SOIL CHANGES DUE TO IRRIGATION 



95 



position of the soil and of the water. To establish equilib- 

 rium between the soil and the water, in conformity with 

 chemical and physical laws, substances dissolved in the 

 irrigation water are absorbed and held by the soil, or 

 corresponding substances are taken from the soil to 

 enrich the drainage water. Because of this soil power of 

 absorption, the water that drains from the soil is propor- 



FIQ. 18. Badly corroded ditch due to excessive fall. On a larger scale this is the 

 action of swift rivers. 



tionally of a much different composition from the water 

 which was originally added to the soil. This is brought 

 out by the analysis on page 77. 



68. Suspended matter in river waters. By far the 

 larger part of river waters carry not only large quan- 

 tities of dissolved substances; they carry, also, considera- 

 ble loads of suspended solid matter. This suspended 

 material is naturally derived from the washing effect of 



