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<br />N <br />I-" <br />en <br />-.1 <br /> <br />Arizona's Growth - Eldridge p.3 <br /> <br />salinity control program -- the on-farm program in the Department of Agricul- <br />ture's budget -- was left out of the budget by Congress this year. That means <br />that the major source of our salinity problems -- agricultural irrigation -- is <br />left in limbo. <br /> <br />Let me expand a bit on how we define the salinity problem. It is easy to get off <br />on the wrong foot by blaming nature for the problem. It is true that the river <br />drains a basin full of salt-laden shales left behind by the evaporation of an <br />ancient inland sea. But the natural salt loading of the river acclJllulates <br />about 400 ppm, below the recommended 500 ppm for clean drinking water, and well <br />below the 800-1,000 ppm range where crops are damaged. The river in its natural <br />state would pose no salinity problem at all. But the river is not left in its <br />natural state; we develop and use its waters in order to live here. It is our <br />use of the river that creates the salinity problem, not nature. <br /> <br />Another mistake people make is to look just at salt sources, as if that alone <br />defines the situation. It doesn't; we must relate salt sources to salt toier- <br />ances. The illustration below does this. <br /> <br />4% M&I <br /> <br /> <br />62% <br />natura 1 <br />cushion <br /> <br /> <br />49% <br />Irriga- Man-made <br />tion <br /> <br />47% <br />Natural <br /> <br />Salt Sources <br /> <br />Sa It To lerances <br /> <br />1,000 ppm <br />Severe plant damage <br /> <br />800 ppm <br />Threshho ld of <br />plant damage <br /> <br />500 ppm <br />Dri nki ng water <br />s tanda rd <br /> <br />_?~ <br /> <br />,;.,,_ ,. .;x.~""'.-,, -""-. <br />