HYDROLOGY OF NEW YORK 



117 



In these formulas, D=discharge in cubic feet per second; C=a 

 coefficient, depending for its value upon rainfall, soil, topographi- 

 cal slope, elevation,, size of the stream, shape of the catchment, etc. 

 and M=area of the catchment in square miles. 



Coefficient table for representative areas. hi Mullins's Irri- 

 gation Manual there are given tables for the value of the 

 coefficients of these two formulas, together with the correspond- 

 ing depth in inches, drained off from the given areas, and the dis- 

 charges in cubic feet per second. These two formulas are cited 

 because they take into account the principle of the sliding coeffi- 

 cient, as does the Kutter formula, a principle which, all things 

 considered, is the most useful thus far devised. It is true that 

 maximum discharge formulas have been devised taking into 

 account average slope, depth, and intensity of rainfall, area of 

 the mountainous part of the catchment and area of the flat part of 

 the same in square miles, and length of stream from source to 

 point of discharge. These formulas, however, also involve from 

 one to two coefficients and become complicated in use without, it 

 is believed, any special gain over the simpler expressions cited. 

 The formulas of Dickens and Kyves. which comprise within the 

 coefficient C everything included in the more complicated form- 

 ulas, were the forerunners of formulas of this class. 



Cooley's formulas. In an able paper 1 Mr George W. Cooley, 

 C. E.. gives the following formulas for runoff: 



For a catchment without lakes. 



F = 0.844 LRC. (16) 



For a catchment with large lakes as receiving reservoirs, 



F=(R+-|^-E)X0.844 W. (17) 



In which. F = flow in cubic feet per second. 

 R =! precipitation in feet. 



L = land surface of catchment in square miles. 

 W= water surface of reservoirs in square miles. 

 E = evaporation in feet. 

 C = coefficient of available rainfall. 



lHydrology of the Lake Minnetonka Watershed, by George W. Cooley, C. 

 E. : Monthly Weather Review. January, 1899. 



