444 DRY LAND FARMING 



state or by the central government. In this way the 

 general course of these underground basins may be so 

 certainly traced that it would be known where water 

 could be obtained over them. 



Why water is scarce. Water is scarce in the arid 

 and semi-arid regions because: (1) of the low precipita- 

 tion; (2) of the character of the precipitation; (3) of 

 the hardness of the unbroken soil ; (4) of the extent 

 to which moisture from snow escapes, and (5) of the 

 relatively rapid evaporation. 



The low precipitation is one of the most potent of 

 the reasons for the scarcity of water in dry areas. It 

 stands to reason that where the precipitation is light 

 the available water supply will be meagre. It is rea- 

 sonable to suppose that where the rainfall is 40 inches 

 per annum water in the soil and subsoil will be much 

 more plentiful than where the rainfall is 20 inches, and 

 where the rainfall is 20 inches it is much more plenti- 

 ful than where it is 10 inches. Where the rainfall is 

 20 inches the moisture should be such as to make it 

 easily possible to grow crops with much certainty and 

 to establish very desirable homes. When the rainfall is 

 15 inches, crops may still be grown with much certainty 

 and homes may also be built, but not so easily as under 

 the conditions previously stated. Where the rainfall 

 is but 10 inches, fair crops may usually be grown, but 

 home building in the true sense of the term is difficult 

 in the absence of irrigating waters. But the conclusion 

 should not be reached, that the amount of the water 

 that falls is the chief factor in determining the amount 

 of the water present. True, it is an important factor, 

 but it is only one of a number. 



The character of the precipitation exerts a greatly 

 important influence on the water supply. Should it 

 come in the winter much of it may be lost to the soil 

 because: (1) of the extent to which the soil may be 



