THE WATER SUPPLY IN DRY AREAS 449 



How water that falls may be saved. The water that 

 falls in dry areas may be saved: (1) by constructing 

 cement lined cisterns; (2) by erecting dams of proper 

 construction ; (3) by piping from more or less distant 

 springs. The reference here, of course, is to the sav- 

 ing of water that is needed for drinking, for economic 

 uses in the household and for live stock. The saving 

 of the water of precipitation for the use of the crops is 

 an entirely different proposition. To discuss that, ques- 

 tion properly is to discuss the whole question of the 

 management of the soil when farming dry areas. 



Water collected from the roofs of buildings can 

 only be preserved in cisterns or in wells. In these the 

 water collected cannot usually be held .in the absence 

 of a cement lining. When water may be stored 

 thus, the loss through evaporation is almost entirely 

 prevented. It may also be protected from contaminating 

 influences. The cost of such storage need not be very 

 large. 



The dams that are to aid in the storage of waters 

 will be costly in proportion to their size, to the avail- 

 ibility of the materials for their construction and to the 

 nature of the materials used. In size they run all the 

 way from a few feet in height and thrown across a 

 narrow neck of a ravine, to the dimensions of a dam that 

 may tax the power of a large corporation to build it. 

 It is only the small dam and the small reservoir that 

 the average farmer should try to build. Even when 

 this is undertaken, the plan is good which seeks advice 

 from those skilled in such work. The materials suitable 

 for construction may be at hand. In other instances they 

 have to be brought some distance. Usually, however, the 

 materials at hand will suffice, providing the aid of cement 

 is called in when necessary. Of course, such dams will 

 be costly of construction in proportion to the extent to 

 which cement is called for. In some instances, however, 



