Taranaki region

Each volcano consists of a core of andesite rock surrounded by an extensive apron of volcaniclastic deposits of laharic debris, ash and tephra. Volumetrically, lahar deposits dominate the volcanics succession. The volcanic succession overlies the Tertiary sedimentary formations and the Marine Terraces in part. The volcanic succession ranges in thickness from approximately 210 metres in Okato and Egmont Village areas, 150 metres at Kapuni, and 65 metres in the Stratford/Eltham area. Aquifers occur in lahar and fluvial deposits. Hundreds of shallow wells and bores draw from unconfined aquifers in the volcanics with yields in the range 0.5-2.5 litres per second. Higher yielding confined aquifers are reported from volcanics aquifers in the Kaitake Ranges (19 l/s), New Plymouth (10 l/s), Okato (20 l/s), and at Kapuni (8l/s).

There are numerous permitted takes (less than 50 cubic metres per day) occurring across the volcanics, providing water for stock and general farm use as well as domestic supply. The generally low yields from the aquifer mean that it cannot sustain high water demand activities such as pasture irrigation, although some higher yielding bores do exisit. There are only 10 consented groundwater takes from the volcanics which exceed 50 cubic metres per day in volume. Monitoring by the Council indicates groundwater levels within the volcanics are not being affected by abstraction pressure, but respond to seasonal variations in recharge volumes.