364 



a slight but not equal rise (.10) in channel production. The 

 March pulse in the river, with a maximum amplitude of .77 on 

 the 22d, is attended by almost equal production in the lake (.67). 



The vernal pulse rises with like abruptness at both stations, 

 increasing from April 1 to May 3 from 1.03 to 42.14 in the 

 lake, and from 1.12 to 35.68 in the river. The decline of this 

 pulse is much more abrupt in the lake, falling from 42.14 on the 

 3d to 4.7 on the 11th — a decrease of 89 per cent, in 8 days, while 

 the decline in the stream is from 35.68 to 10.31, or 71*per cent., 

 in 7 days. The more abrupt change in the lake plankton is due 

 to the fact that the decline in levels of 1. ft. in the interim be- 

 tween the two collections compared, is at the critical point ap- 

 proaching bank height, when the bottom-lands to the north of 

 Quiver Lake are beginning to emerge and cut off and divert 

 some of the run-off of the impounded backwaters which at higher 

 levels make their way to the channel through Quiver Lake (PI. II.). 



There is a very slight July pulse in the lake on the 19th 

 coincident with the July maximum in the river. In the early 

 part of August there is another maximum in the river, but no 

 parallel developement in the lake, owing possibly to the low 

 water then attained and the resulting dominance of vegetation 

 and tributary waters — conditions not incident to these levels 

 in like degree in channel waters. The rise at the close of August 

 and again in September, and the low level and slight change in 

 production in October found in channel waters are all to be 

 traced coincidently, or approximately so, in the less complete 

 records of the lake production. 



The silt-laden flood waters which cause rising levels in No- 

 vember deplete the channel plankton (.25), increase the im- 

 pounding function of the lake, and lead to greater production 

 (.73) in the latter. There are coincident culminations in river - 

 and lake on Dec. 6, but the interval of collection in the lake 

 does not permit comparison in case of the river maximum of 

 Dec. 20. The large December production (1.74), six to eleven 

 times that of July (.16), August (.22), September (.33), or Oc- 

 tober (.23) is noteworthy. 



