WSP00412

• 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

I

I

I

~
~
~
o

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

Additionally, anfarm improvements will include concrete ditches with headgates
and ports or notches, or pipelines and gated pipes with control valves that
accommodate semiautomatic timing devices to shut off the flow of water at the
prescribed lime.

Installation of semiautomatic timing devices for salinity control, although
encouraged by SCS, is optional, available to those who may want them, but not
reqUired for all who choose to participate in the program.

The third solution considered the effect of combining onfarm water management
with lining of the onfarm ditches. Under this third solution two levels of
implementation were examined. The minimum level a~sumes implementing basic
improvements in existing irrigation systems and practices suited to manual
lahar. The maximum level assumes reorganization of existing systems, including
making needed improvements in a sufficient reach of the off-farm water delivery
system to assure proper operation of the onfarm system. The maximum level
also includes the option for designing the onfarm improvements to accommodate
the use of semi automated timing devices to achieve a higher degree of precision
in controlling the time of each irrigation set and to reduce the manual labor
needed for irrigation. Cost estimates for concrete ditch lining shown for
each alternative plan include design and construction features needed to with-
stand freezing action resulting from carrying winter water for livestock.

Plan formulation included evaluation of the 26 watersheds for levels of improve-
ment and t~~es of benefits to be derived. Alternative plans were formulated
under each level of improvement by grouping watersheds to emphasize two planning
objectives:

1. Maximize net benefits - onfarm and downstream.
2. Maximize salt load reduction.

Alternatives were formulated by adding treatment until net benefits approached
zero for each level of treatment. Results of formulating these alternative
plans are shown in Table IV-I.

The next step was to rank the alternative plans by increasing order of total
cost and to compare total cost with salt load reduction.

Off-Farm Lateral Improvements.

This USDA study extended the concept of onfarm ditch lining to include
improving the off-farm laterals that are outside of the Uncompahgre Project
Area under study by the Bureau of Reclamation. Improvement of these off-farm
laterals ~as considered in t~o parts. It is necessary that onfarm improvements
include improving a sufficient length of the distribution laterals to assure
proper operation of the onfarm system improvements. It was estimated that 80
percent of the small laterals should be included as an integral part of the
onfarrn system improvements at the maximum level. The remaining 20 percent of
the small laterals and all of the medium sized laterals are included in this
discussion of off-farm laterals. Improvement of large canals in Delta County
was not cost effective based on prelimlnary analysis of salt reduction benefits,
hut is scheduled for further study by the Bureau of Reclamation under their
planning for additional development of water resources in the area.

1,-3