bluuebunny/crossref_metadata_2025 huggingface dataset:
Freshwater Colloids
Authors: Lead Jamie R.
Published: April 2005

Colloids exist in all environmental compartments, including the atmosphere where they are termed nanoparticles. In this review we will consider only freshwater colloids, primarily in lakes, rivers and groundwaters, although soils and sediments are also an important source of waterborne colloids. Colloids are defined on the basis of size; at least one dimension is in the range 1 nm–1 µm (10
−9
 − 10
−6
 m). Below 1 nm is the dissolved or solution phase, and above 1 µm is the particle phase. In practice, this distinction is usually made by operational methods such as ultrafiltration and filtration.
The
A
ral
S
ea Disaster: Environment Issues and Nationalist Tensions
Authors: Lasserre Frederic
Published: April 2005

The village of Muynak was located on an island in the Amu Daria delta in 1956. In 1962, the island had already become a peninsula; in 1970, the sea was 10 km away, then 40 km away in 1980, and 75 km in 1998. The sea bottom became a vast salted desert. In 1987, the retreating sea divided itself in two parts, a small Aral in the north, where the Syr flows, and a large Aral, where the Amu ends its journey when it reaches the sea.

Between 1960 and 1998, the level of the small Aral dropped by 13 meters, and the level of the larger by 18 m. The total sea volume was cut by 78% (5, 6). The vanishing of the sea constitutes an enormous ecological disaster that radically alters the environmental balance in the region:

Vast deposits of salts, nitrates and pesticides spread in large quantities on the industrial crops upstream were formed, deposited by water of the Amu and the Syr. The wind now blows on these desiccated deposits, lifting nearly 40 million tons of toxic sediments each year, and transporting them far inland: this phenomenon poisons the soil, the vegetation, and the inhabitants. The salt fallout can be as high as 500 to 700 kg/ha, which quickly worsens the problem of salt built‐up due to poorly drained and excessive irrigation.
Gully Erosion
Authors: Erskine Wayne D.
Published: April 2005

Gullies have formed rapidly in many parts of the world during the last 300 years following the change from traditional agriculture or nomadic indigenous lifestyles to more intensive European‐based agriculture. They are deeper erosion channels than rills, but their differentiation is often unclear and arbitrary because of a continuum between the two features. Rills are shallow, ephemeral erosion channels that can be obliterated by standard tillage, alternating cycles of freeze‐thaw, or rain‐impacted shallow overland flows.

Attempts to differentiate between gullies and streams on the basis of flow frequency are difficult for two reasons. First, gullies are not restricted to specific climatic regions but have been described in arid, semiarid, subhumid, and humid areas. Second, flow regimes vary systematically based on drainage basin area and climate, and gullying is not restricted to specifically sized basins nor to areas of ephemeral flow.
Heat Balance of Open Waterbodies
Authors: Jöhnk Klaus
Published: April 2005

From a continuum–mechanical point of view, the heat balance or the thermodynamics of a lake, reservoir, or ocean is governed by three different types of processes: surface fluxes, those through the water surface and the sediment boundary of a water body; internal heat production; and external heat supply. Whereas surface fluxes are accounted for in boundary conditions, supply and production take place in the water volume and are described as additional production terms in the equation of heat (1). Turbulent diffusion and, to a much lesser degree, molecular diffusion lead to a certain temperature stratification, usually dividing a lake into a well‐mixed, upper warm layer, the epilimnion, separated from it by a transition zone a colder hypolimnion. The temperature–depth distribution can be determined from the heat balance equation and boundary conditions describing the surface fluxes into the water. In contrast to this, in a well‐mixed waterbody with a homogeneous temperature distribution, for example, a polymictic lake, all heat production and flux terms are lumped together in a net thermal energy flux. In this case, the heat production terms are treated as fluxes across the surface. Using such a simple system, one can determine the equilibrium temperature of the waterbody for a certain set of meteorologic conditions, that temperature to which the mixed waterbody is driven under the same prevailing meteorologic conditions. For a stratified lake or ocean, such an approach is only of limited use because it does not account for vertical transport of heat in the waterbody. But it can be a good approximation for the surface temperature when the stratification is strong, thus separating the hypolimnion from the well‐mixed epilimnion.
Base Flow
Authors: Jain Sharad K. , Singh Vijay P.
Published: April 2005

This article discusses base flow, an important component of the streamflow hydrograph. The modeling of base flow is described, followed by methods to determine the base flow recession coefficient. The methods to separate base flow are also described.

Water may reach a river by flowing over the catchment surface, moving through the soil, or through groundwater. Based on the path taken by water, streamflow may be divided into surface flow, interflow, and base flow. The ASCE defined base flow as the runoff that has reached the stream or river by passing first through the underlying aquifer, rather than by flowing directly on the ground surface. Thus, base flow is that portion of streamflow that is naturally and gradually withdrawn from groundwater storage or other delayed sources. The other names of base flow are groundwater flow, seepage flow, low flow, and fair weather flow.
Microorganisms in Their Natural Environment
Authors: Koschorreck Matthias
Published: April 2005

In their natural aquatic environment, microbes face conditions that principally differ from the picture of a mixture of different microbes swimming around in a kind of liquid culture. The study of microorganisms in laboratory cultures often gives limited information about the role and behavior of microorganisms in their natural habitat. Our understanding of microbes in their natural aquatic habitat was considerably increased by the development ofin situmethods in the last decades. The introduction of microsensors allowed characterizing the microbial habitat on the size scale of microorganisms. The recent advances in microscopic techniques (confocal laser scanning microscopy, atomic force microscopy) offer the possibility of real 3‐D examination of microbial aggregates or biofilms. Molecular techniques such asin situhybridization to study the phylogeny and physiology of microorganisms in their natural environment are rapidly, improving.
Pollution of Surface Waters
Authors: Priyadarshi Nitish
Published: April 2005

Surface water comes in direct contact with the atmosphere, streams, rivulets, and surface drains. So a continuous exchange of dissolved and atmospheric gases occurs and wastes are added through water conveyance.

There are many causes of surface water pollution but two general categories exist: direct and indirect contaminant sources. Direct sources include effluent outfalls from factories, refineries, waste treatment plants, decomposed plant animal matter, and radioactive materials and wastes. Indirect sources include effluent contaminants that enter the surface water supply from surface soils and from the atmosphere via rainwater. Soils contain the residue of human agricultural practices (fertilizers, pesticides, etc.) and improperly disposed of industrial wastes. Atmospheric contaminants are also derived from human practices (such as gaseous emissions from automobiles, factories, and even bakeries).
Pond Aquaculture—Modeling and Decision Support Systems
Authors: Szumiec Maria A.
Published: April 2005

Physical environment plays a controlling role in all processes and events that occur in waters. Knowledge of water's dynamic characteristics and model elaboration is basic. Shallow stagnant waters are characterized by the individuality resulting from their small capacity. This is displayed in their receptivity to external factors, such as weather variability, that differentiates them from lakes. In a temperate climate, quick and distinct changes in meteorological events are displayed in variations in the solar radiation that penetrates into shallow waters, thus, in variations in light and thermal conditions. These changes are then transferred directly and/or via chemical processes to different levels of the biological chain. In fishponds, the final link in the chain is the stenothermic organism which is affected by the ambient temperature in a complex way. Penetrating light plays the decisive role in fish survival, limiting the concentration of oxygen dissolved in the water. The thermal conditions inhibit development and growth of the warm water fish, such as carp, throughout the considerable part of the year.
River Basins
Authors: Pagliara Stefano , Dellacasa Francesca
Published: April 2005

A river basin (also called drainage basin, watershed, or catchment) is the area that provides runoff to a given section of a stream and is separated from adjacent basins by a divide. All surface runoff produced by precipitation that falls within the area is discharged through the lowest point in the divide.

Basins are delineated on topographical maps, integrated if necessary with aerial photographs or field survey; a line is drawn that encloses all drainage lines and depressions in the basin and passes through the highest points. It is assumed that the movement of groundwater follows the surface divides, but in areas characterized by a particular geologic structure, it is possible that the phreatic divide does coincide with the topographic divide; large amounts of water could be transported below the surface from one basin to another. In this case, the groundwater divide needs to be determined by hydrogeologic prospection.
Stochastic Simulation of Hydrosystems
Authors: Koutsoyiannis Demetris
Published: April 2005

Simulation is defined as a technique for imitating the evolution of a real system by studying a model of the system. The model is an abstraction, a simplified and convenient mathematical representation of the actual system, typically coded and run as a computer program. If the model has a stochastic element, then we havestochastic simulation. The term stochastic simulation sometimes is used synonymously with theMonte‐Carlo method.

Stochastic simulation is regarded as mathematical experimentation and is appropriate for complex systems, whose study based on analytical methods is laborious or even impossible. For such systems, stochastic simulation provides an easy means to explore their behavior by answering specific ‘what if’ questions. Moreover, stochastic simulation can be viewed as a numerical method for solving mathematical problems in several fields such as statistical inference, optimization, integration, and even equation solving. Under certain conditions, stochastic simulation is more powerful than other more common numerical methods (e.g., numerical integration of high‐dimensional differential equations).

Due to their complexity, hydrosystems, including water resource systems, flood management systems, and hydropower systems, are frequently studied using stochastic simulation. A generalized solution procedure for hydrosystems problems, including systems identification, modeling and forecasting, hydrologic design, water resources management, and flood management, is dicussed. Emphasis is given on the stochastic representation of hydrologic processes, which have a dominant role in hydrosystems. Peculiarities of hydrologic and other geophysical processes (seasonality, long‐term persistence, intermittency, skewness, spatial variability) gave rise to substantial research that resulted in numerous stochastic tools appropriate for applications in hydrosystems. Four examples of such tools are discussed: (1) the multivariate periodic autoregressive model of order 1 [PAR(1)], which reproduces seasonality and skewness but not long‐term persistence; (2) a generalized multivariate stationary model that reproduces all kinds of persistence and simultaneously skewness but not seasonality; (3) a combination of the previous two cases in a multivariate disaggregation framework that can respect almost all peculiarities except intermittency; and (4) the Bartlett‐Lewis process that is appropriate for modeling rainfall and emphasizes its intermittent character on a fine time scale.
Stream Classification
Authors: Erskine Wayne D.
Published: April 2005

Stream classification is important for characterizing the features of individual rivers or sections of river and also for determining the similarity of different streams. The latter is essential to assess which rivers are suitable for extrapolating of research results from elsewhere. Various schemes have been proposed for specific disciplines and purposes. There is no universally accepted stream classification scheme because they all require modification to apply to rivers different from those used to construct the scheme Therefore, classificatory schemes should be continuously revised and updated.

A nested hierarchical scheme based on the channel network which places the stream within a drainage basin or watershed context is the best approach to stream classification.
Ancient Water and Soil Conservation Ecosystems of
S
ri
L
anka
Authors: Mendis Lucius O.
Published: April 2005

Sri Lanka, an island of approximately 65,000 sq km, in the Indian ocean, lying between 6° and 8° North latitude, at the southern tip of the Indian subcontinent, experiences two monsoons, the northeast between October and March and the southwest between April and September, with occasional intermonsoon rains. Northeast monsoon rainfall is spread over much of the island, but the southwest monsoon is largely intercepted by a south‐central hill massif, and a dry southwest wind blows over the north and east.

A famous king Parakrama Bahu I, said
“Let not a drop of rain water flow to the sea without being made useful to man!”
(Mahavamsa, quoted in Reference). Human intervention in nature's hydrologic cycle is seen in the plains of ancient Rajarata and Ruhunurata in the form of river diversion systems and small, medium, and large reservoirs. In wet zone uplands, much later, terraced rice fields saw reuse of irrigation water under gravity, benefiting from forest cover induced fertility. In colonial times, destruction of forests for planting coffee, and later tea, led to adverse impacts (2). Ancient diversion systems include stone anicuts (derived from the Tamil language) or weirs, called
amuna
in Sinhala and
tekkam
in Tamil, channels diverting streams for both irrigated agriculture, and storage in reservoirs.
Water Clocks
Authors: Marks William E.
Published: April 2005

Egyptian water clocks were among the earliest timekeeping devices that did not depend on the observation of celestial bodies. One of the oldest was found in the tomb of the Egyptian pharaoh, Amenhotep I, buried around 1500
B.C.E
.

As explained by the National Institute of Standards and Technology Physics Laboratory, early water clocks were named clepsydras (“water thieves”) by the Greeks. The Greeks began using clepsydras about 325
B.C.E
. Clepsydras were stone vessels with sloping sides that allowed water to drip at a nearly constant rate from a small hole near the bottom. The drip‐drip sound of water dropping from a water clock was an ancient precursor to the ticktock sound emitted by certain mechanical clocks invented in later times. Water clocks were replaced by the invention of mechanical clocks about 700 years ago.
History of Pond Fisheries in
P
oland
Authors: Guziur Janusz
Published: April 2005

The origins of carp breeding in Europe and Poland are sunk in the obscurity of bygone times. In Europe, the first historic record of the carp as a cure for ailments is in the writings of St. Hildegard (1098–1170), the prioress of a Benedictine convent. Some time later, carp breeding in ponds was mentioned by the monk, Albertus Magnus (1230–1310), in the archives of the Kladbrubkski monastery in Bohemia (1115), and in an investiture act by King Przemyslaw Otakar II granted in 1227 in Moravia.

Several hypotheses have been suggested concerning the introduction of carp breeding in Poland. It is believed that two routes were taken to bring the carp from its native Black Sea watershed to Poland, but whichever way it traveled, the fish was brought to Poland by the clergy (bishoprics). The oldest monastic order that first engaged in farming and fish breeding was the Order of the Cistercians, which was brought to Poland in twelfth century from the province of Brabant (on the border of Belgium and France).

The domestic mirror carp is known to have been bred in Poland since the mid‐thirteenth century. This breed is not found in the wild in Europe or Asia, unlike the wild river carp (sazan), which has local forms that live free, for example, in the Danube. Because of its inferior body exterior and growth rate, wild sazan differs distinctly from domesticated mirror carp and fine‐scale carp.
G
ordon and
F
ranklin Rivers and the
T
asmanian Wilderness World Heritage Area
Authors: Holst Arthur M.
Published: April 2005

The Tasmanian Wilderness World Heritage Area (TWWHA) is one of the largest temperate wildernesses in the world. Covering more than 8500 square miles, or more than 20% of the island of Tasmania, it contains three state reserves, four national parks, four conservation areas, two protected archaeological sites, and three forest reserves. Mountain ranges, rivers, Australia's deepest caves, waterfalls, and many endangered species are also present, as well as three lakes: Lake Gordon, Lake Peddler, and Lake St. Clair. The TWWHA was adjudged worthy of environmental protection in 1982 by the World Heritage Committee.
Water Resource Organizations
Authors: Black Peter E.
Published: April 2005

Water management organizations evolved at local, regional, state, and federal levels. They were created, in large part, during the twentieth century, exhibit different degrees of formality and authority, and exist for different purposes, serving different groups consisting of individual qualified members and/or of the public at large. The organizations fill specific missions, roles, and meet demands of members and official segments of society. Knowing their missions and responsibilities makes it easier to seek information or how to influence their responsibilities.
Bioluminescent Biosensors for Toxicity Testing
Authors: Philip Jim , Bell Jennifer , Stainsby Fiona , Dunbar Sandra , Wiles Siouxsie , Whiteley Andrew , Bailey Mark
Published: April 2005

This article summarizes recent developments in whole cell bioluminescent biosensors for estimating toxicity at wastewater treatment plants (WWTPs). This started with the use of natural marine bioluminescent bacteria, and there is now at least a 20‐year history of toxicity testing with these organisms. Molecular biology has given rise to many new bioluminescent strains for toxicity testing to overcome some specific limitations ofPhotobacterium (Vibrio) fischeri. Luminescence decay toxicity tests have also been developed in higher organisms, up toCaenorhabditis elegans, to try to improve the relevance of these tests. Custom‐made biosensors for protecting wastewater treatment plants are already in development. These developments coincide with the pattern of environmental legislation in Europe.
CytochromeP450 Monooxygenase as an Indicator ofPCB/Dioxin‐Like Compounds in Fish
Authors: Aoyagi Hannah , Ogunseitan Oladele
Published: April 2005

Polychlorinated biphenyls, dioxins, and furans are ubiquitous and persistent organic pollutants (POPs). These three categories of chemicals are among the 12 priority POPs that have been scheduled for global phase‐out according to the Stockholm Convention on Persistent Organic Pollutants (SCOPOP). SCOPOP was inaugurated in May 2001, and it has been ratified by more than 100 countries under the auspices of the United Nations Environment Program. Despite the stringent regulatory restrictions now placed on the manufacture and distribution of polychlorinated biphenyls and dioxin‐like compounds, their recalcitrance in polluted aquatic environments necessitates the continuation of monitoring programs that have been implemented to reduce negative impacts on biotic and abiotic components of vulnerable ecosystems.

Polychlorinated biphenyls (PCBs) include 209 congeners consisting of two to ten chlorine atoms attached to a biphenyl structure. PCBs are highly soluble, clear, oily liquids at room temperature. They are chemically inert and thermally stable. These properties make them useful as insulators and coolants for capacitors and transformers in a variety of industries. Monsanto began production of PCBs in 1930, marketing congener mixtures under the brand name Aroclor. PCBs were also sold under the names Clophen (Germany), Kanechlor (Japan), Fenchlor (Italy), and Phenochlor (France). PCB production was banned in the U.S. in 1977 due to potential carcinogenicity.

PCBs tend to deposit in sediments and soils where they persist and bioaccumulate, their half‐lives are in the range of months to decades. Due to their high affinity for lipids, PCBs have been detected in the adipose tissues of animals worldwide, including humans. Consumption of contaminated fish is the primary route of exposure for adults, whereas infants can be exposed to high concentrations of PCBs in breast milk.
Arsenic Compounds in Water
Authors: Watt Corinna , Chris Le X.
Published: April 2005

Arsenic is the twentieth most abundant element in the earth's crust; it occurs naturally in the environment in both inorganic and organic forms. Arsenic is also released to the environment by anthropogenic activities such as pesticide use, wood preservation, mining, and smelting. Human exposure to arsenic by the general population occurs primarily from drinking water and food. In areas of endemic arsenic poisoning such as Bangladesh, India, Inner Mongolia, and Taiwan, the main exposure is through drinking water where inorganic arsenic levels can reach concentrations in the hundreds or thousands of micrograms per liter. The arsenic is released from natural mineral deposits into the groundwater in endemic areas. Groundwater is the primary drinking water source in these areas.

Arsenic is present in a variety of inorganic and organic chemical forms in water. This is a result of chemical and biological transformations in the aquatic environment. The specific arsenic compound present determines its toxicity, biogeochemical behavior, and environmental fate.
Indicator Organisms
Authors: Yakub Gary P. , Stadterman‐Knauer Kathleen
Published: April 2005

Indicator bacteria are the most common way of assessing biological water quality. Indicator bacteria are bacteria that can predict the presence of pathogenic organisms. To be a successful indicator, the following criteria must be met:

Indicator bacteria must be easy to cultivate in the laboratory using simple, cost‐effective procedures.

Indicator bacteria must be present in high enough concentrations to be readily detectable in a manageable sample volume.

Indicator bacteria must effectively predict the risk of illness from exposure to the waterborne pathogens present in contaminated water.
Arsenic Health Effects
Authors: Katsoyiannis I. , Zouboulis A.
Published: April 2005

The toxicity of inorganic arsenic species depends mainly on their valence state (usually −3, +3, or +5) and also on the specific physical and chemical properties of the compounds in which it occurs. Trivalent (arsenite, AsIII) compounds are generally more toxic than pentavalent (arsenate, AsV) compounds, whereas arsenic compounds that are more soluble in water, usually are more toxic and more likely to present systemic effects, in comparison with less soluble compounds, which are more likely to cause chronic pulmonary effects, if inhaled. Among the most toxic inorganic arsenic compounds is arsine gas (AsH3). Additionally, note that laboratory animals (commonly used for toxicity evaluation) are generally less sensitive than humans to the toxic effects of inorganic arsenic compounds.
Microbial Enzyme Assays for Detecting Heavy Metal Toxicity
Authors: Ogunseitan Oladele A.
Published: April 2005

Throughout the world, industrial development has been associated with increased mining, refining, and use of potentially toxic metals in large‐scale manufacturing processes. Industrialization is also tightly linked to increases in the combustion of fossil fuels such as coal and petroleum, which produce considerable amounts of toxic metals such as mercury and lead, respectively (1). Inevitably, many industrial activities generate environmental pollution that changes the natural biogeochemical cycling of elements by modifying the size and flux of metal reservoirs. The primary consequence of metal pollution in natural water systems is toxic effects on aquatic organisms, but ultimately human exposure occurs from consumption of contaminated water, seafood, and plant crops that are cultivated in land irrigated with polluted water.

The United States Environmental Protection Agency (EPA) has established maximum contaminant levels (MCL) for eleven metals that dominate the inorganic contaminants most commonly encountered in drinking water and groundwater sources (Table 1). The symptoms associated with these toxic metals range from skin disease from chromium (MCL = 0.1 mg/L) to more serious conditions such as kidney disease from cadmium (MCL = 0.005 mg/L) and mercury (MCL = 0.002 mg/L). In addition, nonenforceable standards have been established for secondary pollutants such as Al, Cu, Fe, Mn, Ag, and Zn because they are regarded as nuisance contaminants with the assumption of negligible health consequences at the established concentrations permitted in water (Table 2).
Emerging and Recalcitrant Compounds in Groundwater
Authors: Mohr Tom , Jacobs James A.
Published: April 2005

During the last two decades, the dominant groundwater contamination issues have focused on petroleum hydrocarbons (including gasoline, diesel, motor oil, lubricants, and jet fuel), chlorinated solvents, metals, and pesticides. Recently, attention has shifted to a variety of newly discovered compounds in groundwater. Some of these compounds were additives to fortify or stabilize the previously mentioned products. As additives, these compounds were present at low ratios, ranging from 10% to less than 1% of the total volume of the product. Though widely used in industry for decades, these emerging compounds were, until recently, not analyzed or regulated. Emerging and recalcitrant compounds include, but are not limited to, methyl tertiary‐butyl ether (MtBE) a gasoline oxygenate additive; perchlorate, the major component of solid rocket motors and a minor ingredient of highway safety flares, and various stabilizers of chlorinated solvents such as 1,4‐dioxane. Many of these recalcitrant compounds are also suspected to be carcinogenic or to cause other adverse health effects. Consequently, advisory drinking water action levels have been adopted for many emerging contaminants; regulatory agencies have added these compounds to their list of Compounds of Interest at remediation sites.
Water Quality
Authors: Mackenthun Kenneth M.
Published: April 2005

To most people, water quality means water whose characteristics represent a high degree of purity for the use to which the water is put. For drinking, this means cool, clear water, free from harmful contaminants and conditions that produce off‐flavors. Other uses require a quality whose characteristics best support the particular use.

The Water Quality Act of 1965 first designated broad water uses when requiring the establishment of water quality standards for “public water supplies, propagation of fish and wildlife, recreational purposes, and agricultural, industrial, and other legitimate uses.” The current Clean Water Act maintains those uses in section 303(c)(2)(A), and adds language to take into consideration the use and value for navigation.
Water Related Diseases
Authors: Walker Mark J.
Published: April 2005

Water‐related diseases can be placed into four categories: (1) water‐based disease, (2) waterborne disease (3) water‐vectored disease, and (4) Water‐washed disease. Infectious microbes that cause disease within these categories include bacteria, enteric viruses, parasitic protozoans, helminthes, and algae. The health effects of infection vary considerably, from symptomless to temporary mild illness to prolonged illness to death. Each category represents a distinct pathway and mechanism for infection by a microbial pathogen. Symptoms of infection, such as gastrointestinal upset, may be common across categories. The categories represent differences in strategies that can be applied to control the prevalence of infection.
Transboundary Water Conflicts in the
N
ile Basin
Authors: Li Rongchao
Published: April 2005

As a typical transboundary case, the Nile River Basin is shared by ten countries: Burundi, Democratic Republic of Congo, Egypt, Eritrea, Ethiopia, Kenya, Rwanda, Sudan, Tanzania, and Uganda. Since the early 1970s, water scarcity has become a matter of concern for the downstream states of the Nile. The engagement of the two downstream states (Egypt and the Sudan) in effective development of irrigated agriculture marked the beginning of real scarcity. The 1960s, in particular, marked the beginning when the two countries engaged in constructing large‐scale water projects; by the end of the decade, three dams (Roseires and Khashm Al‐Girba in Sudan and the High Dam in Egypt) were constructed. Large‐scale agricultural schemes have become dependent on these dams.
Valuing Water Resources
Authors: Dupont Diane , Renzetti Steven J.
Published: April 2005

The starting point for most economic methods for measuring the value of water is an understanding of the structure of household tastes or preferences and firms' productive technologies. This understanding can then be used to develop measures of the benefits of water use and the change in household welfare or firm profits that arise from changes in the price, quantity, or quality of water. These measures, in turn, allow the analyst to determine the maximum willingness to pay (in the case of a change leading to an improvement in welfare) for water. This idea of willingness to pay forms the cornerstone of economic measures of value.
1
Conservation of Water
Authors: Babel Mukand Singh
Published: April 2005

When the ratio of water availability to demand exceeds certain limits, the stress on resources becomes noticeable, and the conflicts among users intensify and increase in frequency. A region that have water availability of about 1700 m
3
per capita/year faces periodic water scarcity, and this is considered a warning if the population continues to grow. Below this limit, “water stress” is periodic. If this limit is even lower, about 1000 m
3
per capita/year, the region is under “chronic water scarcity.” Economic development, well‐being, and health are affected at these levels. The situation is “extremely scarce” if the per capita availability is below 500 m
3
per year. Many countries that used to have plentiful water resources are facing water scarcity, that is likely to be aggravated in coming years.

Water is wasted nearly everywhere; there is great potential for better conservation and management, no matter how water is used. The term water conservation is associated mainly with the policy, managerial measure, or user practice aiming at conserving or preserving water resources and taking care of the degradation of water resources; water saving aims to limit or control water demand and avoid wastage and misuse. Both perspectives are complementary and interrelated in managing scarce water resources.
Water Infrastructure and Systems
Authors: Grigg Neil S.
Published: April 2005

Water infrastructure is the set of constructed elements that operate within water resources systems and interact with environmental elements, or natural systems, such as watersheds, streams, lakes, and aquifers.

In a watershed, sets of these structures may control water for different purposes. Most apparent might be a multiple‐purpose reservoir, that has a dam and hydroelectric plant connected to electric transmission lines. Below might be a diversion dam to enable a canal to take irrigation water from the stream, if it is located in a dry region. There might be a re‐regulating reservoir with locks for navigation. Dams are a special class of hydraulic structure, and they provide barriers to the flow to enable reservoirs to store water.
Application of the Precautionary Principle to Water Science
Authors: Sweet Leonard I.
Published: April 2005

The relative constraints and uncertainties of risk assessment suggest to some that risk managers should abandon the risk framework in favor of the precautionary approach. In water science, it is not prudent to propose one as an alternative to the other. An immediate concern is that the precautionary‐based approach fails to account for risk transfers, priority substances, and costs versus benefits. It is proposed that a variety of precautionary initiatives and decision analysis tools in risk management (e.g., life cycle assessment, weight of evidence, cost–benefit), as well as the open exchange of information and rational thinking, will aid in bridging the dichotomy between risk assessment and the precautionary principle.
Water Pricing
Authors: Renzetti Steven J.
Published: April 2005

The price of water is measured by the value of the economic resources that must be sacrificed to acquire potable water. In many cases, this price is easily understood as the number of dollars and cents that must be paid to obtain a specific volume of water. In other cases, often in low‐income countries, the price of water is best understood as the combination of out‐of‐pocket expenses plus the time required for travel to and from a water source.

The purpose of this article is twofold. First, it describes the nature and range of water prices around the world. Second, it explains the significance of the price of water for decisions regarding the supply of water and the demand for water. The article concludes that, despite the potentially important role of water prices, a lack of attention to water pricing has been a major contributing factor to worldwide problems of water allocation and water quality.
Water Resources Challenges in the
A
rab World
Authors: Young M. E.
Published: April 2005

The water shortage in the Arab World (Fig. 1) is severe and worsening. The region receives only 1% of the world's renewable water resources yet contains more than 5% of the world's population. In most Arab states at the start of the twenty‐first century, the gross volumetric human and environmental demand for water exceeds natural replenishment. Per capita water availability is worsened by a high regional population growth; a 3% annual population growth rate halves the per capita availability every 24 years.

The paramount need, common to all states, therefore, is to find a sustainable balance between use and replenishment by a combination of measures to increase supply and to reduce demand. Both approaches involve technical (engineering) developments, legal and financial measures, improved water resources management through institutional interventions, and adjustments to national policies of water allocation.
Assessment of Ecological Effects in Water‐Limited Environments
Authors: Ryti Randall T. , Markweise James T.
Published: April 2005

We consider that water‐limited environments include arid lands that have less than 250 millimeters (10 inches) of annual precipitation and semiarid lands that have annual precipitation between 250 and 500 millimeters. This paper discusses the characteristics of arid and semiarid environments, approaches for evaluating the potential ecological impacts from anthropogenic contaminant sources, and the issues that make such assessments complex in arid and semiarid environments.
Averting Water Disputes
Authors: Lipford Jody W.
Published: April 2005

Economists recognize the scarcity of valuable resources. Without prices on these resources, there is not enough to satisfy all who want to use them. In most settings, however, market prices allocate resources and allow them to move to those users who value them the most. This market process allocates resources to their most productive uses and maximizes society's wealth. In the case of the ACF River Basin water, however, market prices do not currently allocate water; it is allocated politically.

Economists also recognize that resources have multiple uses. Water, for example, may be used to generate electricity; aid oyster production; provide wildlife habitat; produce industrial products; provide channel depth for barges; provide recreational opportunities for boaters, skiers, and fishers; or supply households with water for drinking, watering lawns, or filling swimming pools. In the ACF Basin, some water is used in each of these ways.

Whether allocation occurs through market prices or other methods, it is rarely all‐or‐nothing. In the Southeast (and the United States generally), there is ample water to supply basic human needs, such as drinking water. Where conflicts occur, as in the ACF Basin, it is over shifting some water, not all water, from one use to another. Simply put, the ACF Basin issue is whether more water should be allocated to Atlanta, presenting Alabama and Florida with the prospect of less water but not complete deprivation.

Although compacts have some advantages over congressional or judicial apportionment, they are poorly suited to allocate water in ways that maximize water's productive value to society. Compacts are highly political and confront intractable information problems, and such was the case with the negotiations over the ACF Basin's waters.
Flood Control History in the
N
etherlands
Authors: Li Rongchao
Published: April 2005

The traditional flood control approach in the Netherlands is fighting against natural dynamics or, restricting the natural dynamics of a river system by canalization and embankments. However, such an approach results in destruction of river scenery, damage to nature and cultural values, as well as continuous dike raising and strengthening. Changing societal views in the Netherlands have aroused discussion of alternative flood management strategies. Around the beginning of the twenty‐first century, new visions appeared such as “living with floods” and the “room for the river” policy.
Integration of Environmental Impacts into Water Resources Planning
Authors: Yurdusev Mehmet Ali
Published: April 2005

Nature is so complicated that we need to idealize or simplify to understand, interpret, and benefit from it. Simplifications are carried out by modeling natural events. Models give us the opportunity to input values representing the observed values of natural phenomena to see what the possible outcome would be. Water is one of the few natural substances without which human beings cannot survive. Water use, therefore, is much more complicated because it has to reconcile an irregular or random natural phenomenon and humans attitudes towards it, which is not less complicated than water in nature itself. Therefore, it has to be managed by employing complicated computer‐based mathematical models. The spatial and temporal dimensions of this complicated issue can then be handled. These modeling studies are generally referred to as water resources planning (WRP). WRP can be defined as matching future demands to potential resources, satisfying some preset objectives such as cost‐effectiveness or environmental quality. The end product of water resources planning is a development plan for some future period, normally 20 to 30 years. As such, WRP mainly encompasses three types of activities:

assessment of available water resources,

assessment of future water requirements, and

matching between available resources and forecast demands.
Institutional Aspects of Water Management in
C
hina
Authors: Li Rongchao
Published: April 2005

In China, the water resource management organization has traditionally been organized along narrow, subsectoral lines. The national government determines the general legislative and policy framework for water management. The Ministry of Water Resources (MWR) is responsible for the state water management and issues the national water legislation and policies. Other ministries such as land and agriculture and electronic, etc. are also involved in water management.
Overview and Trends in the International Water Market
Authors: Piper Randy T.
Published: April 2005

The term “water market” is a slippery concept. Like water, the term water market is free flowing and can take a variety of forms, depending on the cultural environment and who invokes the term. In “The Importance of Getting Names Right: The Myth of Markets for Water,” Joseph Dellapenna argues for greater precision when using the language of water markets. Consequently, when we speak of water markets, we need to identify specifically the rules that governments employ and the roles that governments play in defining, divesting, and defending water markets. In most geographic settings, water markets do not exist without some formal role for government administration.
Land Applications of Wastewater in Arid Lands: Theory and Case Studies
Authors: Mexal J. G. , Rodriguez D. S. , Sammis T. , Picchioni G. , Zachritz W. , Erickson C. , Samani Z.
Published: April 2005

Land application of wastewater is recommended by the Environmental Protection Agency as a method of recycling nutrients and organic matter while protecting freshwater resources (1). Wastewater has been applied to agronomic crops, rangelands, forests, and recreation areas, including parks and golf courses, and to disturbed lands such as mine spoils sites (2, 3, 4, 5). Benefits from recycling wastewater include creating a supplemental irrigation source, thereby conserving drinking water, and reducing fertilizer costs because wastewater contains nitrogen and phosphorus (6). As wastewater moves through the soil profile, the soil and plants act as filters that trap and treat, through various mechanisms, waste particles and contaminants allowing the remaining water to drain through the soil profile (7, 8). Wastewater provides an effective source of nutrients that vegetation roots can absorb and allow the plant to assimilate. The benefit of this system is both the effective remediation of wastes and the recycling of water, nutrients, and carbon via biomass production (4).
Landfill Leachates: Part 2: Treatment
Authors: Samaras P. , Zouboulis A. I.
Published: April 2005

The characteristics (composition) of sanitary landfill leachates are very different from domestic wastewaters, and their quality varies from landfill to landfill, as well as with the particular landfill age. Hence, their treatment is based largely on industrial wastewater treatment processes. However, no single treatment method is considered efficient enough to achieve the high removal rates of pollutants, usually required; therefore, several treatment trains are currently used, including combinations of aerobic/anaerobic processes and several modes of physical–chemical treatment systems. The selection and design of leachate treatment facilities requires knowledge of several parameters, such as leachate quantity and quality, degree of necessary treatment, disposal methods, and effluents guidelines. These are the main problems that have to be considered:

Specific treatment schemes applied in a particular landfill may not be transferable to other sites.

Leachate quantity and quality vary seasonally, depending on climatic and hydrologic factors.

The composition of disposed of solid wastes greatly affects the composition of leachates.
N
ew
Y
ork
C
ity
H
arbor
S
urvey
Authors: Tonjes David J.
Published: April 2005

The New York City Harbor Survey, begun in 1910 and conducted continuously since 1912, may have the longest operational history of any annual water quality monitoring program in the world. Initiated to document decaying water quality in New York Harbor and, therefore, cause changes in waste management practices, it now demonstrates the effectiveness of New York City's comprehensive wastewater treatment program. Data from the 53 stations of the Survey (some of which are monitored year‐round using the dedicated Harbor Survey vessel) show general compliance throughout the Harbor with New York State water quality standards today, despite historical pollution problems.
Reclaimed Water
Authors: Kazmi Absar A.
Published: April 2005

Reclaimed water is water from a wastewater treatment plant (WWTP) that has been treated and can be used for nonpotable uses such as landscape irrigation, cooling towers, industrial processes, toilet flushing, and fire protection. The inclusion of planned water reclamation, recycling, and reuse in water resource systems reflects the increasing scarcity of water resources to meet societal demands, technological advancements, increased public acceptance, and improved understanding of public health risks.

Benefits of Using Reclaimed Water

It saves millions of gallons of drinking water each day.

Its use for nonpotable (nondrinking) purposes is less expensive for the vast majority of of customers.

It delays the need for developing costly new water sources and building very expensive treatment plants.

There is no odor or staining from its use.

It allows a city to comply with permits relating to its water supply and wastewater treatment.

It minimizes negative effects around underground water sources, preserving the quality of life for plants and wildlife.

It reduces fertilizing costs because reclaimed water is rich in nitrogen and phosphorus.
Wastewater Treatment and Recycling Technologies
Authors: Ali Imram , Jain C. K.
Published: April 2005

Due to the continuous population growth, uneven distribution of water resources, periodic droughts, and water pollution, it is very important to develop water treatment and recycling technologies for economic, effective, and fast water treatment and reclamation. Different types of water treatment and recycling techniques and their basic principles, applications, costs, maintenance, and suitability are discussed. In addition, a systematic approach to water treatment and recycling, involving understanding, evaluating, and selecting parameters, is presented. A comparison of the technologies is discussed from the view points of performance, sludge production, life cycle, operation, and maintenance. Brief guidance for selecting appropriate technologies for specific applications is also evaluated.
Wastewater Treatment Techniques—Advanced
Authors: Valenzuela Miguel A.
Published: April 2005

All advanced oxidation processes are characterized by a common chemical feature: production of OH
•
radicals.

These radicals are suitable for achieving complete abatement and mineralization of pollutants. AOP usually operate at or close to ambient temperature and pressure. The potentialities offered by AOP can be exploited to integrate biological treatments by oxidative degradation of toxic substances, entering or leaving the biological stage. The usual two AOP are the Fenton process and photocatalysis.