210 



THE IEEIGATION AGE. 



into the supply ditch and divided between two adjacent 

 field ditches. Various devices are used to make the 

 division, but the canvas dam (Fig. 28), with an open- 

 ing controlled by a flap of canvas, is one of the most 

 convenient. One of these is placed at A (Fig. 29) and 

 an ordinary canvas dam at B. The earth dams at C 

 and E are then cut and part of the stream flows into 

 the field ditch CD and the remainder escapes through 

 the opening in the canvas dam at A and flows to the 

 point B, where it is checked and diverted into the 

 field ditch EF. The earth dam at D checks the flow 

 in CD and permits the water to be distributed through 

 a number of openings to irrigate all thai portion in- 

 eluded in C, D, F and E. When this piece of ground 

 is thoroughly soaked to a depth of twelve inches the 

 dam at D is opened and the water rushes through until 

 checked by the next earth dam. The strip below EF 

 is irrigated in a similar manner, one man attending to 

 both. By this method and with a good head of water 

 one man can irrigate on an average five acres per day. 

 If the flow of water is small and intermittent the aver- 

 age may not be more than two acres. 



The second irrigation is applied in the same way, 

 but the amount of water used is considerably less. 

 Some time after the last watering and before harvest- 



Fig. 27. Dammer Used in C caning and Damming Field Laterals 



ing the field ditches are leveled so as not to obstruct 

 the binder. This is often done with a small walking 

 plow by turning two furrows toward the ditch. A bet- 

 ter contrivance, and one which is used on some of the 

 Gallatin Valley farms, is made from a worn out disk 

 harrow. Four disks, two on each side of the center 

 and set at an angle, are attached to a short beam and 

 drawn along the ditch. 



Clover and alfalfa are irrigated in a somewhat 

 different manner. The ditches in grain fields seeded 

 to clover or alfalfa are spaced farther apart than for 

 grain crops, in order to be adapted to the forage crops 

 of the following years. 



In ordinary practice the ditches for clover and 

 alfalfa are located 100 feet apart, and the dams are 

 made of manure instead of earth. Some time before 

 a field is to be irrigated and after the ditching is 

 done, manure, containing considerable straw, is depos- 

 ited in small heaps about sixty feet apart along each 

 ditch. A day or two before the water is turned on 

 each heap is arranged in a more compact form and 

 receives a covering of earth from one to two inches 

 thick on its upper face. This manure and earth dam 

 retains the water in the ditch sufficiently long to water 

 the small intervening space. It is then broken and 

 the water passes on to the next dam. 



After the first irrigation the coarse manure and 

 straw axe deposited on the edge of the ditch and may 

 be used a second or even a third time. 



Manure dams similar to these just described are 

 frequently used for the second irrigation of grain crops. 

 It should be stated, however, that this practice is less 

 generally used now than in former years. Steel dams 

 are now quite commonly used instead of earth dams 

 in grain fields, and the ordinary canvas dam is being 

 substituted for manure dams wherever clover and alfalfa 

 are extensively grown. 



In some sections of Gallatin Valley, particularly 

 under the West Gallatin Irrigation Company's canal, 

 the field ditches are parallel and extend down the steep- 

 est slope from the supply ditch at the top of the 

 field to the catch ditch at the bottom. In this method 

 both earth and manure dams are used in a manner 

 similar to those of grade ditches, but the distribution 

 of the water is different. This may be seen by a glance 

 at figure 30. Water flows out of the ditch from both 

 sides and, the grade being steep, it is distributed from 

 openings made just above each dam. 



I 



Fig. 28. Canvas Dam with Opening to Divide an Irrigating Stream. 



The common practice of irrigating from steep, 

 parallel field ditches in Beaverhead County, Mont., is 

 thus described by Mr. E. C. Lamme: 



"The laterals are made with a lister attached to 

 a sulky frame and drawn by four bourses and are spaced 

 from 30 to 150 feet apart, according to conditions. The 

 size of each lateral varies from sixteen to eighteen inches 

 in width and from ten to twelve inches in depth. Stable 

 manure or half-rotted straw is used for check dams. 

 These are spaced about sixty-five feet apart. 



When the grain is from three to five inches high 

 the first irrigation is begun. On the extensive farm of 

 J. E. Morse, of Dillon, each irrigator is given 125 

 miner's inches of water, which is divided between two 

 laterals. The water is kept running night and day, the 

 men changing at noon and midnight. As soon as the 

 first irrigation is completed the dams are reset for the 

 second irrigation. In resetting the dams the manure 

 or straw is mixed with the earth while both are kept 



