Lakes Near Laporte 



87 



between low level of 29.42 feet (791.74) in 1901 and high level of 33 

 feet (795.32) in 1909. At the beginning of the period the lake stood at 

 793.19 feet and at the end at 792.79 feet. The average for the whole 

 time was 793.13 feet. These elevations compared with the elevation of 

 791.31 feet late in 1921 shows a decline of less than two feet since 1898. 

 Thus the general decline in Lily Lake has been comparatively small since 

 1898 if the records are all correct. Records upon other lakes are not 

 available except occasional records upon Clear Lake which have been kept 

 by Mr. W. A. Cummings, Park Superintendent, who asserts that Clear 

 Lake has declined five feet or more in the last eight years. 



Relation of Lakes to Ground Water Tabic. This group of lakes 

 has no inlets except sheet drainage of very small areas and has no out- 

 let. Therefore the lake levels are evidently maintained by ground water. 



Fig. 3. Graph showing relation between the rainfall and the level of Lily Lake. 

 Laporte, Indiana, from 1898 to 1914. Rainfall shown by bioken line and referred to 

 inches at right. Lake level shown by solid line and referred to feet at left. Datum of 

 city bench mark. 



The lake levels stand at the level of the water table. They rise and 

 sink with the water table. So-called airholes in the ice in winter indi- 

 cate that there are springs within the lakes which means that there is 

 addition to the lakes by ground water. The mean annual rainfall at 

 LaPorte is 36.83 inches", and the annual evaporation from free water 

 surfaces is about 34 inches'*. Thus, it is evident that these two factors 

 almost balance each other with a small margin in favor of the increase 

 of lake volume. Also, since there is a constant decline of lake level 

 it is evident that there must be a loss through ground water movements. 

 Inasmuch as the movements of ground water are dominated by 

 static head or steepness of slope and porosity of the material through 

 which the movement takes place, the slopes to various possible outlets 

 for the underground water from these lakes have been determined. 

 These slopes are indicated in the following table. 



" Condensed Summaiy of Climatological Data for 1915 by J. H. Armington, Indian- 

 apolis, Indiana, U. S. Weather Bureau. 



"Russell: Monthly Weather Review, Dec. 1904. 



