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Specific Storage
In the field of hydrogeology, ''storage properties'' are physical properties that characterize the capacity of an aquifer to release groundwater. These properties are storativity (S), specific storage (Ss) and specific yield (Sy). According to ''Groundwater'', by Freeze and Cherry (1979), specific storage, S_s −1 of a saturated aquifer is defined as the volume of water that a unit volume of the aquifer releases from storage under a unit decline in hydraulic head. They are often determined using some combination of field tests (e.g., aquifer tests) and laboratory tests on aquifer material samples. Recently, these properties have been also determined using remote sensing data derived from Interferometric synthetic-aperture radar. Storativity Definition Storativity or the storage coefficient is the volume of water released from storage per unit decline in hydraulic head in the aquifer, per unit area of the aquifer. Storativity is a dimensionless quantity, and is always gre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogeology
Hydrogeology (''hydro-'' meaning water, and ''-geology'' meaning the study of the Earth) is the area of geology that deals with the distribution and movement of groundwater in the soil and rock (geology), rocks of the Earth's crust (geology), crust (commonly in aquifers). The terms groundwater hydrology, geohydrology, and hydrogeology are often used interchangeably, though hydrogeology is the most commonly used. Hydrogeology is the study of the laws governing the movement of subterranean water, the mechanical, chemical, and thermal interaction of this water with the porous solid, and the transport of energy, chemical constituents, and particulate matter by flow (Domenico and Schwartz, 1998). Groundwater engineering, another name for hydrogeology, is a branch of engineering which is concerned with groundwater movement and design of Well, wells, Pump, pumps, and drains. The main concerns in groundwater engineering include groundwater contamination, conservation of suppli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compressibility
In thermodynamics and fluid mechanics, the compressibility (also known as the coefficient of compressibility or, if the temperature is held constant, the isothermal compressibility) is a measure of the instantaneous relative volume change of a fluid or solid as a response to a pressure (or mean stress) change. In its simple form, the compressibility \kappa (denoted in some fields) may be expressed as :\beta =-\frac\frac, where is volume and is pressure. The choice to define compressibility as the negative of the fraction makes compressibility positive in the (usual) case that an increase in pressure induces a reduction in volume. The reciprocal of compressibility at fixed temperature is called the isothermal bulk modulus. Definition The specification above is incomplete, because for any object or system the magnitude of the compressibility depends strongly on whether the process is isentropic or isothermal. Accordingly, isothermal compressibility is defined: :\beta_T=-\ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrology
Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and drainage basin sustainability. A practitioner of hydrology is called a hydrologist. Hydrologists are scientists studying earth science, earth or environmental science, civil engineering, civil or environmental engineering, and physical geography. Using various analytical methods and scientific techniques, they collect and analyze data to help solve water related problems such as Environmentalism, environmental preservation, natural disasters, and Water resource management, water management. Hydrology subdivides into surface water hydrology, groundwater hydrology (hydrogeology), and marine hydrology. Domains of hydrology include hydrometeorology, surface-water hydrology, surface hydrology, hydrogeology, drainage basin, drainage-basin management, and water quality. Oceanography and meteorology are not included beca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Groundwater Flow Equation
Used in hydrogeology, the groundwater flow equation is the mathematical relationship which is used to describe the flow of groundwater through an aquifer. The transient flow of groundwater is described by a form of the diffusion equation, similar to that used in heat transfer to describe the flow of heat in a solid (heat conduction). The steady-state flow of groundwater is described by a form of the Laplace equation, which is a form of potential flow and has analogs in numerous fields. The groundwater flow equation is often derived for a small representative elemental volume (REV), where the properties of the medium are assumed to be effectively constant. A mass balance is done on the water flowing in and out of this small volume, the flux terms in the relationship being expressed in terms of head by using the constitutive equation called Darcy's law, which requires that the flow is laminar. Other approaches are based on Agent Based Models to incorporate the effect of complex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soil Mechanics
Soil mechanics is a branch of soil physics and applied mechanics that describes the behavior of soils. It differs from fluid mechanics and solid mechanics in the sense that soils consist of a heterogeneous mixture of fluids (usually air and water) and particles (usually clay, silt, sand, and gravel) but soil may also contain organic matter, organic solids and other matter.Mitchell, J.K., and Soga, K. (2005) Fundamentals of soil behavior, Third edition, John Wiley and Sons, Inc., .Powrie, W., Spon Press, 2004, ''Soil Mechanics – 2nd ed'' A Guide to Soil Mechanics, Bolton, Malcolm, Macmillan Press, 1979. Along with rock mechanics, soil mechanics provides the theoretical basis for analysis in geotechnical engineering, a subdiscipline of civil engineering, and engineering geology, a subdiscipline of geology. Soil mechanics is used to analyze the deformations of and flow of fluids within natural and man-made structures that are supported on or made of soil, or structures that ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Richards Equation
The Richards equation represents the movement of water in Vadose zone, unsaturated soils, and is attributed to Lorenzo A. Richards who published the equation in 1931. It is a Differential equation, quasilinear partial differential equation; its analytical solution is often limited to specific initial and boundary conditions. Proof of the Existence theorem, existence and Uniqueness theorem, uniqueness of solution was given only in 1983 by Hans Wilhelm Alt, Alt and Stephan Luckhaus, 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 [L/T]; :\theta is the Water content, volumetric water content [~]; :h is the liquid pressure head, which is negative for unsaturated porous media [L]; :\mathbf(h) is the unsaturated hydraulic conductivity [L/T]; :\nabla z is the geodetic head gradient, which is assumed as \nabla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subsidence
Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope movement. Processes that lead to subsidence include dissolution of underlying carbonate rock by groundwater; gradual compaction of sediments; withdrawal of fluid lava from beneath a solidified crust of rock; mining; pumping of subsurface fluids, such as groundwater or petroleum; or warping of the Earth's crust by tectonic forces. Subsidence resulting from tectonic deformation of the crust is known as tectonic subsidence and can create accommodation for sediments to accumulate and eventually lithify into sedimentary rock. Ground subsidence is of global concern to geologists, geotechnical engineers, surveyors, engineers, urban planners, landowners, and the public in general.National Research Council, 1991. ''Mitigating losses from land ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydraulic Conductivity
In science and engineering, hydraulic conductivity (, in SI units of meters per second), is a property of porous materials, soils and Rock (geology), rocks, that describes the ease with which a fluid (usually water) can move through the porosity, pore space, or fracture network. It depends on the intrinsic permeability (, unit: m) of the material, the degree of Water content, saturation, and on the density and viscosity of the fluid. Saturated hydraulic conductivity, , describes water movement through saturated media. By definition, hydraulic conductivity is the ratio of volume flux to Hydraulic head#Hydraulic gradient, hydraulic gradient yielding a quantitative measure of a saturated soil's ability to transmit water when subjected to a hydraulic gradient. Methods of determination There are two broad approaches for determining hydraulic conductivity: *In the ''empirical'' approach the hydraulic conductivity is correlated to soil properties like Porosity, pore-size and particle-s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Levelling
Levelling or leveling (American English; see spelling differences) is a branch of surveying, the object of which is to establish or verify or measure the height of specified points relative to a datum. It is widely used in geodesy and cartography to measure vertical position with respect to a vertical datum, and in construction to measure height differences of construction artifacts. In photolithography, the same term is used in a lithography machine calibration step measuring or calibrating wafer surface height with respect to a reference. Optical levelling Optical levelling, also known as spirit levelling and differential levelling, employs an '' optical level'', which consists of a precision telescope with crosshairs and stadia marks. The cross hairs are used to establish the level point on the target, and the stadia allow range-finding; stadia are usually at ratios of 100:1, in which case one metre between the stadia marks on the '' level staff'' (or ''rod'') represents ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extensometer
An extensometer is a device that is used to measure changes in the length of an object. It is useful for stress- strain measurements and tensile tests. Its name comes from "extension-meter". It was invented by Charles Huston who described it in an article in the ''Journal of the Franklin Institute'' in 1879. Huston later gave the rights to Fairbanks & Ewing, a major manufacturer of testing machines and scales. Types There are two main types of extensometers: ''contact'' and ''non-contact''. Contact ''Contact extensometers'' have been used for many years and are also subdivided into two further categories. The first type of contact extensometer is called a ''clip-on'' extensometer. These devices are used for applications where high precision strain measurement is required (most ASTM based tests). They come in many configurations and can measure displacements from very small to relatively large (less than a mm to over 100 mm). They have the advantage of lower cost and e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aquifer Test
In hydrogeology, an aquifer test (or a pumping test) is conducted to evaluate an aquifer by "stimulating" the aquifer through constant pumping, and observing the aquifer's "response" ( drawdown) in observation wells. Aquifer testing is a common tool that hydrogeologists use to characterize a system of aquifers, aquitards and flow system boundaries. A slug test is a variation on the typical aquifer test where an instantaneous change (increase or decrease) is made, and the effects are observed in the same well. This is often used in geotechnical engineering settings to get a quick estimate (minutes instead of days) of the aquifer properties immediately around the well. Aquifer tests are typically interpreted by using an analytical model of aquifer flow (the most fundamental being the Theis solution) to match the data observed in the real world, then assuming that the parameters from the idealized model apply to the real-world aquifer. In more complex cases, a numerical model may ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
