The Use of Reservoirs 323 



The amount of seepage from reservoirs must vary with the 

 character of the soil, but Carpenter cites a case where the loss 

 from this cause did not exceed 2 feet for a whole year, and 

 this is satisfactorily small. 



Where the soil is very open and sandy, it may be necessary 

 to haul on clay or fine soil to use in puddling, or the reservoir 

 may require covering with coal tar, asphalt or cement. These 



Fig. 76. Rectangular reservoir for windmill irrigation. 



materials, however, are expensive, and usually not within the 

 reach of small irrigators. 



The loss of water from a reservoir by evaporation in dry, 

 windy climates is much larger than the necessary seepage, and 

 this can only be lessened by planting windbreaks about the 

 reservoir. 



A circular reservoir 4 feet deep and 40 feet in diameter will 

 supply .35 acres with 4 inches, and .69 acres with 2 inches of 

 water. One, 100 feet in diameter and 4 feet deep will irrigate 

 4.32 acres with 2 inches of water and 2.16 acres with 4 inches, 

 while a reservoir 209 feet on a side and 4 feet deep will supply 

 water enough to irrigate 12 acres with 4 inches of water, 16 

 acres with 3 inches, and 24 acres with 2 inches, 



