PROJ00452

• Contract/PO #: FS0029X
• Contractor Name: Trinidad Project USBR 1964
• Contract Type: Miscellaneous
• Water District: 0
• County: Las Animas
• Loan Projects - Doc Type: Feasibility Study

Hydrology

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WATER SUPPLY

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The water supply analysis covers the 33-year study period,
1925-1957, which was judged to be indicative of future conditions,
At the gaging station, Purgatoire River at Trinidad, uninterrupted
records of stream flow are available for the entire study period.
Flows at this site, consisting of runoff from the 795 square miles
in the basin above the gaging station, are considered representative
of future inflow to Trinidad Reservoir. The annual flow at this
station by water years ranged from 16,300 in 1951 to 197,300 acre-
feet in 19~2, The average annual water year flow for the study
period was 62,100 acre-feet, Flows of like magnitude and variability
are expected to occur in the future.

WATER RNl,UIREMENTS

Much of the irrigation water supply comes from spring snowmelt
runoff or from summer rain storms which usually occur when available
supplies exceed the.requirements. The water supply is very erratic,
with considerable variation by season and from year to year, Usually
only a small portion of the water needed late in the growing season
is available.

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Table 3 shows the computed average annual water requirements
for the Trinidad Project, based upon the period 1925-1957.

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Table 3. --Average annual water requirement

Item

Acre-feet
per acre

Project total
(19,717 acres)

. ,....,.
>~, .;. ';~/ .:

Consumptive use requirement of crops '!:I
Less effective precipitation
Crop irrigation requirement
Add farm losses (30%)
Farm delivery requirement
Add canal and lateral losses C3~)
Diversion requirement at main canal
headgates

2.30
0.78
1.52
0.65
2.17
0.93

3,10

61,200

'!:I Computed by Lowry-Johnson method

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