RESERVOIR BUILDING 59 



reservoir one foot and put in exit pipes of four and six inches to 

 release water in different directions. 



Stone or Brick Walls for Reservoirs. Very shapely but rather 

 more expensive walls can of course be made of stone or brick laid 

 in cement or of reinforced concrete, and in this way the water con- 

 tents of the same diameter can be increased. The bottom can be 

 puddled or clayed or cemented, according to the character of the 

 ground or the taste of the builder. 



Subterranean Reservoirs. Large shallow wells are often the 

 cheapest reservoirs, and with pumps of large outflow- sufficient 

 head is secured for direct application to the distributing ditches. 

 Tunnels are also subterranean reservoirs and are frequently used 

 as such. Both these wells and tunnels are economical of water, a 

 evaporation is very slight. The following is an instance : 



Mr. C. L. Durban says that the cheapest reservoir that a man can build 

 on his land for retaining water for irrigation purposes is a tunnel run into a 

 hill. An open reservoir in a canon or other suitable place, will lose one- 

 third of its water during the summer from evaporation, while in a tunnel 

 there is no loss. A small spring will supply a tunnel with sufficient water 

 for many* purposes. He has illustrated this in a practical manner. On his 

 own land at Mesilla valley, he run a tunnel thirty-five feet long into a hill, in 

 so doing tapping a spring; this tunnel he dammed up, leaving a space thirty- 

 five feet long and the size of the tunnel, which is about five feet by six 

 feet, to be filled with water. He says that the tunnel is the cheapest and 

 best form, and that for each dollar expended one can obtain a space equal 

 to twenty-five cubic feet. 



Sub-irrigation by Trenches. Another form of subterranean 

 reservoir consists of trenches filled up to the plow-depth with broken 

 rock. It is prodigiously expensive and seems only worthy of con- 

 sideration in the improvement of a hillside home place, where satis- 

 faction is not conditioned upon cost. A California instance of the 

 system is the following, found in Lassen county in the improvement 

 of a home garden : 



The grounds have too great a slope for spraying, and instead of supply- 

 ing surface ditches, the owner constructed permanent trenches, which have 

 no outlet except by seepage. These trenches extend one hundred feet in 

 length along the face of the slope, each being eighteen inches deep and thirty 

 inches wide. The earth was scattered on the upper side of each cut, and by 

 a little care in plowing the garden was terraced into slopes of less grade, 

 each one hundred feet long, and twenty-eight feet wide. As a driveway 

 passes along each end of the terraces, nearly all the cultivation is done by a 

 horse turning on the driveways. 



