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98-454: Waterworks is the provision of water supply by public utilities, commercial organisations, community endeavours, or individuals. Waterworks may also refer to: Water supply The cost of supplying water consists, to a very large extent, of fixed costs (capital costs and personnel costs) and only to a small extent of variable costs that depend on the amount of water consumed (mainly energy and chemicals). Almost all service providers in

196-471: A 12 mm pipe, plus ball valve, and then supply the house on 22 or 28 mm pipes. Gravity water has a small pressure (say 1 ⁄ 4 bar in the bathroom) so needs wide pipes to allow for higher flows. This is fine for baths and toilets but is frequently inadequate for showers. A booster pump or a hydrophore is installed to increase and maintain pressure. For this reason urban houses are increasingly using mains pressure boilers ("combies") which take

294-646: A Ministry of Public Works (such as in Ecuador and Haiti ), a Ministry of Economy (such as in German states) or a Ministry of Energy (such as in Iran ). A few countries, such as Jordan and Bolivia , even have a Ministry of Water. Often several Ministries share responsibilities for water supply. In the European Union, important policy functions have been entrusted to the supranational level. Policy and regulatory functions include

392-689: A brass foundry in Rotherham . The first documented use of sand filters to purify the water supply dates to 1804, when the owner of a bleachery in Paisley, Scotland , John Gibb, installed an experimental filter, selling his unwanted surplus to the public. The first treated public water supply in the world was installed by engineer James Simpson for the Chelsea Waterworks Company in London in 1829. The practice of water treatment soon became mainstream, and

490-559: A component of effective policy for health protection." In 1990, only 76 percent of the global population had access to drinking water. By 2015 that number had increased to 91 percent. In 1990, most countries in Latin America, East and South Asia, and Sub-Saharan Africa were well below 90%. In Sub-Saharan Africa, where the rates are lowest, household access ranges from 40 to 80 percent. Countries that experience violent conflict can have reductions in drinking water access: One study found that

588-611: A conflict with about 2,500 battle deaths deprives 1.8% of the population of potable water. Typically in developed countries , tap water meets drinking water quality standards , even though only a small proportion is actually consumed or used in food preparation. Other typical uses for tap water include washing, toilets, and irrigation . Greywater may also be used for toilets or irrigation. Its use for irrigation however may be associated with risks. Throughout history, people have devised systems to make getting and using water more convenient. Living in semi-arid regions, ancient Persians in

686-493: A consumption level of 15 cubic meters per month. Few utilities do recover all their costs. According to the same World Bank study only 30% of utilities globally, and only 50% of utilities in developed countries, generate sufficient revenue to cover operation, maintenance and partial capital costs. According to another study undertaken in 2006 by NUS Consulting, the average water and sewerage tariff in 14 mainly OECD countries excluding VAT varied between US$ 0.66 per cubic meter in

784-467: A deep valley, it will have the same nominal pressure, however each consumer will get a bit more or less because of the hydrostatic pressure (about 1 bar/10 m height). So people at the bottom of a 30-metre (100 ft) hill will get about 3 bars more than those at the top. The effective pressure also varies because of the pressure loss due to supply resistance, even for the same static pressure. An urban consumer may have 5 metres of 15-mm pipe running from

882-675: A few cases such multi-utilities also collect solid waste and provide local telephone services. An example of such an integrated utility can be found in the Colombian city of Medellín . Utilities that provide water, sanitation and electricity can be found in Frankfurt , Germany (Mainova), in Casablanca , Morocco and in Gabon in West Africa. Multi-utilities provide certain benefits such as common billing and

980-503: A great degree of autonomy. In the United States regulatory agencies for utilities have existed for almost a century at the level of states, and in Canada at the level of provinces. In both countries they cover several infrastructure sectors. In many U.S. states they are called Public Utility Commissions . For England and Wales, a regulatory agency for water ( OFWAT ) was created as part of

1078-429: A huge amount of capital investment in infrastructure such as pipe networks, pumping stations and water treatment works . It is estimated that in developing countries investments of at least US$ 200 billion have to be made per year to replace aging water infrastructure to guarantee supply, reduce leakage rates and protect water quality. International attention has focused upon the needs of developing countries . To meet

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1176-415: A layer of calcium carbonate . Corrosion inhibitors are often added to reduce release of metals into the water. Common corrosion inhibitors added to the water are phosphates and silicates . Maintenance of a biologically safe drinking water is another goal in water distribution. Typically, a chlorine based disinfectant , such as sodium hypochlorite or monochloramine is added to the water as it leaves

1274-421: A long term, due to the uncertainty of the future demand”. It is preferable to provide extra pipe capacity to cope with unexpected demand growth and with water outages. The problem changes from a single objective optimization problem (minimizing cost), to a multi-objective optimization problem (minimizing cost and maximizing flow capacity). To solve a multi-objective optimization problem, it is necessary to convert

1372-424: A long time to fill a bath but suit the high back pressure of a shower. A great variety of institutions have responsibilities in water supply. A basic distinction is between institutions responsible for policy and regulation on the one hand; and institutions in charge of providing services on the other hand. Water supply policies and regulation are usually defined by one or several Ministries, in consultation with

1470-410: A mandate to settle complaints by consumers that have not been dealt with satisfactorily by service providers. These specialized entities are expected to be more competent and objective in regulating service providers than departments of government Ministries. Regulatory agencies are supposed to be autonomous from the executive branch of government, but in many countries have often not been able to exercise

1568-453: A metallic taste. Release of lead can occur from the solder used to join copper pipe together or from brass fixtures . Copper and lead levels at the consumer's tap are regulated to protect consumer health. Utilities will often adjust the chemistry of the water before distribution to minimize its corrosiveness. The simplest adjustment involves control of pH and alkalinity to produce a water that tends to passivate corrosion by depositing

1666-496: A poor or very poor quality of service. Continuity of water supply is taken for granted in most developed countries but is a severe problem in many developing countries, where sometimes water is only provided for a few hours every day or a few days a week; that is, it is intermittent . This is especially problematic for informal settlements , which are often poorly connected to the water supply network and have no means of procuring alternative sources such as private boreholes . It

1764-465: A price in the market; water often becomes a business for private companies, which earn a profit by putting a higher price on water, which imposes a barrier for lower-income people. The Millennium Development Goals propose the changes required. Goal 6 of the United Nations' Sustainable Development Goals is to "Ensure availability and sustainable management of water and sanitation for all". This

1862-523: A set of rules and policies to overcome expected future problems. There are many international documents with interesting, but not very specific, ideas and therefore they are not put into practice. Recommendations have been made by the United Nations , such as the Dublin Statement on Water and Sustainable Development . The yield of a system can be measured by either its value or its net benefit. For

1960-459: A single city, town or municipality . However, in many countries municipalities have associated in regional or inter-municipal or multi-jurisdictional utilities to benefit from economies of scale . In the United States these can take the form of special-purpose districts which may have independent taxing authority. An example of a multi-jurisdictional water utility in the United States is WASA ,

2058-543: A sustained improvement track, but many others keep falling further behind best practice. Benchmarking the performance of utilities allows the stimulation of competition, establish realistic targets for improvement and create pressure to catch up with better utilities. Information on benchmarks for water and sanitation utilities is provided by the International Benchmarking Network for Water and Sanitation Utilities. The cost of supplying water consists, to

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2156-461: A system is governed by multiple criteria, one being cost. If the benefit is fixed , the least cost design results in maximum benefit. However, the least cost approach normally results in a minimum capacity for a water supply network. A minimum cost model usually searches for the least cost solution (in pipe sizes), while satisfying the hydraulic constraints such as: required output pressures, maximum pipe flow rate and pipe flow velocities. The cost

2254-576: A trickle of water or so high that it leads to damage to plumbing fixtures and waste of water. Pressure in an urban water system is typically maintained either by a pressurised water tank serving an urban area, by pumping the water up into a water tower and relying on gravity to maintain a constant pressure in the system or solely by pumps at the water treatment plant and repeater pumping stations. Typical UK pressures are 4–5 bar (60–70 PSI ) for an urban supply. However, some people can get over eight bars or below one bar. A single iron main pipe may cross

2352-485: A typical consumption of 15 cubic meters per month vary between less than US$ 1 and US$ 12 per month. Water and sanitation tariffs, which are almost always billed together, can take many different forms. Where meters are installed, tariffs are typically volumetric (per usage), sometimes combined with a small monthly fixed charge. In the absence of meters, flat or fixed rates—which are independent of actual consumption—are being charged. In developed countries, tariffs are usually

2450-738: A utility serving Washington, D.C. and various localities in the state of Maryland . Multi-jurisdictional utilities are also common in Germany, where they are known as "Zweckverbaende", in France and in Italy. In some federal countries, there are water service providers covering most or all cities and towns in an entire state, such as in all states of Brazil and some states in Mexico (see Water supply and sanitation in Mexico ). In England and Wales , water supply and sewerage

2548-509: A utility to better locate distribution losses (technical objective). Fourth, it allows suppliers to charge for water based on use, which is perceived by many as the fairest way to allocate the costs of water supply to users. Metering is considered good practice in water supply and is widespread in developed countries, except for the United Kingdom . In developing countries it is estimated that half of all urban water supply systems are metered and

2646-418: A very large extent, of fixed costs (capital costs and personnel costs) and only to a small extent of variable costs that depend on the amount of water consumed (mainly energy and chemicals). The full cost of supplying water in urban areas in developed countries is about US$ 1–2 per cubic meter depending on local costs and local water consumption levels. The cost of sanitation (sewerage and wastewater treatment )

2744-434: A viable solution including Rainwater harvesting and Stormwater harvesting where policies are eventually tending towards a more rational use and sourcing of water incorporation concepts such as "Fit for Purpose". Water supply service quality has many dimensions: continuity; water quality ; pressure; and the degree of responsiveness of service providers to customer complaints. Many people in developing countries receive

2842-399: A water supply system, the true value or the net benefit is a reliable water supply service having adequate quantity and good quality of the product. For example, if the existing water supply of a city needs to be extended to supply a new municipality , the impact of the new branch of the system must be designed to supply the new needs, while maintaining supply to the old system. The design of

2940-409: A “Municipal Water Reuse System” which is a current approach to manage the rainwater. It applies a water reuse scheme for treated wastewater, on a municipal scale, to provide non-potable water for industry, household and municipal uses. This technology consists in separating the urine fraction of sanitary wastewater, and collecting it for recycling its nutrients . The feces and graywater fraction

3038-411: Is a function of pipe diameters; therefore the optimization problem consists of finding a minimum cost solution by optimising pipe sizes to provide the minimum acceptable capacity. However, according to the authors of the paper entitled, “Method for optimizing design and rehabilitation of water distribution systems”, “the least capacity is not a desirable solution to a sustainable water supply network in

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3136-622: Is also a risk that staff are appointed mainly on political grounds rather than based on their professional credentials. International standards for water supply system are covered by International Classification of Standards (ICS) 91.140.60. Comparing the performance of water and sanitation service providers ( utilities ) is needed, because the sector offers limited scope for direct competition ( natural monopoly ). Firms operating in competitive markets are under constant pressure to out perform each other. Water utilities are often sheltered from this pressure, and it frequently shows: some utilities are on

3234-559: Is an essential governance reform in order to reduce the high levels of Unaccounted-for Water (UAW) and to provide the finance needed to extend the network to those poorest households who remain unconnected. Partnership arrangements between the public and private sector can play an important role in order to achieve this objective. An estimated 10 percent of urban water supply is provided by private or mixed public-private companies, usually under concessions , leases or management contracts . Under these water service contract arrangements

3332-553: Is an integrated system including water intake, water utilization, wastewater discharge and treatment and water environmental protection . It requires reducing freshwater and groundwater usage in all sectors of consumption. Developing sustainable water supply systems is a growing trend, because it serves people's long-term interests. There are several ways to reuse and recycle the water, in order to achieve long-term sustainability, such as: Other possible approaches to scoping models for water supply, applicable to any urban area, include

3430-454: Is another US$ 1–2 per cubic meter. These costs are somewhat lower in developing countries. Throughout the world, only part of these costs is usually billed to consumers, the remainder being financed through direct or indirect subsidies from local, regional or national governments (see section on tariffs). Besides subsidies water supply investments are financed through internally generated revenues as well as through debt. Debt financing can take

3528-404: Is called potable water if it meets the water quality standards required for human consumption. The water in the supply network is maintained at positive pressure to ensure that water reaches all parts of the network, that a sufficient flow is available at every take-off point and to ensure that untreated water in the ground cannot enter the network. The water is typically pressurised by pumping

3626-681: Is collected, together with organic wastes from the households, using a gravity sewer system , continuously flushed with non-potable water. The water is treated anaerobically and the biogas is used for energy production . One effective way to achieve sustainable water management is to shift emphasis towards decentralized water projects, such as drip irrigation diffusion in India. This project covers large spatial areas while relying on individual technological adoption decisions, offering scalable solutions that can mitigate water scarcity and enhance agricultural productivity. Another method that can be utilized

3724-455: Is estimated that about half of the population of developing countries receives water on an intermittent basis. Drinking water quality has a micro-biological and a physico-chemical dimension. There are thousands of parameters of water quality. In public water supply systems water should, at a minimum, be disinfected—most commonly through the use of chlorination or the use of ultraviolet light—or it may need to undergo treatment, especially in

3822-690: Is in recognition of the human right to water and sanitation, which was formally acknowledged at the United Nations General Assembly in 2010, that "clean drinking water and sanitation are essential to the recognition of all human rights". Sustainable water supply includes ensuring availability, accessibility, affordability and quality of water for all individuals. In advanced economies, the problems are about optimising existing supply networks. These economies have usually had continuing evolution, which allowed them to construct infrastructure to supply water to people. The European Union has developed

3920-489: Is increasing, so less water must be wasted and actions must be taken to prevent pipeline leakage. Shutting down the supply service to fix leaks is less and less tolerated by consumers. A sustainable water supply network must monitor the freshwater consumption rate and the waste-water generation rate. Many of the urban water supply networks in developing countries face problems related to population increase , water scarcity , and environmental pollution . In 1900 just 13% of

4018-489: Is insufficient maintenance of the water networks, especially in the major pipe lines in urban areas. The system deteriorates and then needs rehabilitation or renewal. Householders and sewage treatment plants can both make the water supply networks more efficient and sustainable. Major improvements in eco-efficiency are gained through systematic separation of rainfall and wastewater. Membrane technology can be used for recycling wastewater. The municipal government can develop

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4116-448: Is insulated from arbitrary political intervention; and whether there is an explicit mandate and political will to allow the service provider to recover all or at least most of its costs through tariffs and retain these revenues. If water supply is the responsibility of a department that is integrated in the administration of a city, town or municipality, there is a risk that tariff revenues are diverted for other purposes. In some cases, there

4214-548: Is not well distributed in the world. 1.8 million deaths are attributed to unsafe water supplies every year, according to the WHO . Many people do not have any access, or do not have access to quality and quantity of potable water, though water itself is abundant. Poor people in developing countries can be close to major rivers, or be in high rainfall areas, yet not have access to potable water at all. There are also people living where lack of water creates millions of deaths every year. Where

4312-572: Is supplied almost entirely through ten regional companies. Some smaller countries, especially developed countries, have established service providers that cover the entire country or at least most of its cities and major towns. Such national service providers are especially prevalent in West Africa and Central America, but also exist, for example, in Tunisia , Jordan and Uruguay (see also water supply and sanitation in Uruguay ). In rural areas, where about half

4410-786: Is through the promoting of community engagement and resistance against unsustainable water infrastructure projects. Grassroots movements, as observed in anti-dam protests in various countries, play a crucial role in challenging dominant development narratives and advocating for more socially and ecologically just water management practices. Municipalities and other forms of local governments should also invest in innovative technologies, such as membrane technology for wastewater recycling, and develop policy frameworks that incentivize eco-efficient practices. Municipal water reuse systems, as demonstrated in implementation, offer promising avenues for integrating wastewater treatment and resource recovery into urban water networks. The sustainable water supply system

4508-412: Is used, wastewater is typically discharged in a sewer system and treated in a sewage treatment plant before being discharged into a river, lake, or the sea or reused for landscaping or irrigation . A water supply network or water supply system is a system of engineered hydrologic and hydraulic components that provide water supply. A water supply system typically includes the following: In

4606-526: The European Commission is a good example of what has been created there out of former policies. There is great need for a more sustainable water supply systems. To achieve sustainability several factors must be tackled at the same time: climate change, rising energy cost, and rising populations. All of these factors provoke change and put pressure on management of available water resources. An obstacle to transforming conventional water supply systems,

4704-736: The Millennium Development Goals targets of halving the proportion of the population lacking access to safe drinking water and basic sanitation by 2015, current annual investment on the order of US$ 10 to US$ 15 billion would need to be roughly doubled. This does not include investments required for the maintenance of existing infrastructure. Once infrastructure is in place, operating water supply and sanitation systems entails significant ongoing costs to cover personnel, energy, chemicals, maintenance and other expenses. The sources of money to meet these capital and operational costs are essentially either user fees, public funds or some combination of

4802-417: The United States , the typical single family home uses about 520 L (138 US gal) of water per day (2016 estimate) or 222 L (58.6 US gal) per capita per day. This includes several common residential end use purposes (in decreasing order) like toilet use, showers , tap (faucet) use, washing machine use, leaks , other (unidentified), baths , and dishwasher use. During

4900-516: The 1st millennium BC used qanat system to gain access to water in the mountains. Early Rome had indoor plumbing, meaning a system of aqueducts and pipes that terminated in homes and at public wells and fountains for people to use. Until the Enlightenment era , little progress was made in water supply and sanitation and the engineering skills of the Romans were largely neglected throughout Europe. It

4998-716: The United States and the equivalent of US$ 2.25 per cubic meter in Denmark. However, water consumption is much higher in the US than in Europe. Therefore, residential water bills may be very similar, even if the tariff per unit of consumption tends to be higher in Europe than in the US. A typical family on the US East Coast paid between US$ 30 and US$ 70 per month for water and sewer services in 2005. In developing countries, tariffs are usually much further from covering costs. Residential water bills for

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5096-515: The World Bank the average ( mean ) global water tariff is US$ 0.53 per cubic meter. In developed countries the average tariff is US$ 1.04, while it is only U$ 0.11 in the poorest developing countries. The lowest tariffs in developing countries are found in South Asia (mean of US$ 0.09/m3), while the highest are found in Latin America (US$ 0.41/m3). Data for 132 cities were assessed. The tariff is estimate for

5194-503: The adoption of appropriate technology coupled with effective strategies for operation and maintenance. These strategies must include effective management models, technical support to the householders and industries, sustainable financing mechanisms, and development of reliable supply chains . All these measures must ensure the following: system working lifespan; maintenance cycle; continuity of functioning; down time for repairs; water yield and water quality. In an unsustainable system there

5292-475: The beginning of the 21st Century, especially in areas of urban and suburban population centers, traditional centralized infrastructure have not been able to supply sufficient quantities of water to keep up with growing demand. Among several options that have been managed are the extensive use of desalination technology, this is especially prevalent in coastal areas and in "dry" countries like Australia . Decentralization of water infrastructure has grown extensively as

5390-480: The best combination. Returning to the cost objective function, it cannot violate any of the operational constraints. Generally this cost is dominated by the energy cost for pumping. “The operational constraints include the standards of customer service , such as: the minimum delivered pressure, in addition to the physical constraints such as the maximum and the minimum water levels in storage tanks to prevent overtopping and emptying respectively.” In order to optimize

5488-441: The best forms of public management. As Ryutaro Hashimoto , former Japanese Prime Minister, notes: "Public water services currently provide more than 90 percent of water supply in the world. Modest improvement in public water operators will have immense impact on global provision of services." Governance arrangements for both public and private utilities can take many forms (Kurian and McCarney, 2010). Governance arrangements define

5586-427: The case of surface water . Water quality is also dependent of the quality and level of pollution of the water source. Water pressures vary in different locations of a distribution system. Water mains below the street may operate at higher pressures, with a pressure reducer located at each point where the water enters a building or a house. In poorly managed systems, water pressure can be so low as to result only in

5684-446: The chances of the water becoming contaminated after treatment. Traditional surface water treatment plants generally consists of three steps: clarification, filtration and disinfection. Clarification refers to the separation of particles (dirt, organic matter, etc.) from the water stream. Chemical addition (i.e. alum, ferric chloride) destabilizes the particle charges and prepares them for clarification either by settling or floating out of

5782-452: The costs and benefits resulting in a set of solutions that can be used for sensitivity analysis and tested in different scenarios. But there is no single optimal solution that will satisfy the global optimality of both objectives. As both objectives are to some extent contradictory, it is not possible to improve one objective without sacrificing the other. It is necessary in some cases use a different approach. (e.g. Pareto Analysis ), and choose

5880-451: The distribution system, the water quality can degrade by chemical reactions and biological processes. Corrosion of metal pipe materials in the distribution system can cause the release of metals into the water with undesirable aesthetic and health effects. Release of iron from unlined iron pipes can result in customer reports of "red water" at the tap. Release of copper from copper pipes can result in customer reports of "blue water" and/or

5978-564: The following: The Dublin Statement on Water and Sustainable Development is a good example of the new trend to overcome water supply problems. This statement, suggested by advanced economies, has come up with some principles that are of great significance to urban water supply. These are: From these statements, developed in 1992, several policies have been created to give importance to water and to move urban water system management towards sustainable development. The Water Framework Directive by

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6076-538: The following: Water supply networks are often run by public utilities of the water industry . Raw water (untreated) is from a surface water source (such as an intake on a lake or a river ) or from a groundwater source (such as a water well drawing from an underground aquifer ) within the watershed that provides the water resource . The raw water is transferred to the water purification facilities using uncovered aqueducts, covered tunnels or underground water pipes . Virtually all large systems must treat

6174-451: The form of credits from commercial Banks, credits from international financial institutions such as the World Bank and regional development banks (in the case of developing countries), and bonds (in the case of some developed countries and some upper middle-income countries). Almost all service providers in the world charge tariffs to recover part of their costs. According to estimates by

6272-607: The global population lived in cities. By 2005, 49% of the global population lived in urban areas. In 2030 it is predicted that this statistic will rise to 60%. Attempts to expand water supply by governments are costly and often not sufficient. The building of new illegal settlements makes it hard to map, and make connections to, the water supply, and leads to inadequate water management. In 2002, there were 158 million people with inadequate water supply . An increasing number of people live in slums , in inadequate sanitary conditions, and are therefore at risk of disease . Potable water

6370-494: The iron main, so the kitchen tap flow will be fairly unrestricted. A rural consumer may have a kilometre of rusted and limed 22-mm iron pipe, so their kitchen tap flow will be small. For this reason, the UK domestic water system has traditionally (prior to 1989) employed a "cistern feed" system, where the incoming supply is connected to the kitchen sink and also a header/storage tank in the attic . Water can dribble into this tank through

6468-643: The legislative branch. In the United States the United States Environmental Protection Agency , whose administrator reports directly to the President, is responsible for water and sanitation policy and standard setting within the executive branch. In other countries responsibility for sector policy is entrusted to a Ministry of Environment (such as in Mexico and Colombia ), to a Ministry of Health (such as in Panama , Honduras and Uruguay ),

6566-584: The main losers from this institutional arrangement are the urban poor in these countries. Because they are not connected to the water supply network , they end up paying far more per liter of water than do more well-off households connected to the network who benefit from the implicit subsidies that they receive from loss-making utilities. The fact that we are still so far from achieving universal access to clean water and sanitation shows that public water authorities, in their current state, are not working well enough. Yet some are being very successful and are modelling

6664-603: The majority of assets of a water utility. Systematic documentation of maintenance works using a computerized maintenance management system (CMMS) is a key to a successful operation of a water utility. A sustainable urban water supply network covers all the activities related to provision of potable water. Sustainable development is of increasing importance for the water supply to urban areas. Incorporating innovative water technologies into water supply systems improves water supply from sustainable perspectives. The development of innovative water technologies provides flexibility to

6762-459: The national government. This is, for example, the case in the countries of continental Europe, in China and India. Water supply service providers, which are often utilities , differ from each other in terms of their geographical coverage relative to administrative boundaries; their sectoral coverage; their ownership structure; and their governance arrangements. Many water utilities provide services in

6860-541: The network. Most systems are divided into zones. Factors determining the extent or size of a zone can include hydraulics, telemetry systems, history, and population density. Sometimes systems are designed for a specific area then are modified to accommodate development. Terrain affects hydraulics and some forms of telemetry. While each zone may operate as a stand-alone system, there is usually some arrangement to interconnect zones in order to manage equipment failures or system failures. Water supply networks usually represent

6958-401: The operational performance of the water supply network, at the same time as minimizing the energy costs, it is necessary to predict the consequences of different pump and valve settings on the behavior of the network. Apart from Linear and Non-linear Programming, there are other methods and approaches to design, to manage and operate a water supply network to achieve sustainability—for instance,

7056-411: The optimal solution for all the original objectives. The second approach (the constraint method), chooses one of the objective functions as the single objective, and the other objective functions are treated as constraints with a limited value. However, the optimal solution depends on the pre-defined constraint limits. The multiple objective optimization problems involve computing the tradeoff between

7154-545: The option to cross-subsidize water services with revenues from electricity sales, if permitted by law. Water supply providers can be either public, private, mixed or cooperative. Most urban water supply services around the world are provided by public entities. As Willem-Alexander, Prince of Orange (2002) stated, "The water crisis that is affecting so many people is mainly a crisis of governance—not of water scarcity ." The introduction of cost-reflective tariffs together with cross-subsidization between richer and poorer consumers

7252-428: The overall low level of water tariffs in developing countries even at higher levels of consumption, most consumption subsidies benefit the wealthier segments of society. Also, high industrial and commercial tariffs can provide an incentive for these users to supply water from other sources than the utility (own wells, water tankers) and thus actually erode the utility's revenue base. Water supply and sanitation require

7350-541: The privatization of the water industry in 1989. In many developing countries, water regulatory agencies were created during the 1990s in parallel with efforts at increasing private sector participation. (for more details on regulatory agencies in Latin America, for example, please see Water and sanitation in Latin America and the regional association of water regulatory agencies ADERASA. ) Many countries do not have regulatory agencies for water. In these countries service providers are regulated directly by local government, or

7448-467: The problem into a single objective optimization problem, by using adjustments, such as a weighted sum of objectives , or an ε-constraint method. The weighted sum approach gives a certain weight to the different objectives, and then factors in all these weights to form a single objective function that can be solved by single factor optimization. This method is not entirely satisfactory, because the weights cannot be correctly chosen, so this approach cannot find

7546-714: The public entity that is legally responsible for service provision delegates certain or all aspects of service provision to the private service provider for a period typically ranging from 4 to 30 years. The public entity continues to own the assets. These arrangements are common in France and in Spain . Only in few parts of the world water supply systems have been completely sold to the private sector ( privatization ), such as in England and Wales as well as in Chile . The largest private water companies in

7644-451: The public sector. They are owned by the state or local authorities, or also by collectives or cooperatives. They run without an aim for profit but are based on the ethos of providing a common good considered to be of public interest. In most middle and low-income countries, these publicly owned and managed water providers can be inefficient as a result of political interference, leading to over-staffing and low labor productivity. Ironically,

7742-412: The relationship between the service provider, its owners, its customers and regulatory entities. They determine the financial autonomy of the service provider and thus its ability to maintain its assets, expand services, attract and retain qualified staff, and ultimately to provide high-quality services. Key aspects of governance arrangements are the extent to which the entity in charge of providing services

7840-594: The same for different categories of users and for different levels of consumption. In developing countries, the situation is often characterized by cross-subsidies with the intent to make water more affordable for residential low-volume users that are assumed to be poor. For example, industrial and commercial users are often charged higher tariffs than public or residential users. Also, metered users are often charged higher tariffs for higher levels of consumption (increasing-block tariffs). However, cross-subsidies between residential users do not always reach their objective. Given

7938-412: The sea through desalination . The water treatment steps include, in most cases, purification , disinfection through chlorination and sometimes fluoridation . Treated water then either flows by gravity or is pumped to reservoirs , which can be elevated such as water towers or on the ground (for indicators related to the efficiency of drinking water distribution see non-revenue water ). Once water

8036-565: The setting of tariff rules and the approval of tariff increases; setting, monitoring and enforcing norms for quality of service and environmental protection; benchmarking the performance of service providers; and reforms in the structure of institutions responsible for service provision. The distinction between policy functions and regulatory functions is not always clear-cut. In some countries they are both entrusted to Ministries, but in others regulatory functions are entrusted to agencies that are separate from Ministries. Dozens of countries around

8134-483: The steel industry, and for several operations in food processing facilities. It is necessary to adopt a new approach to design urban water supply networks; water shortages are expected in the forthcoming decades and environmental regulations for water utilization and waste-water disposal are increasingly stringent. To achieve a sustainable water supply network, new sources of water are needed to be developed, and to reduce environmental pollution. The price of water

8232-482: The tendency is increasing. Water meters are read by one of several methods: Most cities are increasingly installing automatic meter reading (AMR) systems to prevent fraud, to lower ever-increasing labor and liability costs and to improve customer service and satisfaction. According to the World Health Organization (WHO), "access to safe drinking-water is essential to health, a basic human right and

8330-517: The treatment plant. Booster stations can be placed within the distribution system to ensure that all areas of the distribution system have adequate sustained levels of disinfection . Like electric power lines, roads, and microwave radio networks, water systems may have a loop or branch network topology, or a combination of both. The piping networks are circular or rectangular. If any one section of water distribution main fails or needs repair, that section can be isolated without disrupting all users on

8428-410: The two. It is also important to consider is the flexibility of the water supply system. Metering of water supply is usually motivated by one or several of four objectives. First, it provides an incentive to conserve water which protects water resources (environmental objective). Second, it can postpone costly system expansion and saves energy and chemical costs (economic objective). Third, it allows

8526-450: The virtues of the system were made starkly apparent after the investigations of the physician John Snow during the 1854 Broad Street cholera outbreak demonstrated the role of the water supply in spreading the cholera epidemic. Water supply network A water supply network or water supply system is a system of engineered hydrologic and hydraulic components that provide water supply . A water supply system typically includes

8624-404: The water into storage tanks constructed at the highest local point in the network. One network may have several such service reservoirs . In small domestic systems, the water may be pressurised by a pressure vessel or even by an underground cistern (the latter however does need additional pressurizing). This eliminates the need of a water tower or any other heightened water reserve to supply

8722-632: The water pressure. These systems are usually owned and maintained by local governments such as cities or other public entities, but are occasionally operated by a commercial enterprise (see water privatization ). Water supply networks are part of the master planning of communities, counties, and municipalities. Their planning and design requires the expertise of city planners and civil engineers , who must consider many factors, such as location, current demand, future growth, leakage, pressure, pipe size, pressure loss, fire fighting flows, etc.—using pipe network analysis and other tools. As water passes through

8820-402: The water stream. Sand, anthracite or activated carbon filters refine the water stream, removing smaller particulate matter. While other methods of disinfection exist, the preferred method is via chlorine addition. Chlorine effectively kills bacteria and most viruses and maintains a residual to protect the water supply through the supply network. The product, delivered to the point of consumption,

8918-866: The water supply system cannot reach the slums, people manage to use hand pumps , to reach the pit wells, rivers , canals , swamps and any other source of water. In most cases the water quality is unfit for human consumption. The principal cause of water scarcity is the growth in demand. Water is taken from remote areas to satisfy the needs of urban areas. Another reason for water scarcity is climate change : precipitation patterns have changed; rivers have decreased their flow; lakes are drying up; and aquifers are being emptied. In developing countries many governments are corrupt and poor and they respond to these problems with frequently changing policies and non clear agreements. Water demand exceeds supply, and household and industrial water supplies are prioritised over other uses, which leads to water stress . Potable water has

9016-408: The water supply system, generating a fundamental and effective means of sustainability based on an integrated real options approach. Water is an essential natural resource for human existence. It is needed in every industrial and natural process, for example, it is used for oil refining , for liquid-liquid extraction in hydro-metallurgical processes, for cooling, for scrubbing in the iron and

9114-400: The water; a fact that is tightly regulated by global, state and federal agencies, such as the World Health Organization (WHO) or the United States Environmental Protection Agency (EPA). Water treatment must occur before the product reaches the consumer and afterwards (when it is discharged again). Water purification usually occurs close to the final delivery points to reduce pumping costs and

9212-400: The world are Suez and Veolia Environnement from France; Aguas de Barcelona from Spain; and Thames Water from the UK, all of which are engaged internationally (see links to website of these companies below). In recent years, a number of cities have reverted to the public sector in a process called " remunicipalization ". 90% of urban water supply and sanitation services are currently in

9310-401: The world charge tariffs to recover part of their costs. Water supply is a separate topic from irrigation , the practice and systems of water supply on a larger scale, for a wider variety of purposes, primarily agriculture . Water supply systems get water from a variety of locations after appropriate treatment, including groundwater ( aquifers ), surface water ( lakes and rivers ), and

9408-423: The world have established regulatory agencies for infrastructure services, including often water supply and sanitation, in order to better protect consumers and to improve efficiency. Regulatory agencies can be entrusted with a variety of responsibilities, including in particular the approval of tariff increases and the management of sector information systems, including benchmarking systems. Sometimes they also have

9506-504: The world population lives, water services are often not provided by utilities, but by community-based organizations which usually cover one or sometimes several villages. Some water utilities provide only water supply services, while sewerage is under the responsibility of a different entity. This is for example the case in Tunisia . However, in most cases water utilities also provide sewer and sewage treatment services. In some cities or countries utilities also distribute electricity. In

9604-481: Was in the 18th century that a rapidly growing population fueled a boom in the establishment of private water supply networks in London . London water supply infrastructure developed over many centuries from early mediaeval conduits, through major 19th-century treatment works built in response to cholera threats, to modern, large-scale reservoirs. The first screw-down water tap was patented in 1845 by Guest and Chrimes,

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