Water table in the context of "Urban runoff"

Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs in the vadose zone below plant roots and is often expressed as a flux to the water table surface. Groundwater recharge also encompasses water moving away from the water table farther into the saturated zone. Recharge occurs both naturally (through the water cycle) and through anthropogenic processes (i.e., "artificial groundwater recharge"), where rainwater and/or reclaimed water is routed to the subsurface.

The most common methods to estimate recharge rates are: chloride mass balance (CMB); soil physics methods; environmental and isotopic tracers; groundwater-level fluctuation methods; water balance (WB) methods (including groundwater models (GMs)); and the estimation of baseflow (BF) to rivers.

Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from the surface; it may discharge from the surface naturally at springs and seeps, and can form oases or wetlands. Groundwater is also often withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, also called groundwater hydrology.

Typically, groundwater is thought of as water flowing through shallow aquifers, but, in the technical sense, it can also contain soil moisture, permafrost (frozen soil), immobile water in very low permeability bedrock, and deep geothermal or oil formation water. Groundwater is hypothesized to provide lubrication that can possibly influence the movement of faults. It is likely that much of Earth's subsurface contains some water, which may be mixed with other fluids in some instances.

The United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Sites are places of importance to cultural or natural heritage as described in the UNESCO World Heritage Convention, established in 1972. Cultural heritage consists of monuments (such as architectural works, monumental sculptures, or inscriptions), groups of buildings, and sites (including archaeological sites). Natural features (consisting of physical and biological formations), geological and physiographical formations (including habitats of threatened species of animals and plants), and natural sites which are important from the point of view of science, conservation, or natural beauty, are defined as natural heritage. Egypt ratified the convention on 7 February 1974, the second country to do so, after the United States. There are seven World Heritage Sites in Egypt, and a further 34 sites on the tentative list.

The first sites in Egypt were listed in 1979, when five properties were inscribed. Since then, two more sites have been listed, Saint Catherine Area in 2002 and Wadi al Hitan in 2005. The latter is the only natural site in Egypt, the other sites being listed for their cultural properties. One of the key events that triggered the development of the World Heritage Convention was related to Egypt. Following the decision to construct the Aswan Dam on the Nile which would result in flooding of numerous archaeological sites in Lower Nubia, an international campaign was launched in 1959 to preserve the sites by dismantling them and reassembling them at safe locations. From 2001 to 2025, Abu Mena was listed as endangered because the rising water table was decreasing the stability of clay-based soils, resulting in threats to the structural integrity of the monuments. The situation has improved by 2024. Egypt has served on the World Heritage Committee five times.

The vadose zone (from the Latin word for "shallow"), also termed the unsaturated zone, is the part of Earth between the land surface and the top of the phreatic zone, the position at which the groundwater (the water in the soil's pores) is at atmospheric pressure. Hence, the vadose zone extends from the top of the ground surface to the water table.

Water in the vadose zone has a pressure head less than atmospheric pressure, and is retained by a combination of adhesion (funiculary groundwater), and capillary action (capillary groundwater). If the vadose zone envelops soil, the water contained therein is termed soil moisture. In fine grained soils, capillary action can cause the pores of the soil to be fully saturated above the water table at a pressure less than atmospheric. The vadose zone does not include the area that is still saturated above the water table, often referred to as the capillary fringe.

Infiltration is the process by which water on the ground surface enters the soil. It is commonly used in both hydrology and soil sciences. The infiltration capacity is defined as the maximum rate of infiltration. It is most often measured in meters per day but can also be measured in other units of distance over time if necessary.  The infiltration capacity decreases as the soil moisture content of soils surface layers increases. If the precipitation rate exceeds the infiltration rate, runoff will usually occur unless there is some physical barrier.

Infiltrometers, parameters and rainfall simulators are all devices that can be used to measure infiltration rates.

Cementation is a process where minerals bond grains of sediment together by growing around them. This means precipitation of ions carried in groundwater to form new crystalline material between sedimentary grains. The new pore-filling minerals form "bridges" between original sediment grains, thereby binding them together. In this way, sand becomes sandstone, and gravel becomes conglomerate or breccia.

Cementation occurs as part of the diagenesis or lithification of sediments and occurs primarily below the water table regardless of sedimentary grain sizes present. Large volumes of pore water must pass through sediment pores for new mineral cements to crystallize and so millions of years are generally required to complete the cementation process. Common mineral cements include calcite, quartz, and silica phases like cristobalite, iron oxides, and clay minerals; other mineral cements also occur.

Subirrigation also known as seepage irrigation, is a method of irrigation where water is delivered to the plant root zone. The excess may be collected for reuse.

Subirrigation is used in growing field crops such as tomatoes, peppers, and sugar cane in areas with high water tables such as Florida and in commercial greenhouse operations.

A losing stream, disappearing stream, influent stream or sinking river is a stream or river that loses water as it flows downstream. The water infiltrates into the ground recharging the local groundwater, because the water table is below the bottom of the stream channel. This is the opposite of a more common gaining stream (or effluent stream) which increases in water volume farther downstream as it gains water from the local aquifer.

Losing streams are common in arid areas due to the climate which results in huge amounts of water evaporating from the river generally towards the mouth. Losing streams are also common in regions of karst topography where the streamwater may be completely captured by a cavern system, becoming a subterranean river.