DRAINAGE 



DRAINAGE 



1073 



would be to sink a well and pump the surplus water 

 into a surface ditch. Irrigation with pure water would 

 then sweeten the soil and render it again productive; 

 and the whole process of restoration need not be exces- 

 sively expensive. 



If the hardpan is less than 2 feet in thickness, the 

 land may be improved greatly for orchard and vine- 

 yard purposes by the use of dynamite. Blasting 

 should be deep enough to allow the surplus water to 

 escape into the porous earth or gravelly soil beneath 

 the hardpan. On the Pacific coast this method of 

 draining orchard and vineyard land has been quite 

 successful. In any case, unless the soil has good natural 

 sub-drainage, it is both wise and economicalto blast out 

 holes for trees and vines; for the cost of digging holes, 

 if they are as large and deep as they should be, 

 is lessened by an amount almost equal to the cost of 

 blasting. 



Recently, powerful tractors have solved, to some 

 extent, the problem of drainage in many cases by mak- 

 ing deep plowing possible before planting and during 

 the first few years of subsequent tillage of the orchard 

 or vineyard. This machine with the tillage implement 

 turns easily at the ends of the field within the space 

 allowed for turning a span of horses and a plow; it can 

 pass under limbs where a 14-hand horse (56-inch) can 



1350. Improper method of draining a field. 



pass, and as close to the plants as a span of horses can. 

 It furnishes also power and locomoton for spraying 

 and for opening trenches to a considerable depth (18 to 

 44 inches) for the reception of drain-tile. 



In some regions, drains are placed 200 to 300 feet 

 apart, and serve their purpose well. In others they 

 should not be placed farther apart than 20 to 30 feet. 

 Wherever the subsoil is composed of tenacious fine 

 clay, through which the water moves upward or down- 

 ward with difficulty, the narrower intervals are neces- 

 sary. In some instances the surplus water in the sub- 

 soil is under pressure by reason of water which finds its 

 way into it from higher levels, and if this is not removed, 

 the water has a constant tendency to rise to the sur- 

 face. In many such cases drains placed at wide inter- 

 vals may serve to relieve the pressure and drain the 

 land. Since sub-drains are designed to be permanent, 

 are expensive to construct and difficult to repair, the 

 principles of drainage should be well understood, and 

 the work should be undertaken only after a most careful 

 inspection of the land and after the fundamental 

 principles of the subject have been mastered. 



Mains and sub-mains should be avoided so far as 

 possible, since they greatly increase cost, tend to 

 become obstructed, and are often unnecessary. The 

 three long mains in Fig 1350 are not drains, strictly 

 speaking, since the land may be as fully drained with- 

 out them, as shown in Fig. 1351; therefore, they serve 



only to conduct the water of the drains proper. Tiles 

 of 3 to 4 and 5 inches diameter should be used when the 

 drains are infrequent and the flow of water considerable. 

 Smaller ones, 2 to 3 inches in diameter, will suffice 

 when the intervals between the drains are narrow. 



1351. Best method of draining a field. 



Drains should have as uniform a fall as possible, and no 

 abrupt lateral curves or sharp angles should occur as 

 are seen in many places in Fig. 1350. If the drain has a 

 rapid fall in its upper reaches, as is often the case, and 

 but slight fall in the lower, a silt basin should be con- 

 structed at the point at which the rapid changes into 

 the slight fall, if obstructing silt is present. All drains 

 which may be necessary should be placed before the 

 planting occurs. Orchard lands may be drained in the 

 spring, fallowed in the summer, and planted in the fall 

 or the following spring. Drains placed at frequent 

 intervals because of the tenacity of the soil should be 

 comparatively shallow, for if placed deep or at wide 

 intervals, the water will be too long reaching them. 

 If drains are placed at wide intervals they should be 

 at least 3J/ feet deep to be most efficient. If the parallel 

 system is adopted (Fig. 1351), there may be more out- 

 lets to construct and maintain than is desirable; if so, 

 the system might be modified by constructing a sub- 

 main, one side of which will serve also as a drain, and 

 but one outlet will be required (Fig. 1352). Drains 

 through which water runs for the greater part of the 

 year are likely to become obstructed by roots, if water- 

 loving trees, such as the willow, soft maple, and elm, are 



1352. Showing how the drains may be gathered into one when 

 there is only one place at which an outlet can be secured. 



allowed to grow near them. If floating silt is present, 

 the joints of the tiles should be protected for two- 

 thirds of their upper circumferences by a narrow strip 

 of tarred building paper (Fig. 1353), or collars should 

 be used. Stone drains should receive a liberal covering 

 of straw or some similar material before they are filled. 



I. P. ROBERTS. 



