WSP03721

• File Number: 8276.300
• Description: Lower Gunnison Basin Unit - Colorado River Basin Salinity Control Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 4
• Date: 12/1/1989
• Title: Colorado River Water Quality Improvement Program Lower Gunnison Basin Unit North Fork Area Preliminary Findings Report December 1989
• Water Supply Pro - Doc Type: Report/Study

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CHAPTER II

PIAN FORMULATIOO

Water quality samples collected over the period March 1976 to
October 1983 from four natural drainages wi thin this reach were used to
conduct the analysis. These drainages are Alkali Creek, an unnamed gulch
1/4 mile west of Dieter Gulch, Dieter Gulch, and Dry gulch. To estimate the
base flow concentration associated with these drainages, water quality samples
taken during the nonirrigation season of November through March were evaluated
to determine average TOS values.

The samples from Alkafi Creek were taken during periods of low flow
ranging from 0.1 to 0.3 ft Is and exhibited an average TOS value of
approximately 4,200 mg/L. This quality is considered to be representative of
the drainage's natural base flow condition.

A wide range of flows from 0.1 to 17.7 fe Is occurred in the unnamed
gulch durin~ the collection period. However, for periods where flow was less
than 1.0 ft Is the water quality values ranged from 2,940 to 5,960 mg/L.
These qualities are likely to be representative of this drainage's base flow
condition.

The flow weighted TOS of 2,917 ~/L for Dieter Gulch is based on a narrow
range of low flows from 0.2 to 0.4 ft Is. This value is based on a narrow
range of samples but appears to be significantly lower than the concentrations
for the other drainages in the reach.

The flow weighted TOS of 5,377 ~ for Dry Gulch is based on samples
taken within a range of O.l to 1.5 ft Is range from 2,100 to 10,900 mg/L and
are the highest observed for the four sampling locations in this reach.

None of the Alkali Creek drainage area, and only small portions of the
area in unnamed gulch, Dieter Gulch, and Dry Gulch are located below the canal
systems. Therefore, observed TDS concentrations are likely to be indicative
of natural salt loading conditions and not salt loading due to canal seepage.

The SCS soils map shows that the majority of the land above the North

Delta Canal is located on soils classified as Badlands. Badlands soils
consist of nearly barren outcrops of gypsiferous and saline shale with some
soil material. The mapping also shows that the majority of irrigated land
occurs on Billings silty clay loam which is deep, well drained, and moderately
fine textured. The Billings soil is a grassland type formed on alluvial fans
washed from adjacent exposures of gray and olive shale and siltstone. This
distribution of soils appears to support the assumption that the observed TOS
in this reach of the Gunnison River are due primarily to natural loading
conditions. Therefore, North Delta canal and lateral lining was dropped from
further consideration.

Colona area winter water replacement

Area Description

The Colona area is located approximately 3 miles south of the city of
Montrose, in Montrose and ouray Counties. Irrigation and winter stockwater
deliveries are provided by ten private ditch systems. The systems serve
approximately 6,600 acres of irrigated land. The ditches are the Heiland,

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