Symes. — Fluctuation in Water-level in Artesian Well. 



495 



The Rise after Rain. — As was expected, rain causes a rise of level, the 

 well responding with remarkable rapidity, and on certain observed occa- 

 sions a rise has commenced within an hour of the rain commencing. With 

 a heavy rain the rate of rise may amount to 1 in. in three hours and a half. 

 Shortly after the rain stops the level falls rapidly for a period — about four 

 or five times as long as the rising period. In this fall the greater part, some- 

 times the whole, of the gain disappears. Fig. 2 is a record of a heavy-rain 



Fig. 3. 



Jomparison of monthly average heights of well with monthly rainfalls 



at Christchurch. 



rise in which the whole gain was lost. Fig. 3 is a comparison of the monthly 

 average heights of the well with the monthly rainfalls at Christchurch, and 

 shows how they fluctuate in sympathy. 



The years 1914 and 1915 were very dry, and 1916 is about normal in 

 rainfall. The similarity of the 1916 portion of this well graph to that 

 of the Lincoln well obtained in 1910 by Hilgendorf* is remarkable. 



It was noted that the well rises with very light rains, and on one 

 particular occasion responded to a rain which, terminating a long dry 

 period, wet garden soil to a depth of only \ in. 



Other Fluctuations. — There are occasionally other rises without apparent 

 cause : none could be attributed to the influence of the Waimakariri River. 

 Heavy traffic on the tram-line passing about 30 ft. distant causes a distinct 

 wave-like oscillation in the well. 



The writer's thanks are due to Dr. F. W. Hilgendorf for assistance and 

 advice, and to Mr. H. F. Skey for rainfall data. 



* F. W. Hilgesdorf, Fluctuations of the Level of the Water in some Artesian 

 Wells in the Christchurch Area, Trans. A'.Z. Inst., vol 44, 1912, p. 143. 



