840 



BULLETIN OF THE BUREAU OF FISHERIES 



Two-thirds of the total run-off for the year thus falls during the three spring 

 months, and more than half of it during April and May. This does not exactly 

 represent the natural condition, because the Kennebec is more or less controlled by 

 the several dams; but water-power developments have not been sufficient to mask 

 its spring freshets — still less have they on the Penobscot or the St. John Elvers. 

 Hence, the seasonal fluctuations in the flow of the Kennebec may be taken as gen- 

 erally representative of all the considerable streams that empty into the gulf north 

 and east of Cape Elizabeth and of the Saco as well. 



Origina Uy the Merrimac, also, came into flood in the spring, at the season when 

 the snow blanket melts and the ice goes out; but it is now so largely harnessed for 

 industrial purposes that its seasonal flow no longer shows as pronounced a freshet 

 in April and May as New England waterways do in their natural state. Its largest 

 run-off stUl falls in April, however, and its smallest in September, as appears from 

 the following table: 



Merrimac River at Lawrence, Mass., for the period 1907 to 1916 



Month 



January.. 

 February 

 March .— 



April 



May 



June..'.. . 

 July 



Month 



August --- 



September 



October _ 



November 



December 



Monthly average. 



Sun-off, 

 in inches 



0.8 

 .6 

 .8 

 1.0 

 1.1 



1.4 



Automatic tide gauges, which have been in operation at a number of points 

 around the coastline of the gulf between Cape Cod and the Bay of Fundy, have 

 shown the sea 0.1 to 0.2 feet lower than the mean in the latter part of winter, and 

 about this same amount higher than the mean toward the end of the summer.^* 

 This variation probably reflects the seasonal variation in the inflow of land water. 



RAINFALL AND EVAPORATION 



Although land drainage is the chief source for fresh water for the gulf, rahifall 

 also adds a considerable increment. No record of the precipitation over the offshore 

 parts of the gulf itself is available, but the monthly and annual averages for four 

 representative coast stations — Boston, Portland, Eastport, and Yarmouth — tabu- 

 lated below suggest an annual fall of 40 to 45 inches for the gulf as a whole. 



Average rainfall, in inches 



"Information contributed by U. 3. Coast and Qeodetic Surveyi 



