376 ANNUAL REPORT SMITHSONIAN INSTITUTION, 196 2 



Deprived of water, the human race, with all its thought and emotion 

 and spiritual aspiration, would come to prompt oblivion." ^ 



The American people have become alert to the importance of water 

 in our life and economy. The news media — television, radio, and 

 newspapers — carry stories about pollution of streams, falling water 

 tables, short supplies of water, and the decreasing number of sites left 

 for major waterpower development. Stories are calculated to awaken 

 the reader to the problems of water in the United States and to his 

 responsibility to be aware of these problems and to take part in their 

 solutions. In many instances the stories are exaggerated, but the 

 problems are real. 



In 1960 nearly 270 billion gallons of water per day, or about 1,500 

 gallons per day per person, was used in the United States (MacKichan 

 and Kammerer, 1961). Of this total, 61 billion gallons per day was 

 consumed and was not available for reuse. The estimated and pro- 

 jected withdrawals of water from 1955 to 2000 indicate that in 1980 

 our use of water will be more than double that in 1960 (fig. 1). The 

 estimates for 1980 and 2000, however, may be greatly in error if reuse 

 of water is practiced more widely and intensively than it is now. 



The water that we use comes from many sources which may be 

 shown as parts of a general picture of water movement on the earth. 



THE HYDROLOGIC CYCLE 



The major reservoirs of water on the earth are the oceans, and they 

 form one link in what is known as the "hydrologic cycle." The hydro- 

 logic cycle describes the circulation of water from the ocean into the 

 atmosphere ; the movement of atmospheric moisture across oceans and 

 over the continents ; the precipitation of moisture as snow and rain ; 

 the flow of water in streams and lakes ; the evaporation and transpira- 

 tion of water from the surface back into the atmosphere; the move- 

 ment of water beneath the surface of the ground; and the discharge 

 of water back into the ocean to continue its endless journey. The 

 hydrologic cycle is continuous and cannot be easily separated into 

 its various phases, and in turn its phases are made up of endless and 

 complex details. Water in any one phase of the cycle cannot be treated 

 as a single subject. It must be considered in relation to its total 

 natural environment, to its use by man, and as a function of time. 



Let us begin by considering the moisture in the atmosphere. Water 

 evaporates from the surface of the ocean. It rises in the air and is 

 borne by winds over the landmasses, where a part of it condenses and 

 falls as rain or snow. In the western United States most moisture is 

 brought from the Pacific Ocean and carried east. When winds 

 from the Pacific Ocean meet the west coast, the warm moisture-laden 



2 Meinzer, O. B., Our water supply. Ann. Rep. Smithsonian Inst, for 1937, p. 292, 1938. 



