8 DOMESTIC WATER SUPPLIES FOR THE FARM 



impurities washed into them than in the lakes and large ponds, 

 and even where there are both an inlet and an outlet there is 

 often a tendency for the main current to pass directly from the 

 inlet to the outlet without mixing with the water as a whole, the 

 greater part of the lake thus remaining relatively stagnant. The 

 entrance of a very slight amount of polluting matter into such 

 waters may dangerously affect their quality. 



Owing to the slight circulation in these small bodies of water 

 decaying leaves and twigs will frequently accumulate and, to- 

 gether with the growth of water organisms, will give the water an 

 amber or even a dark-brownish color and a noticeable taste. 

 Such coloration does not make the water dangerous any more 

 than the green algous slime that collects on the surface (most of 

 which is perfectly innocent), but both are indications of stagnant 

 conditions that are repugnant to the mind and may mask danger- 

 ous impurities. On the bottoms of ponds of this sort there are 

 usually accumulations of decaying vegetable matter mixed with 

 silt, which are very objectionable in water to be used for drinking. 

 It is such accumulations which give off the bubbles of gas that 

 may be seen rising to the surface when the bottom is disturbed. 



Not all small ponds, however, should be condemned because 

 of their size. Many are fed by springs, are free from pollution 

 and contain water as clear and cool as could be desired. Such 

 ponds may be used to advantage for domestic supplies, although 

 as the farmhouses are usually situated at a distance from the 

 water they are seldom used except for watering stock. 



Many of the water pockets or " tanks " of the deserts, in part 

 natural and in part artificial, are also entirely unsafe even for 

 stock use, although as they constitute the only source of water in 

 many regions such use is unavoidable. In fact, the upbuilding of 

 considerable grazing industries has been made possible by such 

 water pockets in otherwise waterless regions. 



Artificial Ponds, etc. In some of the prairie and semi- 

 desert regions, where streams are relatively few in number or even 

 absent over large areas, and where wells do not yield sufficient 



