METHODS OF DRAINING IRRIGATED LANDS, 493 



destroy the crop as seepage appears are largely sodium chlorid, or 

 common salt, and disappear quite quickly without special treatment 

 after the fields have been drained. The successful introduction of 

 drainage in Boxelder County has relieved the farmers of a menace 

 which threatened the prosperity of the entire region. Since drain 

 tile can be manufactured in the locality and trenching can be done by 

 steam power, the serious obstacle Avhich stood between the farmers 

 and permanent prosperity has been removed. 



PROGRESS AND DIFFICULTIES IN WESTERN COLORADO. 



The difficulties to be met in draining lands in the Uncompahgre 

 and Grand River Valleys in western Colorado are quite different and 

 more serious. The land is of a shale formation, which when wet 

 becomes exceedingly soft, sometimes to a depth of 10 or 15 feet. The 

 cultivated areas are frequently bordered on one or more sides by lands 

 in Avhich the shale is partially disintegrated and which convey the 

 water from the higher irrigated land, or possibly from irrigating 

 ditches, into the " soil blanket," where it fills up the land so com- 

 pletely as to make a permanent bog. As a preliminary to draining 

 such land soundings or borings are made to locate the position of 

 the shale through which the water reaches the bog. Not infrequently 

 it is entirely impracticable to place a drain through the wet part of 

 the field because of its extremely soft and unstable condition. At 

 least a part of the water must be intercepted and prevented from 

 entering the field before complete drainage can be effected. This is 

 accomplished by placing a drain on the edge of the wet tract in such 

 a way as to penetrate the shale which delivers the water. \A'lien 

 such a drain is constructed small streams of water which pour 

 through the crevices of the shale, usually quite strongly impregnated 

 with alkali, will be encountered. Where shale is found it furnishes a 

 firm bed for the drain. Where, however, it is not found within the 

 limits of the depth at which the drain is placed, it is frequently neces- 

 sary to use a board or prepared frame in the bottom of the trench 

 upon which to lay the pipes, and in addition to this to use gravel to 

 prevent the wet material, which has almost the consistency of water, 

 from entering and filling the drains. After the border drain has 

 operated for a time, by diverting the water from the field, another 

 drain may be laid through the lowest and wettest part of the field, 

 the latter being usually necessary to take care of the surplus water, 

 which is later applied in irrigating. In many instances the inter- 

 cepting drain will effectually dry the land, but the lower soil having 

 been completely filled with water by the process before described, 

 some permanent drains must be provided to take the waste which 

 will accrue from subsequent irrigation. 



