18 GENERAL INTRODUCTION 



determined and the mean of these values for the period of record 

 was taken as the minimum flow. It is obvious that this is some- 

 what higher than the absolute minimum, but the latter is usually 

 of so short duration that it would not be practicable or profit- 

 able to develop a site on this basis. The efficiency of the hydro- 

 electric equipment has been assumed to be 75 per cent. 



The assumed maximum power has been based upon the con- 

 tinuous power indicated by the flow of a stream for the six months 

 of the year showing the highest flow. The average flow for the 

 lowest week of the lowest month of these six highest months was 

 then taken as the assumed maximum for the year. The yearly 

 averages thus obtained were then themselves averaged for a 

 series of years. It is, however, common practice to estimate on 

 the continuous power for nine months instead of six, which would, 

 of course, reduce the amount of maximum power available. 



The above estimates do not include any storage possibilities 

 and a commercial development of the maximum power would 

 have to be based on the assumption that it would be profitable to 

 install auxiliary fuel plants to supplement the deficiencies during 

 the remaining six months of the year. 



An endeavor has been made to determine the maximum power 

 that might be produced if all the practicable storage facilities on 

 the drainage areas were utilized. Surveys on many of the basins 

 make possible a fairly close estimate, but inasmuch as fully three- 

 fourths of the country has not been surveyed in a manner suitable 

 for this purpose, only rough estimates can be given for the entire 

 area. It may, however, be assumed with confidence with all 

 practicable storage sites utilized and the water properly applied, 

 there might be established eventually in the country a total water- 

 power installation of at least ICO million horse-power and possibly 

 more. It should, however, not be assumed that all this power is 

 economically available to-day. Much of it, indeed, would be too 

 costly in development to render it of commercial importance under 

 the present condition of the market and the price of fuel power. It 

 represents, on the other hand, the maximum possibilities in the 

 day when our fuel shall have become so exhausted that the price 

 thereof for production of power is prohibitive, and the people of 

 the country shall be driven to the use of all the water power that 

 can reasonably be produced by the streams. 



The total developed water power of the United States, exclud- 



