WSPC12741

• File Number: 8064.200.A
• Description: Indian Water Rights - Gallup-Navajo
• Date: 9/3/2004
• Author: USDOI/BOR
• Title: Biological Assessment, Navajo Gallup Water Supply Project - Report and Appendices
• Water Supply Pro - Doc Type: Publication

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The total depletion for this analysis is about 1,200 acre-feet greater than the baseline plus
depletions allowed in Part 1 while still meeting the flow recommendations. This represents the
maximum combined development potential for the Navajo Nation while meeting flow
recommendations under full baseline depletion conditions. Since this is greater than that allowed
under Pan 2, implementation of Part 2 of the commitment in this section is conselVative in favor
of the flow recommendations.

3.3.3 Summary

The proposed implementation of the NG\VSP increases depletion over the baseline presented in
Table 3.2 by 1,840 acre-feet. Until depletions in the basin, including the full depletion for
KG\VSP, reach the baseline depletion in Table 32 plus 1,840 acre-feet added to the baseline for
the ~G'VSP, the flow recommendations can be met and the impact to hydrology from operation
of this project will remain at or below that previously considered to be acceptable in Section 7
Consultations. When the total depletion reaches this new baseline depletion, the Navajo Nation
will reduce ~a\'ajo depletion from one or more projects that are presently in the baseline such
that total depletions in the basin remain below the baseline depletion, assuming all other users
are within their baseline depletion. All flow recommendations are met under this case.

The most extreme case analyzed requires reduction of NIIP from 270,000 acre-feet to 247,000
acre- feet of equilibrium depletion and the release of 40 ciS down Ojo Amarillo under certain
:\"avajo Dam release patterns. The hydrologic conditions for this scenario have been compared
to those conditions that result from the baseline depletion represented in Table 3.2. This case is
used as the maximum impact against the baseline case. Table 3.9 compares the flow statistics for
the t\\c-o cases. All flow recommendations are met and the impact to flow statistics is equal to or
less than all baseline values.

Table 3.10 presents the change in flow from baseline to the maximum impact case at the five San
Juan River gauges below Navajo dam. Details are in Appendix A. In general. the average flows
are increased downstream from I\avajo Dam to the PN~f diversion below Farmington to supply
water to this lower diversion point for the project. Below PNM the flows are reduced by an
average of 8 cfs until rerum flow enters below Shiprock where the reduction averages 5 cfs and
continues at this rate downstream past the Bluff gage. The decrease typically occurs during the
base flow months, with an increase during runoff months (see Appendili: A). The winter months
typically see an average decrease in the range of 15 to 20 cfs or about 1.5 to 2.0% below the
PNy1 weir. The maximum decrease in monthly average flow occurs in July (37 cfs, 3 % at
Shiprock. from Appendix A). At some gages, panicularly upstream of the Pl'i'"M diversion, there
is a significant increase in flow, but the decreases in flow that occur in some months and some
stations below the P~"1vf diversion are insignificant.

BIOLOGICAL ASSESSMENT
NAVAJO GALLUP WATER SUPPLY PROJECT
September 3. 2004

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