PHYSICAL OCEANOGEAPHY OF THE GULF OF MAINE 



839 



The run-off from the area tributary to the St. John River may therefore be set 

 at about 24 inches annually. Probably this applies equally to the Nova Scotian 

 streams, while the run-off for the minor rivers along the west and north coasts of the 

 gulf may be estimated at 18 to 22 inches — an average of not less than 18 to 24 inches 

 for the whole watershed of the gulf. 



It is not wise to estimate more precisely from data of this sort, because longer 

 terms of observation or a multiplication of recording stations might alter the results ; 

 but the ratio that has now been established between the rainfall and the annual 

 run-oft' at several observing stations confirms this calculation. Thus, Barrows (1907a, 

 p. 110) found the run-off from the Androscoggin basin to range from 22 to 67 per 

 cent of the rainfall over the period 1893 to 1905, averaging 59 per cent. During the 

 same period, the run-off from the Cobbosseecontee, one of the chief tributaries of 

 the Androscoggin, averaged 44 per cent of the rainfall (Pressey, 1902, p. 70). The 

 average for the Presumpscott basin for 1887 to 1901 was 46 per cent of the rainfall 

 (Pressey, 1902, p. 104), and data for the four-year period, 1914 to 1917, showed that 

 50 per cent of the rain that fell on the Merrimac watershed ran off via that river. 



The average amount of fresh water reaching the gulf via the chief rivers tributary 

 to it may therefore be set at about 50 per cent of the annual precipitation over its 

 watershed, which ranges from about 38 to about 50 inches. 



Assuming a yearly run-off of about 20 inches from the 61,000 square miles of 

 watershed, this is sufficient to form a layer some 31 inches thick over the entire gulf, 

 out to its southern rim, illustrating more concretely the relationship which this vast 

 run-off of river water bears to the area of sea into which it is discharged. If the 

 yearly amount by which rain and snow falling on the gulf exceeds the evaporation 

 from its surface be something over 1 foot (p. 841), the total yearly influx of fresh water 

 is sufficient to raise the level out to Georges Bank by at least 43 inches, or almost 

 % oi a fathom. 



The seasonal distribution of this contribution of fresh water has an important 

 bearing on the seasonal fluctuations of the salinity of the gulf (p. 701), hence demands 

 notice here. As every New Englander knows, our rivers are in flood in spring, of 

 which the Kennebec may serve as an illustration, both because records of its daily 

 discharges have been kept for many years (Barrows, 1907) and because its situation 

 and the general topography of its watershed make it typical of the rivers of Maine 

 and New Brunswick. The following table for the 10-year period, 1893 to 1902, is 

 compiled from Barrow's (1907) records. 



Mean discharge of Kennebec River at Waierville, Me. 



Month 



January . 

 February 

 March ._. 



April 



May 



June 



July 



Eun-ofl, 

 cubic 



feet per 

 second 



2,919 

 3,357 

 8,454 

 24, 8U 

 20,032 

 10, 031 

 6,116 



Eun-ofl, 

 in inches 



0.76 

 .82 

 2.28 

 6.49 

 6.40 

 2.62 

 1.65 



Month 



August- 



September 



October 



November 



December __ 



Monthly mean 



Kun-ofl, 

 cubic 



feet per 

 second 



3,811 

 2,893 

 3,011 

 4,685 

 3,944 



7,838 



Eun-ofl, 

 in inches 



1.03 

 .76 



1.23 

 1.17 



2.10 



