177 



plants* growing in them so that the excess of water is discharged gradu- 

 ally during the months that follow. 



To leave the outlet of a lake undisturbed has many advantages to 

 the lake. First of all, it insures a shore line of considerable age. On 

 the windward side there is usually a wave-cut terrace, which forms the 

 natural breeding ground for most of our lake fish. On the lee side there 

 are usually plants which furnish protection and feeding ground for 

 fish. 



If the outlet is dredged the capacity of the lake as an impounding basin 

 is decreased. The plants whicli obstruct the outlet are destroyed, so that 

 the excess of water is rapidly discharged. For example Lingle Lake was 

 lowered four feet by dredging. Caving of the banks and the obstruction of 

 the outlet by waves has raised the water to within approximately two 

 feet of its original level. This has decreased its area 10,152,800 square feet, 

 and its capacity 40,107,600 cubic feet. See accompanying map. 



The present area of Lingle Lake is .537 square miles. This reduction 

 in level has exposed a large area of wave-cut terrace on the north and east 

 shores, and thus destroyed the best nesting places for fish (especially sim- 

 fish and bass). None of this land is used and apparently cannot be used. 

 On the south and west extensive marl deposits were exposed on which 

 sedges grow, forming an inferior pasture. The possibilities of aquiculture 

 have been limited, while the -available area for agriculture has been in- 

 creased to a much less degree. 



To illustrate the effect of damming lakes, I shall discuss five lakes, 

 whose area is accurately known, and with whose environs I am familiar. 

 These are Eagle Lake (Winona Lake), Little Eagle Lake (Chapman Lake), 

 Webster Lake, Tippecanoe Lake, arid Palestine Lake. If dams were con- 

 structed so thtit the level of these lakes could be fluctuated respectively 

 2, 3, 3, 5, 3 feet they would store and control 27.289 sec. feet per annum, 

 distributed as follows : Eagle 2.02. Little Eagle 4..359, Webster 3.039. Tip- 

 pecanoe 12.99, Palestine 4.509. 



If this excess were discharged during the driest three months it would 

 produce 109.156 sec. feet for that period. The minimum discharge for the 

 Tippecanoe River at Delphi during 1904 was 269 sec. feet. If the excess 

 just cited had been available during that period it would have increased 

 the minimum discharge 40.5 per cent. 



* This stream obstruction by plants may be excessive. It accounts- for part, if not all, of the dis- 

 crepancy between rainfall and discharge noted by Tucker ('11. p. .507). 



12—1019 



