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

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LOw^R GUNSISON SECTION

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A. Introduction

This portion of the supplement to the Colorado River Water Quality
Improvement Program EIS covers the cumulative effects of implementing the
anfacrn irrigation ~ater management and land treatment measures for the Lower
Gunnison Basin UnIt in Colorado. Environmental impacts of indiVidual conserva-
tion practice will be evaluated for each specific practice as it is planned
and implemented.

B,

Alternative Plans Evaluated

Introduction

This section discusses eight alternative plans that address four
levels of resource development for reducing the river's salt load. These
levels are: continuation of the ongoing USDA program (the no accelerated-
action), improved onfarm irrigation water management (the nonstructural alterna-
tive), improved onfarm ditch lining, and combining onfarm irrigation water
management with onfarm ditch lining with two options of onfarm system improve-
ments. One option requires manual labor, while the second option is adapted
to semi automated time controls for operation. Lining portions of the off-farm
delivery systems is displayed as a supplemental action for six of the alterna-
tives. The eight alternative plans are summarized in Table IV-I.

Plan Formulation

The three basic solution alternatives were scoped in plan formulation.
Under the first solution the effect of onfarm management of irrigation water
was examined. Effective and efficient irrigation requires uniform distribution
of water across the field while applying the needed amount of water. Land
leveling enhances opportunity for uniform distribution of ~ater. Measuring
devices are needed to measure the rate at which water is delivered to the
field. The duration of flow must be carefully timed to assure application of
the proper amount of water. Thus, the management only solution requires control-
ling the time of each irrigation set supplemented by land leveling and installing
water measurIng devices. This solution assumes that, using manual labor,
irrigators will irrigate to the recommended time of set thus reducing the
volume of deep percolation and volume of runoff from each field. The recommended
time of set, calculated for each field and crop, will be a part of the landowner's
conservation plan.

The second solution considers onfarm ditch lining where existing earth ditches
would be placed in pipelines, or replaced by gated pipe or impervious lining
to reduce seepage. A significant share of the salt load pickup is attributed
to seepage from earth ditches. Reorganization of onfarm systems will require
that water be delivered to the farm at the proper location, elevation, quantity,
and pressure suited to onfarm improvements. Therefore, the onfarm ditch lining
concept examined the cost and the effect of implementing a program for lining
existing onfarm ditches or installing pipelines. Ditch lining under the maximum
level of implementation includes improving a sufficient reach of the off-farm
~ater delivery system to assure proper operation of the onfarm improvements.

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