SPECIAL FARM TOPICS 281 



posts and brush, of brush and rock or cobbles. Such structures are 

 not usually water-tight, but they will raise the water to the level of 

 outflow into the ditch which is to carry it to the land to be irri- 

 gated or to the reservoir from which it is to be distributed. A bet- 

 ter dam, either of masonry or of earth, made water-tight by a pud- 

 dle-bar of clay, may last for a long time in a small stream if adequate 

 arrangements are made for the passage of ^waste and flood water. 



Raising a small stream in a bed requires a dam of greater 

 strength. In such cases it is safer to make the dam of timber or 

 masonry arching upstream, bedded well into the banks, and pud- 

 dled well above with clay, to prevent leakage, which would soon 

 undermine and carry down an otherwise good structure. Such a 

 dam will cause the bed of the stream above it to fill with sediment, 

 which will reduce the direct pressure. 



Location of the Head Gate. At the point of diversion from the 

 stream a head gate should be put in. This is a very simple construc- 

 tion of plank with a sliding gate capable of being raised and lowered. 

 It will protect the ditch by keeping the water out in time of high 

 water. It should have a cross plank on the stream end, so that the 

 water shall fall over the plank, as this will prevent much heavy sed- 

 iment from entering the ditch. Obviously the dam must raise the 

 water sufficiently to surmount this obstruction. (F. B. 138.) 



On the quality of soil through which the ditch must be con- 

 structed depend the permanency of its channel, the rate of velocity 

 at which water can safely be carried, the cost of first construction and 

 the economic value of the ditch as a water carrier. (Y. B. 1900.) 



The cost of building these ditches is variously estimated at from 

 25 to 50 cents per rod, depending on the local conditions, amount 

 of fluming, etc., though a close estimate is hard to form. The ex- 

 pense of cleaning and maintaining them is about $25 per year for 

 each quarter section, or, as some have apportioned it, 20 cents per 

 acre for each acre under the ditch. (Ex. S. Bui. 133.) 



Proper Location of Ditches. Farm ditches should be located 

 in the right place at the start. It is a mistake to build ditches for 

 the lower part of a farm and then in after years, when there is a 

 desire to irrigate the remainder, to be obliged to build a second series 

 of ditches for the higher land. Sufficient water should first be con- 

 veyed from the canal or other source of supply to the highest point 

 and from there distributed to the various subdivisions. In laying 

 out these permanent ditches an effort should be made to locate them 

 along field or fence boundaries, if possible, in order not to obstruct 

 the passage of teams and implements in fields. When the grade is 

 too steep to permit this a curved location through fields should be 

 chosen. 



Ditches on Uneven Land. It often happens that a farm is 

 more or less cut up by ravines or depressions which intersect or sep- 

 arate fields, and the supply ditches have to be extended across these 

 low places. This is usually done in one of three ways. When the 

 depression is not more than a few feet deep levees are built on each 

 side ; in other cases flumes are built on grade from side to side, and, 



