PUB00027

• Year: 1990
• Title: Final Report Rio Grande Water Supply Study, Phase 1
• CWCB Section: Interstate & Federal
• Author: San Luis Valley Water Conservancy District
• Description: Reconnaissance level determination of the physically and legally available flow at 4 reservoir sites in the Rio Grande Basin upstream of Del Norte, Colorado
• Publications - Doc Type: Brochure

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by water rights administration of the Canejas Basin. Therefore, consideration

of water rights administration in this study focused on mainstem water rights.

There are approximately 310 water rights on the mainstem of the Rio Grande which

affect the legal water availability at an upstream potential reservoir site.

Approximately 70 percent of the mainstem diversions are associated with the

following eight ditch systems: Rio Grande Canal, Farmers Union Canal, Monte

Vista Canal, Empire Canal, San Luis Canal, Prairie Ditch, Costilla Ditch and Rio

Grande & Lariat Ditch. To ease the computational burden in modeling water rights

administration, the water rights of these eight ditches were consolidated from

approximately 110 water rights down to 40 water rights.

Water rights in the Del Norte to Alamosa reach associated with ditches other

than the eight listed above were consolidated into a single water use for

modeling purposes. Water rights outside the Del Norte to Alamosa reach were not

modeled but their effect on the Rio Grande during the 1948 through 1985 study

period was included in the generation of the flow base of the model through

streamflow records.

Two scenarios of Rio Grande mainstem diversions between Del Norte and Alamosa

were tested in the storable flow determinations. The "Step One Mainstem

Diversion" scenario generally constrained mainstem ditch diversions to maximum

levels experienced from 1950 through 1967, which was a period prior to active

administration of the Rio Grande Compact. The uAlternate Step Two Diversion"

scenario allowed diversions greater than the 1950 through 1967 maximum levels

by four diversion systems which provide a majority of their diversions to the

Closed Basin.

An integral part of the allocation of Rio Grande Basin water within Colorado is

the effect of the Rio Grande Compact as discussed in the next section. The Rio

Grande Compact is an obligation that Colorado is committed to satisfying.

Curtailment of diversions of Colorado appropriators has often been required to

satisfy Colorado's Compact obligation.

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