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4 storage dams. The United States, at a cost of over 225 million of dollars, first constructed in the United States Hoover Dam and then Davis Dam to control the floods and regulate downstream flows. Mexico did not pay any of the cost of these structures even though she is a prime beneficiary of their benefits. Upon the completion of Hoover Dam in 1935, thereby assuring for the first time regulated downstream water releases, it became essential that the water rights of Mexico and the United States be determined and the quantity of water available for further development in each country be fixed. Treaty negotiations were opened with Mexico in 1941. During those negotiations two significant factors developed. Mexico at that time sought some guarantee as to the quality of water which would be obtainable in the years to come. At issue were two types of water and names were developed for them during the negotiations. Mexico referred to water which would be released from storage as "white water" and to drainage water and other return flows as "green water". The other significant factor was that there would be irrigation projects constructed in Arizona which would produce a large quantity of return flows to the river just above the international boundary line and at a point where they could not be again diverted or stored in the United States. It was obvious that these return flows would reach the river and pass into Mexico without control. The consideration of these two factors were dominant in fixing the amount and in avoiding any commitment as to the quality of water which Mexico would receivecunder the Treaty. At that time, it was estimated that with full development in the United States, the return flows would approximate 1 million acre feet per year. Predicated upon this assumption, the negotiators for the United States agreed that they would recommend that Mexico be given 1 1/2 million acre feet per year, if Mexico would agree to accept for credit upon the Treaty all of the return flows and would abandon its request for guarantee as to quality. This solution was agreed to by the negotiators of both countries and the Treaty was so drafted as to implement the agreement. In Article 10 of the Treaty, referring to the water to be received by Mexico, the language provided in part that Mexico's share would be from waters of the Colorado River, "from any and all sources." Article 11 provided that delivery of Mexico's water would be made from waters of the Colorado River "whatever their origin." In transmitting the Treaty to President Roosevelt and reEpson Perfection 4870 Photo, 400 dpi, 8 bit, 1,914,408 byte