000 16,200

SOURCES

Water and Salt Budaet:

USDA
Treatment

1,238 mi

Lateral Seepage SP,Z ~",....t; .!~4 mi
" .)f
Deep Percol. 169,000 (135,000)

Tailwater seeoaae

135 mi

60.000

33,800 108,100

c2-~

------

Ac.

115,000

USDA TOTAL

335,000

50,900 166,100

The water and salt budgets developed for the Lower Gunnison
salinity control unit in 1993 based on monitoring and evaluation
by USDA, ARS, CSU, EXT, USGS, and USBR shows a change in
potential salt load reduction. The revised salt load reduction
due to the USDA program is 166,100 tons/year or about one-half of
the anticipated reduction shown in the 1981 USDA report.

Chanaes:

Four basic changes in assumptions between 1981 and 1993.

1. The 1981 plan assumed treatment of 100 percent of the
" irrigated acreage-169,OOO acres; the revised assumption is
) 80 percent of the irrigated area or 135,000 acres would be
treated with the USDA salinity control program.

that

2. Monitoring data indicates that water is in onfarm ditches for
45 days which is about one-third the assumed time in 1981 and
subsequently lowers seepage and salt loading from earth ditches.
This lowers the 1981 value for anticipated salt load reduction
from 125,000 to 41,800 tons/year due to lining or piping earth
ditches.

>

3. No tailwater ditches are being lined and no lining is
anticipated; this eliminates the sal~oad reduction of 60,000
tons/year shown in the 1981 report. ~~:l--J &j);"t- wcv--:-f;;I-"""'J c.J~,\ t . .
. l\o\-c;...-,) s-,..;\I..,,,,,,,,,+- "'- ("'li->vJn...... eLl ""0.~t
4. Monitoring irrigation for the full season {ndicates about a ~~,~.-
foot of deep perculation. Deep percolation was assumed to be 3.5
inches, with a reduction to 1.6 inches in the 1981 USDA report
(p. 81). Based on monitoring, the reduction in deep percolation
is being revised to 3 inches for convential surface systems and
six inch reduction in deep percolation for trickle, sprinkler,
and gated pipe with surge valve systems due to better irrigation
water management.