WSPC02454

• File Number: 8283.200
• Description: Colorado River Basin-Colorado River Computer Models-Colorado River Decision Support System
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 12/1/1995
• Title: San Juan River Basin Modeling-San Juan Special Water Right Operations
• Water Supply Pro - Doc Type: Report/Study

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the terms of the contract, the 8,000 acre-feet can only be used after the San Juan Power Plant
has fully utilized its own 16,200 acre-feet of contract water from Navajo Reservoir and to date,
this lease water has never been used,

Four Comers Power Plant

The Four Corners Power Plant is operated by Arizona Public Service Co. (APS) and is
located on the south side of the San Juan River about 16 miles southwest of Farmington. The
facility includes five coal,fired generation units with a capacity of 2,040 net megawatts. Water
for the operation of the plant is pumped from the river to storage in the 35,000 acre-focit Morgan
lake, located near the plant. The Four Corners Power Plant does not have conventional cooling
towers but rather relies upon Morgan lake for cooling.

Water for the Four Corners Power Plant is obtained pursuant to a permitted New Mexico
water right granted to Utah International and now held by BHP. This right is permitted for 51,600
acre-feet per year with a 1955 priority date that is slightly senior to the United States' storage
right for Navajo Reservoir. According to APS personnel, the power plant currently diverts
approximately 30.000 acre,feet per year of which about 8,000 to 10,000 acre-feet returns to the
San Juan River via the Chaco River. This return flow represents "blowdown" from the reservoir,
necessary to reduce the sediment loading in Morgan lake. In any given year, the amount of the
return flow is dependent upon the sediment loads in the San Juan River at the river pumping plant,
the plant demand and the rate of evaporation from the reservoir. For purposes of the CROSS
WRPM, it is assumed that the annual demand of 30,000 acre-feet per year is evenly distributed
throughout the year (2.500 acre,feet per month) and that the average return flow would be 9,000
acre-feet, also evenly distributed throughout the year (750 acre,feet per month). In the CROSS
WRPM, all of these return flows are assumed to accrue to the river above the USGS Stream Gage
No. 08379500. According to APS personnel. there are presently no plans to construct additional
generating units or to otherwise increase the water demands.

As described above, BHP has also leased up to 8.000 acre-feet of yield from its permitted
water right to the San Juan Power Plant. This lease has not been exercised.

Irrigation Water Rights on the San Juan River

There are a number of large irrigation water rights which divert from the main stem of the
San Juan River downstream of Navajo Reservoir and upstream of the Town of Shiprock. These
are briefly described herein. None of these structures are direct beneficiaries of the Navajo
Reservoir Project, although they all benefit from the regulation of the natural river flows that is
provided by the reservoir.

The Citizens Ditch is permitted for 9.21 cfs with a 1881 priority and 100.56 cfs with a
1907 priority and is used for irrigation of approximately 9,500 acres on the north side of the river
between Navajo Reservoir and Farmington. The ditch delivers water to a number of smaller ditch
companies and also carries a small amount of M & I water. Based on historic diversion practices,
the USBR has estimated the average monthly diversion demands which are summarized in the
following Table 1. These diversions are inclusive of the small amounts of industrial water delivered
through the ditch and are recommended for inclusion in the CROSS WRPM. In the WRPM, 10%
of the irrigation return flows are assumed to return above the headgate of the Hammond Canal and

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