WSP08103

• File Number: 8278.400
• Description: Title I - Minute 242
• Basin: Colorado Mainstem
• Date: 1/1/2002
• Author: INBWC
• Title: Minute 242 2002 Annual Report
• Water Supply Pro - Doc Type: Annual Report

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a)
b)

Waters
Upstream of Morel os Dam
Arriving at Imperial Dam
Salinity Differential

U.S. Count'
fJmm.)
832
691
141

Mexican Count'
fJmm.)
896
754
142

* The difference in the U.S. and Mexican counts is a result of different methods of analysis and of
computing the total dissolved solids used by laboratories in each country. The annual flow weighted
average salinities resulting from operations under Minute No. 242, since it became effective on June
24, 1974, are shown in Table 1.

The annual flow weighted average salinities of the waters arriving at Imperial Dam since 1951, the
first full year of deliveries to Mexico under the 1944 Water Treaty, and of the waters made available
to Mexico at the Northerly International Boundary (NIB) since 1958 are graphically shown on
Exhibit 2, which shows the effect of operations under Minute No. 242. The interim measure adopted
by the United States to effect the agreed upon salinity differential, pending completion and operation
of desalting projects, consists of discharging all Wellton-Mohawk drainage waters into a bypass
channel to convey them to the Santa Clara Slough on the Gulf of California, and substituting for such
waters an equal volume of other waters. The quantities of Wellton-Mohawk drainage waters
discharged and substituted for by other waters for the deliveries to Mexico under Minute No. 242,
since it became effective on June 24, 1974, are shown in Table 2.

Deliveries on the Land Boundarv

Point 1 of Minute No. 242 further provides that:

"The United States will continue to deliver to Mexico on the land boundary at San
Luis and in the lirnitrophe section of the Colorado River downstream from Morelos
Dam approximately 140,000 acre-feet (172,689,000 cubic meters) annually with a
salinity substantially the same as that ofthe waters customarily delivered there."

The annual volumes of water delivered to Mexico on the land boundary at San Luis and in the
lirnitrophe section of the river below Morelos Dam, excluding the Wellton-Mohawk drainage waters
under Minute No. 242, since it became effective June 24, 1974 are shown in Table 3.

The deliveries to Mexico on the land boundary at San Luis and in the lirnitrophe section below
Morelos Dam in 2002 were less than the annual volume of 172,689,000 cubic meters (140,000 acre-
feet) referred to in Minute No. 242. The United States made up the difference by delivering to
Mexico a volume of water equal to the difference. This volume was delivered in the bed of the river
above Morelos Dam, as stipulated in Point I of Minute No. 242.

The average flow weighted annual salinities of the waters delivered to Mexico on the land boundary
at San Luis under Minute No. 242, since it became effective on June 24, 1974 are shown in Table 4.

The data in Table 4 shows that the salinity in 2002 was lower than that of the water customarily
delivered on the land boundary, which averaged about 1,540 ppm for the I O-year period 1963-1972.

Begirming in late 1995, Mexico raised objections to peaks in salinity at the NIB and to the salinity
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