Whataroa groundwater surveys, Westland, New Zealand

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Cox, S.C.; Sims, A.; Sutherland, R. 2013 Whataroa groundwater surveys, Westland, New Zealand. Lower Hutt, N.Z.: GNS Science. GNS Science report 2013/21 15 p.

Abstract: Mapped potentiometric surfaces outline the position of unconfined shallow groundwater (the water table) and its flow out from the Whataora valley north and northwestwards beneath the Whataroa plains. Flow occurs under a hydraulic gradient of 0.005-0.006 m/m in Whataro valley, at 0.008 m/m between the SH6 bridge and Whataroa township, and at 0.003 m/m in the lower Whataroa plains at Rotokino. The shallow alluvium aquifer appears to be recharged by water from the Whataroa River along the eastern side of the plain, which will presumably also receive some recharge from precipitation falling on the overlying land surface. The Waitangitaona catchment provides a lesser, but noticeable contribution to groundwater at the southwestern end of Whataroa plain. During the drought period surveyed in March 2013, Whataroa town straddled a boundary in the groundwater regime between Whataroa-derived groundwater to the east and Waitangitaona-derived groundwater to the west. It would not be unexpected if the boundary were shown to shift, and the source of groundwater beneath Whataroa change, as the recharge changes at higher groundwater levels. (auth)