WSP00945

• File Number: 8442.400
• Description: Missouri Basin - Pick Sloan Project - Reports
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 2/28/1985
• Author: DoI, BoR
• Title: Lake Andes - Wagner Unit Planning Report / draft Enviromental Statement
• Water Supply Pro - Doc Type: Report/Study

The sodium absorption ratio ranges from 1.7 to 2.65 and averages about 2.

This water is classified as C2S1 (medium salinity hazard and low sodium

hazard) and is considered to be good quality water for irrigation.

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Other Water Sources

Lake Andes and Choteau Creek.--Other sources of surface water in the pro-

ject area include Choteau Creek and Lake Andes. Within the project boun-

dary, Choteau Creek is intermittent; flows, are closely related to

precipitation. In the lower 11 miles (from Dante to the mouth) flow is

supplied almost entirely by groundwater discharge from Choteau Aquifer.

The only water quantity and quality data available was a stream gaging site

near the mouth of Choteau Creek, operated by the USGS between May 1966 and

July 1970. The annual average flow at the mouth of Choteau Creek for the

period of record 1966-1970 was 15,900 acre-feet. Two water quality and

quantity recording stations were established in 1983 on Choteau Creek near

Wagner and Dante (Dante is downstream of the project area). Precipitation

in years 1983 and 1984 was exceptionally high. The flow at the site near

Wagner for water year 1983 was 51,420 acre-feet or ,more than three times

the average flow indicated in earlier data. Data, from the first half of

water year 1984 showed that flows will be as large or larger than 1983.

Even in these high water years, the flow in Choteau Creek is not sufficient

to supply the project. The water quality from Choteau Creek is also too

high in salinity for irrigation use most of the time. The mean of 10

samples taken from Choteau Creek near Wagner fr?m June 1983 to June 1984

showed a TDS of 1,014 mg/l with a minimum value of 550 and a maximum of

1,900 mg/l. Sixteen samples were taken at a site on Choteau Creek near

Dante which is downstream from the project. The mean TDS for these samples

was 1,428 mg/l, with a maximum value of 2,100 and a minimum of 630.

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Lake Andes is divided into three sections by dikes--a north, south, and
middle remnant. The majority of water is stored in the south and middle
remnants. At water surface elevation 1437, the capacity of the south and
middle remnants is about 31,400 acre-feet; at elevation 1428 the capacity
is about 1,400 acre-feet. Total surface area at elevation 1437 is about
5,000 acres (north remnant - 700 acres, south remnant - 1,800 acres, middle
remnant - 2,300 acres). Existing outlet works is at elevation 1437.0.

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