336 DRY-FARMING 
-to supply himself with all the water needed for the 
“homestead. Such reservoirs may already be found 
in great numbers scattered over the whole western 
America. As dry-farming increases their numbers 
will also increase. 
When neither canals, nor springs, nor flood waters 
are available for the supply of water, it is yet possible 
to obtain a limited supply by so arranging the roof 
gutters on the farm buildings that all the water that 
falls on the roofs is conducted through the spouts 
into carefully protected cisterns or reservoirs. A 
house thirty by thirty feet, the roof of which is so 
constructed that all that water that falls upon it is 
carried into a cistern will yield annually under a 
a rainfall of fifteen inches a maximum amount of 
water equivalent to about 8800 gallons. Allowing 
for the unavoidable waste due to evaporation, this 
will yield enough to supply a household and some 
live stock with the necessary water. In extreme 
cases this has been found to be a very satisfactory 
practice, though it is the one to be resorted to only 
in case no other method.is available. 
It is indispensable that some reservoir be provided 
to hold the surface water that may be obtained until 
the time it may be needed. The water coming con- 
stantly from a spring in summer should be applied 
to crops only at certain definite seasons of the year. 
The flood waters usually come at a time when plant 
growth is not active and irrigation is not needed. 
