DRY LANDS AND FORESTS 103 



water will run out long before the available 

 supply of land and the residue is of question- 

 able value even under the most refined of dry- 

 farming methods. 



There is an interesting parallel between the 

 land with too much water which we are re- 

 claiming by drainage and the land with not 

 enough water which we are reclaiming by ir- 

 rigation. The swamps lying at low levels are 

 fertile beyond the ordinary, once drained, be- 

 cause for ages they have drawn on the allu- 

 vium of the neighboring prairies. Just so, the 

 irrigated valleys of the Far West are fertile 

 because for the most part they consist of 

 pockets of silt deposited by the erosion of cen- 

 turies. And, just as the swamp lands we are 

 reclaiming by pumping systems need never 

 feel the blight of drought by judicious man- 

 agement, so the irrigated lands are held at 

 their maximum degree of productiveness by 

 regulation of the amount of water turned over 

 them. With drained lands the source of water 

 supply is constant and independent of the 

 heavens through seepage, and on irrigated 

 lands the optimum moisture content is merely 

 a matter of turning on or off the gates. In 

 this respect alone the Gleaners are able to 



