Groundwater: the water stored beneath Earth’s surface in aquifers (layers of water-bearing rock or sand). It is used for human and stock drinking water, irrigation, and industry, and also has a role in sustaining some rivers, lakes, and wetlands, especially during low-flow periods. The health of surface-water ecosystems also depends on groundwater.
Unconfined aquifer: separated from the land surface only by sediment or rock, through which water and any contaminants can freely percolate down from the surface.
Confined aquifer: contained between two units of impermeable material, such as unfractured rock or clay. Water held in confined aquifers is under pressure and may originate from sources located some distance away.
From the dataset Environmental Reporting: Average estimated groundwater volume per year 1994–2014, this data was extracted:
Provided: 63 data points
Dataset originally released on:
September 29, 2015
Method of collection/Data provider
Groundwater volumes are based on estimates of:
- aquifer locations and extents, based on outlines described by White (2001) and Moreau and Bekele (2015)
- the depth or thickness of the aquifer, based on measurements of the winter groundwater level in at least one indicator well for each aquifer (monitored by regional councils)
- an aquifer’s porosity (how much water can be stored per volume of aquifer material; eg gravels with large spaces between pebbles can store more water than a tightly packed material without any void space).