S7_11-15-04

• Basin: Statewide
• Title: SWSI Phase 1 Report - Section 7 Availability of Existing Water Supplies
• Date: 11/15/2004
• Author: CWCB
• SWSI - Doc Type: Final Report

Section 7
Availability of Existing Water Supplies
approximately 300,000 AF total storage, beyond which
no significant gains in firm yield can be achieved with
increased storage. At the asymptotic value, all excess
water is captured, stored, and used, but supply is still
limited (below the average annual) by the timing of the
available flows and reservoir evaporation and seepage.
The critical (limiting) period for this analysis is the late
1970s. Note that yields would likely be significantly
higher if some value or frequency of shortages, greater
than zero, were acceptable.
Potential limitations to the projected supply availability as
a result of the Colorado River Compact are evaluated in
Section 7.4. The Compact includes potential limitations
for the Colorado, Gunnison, Dolores/San Juan/San
Miguel, and Yampa Basins combined as well as
additional limitations on certain subbasins.
The future development of existing conditional water
rights, including the Animas-La Plata Project, are not
included in the Colorado DSS datasets. These water
rights could eventually be developed resulting in less
available water for the rest of the basin. Development of
conditional rights, however, must be applied to beneficial
use and meet a water need. Conditional water rights by
basin are summarized in Section 10. Since the current
Dolores/San Juan/San Miguel DSS dataset covers the
period from 1909 to 1999, once the current drought has
ended, the DSS dataset for the basin should be
extended, including updated irrigated acres and M&I
demands. A new StateMod model run should be
conducted with the updated dataset to determine if the
recent drought is a new critical period.
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Maintaining or enhancing recreational and environmental
flows could affect current and future supply availability.
Environmental and recreational considerations are
further developed in Sections 6 and 10 of this report. For
example, a number of endangered fish species, such as
the Razorback Sucker and the Pikeminnow, are present
in the Dolores/San Juan/San Miguel Basin, and require
special attention with respect to minimum instream flows.
Reoperation of Navajo Reservoir, stocking, and habitat
improvement are options that can help meet the needs of
endangered species in this basin.
Finally, discussions with basin stakeholders have noted
that the impacts of CBM water extractions on supply
availability, particularly in the Pine and Florida River
systems, are unknown and are not included in the
StateMod dataset.
There are minor transbasin diversions from the Dolores/
San Juan/San Miguel to the Rio Grande Basin averaging
1,873 AF from 1971 to 2003 (Upper Colorado River
Commission 2004).
7.3.3.2 Dolores/San Juan/San Miguel
Alluvial Aquifers
No significant alluvial aquifers have been identified.
There are domestic wells in the basin that are recharged
by agricultural return flows and the long-term viability of
these wells is dependent upon the continued pattern of
irrigation return flows.
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Statew~itle Water Supply Inii'iative
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