70 IRRIGATION INARMING. 



contadl with in flowing in a ditch, the greater the fric- 

 tion will be and the less the velocity and quantity of 

 water. Therefore to obtain the greatest velocity and 

 quantity of water the ditch should be as straight as 

 possible. If bends are necessary they should not be 

 abrupt, but as gradual as possible. A very good exam- 

 ple of an easy curve is shown in Fig. lo. 



For a steady flow the grade should be the same the 

 entire length of the ditch, or as nearly vSo as circum- 

 stances will permit. The sides and bottom should be 

 regular and smooth, and clear of stones, weeds, etc. 

 The weak spot in every canal is most apt to be found 

 at the curves and angles, and these must be protecfled. 

 Where, as is the case in some sedlions, there is plenty 

 of stone, the water-line at the curves may be partially 

 protedled by riprapping, but this involves a large 

 amount of labor. Where there are no stones other 

 means must be used. Willows are oftentimes planted 

 to give bank prote(5lion. Where gravel may be had a 

 shore line may be covered with it, thus forming a 

 natural water-break. In some cases it may be best to 

 constru(5l a breakwater of plank sharpened and driven 

 into the bank, or laid to posts set in the bank. The 

 steeper the bank the greater, of course, will be the dis- 

 placement of the earth by water's adlion. In Fig. ii 

 is seen a canal on the hillside. 



Headgates. — The best mechanical effort in build- 

 ing a canal should be expended on the headgate. This 

 should be located within a few hundred feet of the 

 intake at the river with a fore bay of only moderate 

 grade intervening. The old-fashioned headgates were 

 built of lumber and were not usually sufficient to with- 



