METHODS OF DRAINING IRRIGATED LANDS, 499 



assessment of their cost upon the several tracts of land for which 

 they provide drainage. 



There are at least 800,000 acres of irrigated land which now require 

 draining in order to make them profitably productive, the larger joart 

 of which will require the construction of outlet drains in which more 

 or less cooperation of property OAvners will be required. xVfter the 

 land which is drained has become fairly free from alkali, with which 

 it is often highly charged, the water flowing from the main drains 

 becomes highly valuable for irrigating. Such water then becomes 

 an asset, since it may be used to irrigate lands occupying a lower 

 level. These questions have not yet been adjusted satisfactorily in 

 connection with drainage projects. In fact, they are only broached 

 when the necessity for public drainage districts requires their con- 

 sideration. It is quite certain that drainage districts must soon be 

 as much a feature of irrigated farming as they now are of agriculture 

 in the humid sections. 



BENEFICIAL EFFECT OF DRAINING ON ALKALI LAND. 



One of the effects of over saturation in many localities is the accu- 

 mulation of harmful salts, commonly called alkali, in the soil. Their 

 appearance, which is manifested by the failure of crops, is frequently 

 the first intimation the farmer has that his land has become too wet. 

 EfToctive drainage removes the cause of the accumulation, yet spe- 

 cial treatment is frequently required to remove the excess of alkali 

 sufficiently for growing crops. Copious irrigation, followed by 

 thorough and deep cultivation and the growing of alkali-resistant 

 crops for a season or two, quite commonly restores the land to its 

 former productive condition. Some fields, however, are so fully 

 charged with salts, due to seepage and to neglect in the use of pre- 

 ventive measures, that a longer treatment by various methods of 

 flooding, in connection with the relief that is furnished by drainage, 

 is required. Complete drainage, however, is the first essential in 

 such reclamation, but should be followed by liberal irrigation until 

 the alkali has been removed sufficiently to permit the soil to grow a 

 crop, after which the quantity of water may be adjusted to the actual 

 needs of the crops which are to be grown. No fact has been more 

 thoroughly developed or forcibly emphasized by drainage experi- 

 ments and ordinary field practice than the value of timely attention 

 to this subject as a preventive of seeped and boggy fields. 



PUMPING DRAINAGE WATER FROM SUMPS INTO IRRIGATION 



DITCHES. 



This method of disposing of drainage water has been found prac- 

 ticable in the Fresno district of California. That great irrigated 

 plain is not traversed by streams which can be conA^eniently utilized 



