IRRIGATION IN FIELD AND GARDEN. 



BY PROFESSOR E. J. WICKSON. 



(Reprinted from Farmers' Bulletin No. 138, issued by U. S. Dept. of Agriculture. 



FLOODING IN CONTOUR CHECKS. 



Preparing a field for flooding in contour checks consists in throw- 

 ing up low levees approximately on contour lines, with cross levees 

 at intervals to limit the area of the checks. This method is best 

 suited to land of very gentle slope land which the eye would judge to 

 be nearly level. The main idea is to restrain the water with levees 

 which will not prevent crossing with farm machinery, and which 

 therefore should not be much more than one foot in height and usually 

 less than that. The contour lines showing one foot differences in ele- 

 tion must be some distance apart to leave inclosed areas large enough 

 to make it worthwhile, and this can only happen on nearly level land. 

 In order to cover the whole surface the levee on the lower line or side 

 must always be a little higher than the difference in elevation between 

 the bases of the two levees, because it is seldom a check can be made 

 brimful, and unless that is done the water would not be set back to the 

 base of the levee on the higher line. 



On land with very much slope the checks would obviously be too 

 small and the levees too high and expensive, and they would interfere 

 too seriously with the operation of machinery to make the system 

 practicable. On the other hand, for nearly level land to be put down 

 permanently into grasses or clover, the contour-check method is con- 

 stantly growing in favor, and has largely displaced the more elaborate 

 rectangular-check system, which will be discussed later. 



Contour checks were formerly used only in connection with lateral 

 ditches leading down the slope in the line of greatest fall, and the 

 levees were run each way from these ditches and the checks filled 

 from gates or temporary openings in the sides of the ditches. This 

 is still done, and is desirable in large fields suitably laid off by a sur- 

 veyor. For smaller fields, however, and without professional assist- 

 ance, the laterals can be largely dispensed with and the contour 

 checks filled one from the other with very simple gates to control the 

 flow of water. 



It is very common in California to see quite large fields of alfalfa 

 in which all the laying off and levee construction have been done by 

 home skill and with farm teams and tools. The way is, in outline, as 

 follows: Plow the whole field deeply and then begin at the highest 

 point in the field at which water can be delivered by a supply ditch. 



