METHODS OF APPLYING WATER 229 



been put into excellent shape; and just here is where a 

 thorough understanding of the principles governing 

 the wetting, puddling and washing of soils, and possible 

 injury to the crop as a result of irrigation, becomes a 

 matter of the greatest moment." (See page 103 et seq.) 



Mead reports that there are over thirty methods of 

 distributing water in use in the United States. Each 

 of these has its special adaptations as to soil, crop, 

 water supply, climate and land contour. All of these 

 methods may be grouped under four general heads, the 

 further differences being in detail of application and 

 not in essential principles. 



These are: (1) Flooding. (2) Furrow distribution. 

 (3) Overhead sprays. (4) Sub-irrigation. 



103. Flooding. Flooding is practiced in several 

 ways, and is applied to a much larger area than any other 

 system. There are two fundamentally different types 

 of flooding: (1) One covers the surface of the soil with 

 a thin sheet of flowing water, maintained until the 

 desired degree of saturation has been reached. (2) The 

 other covers the surface with a sheet of standing water, 

 which is allowed to remain until the soil is sufficiently 

 saturated, when any balance is drawn off, or may be 

 dissipated by percolation through the soil, as is fre- 

 quently though unwisely done. 



The former system corresponds closely with what is 

 termed wild flooding, where the water is distributed by 

 a minute dendric s}^stem of ditches, and the remnant 

 gathered by a reversed dendric system of ditches, or by 

 a head ditch at the foot of the slope. The essential 

 point is to keep a thin sheet of water moving over the 



