42 IRRIGATION PRACTICE 



field and allowed to run down long furrows, often several 

 feet apart. It is practically impossible so to regulate the 

 stream that all the water is absorbed just at the end of 

 each furrow. In fact, if this is attempted by using a very 

 small stream, it means that the upper end will receive a 

 very large quantity of water, while the lower end will be 

 relatively dry and often without a sufficient supply of 

 moisture for abundant plant-growth. If a large stream is 

 used, the whole furrow is given a thorough wetting, but a 

 large quantity of water is wasted at the end of the furrow. 

 This waste water is usually received by a transverse ditch 

 and used on some lower field. To reduce the run-off and, 

 at the same time, give each furrow a sufficient irrigation, 

 the best plan seems to be to use a small stream and a 

 rather short furrow, repeating the furrow below as many 

 times as may be necessary. The shorter the furrow is, 

 the more thoroughly and uniformly may water be applied 

 to the soil. 



In any event, the run-off water must be carefully and 

 skilfully used on lower fields. The run-off presents a 

 problem which must be solved in its own peculiar way on 

 each individual farm. No general rules can be laid down 

 for using the run-off, since the layout of one farm is 

 generally different from that of any other. 



33. The upward movement of water. Under methods 

 of irrigation that use water in moderation, very little 

 water drains below the zone of root-action, yet under 

 the most favorable conditions water may move upward 

 and be lost from the soil surface. The movement of 

 water is usually from the thick to the thin film, that is, 

 from the moister to the drier parts of the soil. When, 

 therefore, a soil dries at the surface, there is a steady 

 upward movement of water from particle to particle to 



