284 



SOIL EROSION 



comes from good farming lands. This means a reduction of the 

 productive power of the country. ' * _ 



Effects on Irrigation, — Soil erosion is one of the serious dangers 

 that threaten irrigation, as follows: When the blanket of soil is 

 removed from the mountain sides, there is removed that natural 

 reservoir which protects the headwaters of the streams. Because 

 of l^rge amounts of soil brought down by the streams, artificial 

 reservoirs are filled up. Furthermore, water carrying sediment 

 decreases the efficiency and increases the cost of maintaining 



Fig. 188. — Soil erosion damages fertile fields. (Wisconsin Station.) 



/ . • . ■-..-' ._-. __\-\; ... . ■ , I ."'-'\ 



diversion dams, pipe lines, flumes, and canals. When irrigation 

 water carries very much mud it injures the crops to which it 

 is applied. ' " . i \ 



Effect on Water Pother .^Erosion causes a loss of water power 

 in two ways — the blanket of soil is removed from mountain sides, 

 thus destroying the natural reservoir for water; and artificial 

 reservoirs are filled up. In this manner soil erosion interferes 

 with the steady flow of water so essential in developing successful 

 water power. 



Erosion greatly interferes with navigation, especially on the 

 inland waterways of the country. In fact, it is largely because 

 of the bad effects produced by erosion that these waterways have 



