Exhibit A

Ex (??) To accompany Memorandum dated August 23, 1964 COLORADO RIVER SALINITY PROBLEM EFFECTS OF TILE EFFLUENT OF 4,000 TO 5,000 P. P. M. FROM THE WELLTON-MOHAWK IRRIGATION DISTRICT Notes prepared in conference with Dr. Charles A. Bower, August 22, 1964 1. Salt tolerant crops such as wheat and cotton can be grown with irrigation waters having a considerable range in salinity (up to 1,500 p. p. m.) with out significant reduction in yield providing the leaching requirement is met. 2. The leaching requirement, and therefore, the amount of water required to grow a given crop, increases with an increase in the salinity of the water. Hence, with a given volume of water fewer acres can be irrigated as the salinity of the water increases. 3. The permeability of the soil and the drainage facilities must be sufficient to permit the increased leaching required as the salinity of the water increases. 4. Soil salinity was a problem in the Mexicali Valley prior to initiation of drainage of the Wellton-Mohawk Project when the salinity of the irrigation water was about 900 p. p. m. 5. Beneficial consumptive use of about 300,000 acre-feet of water annually and operation of the Wellton-Mohawk Project at a salt balance index of 1 causes the weighted mean salinity of the water delivered to Mexico to increase to about 1,150 p. p. m. It is estimated that the increase in weighted mean salinity of the water delivered to Mexico that is necessary for permanent operation of the Wellton-Mohawk Project and amounting to about 250 p. p. m. might eventually cause the agricultural output (cotton and wheat) of the Mexicali Valley to be about 6% less than it would be otherwise on the lands irrigated with Colorado River waters, and about 4% less than the output would otherwise be on the total lands irrigated in the Mexicali Valley. 6. Substitution of tile drainage (effluent = 4,000 to 5,000 p. p. m.) for pump drainage of the Wellton-Mohawk Project so as to deliver water having a weighted mean salinity of 1,335 to 1,415 p. p. m. to Mexico might cause the agricultural output of the Mexicali Valley to decrease an additional 5 - 7% as compared to what it would be otherwise on lands irrigated with Colorado River waters, and 3 - 5% less than the output would otherwise be on the total lands irrigated in the Mexicali Valley. 7. It is probable that most of the soils in the Mexicali Valley have sufficient permeability to accommodate the increased leaching required with water having a salinity of 1,335 to 1,415 p. p. m., providing drainage facilities are adequate. Some soils will not have sufficient permeability, however, and it could be that the estimated 6 - 10% adverse effect on total agricultural output in the Mexicali Valley would come about from abandonment of the least permeable soil because of salt accumulation with salinity control and crop yields being maintained on most of the land under irrigation. 8. Items 5, 6 and 7 above are based on the assumption that the Mexicali Valley farmers will use their irrigation water intelligently and employ reasonably good water, soil, and crop management practices for the control of salinity.Epson Perfection 4870 Photo, 400 dpi, 8 bit, 19,261,952 byte