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<br />() 0 0 2 7 9. --- <br /> <br />during the 1970's was about 110,000 acre-feet/year and the average for the period was about <br />90,000 acre-feet/year. The plan is to reduce groundwater levels to those of the 1970's as rapidly <br />as practical and then try to maintain those levels. To do so, pumping for the first five years or so <br />would be at the maximum historical rate of about 110,000 acre-feet/year. Thereafter pumping <br />would be continued at the average rate for the 1970's or about 90,000 acre-feet/year. <br /> <br />Question 11: Why were these levels (i.e. 50,000 and 30,000 acre-feet/year above average for <br />the last decade) chosen? <br /> <br />Answer: The average pumping rate for the last decade was about 60,000 acre-feet/year. Thus <br />50,000 acre-feet/year above the average rate corresponds to a total pumping rate of about <br />110,000 acre-feet/year and 30,000 acre-feet/year corresponds to a total rate of about 90,000 acre- <br />feet/year. As explained above, these are the pumping rates which should provide drainage relief <br />similar to that achieved in the 1970's. <br /> <br />Question 12: Up to approximately 20,000 acre-feet of water that is now delivered to the <br />SIB will be delivered to the NIB. Please explain in more detail. <br /> <br />Answer: In 1995 Mexico complained that the water delivered to them in the Sanchez-Mejorada <br />Canal atthe Southerly International Boundary (SID) was too salty and was causing damage to <br />crops they were raising with this water. Consequently, in order to make the water useable for <br />agriculture, they were blending lower saline water diverted at Morelos Dam with the saline water <br />in the Sanchez-Mejorada canal. The blended flow reduces salinity levels so this water can be <br />used for farming. The water used for salinity control by blending could be put to other uses in <br />Mexico. Mexico asked that we look at-and implement ways to reduce the salinity of water <br />delivered to them at the sm. We have been negotiating with Mexico over reducing the salinity <br />levels of water at the sm for a number of years. <br /> <br />The drainage water that is delivered to Mexico at the sm varies in salinity from about 1200 ppm <br />to 1800 ppm. The source of this water consists of drainage inflow to the Yuma Valley Main <br />drain by gravity and from drainage wells in the Yuma Valley. Also, some water delivery canals <br />have waste ways that discharge into the Yuma Valley Main Drain on an intermittent basis. <br /> <br />The plan is to move the discharge of some ofthe valley drainage wells from the Yuma Valley <br />Main Drain into the Yuma Mesa Conduit (approximately 20,000 acre-feet per year). This <br />reduces drainage flows arriving at the Boundary Pumping Plant near the sm and increases <br />drainage flows to the river above NIB. The drainage flows that have been diverted to NIB <br />would be replaced by increasing the pumping rate ofthe 242 well field. The water from this well <br />field would then be blended with remaining drainage flows from the boundary pumping plant for <br />delivery to Mexico at the sm. Since the salinity ofthe water pumped from the 242 well field is <br />of better quality (normally 100 ppm or less) than the drainage flows in the Yuma Valley Main <br />Drain, the salinity of flows delivered to Mexico at the sm would be improved, thus partially <br />addressing Mexico's concerns about the salinity of flows they receive at the sm. <br /> <br />See attached drawings ofthe Yuma Valley facilities. <br />