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Those who oppose ratification of the treaty argue that the amount. I. 500.000 acre-feet. is too much because it represents an amount greatly in excess of th.J.t which was used by Mexico prior to the construction of Boulder Dam. The assertion is made that the Mexican uses before Boulder Dam went into operation did not exceed 750.000 acre-feet annually. No good purpose would be served by speculating as to the amount of wate-r which Mexico could have used under natural flow conditions as they existed before the construction of Boulder Dam and before the beginning in 1931 of the ten-year low water period. What is important is that Mexico has plans which will require consider- ably more than 1.500,000 acre-feet a year and in 1943 actually diverted and used more than 1.800,000 acre-feet, It is true thar of this 1.800,000 acre,feet substantial quantiries were taken through rhe Rockwood heading of the Alamo Canal. Opponents of the treaty assert thar if the use of this facility. which is locared in the United States, was denied to Mexico. then Mexico could not use more than the 750.000 acre-feer annually which it used prior to the regulation of the stream by Boulder Dam, This involves an engineering question as to the abiliry of Mexico to divert rhrough gravity headings or pumps within its own borders. There is somewhat naturally a diversity of engi- neering opinion. However. the fact is certain that in other places substantial diversions are made under conditions which are jusr as adverse, Examples may be found along the Rio Grande, another international stream. It is well to bear in mind that during the five year period 1939-1943 inclusive the average annual releases from Boulder Dam were approximately 12,000.000 acre-feet and the average annual flow of the srream past the Yuma gaging station. and below all important United States diversions. was approximately 8,300,000 acre feet, Wirh such amounts of water passing to Mexico it must be expected that engineering ingenuity will evolve a method of diversion, particularly since there is desirable land in Mexico upon which the water can be used. Attention is directed to the fact that under the contract for the Alamo Canal conc('ssion Mexico had a right to use up to one-half of the water carried by the Alamo Canal. In the thirreen-year period immediately preceding the placing in operation of Boulder Dam the average annual diversions rhrough the Alamo Canal were approximately 3,000.000 acre-feet. Under the terms of the concession, Mexico was entitled to one-half or approximately 1.500.000 acre-feet annually. No technical knowledge is required to understand that the treaty provisions, by which the United States is credit('d with return flows and d('si1ting Water. impos(' a much less sev('r(' obligation than exisud under the provisions of the Alamo Canal Concession. Reference has also been made that in 1929 rhe American Section of the International Boundary Commission suggested that after Boulder Dam was built. 750.000 acre-feet per year be delivered to Mexico according to a schedule, plus an amount of water sufficient to compensate for main canal losses, It is said that the amount guaranteed by the proposed treaty is double the 1929 offer. This is not correct. The 1929 offer would have necessitated deliveries either to the Alamo Canal by the present heading or through the All-American Canal and the Pilor Knob Wasteway. In either case, Mexico would have received. in addition to the 750.000 acre-feer. an estimated 200.000 or 300.000 acre~feet to compensate for canal losses. and all desilting water and all return water accruing to the river below the diversion point. The sum of these quantities might have exceeded the amount guar~ anteed by the proposed treaty, In any event, it is clear that the 750,000 acre-fen to have been de- livered by the All-American Canal far exceeds the amount that Mexico will receive from such source under the present treaty. which requires the United States to deliver through such facility only 500.000 acre-feer annually from the time of the completion of the Davis Dam unril 1980 and 375,000 acre- feet annually thereafter, In discussing the propriety of the amount of water guaranteed to Mexico by the proposed treaty. it is proper to direct attention to the situation regarding the proposed Pilot Knob power plant. The All-American Canal is constructed with a capacity of 15,000 second-feet down to Syphon Drop; from there to Pilor Knob. a capacity of 13.000 second-feet. Beyond Pilot Knob, the capacity is 10,000 second-feet, Proposals have been made by California interests for the construction of a power 9