PROJ00518

• Contract/PO #: C153484
• Contractor Name: San Luis Valley Water Conservation District
• Contract Type: Grant
• Water District: 0
• County: Rio Grande
• Bill Number: FSG
• Loan Projects - Doc Type: Feasibility Study

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Despite its high altitude, low precipitation and relatively short growing season,

the valley sustains a productive agricultural economy. The primary crops include

potatoes, barley and alfalfa.

11.3 WATER SUPPLY

The valley derives its water from surface and ground water sources. Overall

streamflow originates mainly from snowmelt on the San Juan and Sangre de Cristo

Mountains. The average annual (1924-69) water supply these mountains contribute

to the San Luis Valley has been estimated at 1.6 million acre-feet (Emery, 1973).

Approximately 225,000 acre-feet of the 1.6 million acre-feet was estimated by Emery

to accrue to the Closed Basin. A total annual water supply of 2.8 million acre-

feet to the San Luis Valley was derived by Emery by adding the 1.6 million acre-

feet of mountain contribution to 1.2 million acre-feet of estimated precipitation

on the valley floor.

Data for selected gaging stations shown in Table 11-3 were collected and placed on

the LRCWE computer system. Of particular importance to this study is the gaging

station on the Rio Grande near Del Norte because of its proximity to the potential

reservoir sites and its importance in the Rio Grande Compact. The average annual

monthly flow distribution for the 1890 to 1985 period of record at this gage is

shown on Figure II-I.

The 6,000 feet of fill below the valley surface has been estimated to contain

approximately two billion acre-feet of water (USDA, 1978). This water is considered

to be located in two major aquifers, 1) a confined system existing below clay

barriers, and 2) an unconfined aquifer above these barriers. The unconfined ground

water system functions in a manner similar to a surface reservoir with a pattern

of rising levels in the spring and early summer due to recharge from streams and

irrigation return flows, followed by a decline as the streamflow decreases and

pumping increases.

The relation of the ground water system to the surface water system is not well

understood and has been the subject of various studies (Emery, 1972; Hearne,1988;

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