Field Irrigation by Hooding 345 



allel lines from which the lateral spread may be, to 

 a large extent, by capillary creeping, and they guide 

 the flow past minor inequalities, preventing the water 

 from becoming concentrated so as to do injury 

 through increase in volume and velocity and from 

 running around areas, leaving them dry. This mark- 

 ing is so rapidly and cheaply done, and obstructs 

 the surface so little, that it is to be highly recom- 

 mended where applicable. 



A corrugated roller might be used instead of the 

 sliding marker to form the water lines, but this 

 would have no tendency to throw the kernels of grain 

 to one side, and the channels would be more obstructed 

 by the plants. Neither could so great a depth be 

 secured, especially on heavy soils not deeply and 

 recently worked. 



In the second flooding system, where the water is 

 made to stand over the whole surface to any desired 

 depth, the fields must be laid out in areas bounded by 

 ridges or low levees, which check the flow of water 

 and hold it as in a wide and extremely shallow 

 reservoir. 



The size of the checks in which a field is laid out 

 will be determined by its general slope, by the head 

 of water available, and by the height of the levees or 

 check ridges. It is desirable, for meadow and grain 

 irrigation, to make the checks as large as practicable 

 and at the same time to keep the ridges so low 

 as not to interfere with the movement of farm 

 machinery over the field. 



If the slope of the field is 6 inches in 200 feet, 



