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The depth to the water table can change (rise or fall) depending on the time of year. During the late winter and spring when accumulated snow starts to melt and spring rainfall is plentiful, water on the surface infiltrates into the ground and the water table rises.
The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with groundwater, [1] which may be fresh, saline, or brackish, depending on the locality. It can also be simply explained as the depth below which the ground is saturated.
The Groundwater database consists of more than 850,000 records of wells, springs, test holes, tunnels,drains, and excavations in the United States. Available site descriptive information includes well location information such as latitude and longitude, well depth, and aquifer.
We present global observations of water table depth compiled from government archives and literature, and fill in data gaps and infer patterns and processes using a groundwater model forced by modern climate, terrain, and sea level.
The most reliable method of obtaining the depth to the water table at any given time is to measure the water level in a shallow well with a tape. If no wells are available, surface geophysical methods can sometimes be used, depending on surface accessibility for placing electric or acoustic probes.
In some settings, it can be at or near the land surface; for example, near bodies of surface water in humid climates. In other settings, the depth to the water table can be hundreds of feet below land surface. Ground water commonly is an important source of surface water.
The water table, which marks the transition between the saturated and unsaturated zones, can be as close as a foot below the surface or hundreds of feet deep. Aquifers, which are underground layers that hold water, are typically composed of materials like sand, gravel, sandstone, or fractured rock.
In the context of a house, the water table plays a significant role in determining the potential for groundwater seepage into basements or crawl spaces. Understanding its depth and fluctuations is essential for homeowners, builders, and engineers.
The depth of the water table can be measured in existing wells to determine the effects of season, climate, or human impact on groundwater. The water table can actually be mapped across regions using measurements taken from wells.
Groundwater occurs in the saturated soil and rock below the water table. If the aquifer is shallow enough and permeable enough to allow water to move through it at a rapid-enough rate, then people can drill wells into it and withdraw water.