WSP07008

• File Number: 8273.600
• Description: Colorado River Basin Salinity Control - Federal Agencies - USDA
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 4/1/1994
• Author: USDA
• Title: Monitoring and Evaluation Report for the Lower Gunnison Colorado Unit of the Colorado River Basin Salinity Control Program - 1993 Annual Report
• Water Supply Pro - Doc Type: Annual Report

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Deep percolation and seepaae: salt pickup from irrigation is
directly proportional to the amount of deep percolation and
seepage return flow. Initial estimates for salt load in the
return flow water was 4.05 tons of salt per acre foot.

a) reduction in
Current vear
13,819
b) reduction in
1,169

salt loading (tons)
1993 Cumulative of prevo
25,061
deep perc./seepage (acre ft.)
1,340

vears

For FY93: 13,819 divided by 1,169 = 11.82 tons of salt per
acre foot of return flow.

NOTE: Salt loading continues to 'be a topic of discussion and
factors used to determine this'may well be further refined.
Communications are underway in follow-up to meetings held as
recently as November 1993. Among those items being addressed
are: 1) revised seepage and deep percolation factors, 2)
revised salt loading factors, J) proposed changes in practices
and acres to be treated in the original USDA salinity plans,
and 4) a salt load reduction worksheet.

S. Recom=endations
Although only one year of monitoring data has been evaluated,
it now appears that the following 8 recommendations found in
the 1991 Annual report for the Grand Valley, Colorado'unit are
also valid for the LGCU:

1) Producers need to be assisted in the proper management and
operation of an improved irrigation system immediately
after it is installed. '

2) Proper management of individual irrigation events requires a
knowledge of improved water management techniques. This
can be accomplished best when SCS field office personnel
can regularly work with individual irrigators on a one to
one basis during 'the irrigation season so that producers
will apply water based on crop needs. The SCS needs to
target those farmers that manage a large number of acres
with limited man-power, and part-time and week-end farmers.

3) Salt load reduction through IWM can only be achieved through
intensive technical assistance and education programs on
IWM techniques and crop economics tied to water
application. Demonstration projects on irrigation
scheduling would be very effective.

4) The SCS will need to follow-up on IWM design information
provided to farmers. Determine if recommended furrow
stream size, time of set, etc. for the new irrigation
systems are appropriate and are being applied.

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