54 



on different ways of getting rid of the salt. 



Sharp: But the real issue that the nitrogen fed to the crops was 

 inadequate? 



Revelle: Exactly. It wasn't a salt problem at all. 



There were two real problems. One was the water supply for 

 the farmers. It wasn't that the farmers had too much water. It 

 was that they weren't getting enough water because so much water 

 leaked from the canal system into the ground. Besides this 

 corrupt system of distribution. The other problem was there 

 wasn't any fertilizer and the crops were sort of standard, old- 

 fashioned varieties that got along without much fertilizer. 



But there was also a problem with the waterlogging and the 

 salt in many areas. AID had been conducting an investigation of 

 this, with the U.S. Geological Survey, for several years. 



For a long time people had tried pumping down the water 

 table with wells, drilling what were called tube wells which are 

 big wells inside a casing, inside a steel pipe. You put a pump 

 down there at the bottom of the hole and you pump out the water 

 and spread it on the surface and let it evaporate. 



It was thought that this would somehow lower the water 

 table. But they'd never done it on a big enough scale. They had 

 done it in areas maybe one or two or three miles across, in 

 diameter. The result that water flowed in from the sides. As fast 

 as they puit^ed it out from the center, it would flow in from the 

 side. So you got no effect at all. It was sort of like trying to 

 pump water out of a bathtub. You could make a dip with the water 

 here and put the water over here, and it would just flow right 

 back again. 



So the big thing that Harold Thomas and Herb Skibitske did 

 with their linear programming and their mathematical analysis was 

 to show that you had to do this over quite a big area in order to 

 actually lower the water table. An area which was big enough so 

 that you pump water out faster than it flowed in from the sides. 



You see, there's a relationship between area and 

 circumference. The area goes at the square of the radius and the 

 circumference goes at the first power of the radius. So if you 

 have a circle just one mile in radius, the circumference is 2 it 

 r, which is six miles, and the area is Tt r squared, which is 

 three miles. Six miles in circumference and three square miles in 

 area. 



But now suppose you take an area ten miles in radius. 2 u r 

 will be sixty miles, but all of a sudden the area becomes n r 

 squared, which is 300 square miles, do you see? So that area goes 

 up a hell of a lot more rapidly than the circumference does. You 

 go to 100 miles, n r squared is 30,000 square miles and the 

 circumference still is only 600 miles. 



Sharp: So if you're puir^ing the water out, and it spreads out — . 



Revelle: You just put it on the surface and let it evaporate, but the 



