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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To demonstrate the potential for the Navajo Nation to limit total depletions to allow the NGWSP
to move fOlv/ard in the event of full baseline depletion. the model was configured for full
NGWSP depiction IOgelher with full baseline depiction, except NIIP was limited ro a depletion
of 247,000 acre-fect at equilibrium. Both diversions and return flows were modified
proportionately for NIIP. This change resulled in a reduction of the maximum annual
groundwater storage contribution from NIIP from 10,600 to 7,628 acre-feel. Funhcr, an
operating rule change is required that calls for releasing 40 cfs through the NIIP canal down Ojo
Amarillo in May when the April Navajo Dam release is between 2,000 and 2.500 cfs and a
maximum release is called for. Ojo Amarillo discharges to the San Juan River at RM 170, about
10 miles downsrream of the confluence with the Animas River. Increasing. the dam release by 40
cfs or releasing water down Gallegos Canyon would violate the Corps of Engineers flood control
restrictions on the San Juan River above the Animas River confluence. With these conditions,
the flow recommendations are met as shown in Table 3.8. The details of reservoir content and
stream flow are presented in Appendix A.

Table 3.8 Summary Flow Statistics for the NGWSP plus Baseline with NIIP Equilibrium
Depletion Limited to 247,000 Acre Feet

Discharge {cfs}
Duration >10,000 >8,000 >5,000 >2,500
Average Frequency
1 days 33.8% 55.4% 75.4% 95.4%
5 days 27.7% 46.2% 72.3% 86.2'%
10 days 15.4% 38.5% 67.7% 80.0%
15 days 7.7% 30.8% 60.0% 75.4%
20 days 24.6% 70.8%
21 days 55.4%
30 days 13.8% 41.5% 66.2%
40 days 32.3% 55.4%
50 days 26.2% 47.7%
60 days 18.5% 41.5%
80 days 10.8% 27.7%
Maximum Years Without Meeting Criteria
Flow Criteria - Max Duration Allowed _ Modeled
9700 cfs for 5-days - 10-years 10 10
7760 cfs for 10-days - 6-years 6 6
4850 cfs for 21-days - 4-years 4 4
2450 cfs for 1D-days - 2 years 2 2

BIOLOGICAL ASSESSMENT
NAVAJO GALLUP WATER SUPPLY PROJECT
September 3. 2004

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