8 BULLETIN 4!>5, l\ S. DEPARTMENT OF AGRICULTURE. 



aections being commonly used. Only removable suction pipe should 

 be placed in surface supplies which freeze in winter. 



STORAGE WATER. 



In many cases excellent water supplies for spray irrigation plants 

 are obtained from streams, drains, and wells which do not have a 

 continuous flow of water sufficient without storage. In such cases 

 the water may be stored in a small reservoir. Figure 1 illustrates a 

 small stream across which an earthern dam has been built at a point 

 where it will back considerable water over a flat area and hold it 

 until the farmer needs to irrigate. In the Eastern States much 

 smaller reservoirs can be used than in the arid regions, because the 

 rains are more frequent and are sufficient to make the small streams 

 flow every few weeks. Likewise in the more humid sections water 

 from farm drains and rain water flowing from hillsides and roofs 

 of buildings can be conserved by storage in reservoirs or cisterns 

 built of clay brick or cement, and in this way many gardens may be 

 saved in dry periods. 1 A section in eastern Pennsylvania is rep- 

 resentative of the Eastern States where spray irrigation has devel- 

 oped. The writer estimates from a study of rainfall records and 

 drought periods covering 20 growing seasons in this section that 

 the storage of the water falling on the roof of a building during the 

 summer months is sufficient to irrigate a garden which is three times 

 the area of the building. The reservoir in this case would need to 

 hold about two months' rainfall or the equivalent of 6 inches falling 

 on the roof. 



UNDERGROUND WATERS. 



Underground waters may be divided into ground and artesian. 

 To the first belong the waters which are nearest the surface and more 

 or less influenced by local rainfall, seepage, and droughts. The 

 waters of the second group are confined under pressure beneath an 

 impervious stratum, usually located at considerable depth below the 

 surface. Such water, when tapped by boring, will rise in the well 

 and sometimes overflow at the surface. The development of under- 

 ground waters is usually more expensive than obtaining a supply 

 from surface sources. However, when a farmer is able to obtain 

 underground water at a reasonable depth near or in the center of the 

 field 1" be irrigated the saving in cost of piping may largely offset 

 die expense of sinking wells. 



••Various types of small reservoirs which would be of value to readers of this bulletin 

 are discussed in Bulletin No. 179, of the Office of Experiment Stations, and part 1 of 

 Office of Experiment Stations Bulletin No. 249. The department's supply of these bulle- 

 tins has been exhausted, but copies can be obtained from the Superintendent of Docu- 

 . Washington, D. C, at a cost of 20 cents each. 



