145 
MONTHLY MEANS OF GAGE-READINGS (IN FEET) BELOW LAGRANGE DAM 
\ 1883-1899. 
(Basis of reference, low water of 1879.) 
Year | Jan. | Feb.| Mar.|April} May | June] July | Aug. Sept.|Oct. Nov.| Dec vearly 
1883...| 7.41,11.36/16.71/12.77|12. 18|13.04]/10.34] 5.62} 1.67/2.52] 6.89] 8.81} 9.11 
1884...| 6.09|13.04/14.17)14.92|11.22) 8.66] 6.42] 4.04| 2.74|7.62] 6.01] 6.70] 8.47 
1885...|14.17|12.06|13.84}14.20]12. 48) 7.99] 6.40] 4.72| 5.18]/5.69| 9.32) 8.15] 9.52 
1886. . .|12.83]13.77|14.24|13.79|12.77| 9.31} 2-79] 1.54] 1.68/2.53] 2.12] 2.32] 7.47 
1887...| 3.70|12.71|13.64| 7.36] 3.75] 1.70] 0.72| 0.23] 0.24/0.79] 0.83] 2.21] 3.99 
1888...| 6.25] 7.62| 9.87/12.01| 9.02/10.78] 8.61) 3.93] 1.21/0.95| 1.79] 2.05] 6.17 
1889*..| 4.33] 3-59] 7-27] 5-78] 3-72] 9-48] 9.05] 4.00] 2.45/0.92| 3.75] 5.43} 4.98 
1890... .|10.22] 9.41) 8.92|/10.43] 9.39) 8.82] 6.83) 1.39 1,111.58 1.86] I.92| 5.96 
1891...| 2.21] 2.67| 6.06/10.13] 9.00] 5.18] 3.56, 2.16) 0.92/0.32) 1.23) 2.83) 3.86 
1892...| 3.42! 4.84] 6.69 12.70]17.16)15.97|14.39| 5.84 2. 1311.29 1.69! 2.94] 7.42 
1893...| 2.46] 8.31/15.44'13.74]15.87|12.00] 4.24] 0.68] 0.34/1.28] 1.09] 2.24] 6.45 
1894...| 2.70] 4.19] 7.38| 6.28] 5.80) 3.24] 1.26) 0.57] 2.96/1.56| 1.73) 2.12] 3.30 
1895. 1.96] 2.70] 4.98] 4.05] 2.32) 0.73] 1.96] 1.55] 2.74|0.86] 1.02] 4.99] 2.49 
1896... .|10.06] 8.64! 8.92) 6.61] 5.90) 7.09] 4.77] 7.59] 4.32|5-28] 5.20) 4.85] 6.60 
1897. :|11.50)10.95/14.50,15.49]10.28 4.99] 5.65] 1.80) 0.98/0.86] 1.43) 1.93) 6.67 
1898...| 4.55] 9.09/13. 15]16.33]12.74/12.85] 5.44] 3.29] 3.96/3.57| 6.75] 6.40) 8.14 
1899...| 7.87) 7.87|13.79|11.58] 8.92) 8.93] 3.94] 2.28) 1.08/1.23) 2.45) 3.19] 8.09 
Means 
for 17 
years.| 6.57| 8.40/11.15!11.07| 9.56) 8.28] 5.67| 3.01] 2.11/2.28] 3.25] 4.07] 6.40 
*Dam practically completed in November of this year. 
accounts for much of this change. Records during a period of 
abundant rainfall are necessary for an adequate discussion of 
the problem. 
The foregoing tables give the monthly means and monthly 
and yearly averages at the two dams for the period above named. 
In Tables I. and II. are to be found tabulations of the ex- 
tremes of low and high water, the range of movement, and the 
total of the + and — movements for each month in the periods 
covered by the records at the two dams. The appended table 
also gives some data pertaining to the major fluctuations at 
Copperas Creek. The rainfall statistics refer to the state as a 
whole and are taken from Leverett (’96). 
From the data presented in the hydrographs and these 
tabulations the variations and the average condition of the 
Illinois River may be determined, and some estimate made of 
the normal regimen of the stream. In general terms this is as 
follows: There is in each year a period of high water—that is, 
