119 



Uiinimum aunual precipitation for tliese stations is as follows : Blooin- 

 ington, 33.14 (in 1901); Paoli, 20.12 (in 1901); Jeffersonville, 30.18 (in 

 1904) ; Marengo, 32.37 (in 1!X)1) ; Evansville, 28.0.5 (in 1SS7) ; Rome, 

 35.8G (in 1904); Mt. Vernon, 34.10 (in 1902).^ At Indianapolis, which 

 has a rainfall record going back without interruption to 1871, a period 

 of forty years, the minimum recorded precipitation for any one year 

 is 30.33 Inches, in 1901. 



An analysis of these data by seasons is interesting, and for our 

 purposes more valuable than ai^y other. Water-supply engineers are 

 agreed on dividing the year into three periods, as follows: (a) The 

 storage period, which in tliis latitude is ordinarily made to include the 

 months from Dtcember to May, inclusive; (b) the growing period, from 

 June to August, inclusive; and (c) the replenishing period, from September 

 to November, inclusive. It is a well-known fact that in many years, 

 and especially in dry years, the run-off is practically confined to the 

 months from December to May, inclusive. It is imiwrtant to ascertain, 

 therefore, what is the minimum expectation of rain in these months. 

 From the stations reporting there have been the following low precipita- 

 tions during the storage period: Bloomington, 14.35 (Dec, 1895, to May, 

 1896) 16.58 (Dec. 190O, to May, 1901) ; Pjioli, 13.03 (Dec. 1900 to 

 May, 1901); Jeffersonville, 15.80 (Dec, 1888, to May, 1889), 13.02 (Dec, 

 1900, to May, 1901) ; Marengo, 14.58 (Dec, 1900, to May, 1901) ; Evans- 

 ville, 11.83 (Dec, 1900, to May, 1901) ; Mt. Vernon, 12.70 (Dec, 1900, to 

 May, 1901). The year 1901 will be remembered as one of the most dis- 

 fistrously dry seasons on record. It Is clear, from the above data, that 

 as low as 12 inches of rain may be expected within the area, during the 

 slorage period. A deficiency in this period is rarely made up by an 

 excess of rainfall in the other periods of the year. In fact, a very 

 considerable excess would be necessary to overbalance the effects of a 

 deficiency in the winter and spring months. In other words, a relatively 

 wet summer, following a dry \yinter and spring does not necessarily 

 mean an ample supply of water for municipal use. During the summer 

 months not only is all of the rainfall ordinarily consumed in the gi'owth 

 of plants and in other sources of evaporation, but in addition the ground- 

 water is more or less extensively drawn upon, leaving a deficiency of 

 ground-water at the end of the growing season, that must be made good 



^1901, for which one mouth's rpport is lacking, was undoiibtodly drier by 

 several inches than 1902. 



