112 



Irrigation and Drainage 



How completely water will drain out of sands by percolation 

 under conditions in which almost no evaporation can take place, is 

 shown by the data in the table which follows, in which the results 

 were obtained by a set of apparatus shown in Fig. 21. It will be 



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Fig. 21. Method of determining water-holding power of long columns of sand. 



seen that the conditions provided by the apparatus are such that 

 standing water was maintained continuously in the soil at a level 

 of 8 feet below the surface, and, hence, that the amount of water 

 retained in the whole column was much greater than it would 

 have been were it under such field conditions as when standing 



