Groundwater is water stored below the water table in rocks or other geological strata which we call aquifers.
In England aquifers are divided into four types based on their geology and the amount and ease with which we can take water from them.
1.Principal aquifers provide significant quantities of water for people and may also sustain rivers, lakes and wetlands.
2.Secondary aquifers can provide modest amounts of water, but the nature of the rock or the aquifers structure limit their use. They remain important for rivers, wetlands and lakes and private supplies in rural areas.
3.Significant drift aquifers. Drift is sediment laid down during the most recent ice ages (usually clay, silt, sand and gravel). These are labelled as significant drift aquifers where good water supplies are available or they support surface water. This is generally where the drift is overlying unproductive strata.
4.Unproductive strata. These are rocks which are generally unable to provide usable water supplies and are unlikely to have surface water and wetland ecosystems dependent upon them.
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