WSP06888

• File Number: 8270.100
• Description: Colorado River Basin Water Quality/Salinity -- Misc Water Quality
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 4/1/1982
• Author: USDA
• Title: Colorado River Water Quality Improvement Program - Final Environmental Impact Statement for Lower Gunnison Basin Unit - Montrose and Delta Counties CO and Uintah Basin Unit
• Water Supply Pro - Doc Type: EIS

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needed for gro~th. Excess irrigation ~ater lost through deep percolation,
seepage from anfacm delivery ditches, and seepage from tailwater collection
ditches increases the totdl salt load by passing through the saline soil and
shale formation and resurfacing at the deeper manmade drains and natura! ""3shes

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IV
,:;.

TABLE 1\'-4
Sutl'1ARY OF SALT LOADISG AND POTESTIAL REDUCTIOJi
ATTRIBUTED TO IRRIGATED AGRICULTo~ IN THE LOwER GUKJiISOJi BASIN UXIT ~I

Source

Length of
Lateral
(miles)

Salt Loading
Quantity Potential Reduction
(------------tons/year---------)

Onfarm:
Head Ditch Seepage
Deep Percolation
Tailwaler Ditch Seepage
Subtotal Cofam

210,000
135,000
95,000
440,000

160,000
115,000
60,000
335,000

Off-farm !I
Small Laterals 2/
Large Laterals 3/
."lain Canals 4/
Subtotal Off-farm

135
210
140
4B5

25,000
110,000
65,000
200,000

20,000
90,000
55,000
165,000 51

Total 485 640,000 11 500,000
l/ Does not include data for laterals within the Uncompahgre Project Area
being studied by the USSR ~.Ihich contribute about 200,000 tons annually.
~/ Small laterals c~rry flo~ rate less than 20 cubic feet per second (cfs).
3/ Large laterals carry flo~ rates between 20 and 100 cfs.
4/ Main canals carry flow rate greater than 100 cfs.
~/ Reduction of this magnitude is not cost effective.

that ultimately convey the excess water back to the river.
drains occurs near the ground...'ater level. so essentially no
occur from the deep drains and ....ashes.

Flolo' in
seepage

these
losses

Volume of ditch seepage and deep percolation, determined for each of 26 drainage
areas, ....as used to calculate the salt load from each area. Although average
deep percolation is nearly constant, ranging from 0.8 to 1.5 acre-feet per
acre per year, the salt load from each area varies considerably, ranging from
0.1 to 9.6 tons per acre per year. This range in salt loads suggest examining
the total salt load from each drainage area and setting priorities for treatment.

Present Land and water Uses

Irrigated agriculture is well suited to the area. Three primary
crop groups comprise the major agricultural activities (See Table IV-S).
Pasture and livestock feed crops occupy about 55 percent (92,300 acres) of the
area, small grains and rolo crops are gro~n on about 39 percent (66,700 acres)
and fruit orchards and other crops occupy about 6 percent (12,000 acres).

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