WSP06126

• File Number: 8200.750
• Description: San Juan River General
• State: CO
• Basin: San Juan/Dolores
• Water Division: 7
• Date: 6/1/1987
• Author: Wheeler and Assoc
• Title: Documentation for Animas River Hydrology Analysis - Historic and Virgin Flow Conditions - June 1987
• Water Supply Pro - Doc Type: Report/Study

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Irrigated areas along the Animas River and its tributaries (exluding the

Florida River) are located near the stream channel. Groundwater and surface

water return flows were estimated to return to the stream within one month,

resulting in a negligible return flow lag. Thus, stream depletion associated

with irrigation along the Animas River was estimated to be approximately equiva-

lent to the monthly consumptive use values.

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Examination of Animas River gage records and diversion records indicates

that sufficient water for crop irrigation was available and ample water was

generally diverted. Some isolated irrigation shortages may have occUlTed on

Basin, Junction, and Lightner creeks. Since these potential shortfalls are insignif-

icant in comparison with the overall irrigation water usage along the mainstem

Animas River, no attempt was made in the analysis to adjust the irrigation

depletion estimates to take into account such potential water shortages.

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Return Flows from the Florida Mesa

Diversions from the Florida River through the Florida Farmers Ditch

and Florida Canal provide an irrigation water supply for about 16,800 acres

of land on the Florida Mesa. Approximately Z5 percent of the Florida Mesa

area is within the drainage basin of the mainstem Animas River. It is assumed

that return flows from irrigation of this area return to the Animas River. The

timing of return flows is affected by the reuse of surface return flows on the

Mesa and variable topography and subsurface conditions. Based on the calcula-

tions summarized in the "Florida River Hydrology Analysis," return flows to

the Animas River from irrigation on the Florida Mesa are estimated to occur

on a lagged basis throughout the year. A summary of the estimated volume

of return flows from the Florida Mesa is provided below:

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Reach Where
Animas River
Return Flows Occur
1
Z
3
Totals

Florida River
Irrigated Area
(acres)
656
394
3,163
4,Z13

Average Annual
Return Flows
(acre-feet)
390
Z40
1,900
Z,530

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