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I I Ie I I I I I I I. I I I I I I I Ie I - ... .. - . Q \.,,, (,000 drain water with additional water released from upstream storage; and constructing more wells at Wellton-Mohawk to permit selective pumping of drainage. The Basin states were initially unwilling to make any concessions to Mexico on water quality. They pointed to the language and legislative history of the treaty as proof that Mexico was compelled to accept drainage water of any quality (except brine aquifers) as part of its allotment.' In the eyes of many western U.S. water users, the provisions in the treaty were consistent with their own state water laws. Water law in the western United States recognizes the right to appropriate water for beneficial consumptive use-with some inevitable decrease in quality-and decrees that "first in time is first in right." International water law, however, generally follows the doctrine of riparian rights, under which downstream users have the right to receive water that has not been degraded by upstream users. By the late 1960s, the states were convinced of the need to reach an accommodation with Mexico. U.S. interests proposed a new basis for settlement: "equivalent salt balance," based on a concept from agronomy and irrigation engineering.5 An irrigation system that is in "salt balance" returns the same amount of salt in its drainage waters as was applied to the land. Salt neither accumulates in nor is leached from its soiL Proponents of the equivalent salt balance position recommended that the U.S. dilute Wellton-Mohawk drainage with a quantity of purer water sufficient to reduce the differential in salinity between Imperial and Morelos Dams to that which would exist if the project were in salt balance-about 280 ppm. In theory, as excessively salty waters were gradually drained from beneath Wellton-Mohawk, the amount of dilution water needed would decrease. Once the project reached salt balance, substitution for drain flows would no longer be necessary. 6 The salinity of the water reaching Mexico would be that which the next downstream user would be entitled to under U.S. water laws. Myron B. Holburt, a member of the Committee of Fourteen from California, explained the assumptions on which the equivalent salt balance concept rested as follows: "(1) water users in the United States have a right to irrigate lands below Imperial Dam, (2) Mexico has to receive drainage water under the Treaty, (3) creating a situation of ideal return flow conditions below Imperial Dam with respect to salinity would be the best Mexico could expect, (4) the total deliveries should be water of a quality that would be usable for irrigation of the type of crops grown by Mexico, considering its soil conditions. ,,7 In the last days of the Diaz Ordaz administration, the U.S., with the support of the Colorado Basin states, offered to negotiate a new Minute based on salt balance equivalence. The Mexican government called the proposal constructive, but chose not to enter negotiations on a long-term agreement until a new president, Luis Echeverria Alvarez, took office in December 1970. The Search for a "Permanent, Definitive and Just Solution" During 1971, the U.S. and the new Mexican administration discussed a settlement based on the equivalent salt balance concept. By November, U.S negotiators believed that they were close 3