DRAINAGE OF IRRIGATED SHALE LAND. 



11 



earlier, Harris found that these two salts are extremely injurious to 

 plant life, both ranking ahead of sodium carbonate in this respect. 



The different alkalies, including the nitrates, present in large quan- 

 tities in the shales and in the soils formed from the shales, had their 

 origin in the brackish waters of the old inland seas.^ That the 

 nitrates present in the water samples of Table I are an inherent 

 part of the virgin shales and not dependent upon conditions following 

 cultivation is shown clearly by the analyses of the seepage waters 

 in Table II, as all three of these samples came from tracts of desert 

 lands that never were cultivated, nor was any land lying above them 

 ever cultivated. The water represented by samples A and B in 

 Table II was the direct result of losses from a new canal through 

 which water had been run only for about six weeks during the lat- 

 ter part of the same season the samples were taken. Sample C rep- 

 resents seepage water just beneath Mount Garfield in the Bookcliff 

 Range in western Colorado. The quantities of nitrates in these 

 samples are remarkable, especially in samples A and C. 



DRAINAGE METHODS. 



Among the owners of shale lands many conflicting opinions are 

 expressed as to the cause of seepage, and almost as many remedies 

 suggested. Many drainage systems have been installed by land- 

 owners, with but little success. The ineffectiveness of ordinary drain- 

 age methods has been demonstrated repeatedly by the many failures 

 in the arid West of methods which commonly are successfully prac- 

 ticed in the Middle West and in the East. Furthermore, even the 

 methods that have been employed successfully in the drainage of the 

 ordinary type of affected land in the arid West have failed when 

 applied to shale lands. Shallow drainage is of absolutely no avail, 

 and deep drainage with a small interval between drains fails also 

 when the seepage water is supplied under pressure by outcropping or 

 immediately underlying shale formations. Soil which is largely 

 made up of shale belongs to the " adobe " type and does not respond 

 readily, under ordinary conditions, to any type of drainage; and 

 where shale furnishes the water under pressure, drainage systems 

 must be designed which will take the water from the shale before it 

 reaches the soil. 



EFFECTIVE DRAINAGE 



PEELIMINAEY EXAMINATIONS. 



Effective drainage of shale lands depends upon the location and 

 depth of the drains and upon the proper installation of relief wells. 

 To locate the drains properly is a slow and laborious process, for it 



1 Stewart, Robert, and Peterson, William. The Nitric Nitrogen Content in the Country 

 Eock, Utah Experiment Station, Bulletin 134, 1914. 



