bluuebunny/crossref_metadata_2025 huggingface dataset:
Groundwater Dating with
H
–
He
Authors: Divine Craig E. , Humphrey John D.
Published: April 2005

During 1951, it was demonstrated that significant energy is released during hydrogen fusion to provide the basis for developing thermonuclear superbombs. Atmospheric testing (detonation) of these weapons during the next decade resulted in a dramatic increase in atmospheric
3
H concentration, until implementation of a Soviet–American atmospheric test ban treaty in 1963 (Fig. 2). Atmospheric thermonuclear weapons testing released vast quantities of high‐energy neutrons that interacted with
14
N and led to the production of
3
H (Eq. 1). The incredible amount of
3
H produced in the atmosphere resulted in a distinct precipitation input signal of anthropogenic
3
H (Fig. 3), and a notable peak in 1963.

The mid‐1960s
3
H peak has been widely used as a direct time marker to determine groundwater ages. However, because of the relatively short half‐life of
3
H, this peak has become difficult to differentiate in many systems. This is particularly true in the Southern Hemisphere where the anthropogenic
3
H in precipitation was notably lower than in the Northern Hemisphere. However, measurement of both parent
3
H and increases in its decay product,
3
He, can dramatically increase the sensitivity of the method.
Groundwater Dye Tracing in Karst
Authors: Bednar David M.
Published: April 2005

Groundwater dye tracing has proven to be an effective tool for aquifer characterization, protection, and to provide remediation strategies in karst areas. Tracing groundwater flow routes with fluorescent dyes is highly successful because they are water soluble and inexpensive. Fluorescent dyes are usually the best tracers to use in karst because they are easily detected in concentrations that are one to three orders of magnitude less than those at which nonfluorescent dyes can be measured spectrometrically. Additionally, they are safe to use, work effectively in different hydrogeologic settings, and can be used effectively to trace water from subsurface to surface water bodies. Dye tracing in karst has been used successfully to (1) delineate spring recharge areas and subsurface basins, (2) determine site‐specific hydrology, (3) estimate groundwater flow velocities, (4) trace groundwater flow from areas of recharge to discharge, (5) delineate wellhead protection areas, (6) map and characterize conduit flow routes, (7) detect leakage from residential sewage disposal systems, (8) identify sources of potential pollution from hazardous waste sites, (9) detect leakage from dam sites, and (10) characterize groundwater flow routes to important springs and cave streams along highway corridors.
Ambient Groundwater Monitoring Network Strategies and Design
Authors: Towne Douglas C.
Published: April 2005

Groundwater quality can be negatively impacted by a variety of physical features and cultural activities that are not always easily discerned by empirical observations. The detection and continued monitoring of groundwater quality constituents and contaminants requires expensive field sampling operations and laboratory analyses. Once deterioration of groundwater quality begins, it may be difficult to reverse, and treating the impacted water can be prohibitively expensive.

An ambient network is a proactive strategy that uses groundwater monitoring and characterization along with scientific methods and hydrologic models to assess holistically the groundwater of a given area, usually a defined hydrologic basin. Ambient networks are designed to identify regional changes in groundwater levels and/or degradation of groundwater quality such as occurs from widespread nonpoint sources of pollution or a high density of point sources. Information gleaned from an ambient network includes determining where groundwater levels are fluctuating, locating areas of poor water quality, and identifying spatial and temporal water quality patterns. When correctly designed, the data collected in ambient monitoring programs can be statistically analyzed to make broad statements about the groundwater of a basin that have a known degree of confidence using a relatively small number of investigated sites. Several states such as Arizona and Idaho (1) have redesigned their ambient networks because of subjective, rather than statistical, selection of sites. Others such as Minnesota (2) initiated new ambient networks because the previous design failed to meet objectives.
Aquifers
Authors: Harter Thomas
Published: April 2005

An aquifer is a geologic formation or geologic unit from which significant amounts of groundwater can be pumped for domestic, municipal, or agricultural uses. The four major types of rock formations that serve as aquifers are unconsolidated sand and gravel, sandstone, carbonate rocks, and fractured volcanic rocks. Aquifers may also occur in other geologic formations, particularly in fractured zones of igneous, metamorphic, or sedimentary rocks.

The word aquifer was probably adopted around the early twentieth century from the French word aquifère, which originates from the two Latin words aqua (water) and ferre (to carry, to bear). Hence, literally translated from Latin, aquifer means ‘that which carries water.’

There is no strict definition of the hydrogeologic attributes or volumetric extent necessary to make a geologic formation or geologic unit an aquifer. Rather, the term aquifer is used for local formations that have relatively higher permeability than surrounding formations. Geologic units that form an aquifer in one setting may therefore not be considered to constitute an aquifer in other settings.
Groundwater Tracing
Authors: Jahani Hamid R.
Published: April 2005

Groundwater tracing is now a major field in groundwater hydrology aiming mainly at demonstrating the direction of groundwater flow and secondly, at giving as much information on the hydrologic setting as possible. It has been used for several decades to study flow conditions, for groundwater reconnaissance, and for managing water resources. During the last decades, water protection has been one of the main issues due to strong pollution of the environment. A groundwater tracer is a substance or a sort of energy conveyed by water to be detected at a sampling point and to be used in analyzing the temporal and spatial distribution of water and the pollutant. Artificial and natural tracers can help in various ways to assess and to predict contaminant transport in surface and groundwater.
Hydraulic Properties Characterization
Authors: Loo Walter W.
Published: April 2005

Groundwater is becoming an important issue as a source of fresh water. The groundwater that exists at the subsurface is called an aquifer. An aquifer is a geologic unit that can store and transmit water at rates fast enough to supply reasonable amounts to wells. Thus, understanding a groundwater body is an essential factor in groundwater development and protection.

The geohydrologic properties of a groundwater body consist of physical, chemical, and biological parameters of the solid matrix and liquid within its pore space. These parameters determine the quantitative, qualitative, and interpretive aspects of the groundwater body. The solid matrix may consist of various sedimentary deposits or rock types. The liquid within the pore space of the groundwater body consists of water, dissolved minerals and gases, microorganisms, and colloidal material.
Assessment of Groundwater Quality in
D
istrict
H
ardwar,
U
ttaranchal,
I
ndia
Authors: Jain Chakresh K.
Published: April 2005

The groundwater quality of District Hardwar in the state of Uttaranchal (India) has been assessed to see the suitability of groundwater for domestic use. Forty‐eight groundwater samples from shallow and deep aquifers were collected each during pre‐ and postmonsoon seasons during the year 2002. Various water quality constituents, pH, conductance, total dissolved solids, alkalinity, hardness, sodium, potassium, calcium, magnesium, chloride, sulphate, phosphate, fluoride, total coliforms, and fecal coliforms were determined. The data were analyzed with reference to BIS and WHO standards, and hydrochemical facies were determined. The concentration of total dissolved solids exceeded the desirable limit of 500 mg/L in about 25% of the samples analyzed, but the values were well within the maximum permissible limit of 2000 mg/L. The alkalinity exceeded the desirable limit of 200 mg/L in about 50% of the samples, but these were also within the maximum permissible limit of 600 mg/L. From the hardness viewpoint, about 80–85% of the samples were within the desirable limits. One sample of the study area exceeded the maximum permissible limit of 100 mg/L for nitrate. Other constituents such as chloride, sulphate, and fluoride were within the desirable limits. The bacteriological analysis of the groundwater samples indicated bacterial contamination in about 40% of the samples analyzed. Inadequate maintenance of hand pumps, improper sanitation, and unhygienic conditions around the structure may be responsible for bacterial contamination in groundwater of the region and is a cause of concern. It is recommended that the water drawn from such sources be properly disinfected before being used for drinking and other domestic purposes. The grouping of samples according to their hydrochemical facies indicates that all the samples of the study area fall under Ca–Mg–HCO
3
hydrochemical facies.
In SituElectrokinetic Treatment ofMtBE, Benzene, and Chlorinated Solvents
Authors: Loo Walter W.
Published: April 2005

The basic mechanism of bioremediation is triggering the growth of microorganisms that are adapted to organic wastes spilled in the soil and groundwater. Stimulation of the growth of the microorganism is controlled by proper temperature, oxygen, moisture, nutrients, and cosubstrates, and distribution of such in the impacted media. During growth, the microorganism will secrete enzymes and biosurfactants to break down the hazardous organic molecules (detoxification) and to make them available through cellular absorption. Subsequently, the microorganism will grow and multiply, and the process repeats until the food source is depleted. The end result is mineralization of the carbon source (from spilled hazardous organic wastes) aerobically into carbon dioxide, water, and biomass without undesirable side effects. The cometabolic processes for bioremediation of chlorinated solvents and petroleum hydrocarbons are the most promising trouble‐free biotreatment processes and are very efficient. The cometabolic process can be defined as the introduction of an easily biodegradable substrate into the environment, which triggers the secretion of enzymes from microorganisms that are adapted to the spilled hazardous organic waste.
In Situ
Groundwater Remediation for Heavy Metal Contamination
Authors: Jacobs James A.
Published: April 2005

Remediation of heavy metals such as lead, chromium, arsenic, and others in soil and groundwater frequently uses reduction reactions to lower the solubility of an oxidized metal in the higher of two or three valence states to a lower energy and less toxic state. Ultimately, the metal is precipitated as a sulfide or in another immobile and low toxicity form.

The solubilities of arsenic, lead, copper, zinc, cadmium, molybdenum, uranium, and cyanide are pH dependent. Recently, sulfur‐based metals treatment technologies have been the focus of an increasing number of research studies and commercial applications for treating metal contamination in soil and groundwater.

In situ
metal remediation by reduction can be either chemical or biological. For chemical reactions, sulfur compounds have been used successfully in a variety of settings. Precipitation of metals in reducing environments as sulfides, hydroxides, and carbonates has been documented as a remediation method. Even zero‐valent iron has been used to reduce hexavalent chromium in groundwater through reactive permeable barrier walls, as part of a funnel and gate system. Reactive barriers for
in situ
metal treatment are documented.
Infiltration and Soil Water Processes
Authors: Holden Joseph
Published: April 2005

Water at the soil surface is drawn into the soil pores under the influence of both suction and gravity. Suction (or tension/capillary) forces are largest in the small pore spaces between soil particles. Therefore, small pores fill first, and large pores empty first. As a soil becomes saturated, suction forces approach zero. As a soil dries, suction forces dominate, and there is little or no gravitational flow. For a dry soil during the early stages of wetting, the effect of soil pore suction is predominant. However, as the depth of wet soil increases, the suction gradient decreases (the same difference in suction is spread over an ever increasing depth interval) and the gravitational head gradient becomes the main driving force.

Infiltration processes cannot easily be separated from the processes involved in movement of water within soil because the rate of infiltration is partly controlled by the rate of soil water movement below the surface. Soil water movement continues after an infiltration, as the infiltrated water is redistributed. Infiltration and soil water processes play a key role in surface runoff, groundwater recharge, ecology, evapotranspiration, soil erosion, and transport of nutrients and other solutes in surface and subsurface waters.
Karst Hydrology
Authors: Bednar David M.
Published: April 2005

The most interesting aspect of a karst landscape is its unique hydrologic system. Karst landscapes are primarily underlain by carbonate, primarily limestone and dolomite, where surface water and groundwater are interconnected to form one functional unit. The end result of this hydrologically integrated flow system is the karst spring. Springs provide substantial quantities of water for human consumption and commercial enterprises. Because karst aquifers provide effective natural cleansing, it is imperative to understand the dynamic flow systems within these aquifers to protect these vulnerable water supplies from contamination.
Karst Topography
Authors: Bednar David M.
Published: April 2005

Karst is an irregularly shaped area of land where underground drainage dominates and has resulted in dissolving the bedrock to form distinctive surface and subsurface features. Karst predominately develops on lands underlain by soluble bedrock such as limestone and dolomite, but can also form in marble, gypsum, and halite. Due to differences in climate, cover, rock type, hydrology, and geologic structure, some areas show significant expression of karst development at the surface, and others show no obvious signs at all. Chemical solution of the bedrock by groundwater leads to the formation of open passageways into and through the subsurface. The degree of development of these features varies greatly from one region to another.
Lysimeters
Authors: Brye Kristofor R.
Published: April 2005

Lysimetry is a measurement technique that employs sampling devices called lysimeters to measure the movement of water and solutes through a porous medium. Lysimeters have most commonly been used to quantify water movement (i.e., drainage) through soil and typically consist of a porous plate surface of varying pore sizes through which water moves from the soil into a collection reservoir.
Methane in Groundwater
Authors: Priyadarshi Nitish
Published: April 2005

Methane is a colorless, odorless, and tasteless gas, which is produced by biological decay of organic materials or by high temperatures acting on organic materials in unconsolidated and geologically young deposits. These materials include coals, organic rich shales, landfill materials, compost piles, and other accumulations of organic materials both above and underground. For example, a buried oak log, only 1 ft in diameter and 5 ft long, can generate enough methane when it decomposes underground to form an explosive mixture in 400 to 1200 m
3
of air (1).

Methane is produced by biological processes where oxygen is excluded (anaerobic conditions). Methane can be oxidized in water that contains dissolved oxygen, so the amount that reaches the surface depends on the depth of water. Its rate of production generally increases with temperature.
Nitrate Contamination of Groundwater
Authors: Azadpour‐Keeley Ann , Keeley Jack
Published: April 2005

Groundwater supplies drinking water for half of the people in the country and represents the total water supply for many of the western states. Numerous contaminants are anthropogenic, including petroleum products, chlorinated solvents, and pesticides, but nitrate contamination can be either natural or man‐made and is one of the most common chemical contaminants of groundwater. Nitrate levels in uncontaminated groundwater are generally less than 2 mg/L, but levels have been increasing during the past five to six decades in areas where contamination has occurred.
Nonpoint Sources
Authors: Jain Chakresh K.
Published: April 2005

In recent years, it is being recognized that the nonpoint sources of water pollution have greater importance than point sources. This is due in part to the continuing efforts to reduce pollution from point sources during the past few decades, as well as recognition that nonpoint sources, such as storm water, may contain harmful contaminants. Modern agriculture has also relied, among other things, on heavy use of fertilizers and pesticides. This has largely occurred without any serious regard to the environmental consequences, especially pollution of both surface and groundwater resources. Chemicals (fertilizers and pesticides) applied in agroecosystems invariably enter the hydrologic cycle and contaminate both surface and groundwater resources. Nutrients and pesticides, particularly, are of major concern because of eutrophication and toxicity. Nutrients and pesticides are transported from cropland either by being absorbed onto eroded soil particles or dissolved in runoff water. This has increased the need to identify and quantify major sources of nutrients and pesticides deposited within river systems. In this article, some basic concepts of nonpoint source pollution, including the effects and extent of pollution in surface and groundwater bodies, pollution control measures, monitoring and modeling approaches, and management options are presented.
Perched Groundwater
Authors: Leonhart Leo S.
Published: April 2005

Perched ground water is subsurface water that forms a saturated horizon within porous media at an elevation higher than the local or regional groundwater table. This condition may result from various field conditions, but the requisite condition is a soil or rock horizon of significantly lower vertical hydraulic conductivity (
K
v
) (perching unit) amid contrastingly higher
K
v
strata. Downward movement of infiltrating water through the higher
K
v
materials is retarded and accumulates above and/or within the perching unit. This typically “mounds” saturated water above the perching unit, leaving an unsaturated (vadose) horizon below the perching unit. The upper limit of saturation in a perched zone is referred to as a perched water table, whereas the lower limit has been defined as an inverted water table.
Permeability
Authors: Priyadarshi Nitish
Published: April 2005

Permeability is a measure of the ease with which fluids pass through a porous medium. It was established experimentally by Darcy in 1856 that

urn:x-wiley:9780471478447:media:gw826:xm1

in which
k
is the permeability,
Q
is the volume of fluid which passes in unit time through area
A
in the direction
s
of the pressure gradient d
p
/d
s
, and
n
is the viscosity of the fluid. The unit of permeability in most common use by geologists and members of the oil industry is the darcy (D), which corresponds to a flow of 1 cm
3
s
−1
cm
−2
at a pressure gradient of 1bar cm
−1
. If the fluid is water, material with a permeability of 1D will pass 10
−3
cm
3
s
−1
cm
−1
at a pressure gradient of 1 g cm
2
 cm
−1
.
Phytoremediation of Selenium‐Laden Soils
Authors: Datta Rupali , Sarkar Dibyendu
Published: April 2005

Selenium (Se) is a naturally occurring metalloid that is toxic at high concentrations but is also a nutritionally essential element. In the 1980s, Se‐contaminated water at the natural wildlife refuge at Kesterson Reservoir, California was responsible for widespread reproductive failure, developmental defects, and death in migratory aquatic birds and fish. The environmental and health impacts of this incident have resulted in extensive research on the behavior of Se in soils and plants. The cost of using conventional remediation technologies for cleaning up Se‐contaminated soils is very high, so recent research has focused on phytoremediation of Se from contaminated soils. Selenium accumulation by plants and its subsequent volatilization are very effective in remediating Se‐contaminated soil and water. Natural hyperaccumulator plants such as
Astragalus
growing in seleniferous soils accumulate high concentrations of Se in their tissues. However, the main drawback of using these plants for phytoremediation is their slow growth rate and low biomass. This has prompted researchers to investigate the possibility of developing genetically engineered plants with better Se phytoextracting capacity. Understanding the speciation and bioavailability of Se in soils and the biochemistry of Se in plants and microorganisms is the first step toward developing effective phytoremediation strategies for Se‐laden soils.
Recharge in Desert Regions Around the World
Authors: Uhlman Kristine
Published: April 2005

Following Potter's classification, arid and semiarid regions are those whose precipitation to evaporation (P/E) ratios are smaller than 0.5 and between 0.5 and 1.0, respectively. In addition to a lower net precipitation rate, rainfalls are typically infrequent and of short duration; high‐intensity seasonal storms contribute a major portion of the annual rainfall over short periods of time. Under these conditions, the shallow soil surface layer infiltration capacity may be exceeded and excess overland flow propagates rapidly to flash flooding. Even low‐intensity rainfalls, can lead to significant surface runoff when desert soil crusts have formed.

Water focused and concentrated by topography into ephemeral washes, wadis, sabkhas, and playas provides locations of enhanced recharge in arid areas. A significant component of recharge to arid basin aquifers occurs along mountain fronts. Important aspects along the mountain front include the partitioning of rainfall and snowmelt into surface runoff, deep infiltration along fractures and faults, and vegetation‐controlled evapotranspiration. Focused flow along mountain stream channels into the major washes in the Tucson Basin (Arizona) visibly infiltrates flood‐plain sediment, and surface water commonly does not leave the watershed. Half the annual recharge of 9 to 10 mm/year to the Ogallala Aquifer in the southern High Plains (Oklahoma and Texas) occurs through playa floors that cover only 6% of the aquifer land surface area.
Polycyclic Aromatic Hydrocarbons
Authors: Ashworth Samuel C.
Published: April 2005

Polycyclic aromatic hydrocarbons (PAHs) are a large group of organic compounds that have two or more fused aromatic rings. They have relatively low solubility in water and are highly lipophilic. The term polycyclic organic matter (POM) defines a broad class of compounds that generally includes all organic structures that have two or more fused aromatic rings. Polycyclic organic matter has been identified with as many as seven fused rings and, theoretically, millions of POM compounds could exist; however, only about 100 species have been identified and studied, and typically only a small fraction of them are regularly tested for as part of emissions measurement programs. Any effort to quantify emissions of POM relies on the group of compounds or analytes targeted by the test method employed. The EPA has defined these eight major categories of compounds in the class known as POM.

polycyclic aromatic hydrocarbons (PAHs);

aromatic hydrocarbons that contain nitrogen in a heterocyclic ring;

aromatic hydrocarbons that contain a carbon–nitrogen double bond (CNH);

aromatic hydrocarbons that contain a one‐ring carbonyl divalent group (CO), also known as quinones; contain two‐ring carbonyl divalent groups;

carbonyl arenes that contain hydroxy groups and possibly alkoxy or acyloxy groups;

oxa arenes are aromatic hydrocarbons that contain an oxygen atom in a heterocyclic ring; thia arenes are aromatic hydrocarbons that contain a sulfur atom in a heterocyclic ring; and

some polyhalo compounds, such as polychlorinated dibenzo‐p‐dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), may be considered POM although they do not have two or more fused aromatic rings.
Water Treatment in Spent Nuclear Fuel Storage
Authors: Ashworth Samuel C.
Published: April 2005

Some of the variables that affect the growth of microorganisms include food/nutrient availability, temperature, pH, biocide concentrations, radiation, makeup water microorganism concentration, and predation. There are practical limitations to the types of activities that can be used to control microorganisms, for example, restricting the use of biocides or pH out of the range of water chemistry requirements.

The first substances on a surface during biofilm formation are trace organics (2). Almost immediately after the clean pipe surface comes into contact with water, an organic layer deposits on the water/solid interface (3). These organics form a conditioning layer that neutralizes excessive surface charge and surface free energy that may prevent a bacterial cell from approaching near enough to initiate attachment. In addition, the absorbed organic molecules often serve as a nutrient source for bacteria.
Economics of Industrial Water Demands
Authors: Renzetti Steven J.
Published: April 2005

This article examines what is known regarding the economic characteristics of industrial water use. Understanding the economic dimension of industrial water use is important for several reasons. First, in some countries, industrial water use is already an important part of total water use. Furthermore, in a number of countries, the proportion of total water use accounted for by industry is rising rapidly. Second, much of industrial water use results in significant alterations in water quality. Third, industrial water use differs from water use in other sectors because many firms recycle water and because many firms may choose their source of water supply.
Water Use in Energy Production
Authors: Inhaber Herbert
Published: April 2005

The United States uses far more water to produce energy and electricity than any other sector. A slight reduction in water use in the electricity sector would far outweigh other modes of saving—toilets using less water, low‐flow shower heads,—in the household sector.

Most attention here will be devoted to thermoelectric and hydroelectric plants. Thermoelectric plants can be divided into fossil fuel—coal, oil, and natural gas—and nuclear. These constitute almost all the electricity producers in this country. Water use is usually defined and measured in terms of withdrawal or consumption. The former is what is taken, and the latter is that which is used up. Water withdrawal in energy production is much greater than consumption. In hydroelectric plants, far more water is used than in any other energy source. However, the amount of water consumed—that is, not available for further use—is a small fraction of the water used and is attributable to evaporation from lakes behind hydro dams. Energy consumption for thermoelectric plants is of the order of 2% of water used.

Some of the water used to produce energy becomes contaminated with pollutants. This aspect of energy production is not discussed in this article; it is treated in detail in other articles in this publication.
Energy Dissipation
Authors: Bott T. R.
Published: April 2005

Many process industries, such as oil refining or chemical manufacture, need to cool products or intermediate streams that may be either liquids or gases, before storage or further processing. To conserve heat and hence costs, it is usual to transfer as much heat energy as possible from an outgoing “hot” stream to an incoming cold stream or intermediate. However as the temperature of the “hot” stream is reduced, there comes a point where it is no longer economical or feasible to reduce the temperature of the stream to be cooled by further interchange of heat. As the temperature of the “hot” stream approaches the temperature of the incoming stream, the temperature driving force for heat transfer is reduced so that a relatively large heat transfer area is required to complete the cooling process. In general, naturally occurring water has a relatively low temperature and because there is so much of it in the world—in seas, lakes, rivers, canals, and boreholes—water is used as a universal cooling medium. The increasing world shortage of water, however, requires effective water management to conserve supplies and to protect the environment.
Industrial Cooling Water—Biofouling
Authors: Bott T. R.
Published: April 2005

The accumulation of living matter in cooling water systems may be the result of the activity of microorganisms such as bacteria, algae, and fungi, or the growth of macroorganisms that include mussels, barnacles, hydroids, and serpulid worms and plant material such as water weeds. The extent of the deposition of both micro‐ and macroorganisms, depends very much on the origin of the water employed in the cooling water circuit. In general, the water is taken from a natural source, which contains the organisms and nutrients to sustain life and growth. Some sources, such as borehole water, are relatively free of organic material, but in “open” cooling water circuits, it rapidly becomes contaminated from contact with the atmosphere. Water from other sources, including freshwater rivers, canals or lakes, estuarine or seawater, is already heavily contaminated before it is taken into an industrial system.
Evapotranspiration
Authors: Payero Jose O.
Published: April 2005

Liquid water from a surface can be transformed into water vapor by either evaporation or by transpiration.Evaporationis the process for converting liquid water to water vapor and removing it from the evaporating surface.Transpirationis the vaporization of water contained in plant tissues and the removal of vapor to the atmosphere through leaf stomata. Evaporation and transpiration occur simultaneously in cropped surfaces, and there is no easy way of quantifying the magnitude of each component. For practical applications, such as irrigation scheduling and irrigation system design, it has been more useful to consider both processes combined. The combination of these two processes is calledevapotranspiration. The proportion of each component in a cropped surface is affected by factors such as vegetative cover, available water in the soil, and surface wetness. For an annual crop like corn, evaporation is the dominant component of evapotranspiration at the beginning of the season when the soil surface is exposed to solar radiation. As the crop grows and the canopy covers the surface, evaporation is minimized, and transpiration becomes the dominant component.
Hydrosphere
Authors: Araya Yoseph Negusse
Published: April 2005

The hydrosphere [Greek
hydor
water and
sphera
sphere] refers to the water on or surrounding the surface of the globe, as distinguished from those of the lithosphere (the solid upper crust of the earth) and the atmosphere (the air surrounding the earth). More specifically, the hydrosphere includes the region that includes all the earth's liquid water, frozen and floating ice, water in the upper layer of soil, and the small amounts of water vapor in the earth's atmosphere. The hydrosphere is the major setting for the earth's hydrologic cycle [see H
YDROLOGIC
C
YCLE
].

The earth's water has six major reservoirs in which water resides. These include the oceans, the atmosphere (split into two reservoirs, one over the land and one over the oceans), surface water (including water in lakes, streams, and the water held in the soil), groundwater (water held in the pore spaces of rocks below the surface), and snow and ice.

The quality of natural water in the various reservoirs of the hydrosphere depends on a number of interrelated factors. These factors include geology, climate, topography, biological processes, land use, and the time for which the water has been in residence.
Monsoon
Authors: Holst Arthur M.
Published: April 2005

Cyclic air masses accompanied by either much or little rain, carried by winds that reverse direction semiannually, are called monsoons. The word monsoon comes from the Arabic word “mausim,” which is translated as “season.” Monsoons occur over almost every continent, but they come in varying degrees of strength, as judged by rainfall production and wind speed. The most powerful and well‐known monsoons occur in India and Southeast Asia.
Chinook
Authors: Holst Arthur M.
Published: April 2005

Wind is defined as the movement of air. Although we commonly define wind as a gentle breeze or a harsh gust of cold air, there is a wind phenomenon that can increase the temperature instead of lowering it. It is called a Chinook wind. Chinooks are most commonly associated with the Rocky Mountain range in North American but can also be found in the Swiss Alps and the Andes. They can increase temperatures high enough to melt the snow in their path as they travel down the mountainside. The Chinook wind falls under the classification of katabatic wind, which means that it moves downhill.
Radar Use in Rainfall Measurements
Authors: Endreny Theodore A.
Published: April 2005

Meteorologists, hydrologists, and other environmental scientists use microwave radar (radio detection and ranging) techniques to observe remotely the location, type, and intensity of atmospheric precipitation. Doppler radar units provide an additional measurement of storm movement and wind rotational strength. Hence, microwave radar units are used for remotely sensing precipitation and winds.

Radar operates by emitting electromagnetic radiation into the air at various scan heights and then detecting the part of that radiation that is reflected back by hydrometeors (e.g., backscattered) to the radar device and considered reflectivity. Hydrometeors refer to liquid and frozen precipitation, but backscattering can also occur from large flocks of birds, insects, and other large airborne particles. Based on the density, size, and shape of the hydrometeors (e.g., spherical liquid vs. angular frozen crystals) and the polarization of the radar beam, the algorithms processing the radar signal can determine precipitation type and intensity.
Rain Simulators
Authors: Holden Joseph
Published: April 2005

There are two rainfall simulator systems: spray nozzles (including rotating sprays) and drip‐screens. Spray systems generally supply rainfall in pulses to the ground, and rotating sprays deliver rainfall across a large surface area although intensity usually decreases with distance from the rotating nozzle. The spray‐type systems often provide rainfall at terminal velocities which approach that of natural rainfall. Drip systems use hypodermic syringes or other drop formers across a fixed grid to produce rainfall across relatively small surface areas. The drop formers are often not raised high enough to allow representative terminal velocities, but they generally allow a constant rainfall rate whose drop sizes are more easily controlled than in the spray systems.
Snow Density
Authors: Singh Pratap
Published: April 2005

Density is one of the fundamental and important characteristics of snow. It is defined as the mass of snow per unit volume. To determine the density of snow, a core sample of snow is extracted from the accumulated snow on the ground using a snow sampler of known volume. The extracted snow sample is weighed and its mass is determined. The density of the sampled snow is determined by dividing the mass by the volume. The most common unit used for representing the density is g/cc or kg/m
3
.
U
nited
S
tates
W
eather
B
ureau
Authors: Holst Arthur M.
Published: April 2005

From 1890–1970, the United States Weather Bureau provided various weather‐related services to the nation. Weather analysis had been considered for hundreds of years, but real progress was not made until the nineteenth century, when techniques and technology began to make accurate and useful weather forecasting possible, the main purpose of the United States Weather Bureau, its predecessors, and its successor, the National Weather Service. The first national American weather service was initiated on February 9, 1870, when President Ulysses S. Grant signed into existence what was then known as The Division of Telegrams and Reports for the Benefit of Commerce. This service began in November 1870. It lasted until 1890, when it was renamed the United States Weather Bureau, and Congress reassigned it from the Department of War to the Department of Agriculture at the behest of President Benjamin Harrison. Then, in 1940, President Franklin Delano Roosevelt reassigned the Weather Bureau again, this time to its current home, the Department of Commerce. The United States Weather Bureau existed until 1970, when its name was again changed, this time by President Richard Nixon, to the National Weather Service, the name it is known by today.
Degree Day Method
Authors: Messina Carlos D.
Published: April 2005

An adequate description and prediction of plant development is critical for understanding plant growth and its responses to the environment. Only then we can assess the impact of a changing environment on plant productivity and survival, understand plant adaptation, design adequate agricultural production systems, and optimize natural resources management. Of particular importance for water resource management are the effects of plant ontogeny on plant water use and productivity throughout the regulation of leaf area. This determines the patterns of plant water demand and the partitioning between transpiration and evaporation components. Therefore, plant development dictates the selection of cultivars that best fit the water availability patterns under dryland conditions, and the amount, frequency and timing for irrigation otherwise.
Fluoridation
Authors: Dodes John E.
Published: April 2005

Fluoridation of water supplies has been a controversial subject for more than 60 years. Much of the debate is concerned with questions of safety, but recently questions have been also raised about the efficacy of fluoridation. More than 35,000 papers on fluoridation have been published in the years since fluoride supplementation was first proposed as a safe and effective way of decreasing tooth decay. The overwhelming conclusion is that fluoride is safe and cost‐effective.
Granular Bed and Precoat Filtration
Authors: Au Kwok‐Keung
Published: April 2005

Various filtration processes are used in potable water treatment. Granular bed and precoat filtration processes are described in this article, and focus is on descriptions of these processes and their particle removal efficiencies. Filtration processes are some of the major tools that are used to minimize microbial pathogens in drinking water, so the descriptions of their removal efficiencies contained herein emphasize their removal of microbes. This type of efficiency is characterized by a term called log removal, which is defined as logCo/C, whereCoandCare the pathogen concentrations in a filter's inlet and outlet flows, respectively. Thus, a 1‐log removal is equivalent to 90% removal. Current drinking water regulations target log removals of pathogens. Filter performance is also based on the amount of turbidity in the filtered water. Turbidity is a measure of water clarity. Turbidity reduces the aesthetic acceptability of drinking water and also shields pathogens from disinfectants that are added downstream of filters.
Lime–Soda Ash Processes
Authors: Viadero Roger C.
Published: April 2005

As in other chemical water softening technologies, the objective of the lime–soda ash process is to precipitate polyvalent cations from solution by pH adjustment. In water treatment applications, Ca
2+
and Mg
2+
are the two major cations of concern, though Fe
2+
, Fe
3+
, Al
3+
, and Mn
2+
may also be present at problematic concentrations, depending on the properties of soil or geological material encountered by the surface or groundwater. Typically, a total hardness ranging from 75–120 mg/L as CaCO
3
, is sought in domestic water softening.

In this process, lime and soda ash are added to solution, Ca
2+
precipitates as CaCO
3
(↓), and Mg precipitates as Mg(OH)
2
(↓). To precipitate CaCO
3
, the pH of the water must be raised to approximately 10.3. Similarly, Mg(OH)
2
(↓) forms when the pH is raised above 11. When there is not enough naturally occurring bicarbonate alkalinity (HCO
3
−
) in water to form the CaCO
3
precipitate, alkalinity must be added (typically as Na
2
CO
3
).
Microbiological Concerns of Drinking Water Distribution Systems
Authors: Karim Mohammad R. , Lechevallier Mark W.
Published: April 2005

Drinking water in a distribution system may contain microbes that enter the distribution system through treatment breakthrough, regrowth, or contamination of water in the system. The majority of these organisms are harmless. However, pathogenic organisms may also be present. A number of waterborne disease outbreaks related to distribution systems have been reported. Many factors contribute to the regrowth and contamination of drinking water in distribution systems. This article discusses the factors that contribute to microbial regrowth and contamination of distribution systems. To ensure protection of public health, these factors should be adequately addressed to safeguard drinking water from contamination in distribution systems.
Removal of Pathogenic Bacteria, Viruses, and Protozoa
Authors: Au Kwok‐Keung
Published: April 2005

Pathogenic bacteria, viruses, and protozoa can be removed from potable water by various processes. These removal processes can be categorized into three groups: (1)initial, (2)principal, and (3)alternative/supplemental. Initial removal processesare used to remove microbial pathogens before they enter or as they enter a treatment plant. The main objective of these processes is to reduce the particulate loadings, including microbial loadings, to the subsequent treatment processes of a treatment plant. Examples of initial removal processes are roughing filters, microstrainers, off‐stream storage, bank filtration, and presedimentation with coagulation.Principal removal processesare those most frequently used to remove the majority of the microbes in the water being treated. These processes are sedimentation, flotation, and high‐rate granular media filtration. They are often used in conjunction with coagulation and flocculation.Alternative/supplemental removal processesare used either as (1) alternatives to principal removal processes or (2) supplemental processes to enhance drinking water quality. These processes include slow sand filtration, precoat filtration, membrane filtration, bag filtration, and cartridge filtration.
Pharmaceuticals in Water Systems
Authors: Pollack Kelly , Ogunseitan Oladele
Published: April 2005

As the demographic pattern in most regions of the world changes in response to epidemiological transition, life expectancy is lengthened, and human reliance on medications to maintain the quality of life intensifies. It is now indisputable that widespread use of pharmaceutical products results in their release into the environment. This occurs primarily through the excretion of partially metabolized doses and the disposal of expired or unused medication. It is inevitable that that these fugitive releases lead to exposures of aquatic organisms and other natural ecosystem components. However, the driving force behind recent concerns is the potential for large‐scale human exposures through natural drinking water recycling processes. Historically, most investigations of anthropogenic chemicals in the environment have focused on acutely toxic industrial chemicals from mining, energy, and agricultural industries. The environmental impacts of products emanating from the pharmaceutical industry have largely been excluded from scrutiny. The U.S. Geological Survey conducted the first national survey of pharmaceutical products in natural water systems in 2000. The results of that study confirmed prior suspicions about the widespread contamination of aquatic systems by these products.
Physical Water Conditioning
Authors: Sanderson Charles H.
Published: April 2005

Magnetic water treatment technology that was used two centuries ago to control hard water scale is now being used in hundreds of different kinds of beneficial applications throughout the world. Permanent magnetic water conditioning (PMWC) does not change the chemistry of the water; only aphysicalchange takes place. It is therefore referred to as physical water conditioning.

Physical water conditioning (PWC) has been highly controversial for many years; however, due to numerous successful installations on boilers, cooling towers, and other HVAC equipment, the technology has gained credibility throughout the industry in recent years. The ASHRAE Handbook (considered the “bible” of the industry) states, “Equipment based on magnetic, electromagnetic, or electrostatic technology has been used for scale control in boiler water, cooling water, and other process applications.” Several laboratory tests have been conducted to evaluate the results of magnetically treated water for scale and corrosion control in heat transfer equipment.

When water flows through a magnetic field of relatively low intensity, the formation of scale in the treated water is prevented in many instances.
Public Water Supply World
Authors: Buenfil‐Rodriguez Mario O.
Published: April 2005

In cities of high housing densities,public water supplystarted as a measure to improve hygiene and health, as well as a need for fairness among citizens, to give them an equal chance to have water and to pay similar amounts via taxes or equivalent. It is also much cheaper and less chaotic to have collective solutions than individual ones.

A public water service can concentrate and pay specialized personnel, devoted full time to these highly technical matters of searching, treating, transporting, raising, distributing, maintaining, and charging for water service.

Water service in most cities of the world is provided by governmental institutions (either national. regional. municipal), but in many other locations is operated by private utilities. There also exist mixtures of private and governmental (public) responsibilities. Nowadays, there is a tendency, often promoted by lending institutions, to give up (“privatize”) governmental services that have too many conflicts and poor quality.

In this article, the term “public water supply” refers to the water service provided by some official concessionaire (independently if is private or government) that attends to the needs of various clients in a city.