Groundwater, Water Table, Aquifers and Springs
Table of Contents
Groundwater is a permanent area underground saturated by water in between pore spaces and gaps. Water slowly percolate downward until it reaches an area where it accumulates and forms a zone of complete saturation.
This zone is usually confined to pore spaces and crevices. Sandy soils with and porous rocks such as limestone are more easily filled with water and forms good aquifers.
Water Table: The water table marks the beginning of the groundwater and separates the saturated from the unsaturated zone. On higher elevations the water table rises and falls on lower elevations.
Perched Water Table: A perched water table is a small groundwater area isolated from the main groundwater source. It can form when water encounters an area where it can easily saturate and accumulates there.
Unsaturated Zone/Aeration Zone
The unsaturated zone is mainly composed of impervious rocks that are well jointed. The aeration zone is further divided into soil moisture and the capillary fringe. Soil moisture is a zone that stretches all the way from the ground to where tree roots end.Capillary fringe
Is the slow seepage of water upwards from the groundwater source.
An aquifer is a rock or soil that transmit and stores water. Sand soils, and limestone forms good aquifers. A confined aquifer is embedded between hard impervious rocks that don’t store water (confining units)
Aquitard: An aquitard disallow (impermeable) or hinders water to pass or be stored in it e.g. granite or clay.
When people pump groundwater through wells a zone of depression is formed where the water table table and groundwater sinks. This can also affect neighbouring wells. Artesian Well are naturally flowing wells formed when groundwater under pressure oozes to the surface. Usually the groundwater will be embedded/confined between aquitards(see diagram below.
A spring occurs when the water table intersects the surface and forms a permanent source of surface water. In deserts a spring can occur as an oasis