9581

• UCREFRP Catalog Number: 9581
• Author: U.S. Bureau of Reclamation.
• Title: Final Environmental Impact Statement - Navajo Reservoir Operations Volume II Technical Appendices.
• USFW Year: 2006.
• USFW - Doc Type: Grand Junction - Durango, CO.
• Copyright Material: NO

But these two projects are many years away from completion and using their total depletion
allocations. Therefore, it has been assumed that there is "flexibility" in increasing the minimum
release from Navajo Dam of 250 cfs as defined in the Preferred Alternative to some higher
value. This report will summarize the analysis made to verify that flexibility may exist during
non-drought years and during an interim period of time before full development occurs.

Method.- The San Juan River Basin Hydrology Model, using the RiverWare software,
was the tool used to evaluate alternatives for the EIS.1 The model configuration of the Preferred
Alternative was modified to show reduced depletions for NIIP and ALP that would represent
development for these two projects about 10 years in the future from current uses. Table 1,
"NIIP development schedule reflecting the acreage farmed or projected to be farmed in each
year through full development," from pages 8 and 9 of the Navajo Indian Irrigation Project
Biological Assessment - June 11, 1999, was used to estimate project completion for NIIP. It was
assumed that SJWC and the ALPWCD would be using their entire allocation, while the two
Ute Tribes would not be using any water.

NIIP's average annual usage 10 years in the future was estimated to be 288,504 af of diversions
to support 230,803 af of depletions on 94,570 acres. From table 1, this would occur in the year
2007. Current use is projected to be 204,000 af, which occurred in the year 1999 from table 1.
Since they do not appear to be on schedule, it was assumed that only 8 years of development
could be completed in the next 10 years, so 2007 from table 1 should represent water use
10 years from now.

ALP would be delivering 5,200 af to ALPWCD in Colorado, 20,800 af to SJWC in New Mexico
and 4,680 af to the Navajo Nation in Shiprock, for a total diversion amount of 30,680 af per year.
All other ALP uses were set to zero.

Total reduction in annual diversions are: NIIP: 337,500 - 288,504 = 48,996 af plus
ALP: 109;749 - 30,680 = 79,069 af; total = 48,996 + 79,069 = 128,065 af.

These new adjustments to San Juan River Basin demands and depletions were read into the
model and the minimum release from Navajo Reservoir was increased from 250 cfs to 350 cis
for the months of May-october. November-April remains at 250 cis.

Results.- The model was run and the water supply was checked for shortages. None
were found. Flow Recommendations were evaluated through the post-processing analysis and
no violations of those recommendations occurred.

1 Use of the model in the work of the SJRBRIP does not necessarily constitute agreement or approval by
individual program participants with the model data, methodologies, or assumptions. Use of the model does not
change the responsibilities of the respective States to maintain records of water rights and water use. Official records
of water rights and water use are maintained by the State agencies statutorily charged with that responsibility.

B-2

I
I
I
I
I
I
I
I
I.
I
I
I
I
I
I
I
I
I
I