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-2- .. Comparative data for recent years are tabulated below, and for prior years beginning in 1951 are shown graphically on Exhibit 1. '. SALINITY OF DELIVERIES AX THE NORTHERLY BOUNDARY Average Annual Salinity a) Under b)Ninute No. 218 measures Yearl) Minute No. 218, plus Mexico's voluntary Period U.S. Operations bv-pass Previous year to Agreement Operations 1965 1375 ppm 1375 ppm 1st year of Operation 1966 1330 ppm 1227 ppm 2nd year of Operation 1967 1307 ppm 1213 ppm 3rd year of Operation 1968 1316 ppm 1194 ppm 4th year of Operation 1969 1289 ppm 1184 ppm 5th year of Operation 1970 1278 ppm 1139 ppm2) 6th year of Operation 1971 1245 ppm 1161 ppm Final period of Operation 3) 1972 1266 ppm 1174 ppm . 1) Operation year - November 16 of preceding year through November 15 of designated operation year. 2) The voluntary by-pass by Nexico of Well ton-Mohawk drainage during the 5th year exceeded those requested during the 4th and 6th years by more than 50%. 3) November 16, 1971 through June 30, 1972. This period is prior to the usual period of greatest improvement which generally occurs in July and August. 1hus, the salinities are not comparable with full years of operation, The daily salinity of Colorado River treaty deliveries to Mexico during the final period at the northerly boundary with only United State'boperations under Ninute No. 218 varied from about 1100 ppm to about 1400 ppm ,reference E.xhibit 2. Hith the combination of United States measures under Ninute No. 218, plus the voluntal-Y by-pass by Nexico of additional \1ellton,Nohm,k drainage waters, daily salinities of waters diverted by Nexico varied from about 950 ppm to about 1250 ppml), reference E.xhibit 3. 2. Colorado River FlmlS to Mexico . The total flows of the Colorado River reaching the boundary section during the first six months of the calendar year 1972 Were 848,143 acre- feet (including flows crossing the land boundary at San Luis), This quantity is within 2% of the scheduled deliveries of 833,872 acre-feet, for the period, requested by Nexico as part of the guaranteed annual allotment of 1,500,000 acre-feet. The 14,271 acre-feet, over the scheduled delivery consists of: 1) E.xcludcd from this range arc daily salinities during the middle of December 1971 and January 1972, when the most saline return ,,,aters were discharged from the Hellton,Hohm"k District.