ACTIVITIES 53 



when correlated with records of discharge, show the varia- 

 tions in character of the water with changes in discharge and 

 seasons. They also furnish the basis for classifying the water 

 for irrigation, domestic, and various industrial uses. 



For the publication of the results of stream measurements 

 the country has been divided into twelve primary drainage 

 basins, and an annual progress report is published separately 

 for each of these basins. For the publication of the data as 

 to quality of water, utilization of streams, and other special 

 data, no fixed territorial basis is used. Most of the data con- 

 cerning either surface or ground water are now published 

 in the Survey's series of "Water Supply Papers." Occasion- 

 ally the study of the water resources of an area for a special 

 purpose, as municipal water supply, results in a publication 

 covering both surface and ground waters in the area studied. 



The Survey's investigations of surface waters are put to 

 numerous and important uses. They furnish valuable, and 

 concerning some streams, absolutely indispensably data needed 

 in the consideration and development of irrigation, power, 

 water supply, navigation, and flood protection projects. Their 

 results have been of high value in connection with the irri- 

 gation of the arid lands of the West. The location of rec- 

 lamation projects not only by the national government but 

 by state and private enterprise has for the greatest part been 

 guided by the data gathered by the Survey. Less well known 

 but hardly less important is the part which the Survey's find- 

 ings have played in aiding power development on the streams 

 of the country. 



It is difficult to define in terms of time or of magnitude the 

 entire project of surveying the surface waters of the country, 

 and it is indeed to be questioned whether the work may prop- 

 erly be regarded as definitely terminable, for it is not yet 

 apparent that a point will be reached when the collection of 

 stream measurements and the analyses of water will become 

 unnecessary ; on the contrary it is believed that this work, like 

 the collection of climatic data, must be continued indefinitely. 



