4 DOMESTIC WATER SUPPLIES FOR THE FARM 



evaporated to a greater degree than rain, especially during periods 

 of sunshine and warm winds that follow storms. The evapora- 

 tion from different areas also differs greatly. From forest- 

 covered soils it is relatively small ; from open plains it is relatively 

 large. 



Absorption. - - The rain water that is not evaporated immedi- 

 ately or carried off by streams sinks into the ground. The ground 

 receives the greater part of the rainfall, probably nearly 80 per 

 cent in the eastern United States and 90 or 95 per cent in much of 

 the West. Absorption by the underlying rocks takes place both 

 directly and indirectly. Rain may fall on the surface of the rocks 

 and be absorbed in their pores, fissures and cavities, or it may be 

 first absorbed by loose, unconsolidated surface deposits and after- 

 wards carried down into the rocks, or it may be gathered into 

 streams that flow over rock surfaces and from these gradually 

 absorbed by the underlying rocks. The amount of rainfall that 

 the rocks absorb indirectly is far greater than that which they 

 absorb directly. 



Water that enters sands and gravels generally moves toward 

 the streams rather than away from them, but in regions where the 

 rainfall is small the gravels may absorb water from the streams 

 which rise in regions of greater rainfall. 



Recovery of Natural Supplies. Of the surface waters ponds 

 and lakes are directly available as sources of water supplies, and 

 streams may be made so by the simple process of impounding the 

 waters by dams. The waters of springs may likewise be collected 

 in reservoirs and distributed as desired. 



The recovery of ground waters presents more difficulties. Not 

 only must wells be sunk, often to great depths and at heavy ex- 

 pense, but pumps and even power must usually be provided for 

 raising the water to the surface, the only exception being those 

 artesian wells whose waters are under sufficient head to bring 

 them to the surface and give rise to natural flows. 



Sources of Farm Supplies. - - The sources of the water used on 

 the farm are numerous lakes, streams, springs, drilled, bored, 



