Water resources

Auckland's volcanoes and their eruptive products have developed some very valuable water resources. Not only have some explosion craters formed lakes e.g. Lake Pupuke, but basaltic lava flows have formed aquifers to become significant sources of water supply.

 Basalt lava flows are very porous and allow water to seep into the rocks. These aquifers are currently being tapped for water supply. For example at Onehunga, water "is extracted from four wells sunk into the One Tree Hill lava flows. An estimated 27 300 cubic metres of water per day flows through that aquifer, reaching from as far as five kilometres away." (Jamieson, 1992). Most of Auckland's volcanic cones support water supply reservoirs.