Fluctuations in the water-level of some artesian wells in the Christchurch area

Abstract

In 1896 Hutton recorded the fluctuations of two artesian wells at the Christchurch Museum. Speight continued the observations on one of the wells in 1910, and since then has taken occasional readings, copies of which he has kindly given me for the purposes of this paper. In 1911 I took a series of readings on a 340 ft. well at Lincoln College, fourteen miles south-west of Christchurch, and have taken monthly readings ever since. From 1912 till the present time Mr. A. D. Dobson, Christchurch City Surveyor, has taken observations on a 217 ft. well at Merivale, a mile and a quarter north-west of the Cathedral, and has given me his readings. In 1914 Mr. Symes and I, aided by a grant from the Hutton Fund, erected a continuous-record machine on a well of uncertain depth on Papanui Road, about three miles north-west of the Cathedral, and the readings of this well have been used here. The graph shows the fluctuations in the static level of the water, in these four wells. The comparatively small variation in the three Christchurch wells as contrasted with the large variation of the Lincoln well affords conclusive proof that the wells in the neighbourhood of Christchurch have a relatively constant source of supply, while the well at Lincoln has a relatively intermittent one. The most reasonable explanation of this feature of the graph is that the main supply of the Christchurch artesian wells comes from the Waimakariri River, while the Lincoln well is supplied chiefly by the rainfall direct, or by percolation from the Selwyn River, which in its middle course flows only during or after heavy rains.