by Lordo » Thu Jan 10, 2019 1:09 am
in a given geology water table is level controlled by the controlled by the geology it is in. If two aqufiers are connected in any way they will find a balance and they wil be level. I live near a river and a field above the river level occasionally becomes a lake and always after heavy rainfall.
here is an explenation of why water table changes.
A water table describes the boundary between water-saturated ground and unsaturated ground. Below the water table, rocks and soil are full of water. Pockets of water existing below the water table are called aquifers.
An area's water table can fluctuate as water seeps downward from the surface. It filters through soil, sediment, and rocks. This water includes precipitation, such as rain and snow. Irrigation from crops and other plants may also contribute to a rising water table.
This seeping process is called saturation. Sediment or rocks that are full of water are saturated. The water table sits on top of what experts call the zone of saturation, or phreatic zone. The area above the water table is called the vadose zone.
Unlike the tables you'd find in your house, a water table usually isn't flat, or horizontal. Water tables often (but not always) follow the topography, or upward and downward tilts, of the land above them.
Sometimes, a water table runs intersects with the land surface. A spring or an oasis might be the water table intersecting with the surface. A canyon, cliff, or sloping hillside may expose an underground river or lake sitting at the area's water table.
In addition to topography, water tables are influenced by many factors, including geology, weather, ground cover, and land use.
Geology is often responsible for how much water filters below the zone of saturation, making the water table easy to measure. Light, porous rocks can hold more water than heavy, dense rocks. An area underlain with pumice, a very light and porous rock, is more likely to hold a fuller aquifer and provide a clearer measurement for a water table. The water table of an area underlain with hard granite or marble may be much more difficult to assess.
Water tables are also influenced by weather. They will be usually be higher in rainy seasons or in the early spring, as snowmelt filters below the zone of saturation.
Ground cover can contribute to an area's water table. The spongy, absorbent vegetation in swamps, for instance, are saturated at least part of every year. Water tables in swamps are nearly level or even higher than the surface.
Land use can also influence an area's water table. Urban areas often have impervious surfaces, such as parking lots, for instance. Impervious surfaces prevent water from seeping into the ground below. Instead of entering the area's zone of saturation, water becomes runoff. The water table dips.