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NEW YORK STATE MUSEUM 



From these figures avo learn that an estimate of 33 per cent of 

 void space in the soils of the flats would be very conservative. 

 The mean low-water surface of the river channel is mostly from 

 15 to 20 feet below the surface of the flats. We will also assume 

 that the water runs out of the upper 5 or 6 feet quickly, but that 

 it is retained and delivered slowly from the balance. We have 

 then 33 per cent of say 12.0 feet or 4.0 feet in depth over SO square 

 miles as the probable available ground-water storage of the flats. 

 For SO square miles this amounts to (80x 640x43.500x4) = 

 8,921,088,000 cubic feet. If there were any way to control this* 

 gTound-water storage of the flats it would by itself furnish an 

 outflow of 800 cubic feet per second for four months, or 130 days. 



During June and July, 1893, the rainfall was used up by the 

 demands of growing vegetation, and the flow of the stream was 

 Thar due to stored ground water only, except possibly a very 

 slight effect from the rainfall on June 6. By July 24, what may 

 be termed the high level rapid runoff ground water of the flats 

 was entirely exhausted, and from that time on the flow was 

 merely due to the deeper seated ground water of the whole area, 

 assisted, however, by the relatively more rapid delivery of the 

 Hats. It may be remarked that the surface storage of the lakes 

 of the lower-river system is usually about exhausted by July 24. 



However, it should not be overlooked that in a long continued 

 drought the storage of these flats becomes exhausted, and when 

 this occurs there will be very low water at Rochester until this 

 storage is renewed by copious rainfall. 



As to the propriety of including iu this discussion the area of 

 the Canaseraga flats it may be mentioned that high water is 

 stated by the inhabitants to only occur there when the Genesee 

 is full to overflowing and is therefore mostly the result of back- 

 water from the Genesee. The catchment area of the Canaseraga 

 creek is 259 square miles, and although the creek channel 1ms 

 Pot several miles only slight declivity, it probably has capacity 

 enough to discharge the ordinary flood-flows, provided the Genesee 

 were kept within its banks. 



The value of a reservoir on Genesee river in mitigating floods. 

 The question will arise in storage projects as to the value of a 

 reservoir in mitigating flood-flows. As this matter has been 



