RAISED AND LOWERED BEDS. 



63 



the tendency is to use the ditches too long and allow 

 them to become cemented by action of water and deposit 

 of slime. Besides, they grow weeds and distribute seeds 

 if their banks are neglected. In most cases it is better 

 to employ less permanency breaking up the ground and 

 locating new ditches at shorter intervals of time. 



Lowland Irrigation by Seepage. Another form of irri- 

 gation by means of permanent ditches is that practiced 





DEPRESSED BEDS AND IRRIGATION SYSTEM. 



RAISED BEDS OR RIDGES IRRIGATED BY CAPILLARITY. 



on reclaimed lands along the interior rivers. When the 

 rivers are swollen from summer melting of snow in the 

 high Sierra, the water is brought to the land by flood- 

 gates in the levees. When the rivers are low very capa- 

 cious pumping plants are used the same serving at other 

 times to drain the lands when they are too wet from the 

 rainfall or seepage. The soils of these reclaimed lands 

 are loose and prone to dry out because of their lack of 

 capillarity, so that at times irrigation is as necessary as 



