THE RAINFALL OF GUERNSEY. 



161 



It will be worthy of notice that the two winters 1900-1901 

 and 1901-1902 were, with the single exception of 1896-1897, 

 the two giving the least rainfall, for these years gave 15*43 

 and 13*83 against an average of 22*42, reducing that average 

 to 22*28. Now, inasmuch as the winter rains only (as will be 

 seen when evaporation is discussed) add to the underground 

 water, this falling off of 15^ inches is practically the cause of 

 our partial water famine. 



Evaporation is unimportant in winter, but in summer it 

 not only carries away the whole rainfall, but draws largely on 

 the underground stocks. I have prepared a table which will 

 show the loss by evaporation and from surface drainage. 



TABLE VI. 



INFLUENCE OF EVAPORATION AND SURFACE DRAINAGE ON 



THE PERCENTAGE OF EFFECTIVE RAINFALL. 



Factors — Annual Rainfall, 36 52. Area, 24 sq miles. 1 in. 



Area, 24 sq miles 

 per acre. 



22,688 gallons 





Rainfall. 



Evaporation. 



Surface 

 Drainage. 



Loss. 



Evaporation 



and 



Drainage. 



Effective 

 Rainfall. 







«H 













Months. 





4J O 















?„>> • 



S GO . 













S 









iva 

 Lllio 



lion 



In 



w • 



1 A °° 



In B~ 



«4— 1 CO 



In 



fc 



In 

 inches. 





^ 



p a °= 



inches 



1-1 75 to 



inches. 



£ 6C 



20 



inches 

 0-79 



o 



80 





January .... 



3-81 



1,318 



0-41 



141 



0-38 



140 



3-02 



February . . 



2-62 



900 



0-22 



72 



0-26 



95 



18 



0-48 



82 



2-14 



March 



2 47 



858 



1-07 



368 



0.24 



90 



52 



1-31 



48 



1-16 



April 



2-35 



816 



1-95 



672 



0-23 



87 



92 



2-18 



8 



0-17 



May 



2-15 



740 



3-85 



1,327 



0-22 



83 



190 



4-07 







June 



2-01 



7,0 



4-11 



1,418 



0-20 



75 



213 



4-31 



• • 





July 



2-20 



720 



3T0 



1,078 



0-22 



82 



151 



3-32 







August .... 



2-42 



795 



2-83 



975 



0-24 



88 



126 



3-06 



. . 





September . . 



3-11 



1,070 



1-71 



590 



0-30 110 



65 



2-01 



35 



1-01 



October .... 



4-83 



1,652 



0-83 



286 



0-49 180 



27 



1-32 



73 



3-51 



November . . 



4-40 



1,515 



0-50 



172 



0-44 



160 



21 



0-94 



79 



3-46 



December . . 



4-15 



1,460 



045 



51 



0-41 



150 



13 



0-56 



87 

 34 



3-59 



The Year.. 



36-52 



12,544 



20-72 



7,150 



3-63 



1340 



66 



24-35 



18-06 



In this table we see that out of the 36*52 inches of rain 

 which falls annually, practically 21 inches go off again into the 

 air. This quantity is spread out very unequally during the 

 year, the smallest amount evaporated being in December, when 

 0*15 inch only out of 4*15 inches is lost. On the other hand, 

 in June, when the rainfall is 2 inches, over 4 inches are eva- 

 porated. Besides the evaporation we have to allow for the 

 surface drainage and other waste. From the figures obtained 



