a 
418 DISCUSSION : FORESTS, RESERVOIRS, AND STREAM FLOW 
Mr. Leighton. of July. On July 1st, the Aitkin gauge was more than 6 ft. above 
full-bank stage; yet the controlled flow from Pokegama was about 
1200 cu. ft. per sec., or less than one-half full-bank capacity. The 
Aitkin flood on July 1st was due, therefore, to the discharge from the 
uncontrolled area above Aitkin. Supposing, now, that the Pokegama 
area had been uncontrolled, the discharge on July Ist, according 
to Fig. 2, would have been 2700 cu. ft. per sec. greater, which is 
equivalent to an increase of nearly 200% in excess of discharge over 
bank-full capacity at that time. The high point at Aitkin appears 
to have occurred on or about July 5th, at which time the reservoir 
discharge was approximately 2 200 cu. ft. per sec., or nearly 2 000 cu. ft. 
per sec. less than it would have been without the Pokegama control. 
The sharp increase in the controlled Pokegama discharge which 
took place between July 5th and 31st, is accompanied by an equally 
sharp decrease in gauge height at Aitkin. When the gauge again 
began to increase on August Ist, the controlled discharge was 1500 
cu. ft. per sec. less than it would have been under natural flow, and, 
on or about August 10th, the date of the secondary flood crest at 
Aitkin, the natural flow would have still been teeming on, reaching 
its maximum some 10 days later; yet, in spite of the fact that the 
controlled flow continued to increase from that date until about 
September 12th, the flood at Aitkin showed. practically continuous 
subsidence. Now, this secondary flood, culminating on or about 
August 10th, indicates a discharge of nearly 800 cu. ft. per sec. less 
than that culminating on July 5th; yet the natural flow at Pokegama 
would have been about 800 cu. ft. per sec. greater than is indicated at 
the height of the July flood. 
The defect in Fig. 2 is that, while the author has introduced an 
hypothetical curve for the natural flow at Pokegama, he has not 
balanced it by a similar hypothetical gauge record for Aitkin, but has 
attempted to draw deductions by basing his computed natural-flow 
curve upon his controlled Aitkin gauge-height record. He observes 
that the sharp increase in controlled Pokegama discharge from August 
1st to 10th, is accompanied by a sharp increase in gauge height at 
Aitkin for the same period, and, inasmuch as the controlled flow at 
Pokegama on August 10th is only about 350 cu. ft. per sec. less than 
it would have been under conditions of natural flow, he believes that 
the reservoirs nearly operated to increase the flood. Of course, this is 
a fallacy, because, under natural flow conditions at Pokegama, the 
Aitkin gauge record would have been entirely different. 
The excess of computed natural flow over controlled flow at Poke- 
gama between July 1st and August 10th (the crucial point at which 
the reservoirs seem to have become nearly inefficient) is approximately 
5 230000 000 cu. ft., and it is unquestionable that this would have 
changed the flood occurrences at Aitkin by carrying the highest gauge 
