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 or environmental science, 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 environmental preservation, natural disasters, and water management.
An aquifer is an underground layer of water-bearing material, consisting of permeable or fractured rock, or of unconsolidated materials. Aquifers vary greatly in their characteristics. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include aquitard, which is a bed of low permeability along an aquifer, and aquiclude, which is a solid, impermeable area underlying or overlying an aquifer, the pressure of which could lead to the formation of a confined aquifer. The classification of aquifers is as follows: Saturated versus unsaturated; aquifers versus aquitards; confined versus unconfined; isotropic versus anisotropic; porous, karst, or fractured; transboundary aquifer.
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 freshwater 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 Groundwater is also often withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells.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.
Hydrogeology is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust. The terms groundwater hydrology, geohydrology, and hydrogeology are often used interchangeably, though hydrogeology is the most commonly used.
Permeability in fluid mechanics, materials science and Earth sciences is a measure of the ability of a porous material to allow fluids to pass through it.
Darcy's law is an equation that describes the flow of a fluid through a porous medium. The law was formulated by Henry Darcy based on results of experiments on the flow of water through beds of sand, forming the basis of hydrogeology, a branch of earth sciences. It is analogous to Ohm's law in electrostatics, linearly relating the volume flow rate of the fluid to the hydraulic head difference via the hydraulic conductivity. In fact, the Darcy's law is a special case of the Stokes equation for the momentum flux, in turn deriving from the momentum Navier-Stokes equation.
In materials science, a porous medium or a porous material is a material containing pores (voids). The skeletal portion of the material is often called the "matrix" or "frame". The pores are typically filled with a fluid. The skeletal material is usually a solid, but structures like foams are often also usefully analyzed using concept of porous media.
In science and engineering, hydraulic conductivity, is a property of porous materials, soils and rocks, that describes the ease with which a fluid can move through the pore space, or fracture network. It depends on the intrinsic permeability of the material, the degree of saturation, and on the density and viscosity of the fluid. Saturated hydraulic conductivity, Ksat, describes water movement through saturated media. By definition, hydraulic conductivity is the ratio of volume flux to hydraulic gradient yielding a quantitative measure of a saturated soil's ability to transmit water when subjected to a hydraulic gradient.
The analytic element method (AEM) is a numerical method used for the solution of partial differential equations. It was initially developed by O.D.L. Strack at the University of Minnesota. It is similar in nature to the boundary element method (BEM), as it does not rely upon the discretization of volumes or areas in the modeled system; only internal and external boundaries are discretized. One of the primary distinctions between AEM and BEMs is that the boundary integrals are calculated analytically. Although originally developed to model groundwater flow, AEM has subsequently been applied to other fields of study including studies of heat flow and conduction, periodic waves, and deformation by force.
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.
Porosity or void fraction is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure the "accessible void", the total amount of void space accessible from the surface.
The following outline is provided as an overview of and topical guide to hydrology:
Seyed Majid Hassanizadeh is a professor of hydrogeology at Utrecht University, where he heads the Hydrogeology group at the Faculty of Geosciences. His research focuses on flow of fluids and transport of solutes and colloids in porous media, through theory development, experimental studies, and modeling work. In particular, he focuses on two-phase flow, reactive transport in variably-saturated porous media, transport of micro-organisms, and biodegradation.
Reactive transport modeling in porous media refers to the creation of computer models integrating chemical reaction with transport of fluids through the Earth's crust. Such models predict the distribution in space and time of the chemical reactions that occur along a flowpath. Reactive transport modeling in general can refer to many other processes, including reactive flow of chemicals through tanks, reactors, or membranes; particles and species in the atmosphere; gases exiting a smokestack; and migrating magma.
The Yarkon-Taninim Aquifer, also known as the Western Mountain Aquifer of Israel/Palestine, is the western and larger part of the Mountain Aquifer, which also contains the Eastern and the smaller North-Eastern (Mountain) Aquifers. The Mountain Aquifer and the Coastal Aquifer are the main aquifers shared by Israel in its pre-1967 borders, and Palestine .It has been the main longterm reservoir of the Israeli water system.
Lynn Walter Gelhar is an American civil engineer focusing in hydrology and is currently Professor Emeritus at Massachusetts Institute of Technology. He is recognized for pioneering research in stochastic subsurface hydrology, has leading research in the area of field-scale contaminant transport experiments, and has extensive experience on the hydrologic aspects of nuclear waste disposal.
Noam Weisbrod is a Hydrology Professor at the Department of Environmental Hydrology and Microbiology of the Zuckerberg Institute for Water Research (ZIWR), which is part of the Jacob Blaustein Institutes for Desert Research (BIDR) at Ben-Gurion University of the Negev (BGU). Weisbrod served as director of ZIWR from 2015 to 2018. In 2018 he became director of BIDR and was reelected for a second term in summer 2022.
Shirley Jean Dreiss (1949–1993) was an American scientist working in the fields of hydrology and hydrogeology. After gaining her PhD from Stanford University, she joined the faculty of the University of California at Santa Cruz, where she became Professor and Chair of the Department of Earth Sciences. She made important contributions to the understanding of water flow through karst aquifers and fluid flow in subduction zones. At the time of her early death in a car accident, she was studying the groundwater system of Mono Lake in California. She was awarded the Birdsall Distinguished Lectureship from the Geological Society of America, which was renamed the Birdsall-Dreiss Distinguished Lectureship after her death.
J. Jaime Gómez-Hernández is a Spanish civil engineer specialized in geostatistics and hydrogeology. He is a full professor of hydraulic engineering at the School of Civil Engineering of the Technical University of Valencia. He was conferred the William Christian Krumbein Medal in 2020 from the International Association for Mathematical Geosciences. He also received the 2020 Prince Sultan bin Abdulaziz International Prize for Water in the field of groundwater.
Coastal Hydrogeology is a branch of Hydrogeology that focuses on the movement and the chemical properties of groundwater in coastal areas. Coastal Hydrogeology studies the interaction between fresh groundwater and seawater, including seawater intrusion, sea level induced groundwater level fluctuation, submarine groundwater discharge, human activities and groundwater management in coastal areas.
