Hydrogeophysics

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Hydrogeophysics is a cross-disciplinary area of research that uses geophysics to determine parameters (characteristics; measurements of limitations or boundaries) and monitor processes for hydrological studies of matters such as water resources, contamination, and ecological studies. [1] The field uses knowledge and researchers from geology, hydrology, physics, geophysics, engineering, statistics, and rock physics. It uses geophysics to provide quantitative information about hydrogeological parameters, using minimally invasive methods. Hydrogeophysics differs from geophysics in its specific uses and methods. Although geophysical knowledge and methods have existed and grown over the last half century for applications in mining and petroleum industries, hydrogeological study sites have different subsurface conditions than those industries. Thus, the geophysical methods for mapping subsurface properties combine with hydrogeology to use proper, accurate methods to map shallow hydrological study sites. [2]

Contents

Background

The field of hydrogeophysics developed out of a need to use minimally invasive methods for determining and studying hydrogeological parameters and processes. Determination of hydrogeological parameters is important for finding water resources, which is a growing need, and learning about water contamination, which has become relevant with the growing use of potentially hazardous chemicals.

The methods and knowledge of geophysics had been developed for mining and petroleum industries, which involve consolidated subsurface environments with high pressure and temperature. Since the subsurface environments in hydrogeological studies are less consolidated and have low temperature and pressure, combining geophysics with hydrogeology was necessary to develop proper geophysical methods that work for hydrological purposes. [2]

Traditional hydrogeological methods for characterizing the subsurface usually involved drilling and taking soil samples from the site, which can disturb the study site, cost too much time or money, or expose researchers and people to harmful chemicals and contaminants. They also only provide localized information, rather than the necessary field-scale information. Using geophysical methods and digital technology allows hydrogeologists to more quickly study hydrological characteristics on a larger scale with a lower cost and less invasive techniques.

A Hydrogeophysics Advanced Study Institute was held at the Trest Castle in the Czech Republic in July 2002 and funded by NATO when they acknowledged the necessity for fully developed, minimally invasive procedures for investigating and monitoring hydrogeological processes and parameters in shallow subsurface conditions. The institute brought together geophysicists working in hydrogeological characterization with hydrogeologists interested in using geophysical methods and data for characterization. This group, plus other international researchers, discussed the possibilities and challenges of using geophysical methods for investigating hydrogeological parameters.

They determined the main obstacles of hydrogeophysics are gaps in the knowledge and understanding of the correlation between hydrogeological parameters and geophysical characteristics, and difficulty in being able to integrate those different sets of information. One of the biggest challenges is using an organized, methodical, and efficient way to combine geophysical and hydrogeological data sets that measure different parameters over different spatial scales. This is the largest obstacle because the foundation of hydrogeophysics is integrating hydrogeology with geophysics. [3]

Methods

There are many different methods for determining subsurface properties and features that can be done from different locations/ proximities to the study sites:

Applications

Geophysics helps to learn about many hydrogeological matters such as:

These parameters are then used to investigate matters including searching for underground water resources, aquifer control or contamination from sea water or industrial sources, and storing harmful substances underground. Having a good measurement of these hydrogeological parameters helps to better understand water contamination transport and develop more sustainable water resources. [4]

Related Research Articles

Hydrology Science of the movement, distribution, and quality of water on Earth and other planets

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 environmental watershed 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.

Aquifer Underground layer of water-bearing permeable rock

An aquifer is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials. Groundwater from aquifers can be extracted using a water well. 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 create 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.

Environmental geology, like hydrogeology, is an applied science concerned with the practical application of the principles of geology in the solving of environmental problems created by man. It is a multidisciplinary field that is closely related to engineering geology and, to a lesser extent, to environmental geography. Each of these fields involves the study of the interaction of humans with the geologic environment, including the biosphere, the lithosphere, the hydrosphere, and to some extent the atmosphere. In other words, environmental geology is the application of geological information to solve conflicts, minimizing possible adverse environmental degradation or maximizing possible advantageous conditions resulting from the use of natural and modified environment. With an increasing world population and industrialization, the natural environment and resources are under high strain which puts them at the forefront of world issues. Environmental geology is on the rise with these issues as solutions are found by utilizing it.

Hydrogeology Study of the distribution and movement of groundwater

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.

An aquifer 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.

Hydraulic conductivity, symbolically represented as , is a property of vascular plants, soils and rocks, that describes the ease with which a fluid can move through pore spaces or fractures. 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.

A slug test is a particular type of aquifer test where water is quickly added or removed from a groundwater well, and the change in hydraulic head is monitored through time, to determine the near-well aquifer characteristics. It is a method used by hydrogeologists and civil engineers to determine the transmissivity/hydraulic conductivity and storativity of the material the well is completed in.

Magnetotellurics Electromagnetic geophysical technique

Magnetotellurics (MT) is an electromagnetic geophysical method for inferring the earth's subsurface electrical conductivity from measurements of natural geomagnetic and geoelectric field variation at the Earth's surface.

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.

SahysMod

SahysMod is a computer program for the prediction of the salinity of soil moisture, groundwater and drainage water, the depth of the watertable, and the drain discharge in irrigated agricultural lands, using different hydrogeologic and aquifer conditions, varying water management options, including the use of ground water for irrigation, and several crop rotation schedules, whereby the spatial variations are accounted for through a network of polygons.

Hydrological model

A hydrologic model is a simplification of a real-world system that aids in understanding, predicting, and managing water resources. Both the flow and quality of water are commonly studied using hydrologic models.

A buried valley is an ancient river or stream valley that has been filled with glacial or unconsolidated sediment. This sediment is made up of predominantly gravel and sand, with some silt and clay. These types of sediments can often store and transmit large amounts of groundwater and act as a local aquifer.

The following outline is provided as an overview of and topical guide to hydrology:

GIS in environmental contamination is the use of GIS software in mapping out the contaminants in soil and water using the spatial interpolation tools from GIS. Spatial interpolation allows for more efficient approach to remediation and monitoring of soil and water contaminants. Soil and water contamination by metals and other contaminants have become a major environmental problem after the industrialization across many parts of the world. As a result, environmental agencies are placed in charge in remediating, monitoring, and mitigating the soil contamination sites. GIS is used to monitor the sites for metal contaminants in the soil, and based on the GIS analysis, highest risk sites are identified in which majority of the remediation and monitoring takes place.

Near-surface geophysics Geophysics of first tens of meters below surface

Near-surface geophysics is the use of geophysical methods to investigate small-scale features in the shallow subsurface. It is closely related to applied geophysics or exploration geophysics. Methods used include seismic refraction and reflection, gravity, magnetic, electric, and electromagnetic methods. Many of these methods were developed for oil and mineral exploration but are now used for a great variety of applications, including archaeology, environmental science, forensic science, military intelligence, geotechnical investigation, treasure hunting, and hydrogeology. In addition to the practical applications, near-surface geophysics includes the study of biogeochemical cycles.

Prabhat C. Chandra Indian geophysicist

Prabhat C Chandra is an Indian geophysicist. Since 1973, he has done extensive work in the field of hydrogeophysics, encompassing groundwater exploration, development and management with a specialization in groundwater geophysics using various geophysical methods.

Groundwater pollution Pollution that occurs when pollutants are released to the ground and seep down into groundwater

Groundwater pollution occurs when pollutants are released to the ground and make their way into groundwater. This type of water pollution can also occur naturally due to the presence of a minor and unwanted constituent, contaminant, or impurity in the groundwater, in which case it is more likely referred to as contamination rather than pollution. Groundwater pollution can occur from on-site sanitation systems, landfill leachate, effluent from wastewater treatment plants, leaking sewers, petrol filling stations, hydraulic fracturing (fracking) or from over application of fertilizers in agriculture. Pollution can also occur from naturally occurring contaminants, such as arsenic or fluoride. Using polluted groundwater causes hazards to public health through poisoning or the spread of disease.

Surface nuclear magnetic resonance (SNMR), also known as magnetic resonance Sounding (MRS), is a geophysical technique specially designed for hydrogeology. It is based on the principle of nuclear magnetic resonance (NMR) and measurements can be used to indirectly estimate the water content of saturated and unsaturated zones in the earth's subsurface. SNMR is used to estimate aquifer properties, including the quantity of water contained in the aquifer, porosity, and hydraulic conductivity.

Kamini Singha American hydrogeologist

Kamini Singha is a Professor in the department of Geology and Geological Engineering at the Colorado School of Mines, where she works on questions related to hydrogeology.

Susan Sharpless Hubbard is an American hydrologist and geophysicist, and Hubbard is the Deputy for Science and Technology at Oak Ridge National Laboratory. She was elected a member of the National Academy of Engineering in 2020 for contributions to hydrogeophysics, biogeophysics, and the geophysics of permafrost.

References

  1. ↑ "Applied Geophysical Research". USGS.
  2. 1 2 Rubin, Yoram; Hubbard, Susan S. (2005). Hydrogeophysics. The Netherlands: Springer. ISBN   9781402031014.
  3. ↑ Hubbard, S.; Rubin, Y. (17 December 2002). "Study institute assesses the state of hydrogeophysics". Eos, Transactions American Geophysical Union. 83 (51): 602, 606. Bibcode:2002EOSTr..83..602H. doi: 10.1029/2002eo000412 .
  4. 1 2 Nwakwoala, H.O.; Udom, G.J. (December 2008). "Hydrogeophysics: An Overview of General Concepts, Applications and Future Perspectives". Scientia Africana. 7 (2): 54–63.
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