WSP11307

• File Number: 8200.300.10.A
• Description: Colorado River Basin Legislation/Law - Interstate Water Transfers
• Basin: Colorado Mainstem
• Date: 12/1/1997
• Author: USDOI/BOR
• Title: Draft: Programmatic Environmental Assessment for Proposed Rule Making for Offstream Storage of Colorado River Water and Interstate Redemption of Storage Credits in the Lower Division States
• Water Supply Pro - Doc Type: Publication

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water Arizona expects to store for the next 10 years. Existing facilities will be used to store
water off stream in Arizona, using both indirect and direct storage, Without the proposed rule it
is possible that off stream storage credits could be developed between California and Nevada,
Reclamation would complete the appropriate level ofNEP A documentation for such actions on a
case-by-case basis.

2. Third Party Imoacts

Third parties are entitlement holders or other entities who may be impacted by the management
or operation of the Colorado River,

Preferred Alternative

Although implementation of the Preferred Alternative would not cause the operating criteria for
the Colorado River in the Lower Basin to depart from the current and projected mode as
discussed above, under certain circumstances reductions in water supplies made available to
individual water users could occur due to a change in the allocation and utilization of unused
apportionments. In the past, both Nevada and Arizona have had unused apportionment which
has been utilized by California entities, primarily MWD. Recently, use in Arizona has increased
to the point where all of its 2,8 mafapportionment is being used within the State, Nevada's use
is expected to reach its full apportionment of300,000 afper year by 2004,

Off stream storage associated with the Preferred Alternative could reduce the amount of unused
apportionment which could be made available by the Secretary to other States. The Decree
stipulates that the Secretary may allow a Lower Division State to use another Lower Division
State's unused apportionment, but no rights to the recurrent use of such water shall accrue,
Thus, no rights would be impacted by off stream storage under the Preferred Alternative, During
years of surplus supplies, impacts on water supplies made available to third parties would be
eliminated or reduced in scope.

The California Colorado River water users are presently developing a plan for dealing with a
Colorado River water supply which is limited to 4,4 mafper year. Implementation of the
Preferred Alternative may reduce to a small extent the amount of water in excess of 4.4 maf
available for use in California, thus forcing the California users to implement the California plan
at a slightly earlier date.

Water supply conditions and present levels of use are such, however, that there is a likelihood of
surplus water years in the near future, which is the time frame during which much of the
off stream storage for interstate purposes is expected to occur (Figure 8), If, for example, the rule
had been in place for 1997, the amount of unused Nevada apportionment which could have been
redirected from California's use to off stream storage in Arizona on behalf of Nevada entities
would have been approximately 30,000 af However, this action would have had no impact on
California users because 1997 was a surplus water supply year and all Lower Basin demands
were met.

LC Region DEAl 1

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12/97