Depression focused recharge
Encyclopedia
Also referred to as depression focused groundwater recharge. In hydrology recharge
implies replenishing a supply of water held within a geological formation underground. Even surface aquifer
s are within soil.
of the soil is not exceeded, then negligible water percolates to groundwater
. If instead water puddles in low lying areas, the same water volume concentrated over a smaller area may exceed field capacity resulting in water that percolates down to recharge groundwater. The larger the relative contributing runoff area is, the more focused infiltration is. The recurring process of water that falls relatively uniformly over an area, flowing to groundwater selectively under surface depressions is depression focused recharge. Water tables rise under such depressions.
Depression focused groundwater recharge also profoundly effects contaminant transport into groundwater. This is of great concern in regions with karst
geological formations because water can eventually dissolve tunnels all the way to aquifer
s, or otherwise disconnected streams. This extreme form of preferential flow, accelerates the transport of contaminants and the erosion
of such tunnel
s. In this way depressions intended to trap runoff
water—before it flows to vulnerable water resources—can connect underground over time. Cavitation
of surfaces above into the tunnels, results in pot holes or caves.
Deeper ponding exerts pressure
that forces water into the ground faster. Faster flow dislodges contaminants otherwise adsorbed on soil and carries them along. This can carry pollution
directly to the raised watertable below and into the groundwater supply. Thus the quality of water collecting in rapid infiltration basins is of special concern.
collects in retention basins. Concentrating degradable contaminants can accelerate biodegradation
. However, where and when water tables are high this affects appropriate design of detention ponds, retention ponds and rain garden
s.
Recharge
Groundwater recharge or deep drainage or deep percolation is a hydrologic process where water moves downward from surface water to groundwater. This process usually occurs in the vadose zone below plant roots and is often expressed as a flux to the water table surface...
implies replenishing a supply of water held within a geological formation underground. Even surface aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
s are within soil.
Recharge
If water falls uniformly over a field such that field capacityField capacity
Field capacity is the amount of soil moisture or water content held in soil after excess water has drained away and the rate of downward movement has materially decreased, which usually takes place within 2–3 days after a rain or irrigation in pervious soils of uniform structure and texture...
of the soil is not exceeded, then negligible water percolates to groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. 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...
. If instead water puddles in low lying areas, the same water volume concentrated over a smaller area may exceed field capacity resulting in water that percolates down to recharge groundwater. The larger the relative contributing runoff area is, the more focused infiltration is. The recurring process of water that falls relatively uniformly over an area, flowing to groundwater selectively under surface depressions is depression focused recharge. Water tables rise under such depressions.
Depression pressure
Depression focused groundwater recharge can be very important in arid regions. More rain events are capable of contributing to groundwater supply.Depression focused groundwater recharge also profoundly effects contaminant transport into groundwater. This is of great concern in regions with karst
KARST
Kilometer-square Area Radio Synthesis Telescope is a Chinese telescope project to which FAST is a forerunner. KARST is a set of large spherical reflectors on karst landforms, which are bowlshaped limestone sinkholes named after the Kras region in Slovenia and Northern Italy. It will consist of...
geological formations because water can eventually dissolve tunnels all the way to aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
s, or otherwise disconnected streams. This extreme form of preferential flow, accelerates the transport of contaminants and the erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
of such tunnel
Tunnel
A tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers...
s. In this way depressions intended to trap runoff
Runoff
Run-off or runoff may refer to:* Surface runoff, the flow of water, from rain, snow melt, or other sources, over land* Runoff model , a mathematical model describing the rainfall-runoff relations of a rainfall catchment area or watershed...
water—before it flows to vulnerable water resources—can connect underground over time. Cavitation
Cavitation
Cavitation is the formation and then immediate implosion of cavities in a liquidi.e. small liquid-free zones that are the consequence of forces acting upon the liquid...
of surfaces above into the tunnels, results in pot holes or caves.
Deeper ponding exerts pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
that forces water into the ground faster. Faster flow dislodges contaminants otherwise adsorbed on soil and carries them along. This can carry pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
directly to the raised watertable below and into the groundwater supply. Thus the quality of water collecting in rapid infiltration basins is of special concern.
Pollution
Pollution in stormwater runoffSurface runoff
Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...
collects in retention basins. Concentrating degradable contaminants can accelerate biodegradation
Biodegradation
Biodegradation or biotic degradation or biotic decomposition is the chemical dissolution of materials by bacteria or other biological means...
. However, where and when water tables are high this affects appropriate design of detention ponds, retention ponds and rain garden
Rain garden
A rain garden is a planted depression that allows rainwater runoff from impervious urban areas like roofs, driveways, walkways, parking lots, and compacted lawn areas the opportunity to be absorbed...
s.
See also
- Hydrology (agriculture)Hydrology (agriculture)Agricultural hydrology is the study of water balance components intervening in agricultural water management, notably in irrigation and drainage.-Water balance components:...
- Infiltration (hydrology)Infiltration (hydrology)Infiltration is the process by which water on the ground surface enters the soil. Infiltration rate in soil science is a measure of the rate at which soil is able to absorb rainfall or irrigation. It is measured in inches per hour or millimeters per hour. The rate decreases as the soil becomes...
- International trade and waterInternational trade and waterInternational trade and water is a term that is used to describe the relationship between international trade and the water being used by humans. The substantial increase in human population during the 20th century combined with rapid increases in overall global economic development has resulted in...
- Groundwater recharge
- Subsurface dykeSubsurface dykeA subsurface dyke is a barrier impermeable to water that is placed underground to control the groundwater flow in an aquifer, and to raise the water table.-Introduction:...