OVER-IRRIGATION AND ALKALI 375 



the natural drainage outlets of the district, into water- 

 logged lands which had to be abandoned. In that way the 

 danger of seepage has from the beginning been called to 

 the attention of the irrigation communities. 



True, the water that seeps from the canals and the 

 farms is not wholly lost. Some finds its way into the 

 lower canals or rivers and is used elsewhere. The "lost 

 rivers" of the West are examples of this condition. The 

 Sevier River of Utah flows full near its head, and gradually 

 disappears until it is nearly dry; but, lower down, the 

 water reappears and the river flows full again. Where the 

 underflow can be caught, canals have been built for the 

 purpose. Moreover, the underground waters of the 

 country, especially in the arid West, will be used more 

 and more as irrigation by pumping becomes better under- 

 stood. Under the best of conditions, however, much of 

 the water that disappears by seepage is permanently 

 lost. Seepage must be reduced to the minimum. 



225. Comparison with humid areas. The danger from 

 unnecessary seepage, due to excessive irrigation and canal 

 losses, is certainly great; but, the area of resulting water- 

 logged lands is not nearly so great in proportion to the 

 land surface as are the water-logged lands of humid re- 

 gions. According to the last government census, the 

 swamp and marsh lands east of the Rocky Mountains, 

 subject to reclamation, cover an area of 77,000,000 acres 

 nearly equal to the combined area of Illinois, Indiana and 

 Ohio. This area of swamp and marsh land varies roughly 

 with the rainfall, which is another proof of the doctrine 

 that such lands are determined by the quantity of water 

 brought upon the soil surface. The water-logged lands of 

 the irrigated regions form a very small fraction of the 

 cultivable land, and it lies within the power of the irri- 



