WSP12637

• File Number: 8282.300
• Description: Colorado River Operations and Accounting - Lower Basin Administrative Procedures
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 8/1/1996
• Author: DOI-BOR
• Title: Description and Assessment of Operations-Maintenance and Sensitive Species of the Lower Colorado River - Volume I - Report - 08-01-96
• Water Supply Pro - Doc Type: Report/Study

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002356

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Flows below Laguna qam usually range between 300 and 500 cfs. Occasionally flows may
range up to 4,000 cfs qr higher if a heavy rainfall has occurred.

Flows below Imperial Dam into the Colorado River Channel (California Sluiceway) normally
range from about 250 cfs to about 350 cfs and are made up principally of return flows from
the All-American desilting basins and gate leakage from the California sluiceway gates at
Imperial Dam.

Sluicing flows are released to remove sediment accumulated from the desilting basins in the
sluiceway channel. TQese sluicing flows usually occur 2 to 3 times a month and consist of
flows ranging from 8,000 to 10,000 cfs which are released for periods of about 20 minutes.
These flows carry sediment to the Laguna Desilting Basin located about 2 miles downstream
from Imperial Dam. .

4. Wat~r Delivery Requirements to Mexico in Accordance with the
MexicaI) Water Treaty of 1944

Mexico is entitled to receive a total of 1.5 maf of water delivered at the NIB and SIB each
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year - of which at least 1.36 maf are to be delivered via the Colorado River (normally
consisting of releases trom Colorado River system storage and drainage returns) to the NIB;
up to 140,000 acre-feet of Colorado River water (normally consisting of drainage returns and
wasteway flows) can b~ delivered at the SIB. In the event a surplus year is declared by the
Secretary, Mexico may increase its annual water order by 200,000 acre-feet to a total of
1.7 maf. In the event iof a declared shortage, water deliveries to Mexico would be reduced
in the same proportion as consumptive uses in the United States are reduced.

In December of each )fear, Mexico provides the United States with an advance monthly water
order for the following year. This water order can only be changed by providing the
United States 30 days': advance notice, and each monthly water order can be increased or
decreased by no more ;than 20 percent of the original monthly water order. The treaty
further stipulates that Mexico's total water order must be no less than 900 cfs and no more
than 5,500 cfs during the months of January, February, October, November, and December.
During the remainder Of the year, Mexico's water order must be no less than 1,500 cfs and
no more than 5,500 cfs. Daily water orders are usually not allowed to increase or decrease
by more than 500 cfs.

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Minute 242 defines the salinity requirements of Colorado River water delivered to Mexico.
A salinity monitoring program is conducted at points below Parker Dam to the NIB.
Computations are mad~ projecting the annual salinity requirements from these data. If
necessary, actions are taken to reduce salinity, such as reducing drainage pumping, or
operating the YDP. Operating the YDP for salinity control is not expected to occur within
the next 5 years.

5. Process for Daily Water Requirements and Hourly Release Schedule

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