WSP05106

• File Number: 8276.150
• Description: Grand Valley Unit-Colorado River Basin Salinity Control Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 12/1/1977
• Title: Final Report of the Grand Valley Salinity Study - On-Farm Program for Salinity Control
• Water Supply Pro - Doc Type: Report/Study

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SUMMARY

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:~' Overall objectives of the U. S. Department of Agriculture's participa-
tion in the Grand Valley Salinity Control Studies are to determine:

1. The contribution of salt loading from irrigated and related
upland areas; and

2. The opportunity for reducing salt loading through improvements
on irrigated farmland and reducing erosion and sediment
delivery from privately owned upland areas.

The Grand Valley contributes about 600,000 to 700,000 tons of salt
annually to the Colorado River. Most of the salt is leached from the
soil and the underlying Mancos shale, and carried to the river by deep
percolation from irrigation and by seepage from the irrigation delivery
system. Of this amount on-farm irrigation practices and systems con-
tribute about 300,000 tons while runoff and erosion from upland areas
adds an additional 80,000 tons.

The plan selected for imp,lementation can be effective in reducing the
annual salt load from irrigated farmland by 130,000 tons at a total cost
of $21,050,000; an additional 4,000 tons of salt can be el iminated by
improvements on privately owned range and grazed woodlands at a cost of
$2,570,000. Treatment of publicly owned range and grazed woodland also
is needed to achieve significant reductions in sediment and salt origi-
nating from upland diffused sources.

The total effect of the selected plan is an estimated salt load reduction
of 130,000 tons (rounded) at a cost of $23,620,000. Technical assistance
during the 10-year implementation period is estimated to cost $378,000
annually including $178,000 for continuing the present program for irri-
gation research. The landowners' cost for operation and maintenance of
the improved system is estimated at $400,000 annually.

The selected plan is comprised of individual conservation plans to be
implemented by farmers and ranchers on land under their ownership or
control. The plan can be implemented by the U. S. Department of Agri-
culture through a~thority of PL-46. However, implementation at 75
percent federal cost share requires annual funding of $2,120,000 for 10
years, including technical assistance, a level that greatly exceeds all
previous funding. The annual funding needed from private landowners is
$790,000 including costs for operation and maintenance. Long-term
contracts with individual landowners is recommended in order to achieve
full implementation of the plan within ten years.

The selected plan Includes recommendations for management in addition to
physical improvements. Management practices necessary for control of
irrigation water include the size of streamflow, the number of irri-
gations, and the duration and frequency of each irrigation. Because of