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Groundwater Model
Groundwater models are computer models of groundwater flow systems, and are used by hydrologists and hydrogeologists. Groundwater models are used to simulate and predict aquifer conditions. Characteristics An unambiguous definition of "groundwater model" is difficult to give, but there are many common characteristics. A groundwater model may be a scale model or an electric model of a groundwater situation or aquifer. Groundwater models are used to represent the natural groundwater flow in the environment. Some groundwater models include (chemical) quality aspects of the groundwater. Such groundwater models try to predict the fate and movement of the chemical in natural, urban or hypothetical scenario. Groundwater models may be used to predict the effects of hydrological changes (like groundwater pumping or irrigation developments) on the behavior of the aquifer and are often named groundwater simulation models. Groundwater models are used in various water management plans for u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Simulation
Computer simulation is the running of a mathematical model on a computer, the model being designed to represent the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be determined by comparing their results to the real-world outcomes they aim to predict. Computer simulations have become a useful tool for the mathematical modeling of many natural systems in physics (computational physics), astrophysics, climatology, chemistry, biology and manufacturing, as well as human systems in economics, psychology, social science, health care and engineering. Simulation of a system is represented as the running of the system's model. It can be used to explore and gain new insights into new technology and to estimate the performance of systems too complex for analytical solutions. Computer simulations are realized by running computer programs that can be either small, running almost instantly on small devices, or large-scale ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Initial Condition
In mathematics and particularly in dynamic systems, an initial condition, in some contexts called a seed value, is a value of an evolving variable at some point in time designated as the initial time (typically denoted ''t'' = 0). For a system of order ''k'' (the number of time lags in discrete time, or the order of the largest derivative in continuous time) and dimension ''n'' (that is, with ''n'' different evolving variables, which together can be denoted by an ''n''-dimensional coordinate vector), generally ''nk'' initial conditions are needed in order to trace the system's variables forward through time. In both differential equations in continuous time and difference equations in discrete time, initial conditions affect the value of the dynamic variables (state variables) at any future time. In continuous time, the problem of finding a closed form solution for the state variables as a function of time and of the initial conditions is called the initial valu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Richards' Equation
The Richards equation represents the movement of water in unsaturated soils, and is attributed to Lorenzo A. Richards who published the equation in 1931. It is a quasilinear partial differential equation; its analytical solution is often limited to specific initial and boundary conditions. Proof of the existence and uniqueness of solution was given only in 1983 by Alt and Luckhaus. The equation is based on Darcy-Buckingham law representing flow in porous media under variably saturated conditions, which is stated as :\vec=-\mathbf(\theta) (\nabla h + \nabla z), where :\vec is the volumetric flux /T :\theta is the volumetric water content :h is the liquid pressure head, which is negative for unsaturated porous media :\mathbf(h) is the unsaturated hydraulic conductivity /T :\nabla z is the geodetic head gradient, which is assumed as \nabla z = \left(\begin 0 \\ 0 \\ 1 \end \right) for three-dimensional problems. Considering the law of mass conservation for an incom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydraulic Head
Hydraulic head or piezometric head is a measurement related to liquid pressure (normalized by specific weight) and the liquid elevation above a vertical datum., 410 pages. See pp. 43–44., 650 pages. See p. 22, eq.3.2a. It is usually measured as an equivalent liquid surface elevation, expressed in units of length, at the entrance (or bottom) of a piezometer. In an aquifer, it can be calculated from the depth to water in a piezometric well (a specialized water well), and given information of the piezometer's elevation and screen depth. Hydraulic head can similarly be measured in a column of water using a standpipe piezometer by measuring the height of the water surface in the tube relative to a common datum. The hydraulic head can be used to determine a ''hydraulic gradient'' between two or more points. Definition In fluid dynamics, the ''head'' at some point in an incompressible (constant density) flow is equal to the height of a static column of fluid whose pressure at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Groundwater Recharge
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. Text was copied from this source, which is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evapotranspiration
Evapotranspiration (ET) refers to the combined processes which move water from the Earth's surface (open water and ice surfaces, bare soil and vegetation) into the Atmosphere of Earth, atmosphere. It covers both water evaporation (movement of water to the air directly from soil, Canopy interception, canopies, and water bodies) and transpiration (evaporation that occurs through the stomata, or openings, in plant leaves). Evapotranspiration is an important part of the local water cycle and climate, and measurement of it plays a key role in water resource management Irrigation, agricultural irrigation. Definition ''Evapotranspiration'' is defined as: "The combined processes through which water is transferred to the atmosphere from open water and ice surfaces, bare soil and vegetation that make up the Earth’s surface." Evapotranspiration is a combination of evaporation and transpiration, measured in order to better understand crop water requirements, irrigation scheduling, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soil Moisture
Soil moisture is the water content of the soil. It can be expressed in terms of volume or weight. Soil moisture measurement can be based on ''in situ'' probes (e.g., capacitance probes, neutron probes) or remote sensing methods. Water that enters a field is removed from a field by Surface runoff, runoff, drainage, evaporation or transpiration. Runoff is the water that flows on the surface to the edge of the field; drainage is the water that flows through the soil downward or toward the edge of the field underground; evaporative water loss from a field is that part of the water that evaporates into the atmosphere directly from the field's surface; transpiration is the loss of water from the field by its evaporation from the plant itself. Water affects soil formation, soil structure, structure, stability and erosion but is of primary concern with respect to Plant development, plant growth. Water is essential to plants for four reasons: # It constitutes 80–95% of the plant's proto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surface Runoff
Surface runoff (also known as overland flow or terrestrial runoff) is the unconfined flow of water over the ground surface, in contrast to ''channel runoff'' (or ''stream flow''). It occurs when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when the soil is #Saturation excess overland flow, saturated by water to its full capacity, and the rain arrives #Infiltration excess overland flow, more quickly than the soil can absorb it. Surface runoff often occurs because wikt:impervious#Adjective, impervious areas (such as roofs and Road surface, pavement) do not allow water to soak into the ground. Furthermore, runoff can occur either through natural or human-made processes. Surface runoff is a major component of the water cycle. It is the primary agent of Soil erosion#Rainfall and runoff, soil erosion by water. The land area producing runoff that drains to a common point is called a drainage basin. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vadose Zone
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. Freeze, R.A. and Cherry, J.A., 1979. Groundwater. Englewood Clif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surface Water Cycle
A surface, as the term is most generally used, is the outermost or uppermost layer of a physical object or space. It is the portion or region of the object that can first be perceived by an observer using the senses of Visual perception, sight and Somatosensory system, touch, and is the portion with which other materials first interact. The surface of an object is more than "a mere geometric solid", but is "filled with, spread over by, or suffused with perceivable qualities such as color and warmth". The concept of surface has been abstracted and formalized in mathematics, specifically in geometry. Depending on the properties on which the emphasis is given, there are several inequivalent such formalizations that are all called ''surface'', sometimes with a qualifier such as algebraic surface, smooth surface or fractal surface. The concept of surface and its mathematical abstractions are both widely used in physics, engineering, computer graphics, and many other disciplines, pri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soil Salinity
Soil salinity is the salt (chemistry), salt content in the soil; the process of increasing the salt content is known as salinization (also called salination in American and British English spelling differences, American English). Salts occur naturally within soils and water. Salinization can be caused by natural processes such as mineral weathering or by the gradual withdrawal of an ocean. It can also come about through artificial processes such as irrigation and Sodium_chloride#Road_salt, road salt. Natural occurrence Salt (chemistry), Salts are a natural component in soils and water. The ions responsible for salinization are: Sodium, Na+, Potassium, K+, Calcium, Ca2+, Magnesium, Mg2+ and Chlorine, Cl−. Over long periods of time, as soil minerals weathering, weather and release salts, these salts are flushed or leached out of the soil by drainage water in areas with sufficient precipitation. In addition to mineral weathering, salts are also deposited via dust and precipitatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
