32 University of California Publications in Zoology [Vol. 18 



river system for a series of ten years has been computed for the bio- 

 logical survey of San Francisco Bay (Sumner, et al., 1914, p. 77) by 

 a summation of the measured flow of the principal tributaries of this 

 system. Througli the courtesy of Mr. H. D. McGlashan of the United 

 States Geological Survey, who has furnished data for the years 1911-12 

 to 1914—15, it has been possible to complete these data for the years 

 of the survey, and also for the two following years. Though not rep- 

 resenting absolutely the total amount of fresh water passing through 

 Carquinez Strait from these rivers, these data, compiled according to 

 a uniform method for the fourteen years represented, furnish at least 

 a fairly accurate picture of the relative variation above or below the 

 average in the discharge of these rivers. 



It is to be noted from the table below for the annual discharge 

 from the Sacramento-San Joaquin river system that the years 1912 

 and 1913 were both years of unusually small discharge, the runoff 

 amounting to less than half the average amount for the fourteen 

 years for which acceptable data are available. In the season 1913-14, 

 however, the discharge of fresh water was over 22 per cent more than 

 the normal amount. 



DISCHAEGE OF SACRAMENTO AND SAN JOAQUIN RIVER SYSTEMS 

 In Acre-Feet, Based Upon Records For Fourteen Years' 



' Care has been taken to complete this table according: to the same method as that employed 

 by Sumner in compiling the data for the years 1878-79 to 1910-11 inclusive (Sumner, et al., 

 1914, p. 77). 



2 The runoff year is computed from October 1 to September 30. 



