BULLETIN OF THE 



II 



No. 190 



Contribution from the Office of Experiment Stations, A. C. True, Director. 

 April 24, 1915. 



THE DRAINAGE OF IRRIGATED LAND. 



By R. A. Harp, Supervising Drainage Engineer. 



CONTENTS. 



Page. 



Introduction 1 



Manifestations ol poor drainage conditions. . . 2 



Specific objects oi draining 2 



Preliminary investigations 2 



Open canals 4 



Covered drains 5 



Choice of type of drain 8 



Location of open canals 10 



Depth and location of covered drains 10 



Protective devices for open canals 13 



Protective devices for covered drains 15 



Some typical problems and their treatment. . 18 



Construction of drains 24 



Maintenance 28 



Subsequent treatment of land 29 



What drainage accomplishes 31 



Cost of drairung 32 



Cooperative drainage 33 



Conclusion 34 



INTRODUCTION. 



It is now generally recognized that iiTigated land may become 

 waterlogged and impregnated with harmful mineral salts, and that 

 drainage must be the means of the reclamation of land so affected. 

 Already, in the United States, more than 10 per cent of the entire 

 area that has been irrigated for any considerable period is either 

 absolutely unproductive or is given over to the less valuable crops 

 or to poor pastures; while even in the most recently developed irri- 

 gation projects serious injury is being wrought. These injured 

 lands are to be found in all the arid and semiarid States and in 

 practically every valley where irrigation is a factor in the agricul- 

 tural development. 



The feasibility of reclaiming these waterlogged and alkali lands 

 has been demonstrated in numerous experiments, and methods have 

 been developed by which the work can be done cfTectivcly and 

 (sconomically. It is the purpose of this bulletin to present in con- 

 cise form the fundamental principles upon which the reclamation of 

 such land is basted, to describe typical conditions and the best 

 methods of treating llictn, and (o giv(^ ixucliciil u(lvic(^ mh to a(;tual 

 operations. 



Note.— Tlio Information In this bulletin Is iiitoii'lo'l for dmliiii«o oiif^inuors und lumlowiuirs of tlio arid 

 West. It lsnotappll(»l)lo to thohiimid .soctlon of Uio United Htulos. 

 777rH»— Dull. 1W)— 15 1 



