242 



THE IRRIGATION AGE. 



THE SCOPE AND PURPOSE OF THE IRRIGATION 



INVESTIGATIONS OF THE OFFICE 



OF EXPERIMENT STATIONS. 



BY ELWOOD MEAD, IRRIGATION EXPERT IN CHARGE. 



Courtesy U. S. Department of Agriculture. 



With relation to rainfall the territory of the 

 United States is divided into three parts the humid, 

 the subhumid and the arid. In the humid region the 

 rainfall is ordinarily abundant, but there are occasional 

 seasons when it is insufficient for the raising of crops, 

 and in most seasons there are times when crops are 

 checked in their growth by periods of drought lasting 

 from a few days to a few weeks. The subhumid region 

 includes the territory where dry periods in summer are 

 the rule. ' The injury to crops in subhumid regions is 

 due to two causes insufficient moisture and great ir- 

 regularity in its distribution. The arid region includes 



all of these regions. It is a necessity in the arid region, 

 of great value in the subhumid district, and is proving 

 highly profitable in the growing of certain crops in 

 the humid region. There are also large areas in the 

 recently acquired insular possessions of the United 

 States where irrigation is required, and where the 

 value of the products permits of a large outlay to pro- 

 vide for its use. The work of the irrigation investiga- 

 tion of the Office of Experiment Stations covers, there- 

 fore, the whole of the United States. 



INVESTIGATIONS IN THE ARID REGION. 



The greater part of the irrigation work of this 

 office has been carried on in the region where farming 

 is impossible without the artificial application of water 

 to crops. This includes all of- the Territories of 

 Arizona and New Mexico, the States of Colorado, Utah, 

 Nevada, Montana and Wyoming, and large parts of 

 California, Oregon, Washington, Idaho, North Dakota,. 



Irrigation Investigations Measuring Station on Jackson Lateral, Laguna Canal, Rockyford, Colorado. 



the areas where cultivated crops can not be grown by 

 the aid of rainfall alone. 



Geographically, these regions are arranged from 

 east to west, although no exact line can be drawn sep- 

 arating them. The humid region, as generally de- 

 scribed, includes all of the United States westward to 

 a line which would cross Nebraska and Kansas about 

 halfway between their eastern and western borders. 

 The subhumid region lies between the humid and arid 

 regions, extending from the Gulf of Mexico to Canada 

 and including irregular areas in the different Pacific 

 coast States ; while the arid region includes all the 

 territory lying west of the eastern subhumid belt with a 

 considerable exception along the Pacific coast, and with 

 smaller local areas in each of the arid States. 



Irrigation is employed as an aid to agriculture in 



South Dakota, Nebraska, Kansas and Texas. The- 

 greater attention paid to the problems of this section 

 of the country is justified by the fact that here irrigation 

 is a necessity rather than a valuable adjunct to agri- 

 culture. It measures agricultural settlement and very 

 largely controls the development of other industries, 

 because both the cost and comfort of living are very 

 largely determined by the production of a home food 

 supply. In the regions farther east, the adoption of 

 irrigation is determined by whether or not it will im- 

 prove conditions already favorable, but in the arid re- 

 gion it is the choice between civilization and desert 

 condtion. 



The work in this region has followed two general 

 lines agricultural and engineering, legal and social. 

 Of these, the legal and social problems present the- 



