Water supply
Water supply is the provision of water by public utilities, commercial organisations, community endeavors or by individuals, usually via a system of pumps and pipes. Public water supply systems are crucial to properly functioning societies. These systems are what supply drinking water to populations around the globe. Aspects of service quality include continuity of supply, water quality and water pressure. The institutional responsibility for water supply is arranged differently in different countries and regions. It usually includes issues surrounding policy and regulation, service provision and standardization.
The cost of supplying water consists, to a very large extent, of fixed costs and only to a small extent of variable costs that depend on the amount of water consumed. Almost all service providers in 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.
Technical overview
Water supply systems get water from a variety of locations after appropriate treatment, including groundwater, surface water, and 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. Once water 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.Supply network
Use
In the United States, the typical single family home uses about of water per day or per capita per day. This includes several common residential end use purposes like toilet use, showers, tap use, washing machine use, leaks, other, baths, and dishwasher use.| Activity | Minimum, litres / day | Range / day |
| Drinking Water | 5 | 2–5 |
| Sanitation Services | 20 | 20–75 |
| Bathing | 15 | 5–70 |
| Cooking and Kitchen | 10 | 10–50 |
During 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 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".
Service quality
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 a poor or very poor quality of service.Continuity of supply
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 is estimated that about half of the population of developing countries receives water on an intermittent basis.Water quality
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 the case of surface water. Water quality is also dependent of the quality and level of pollution of the water source.Water pressure
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 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 for an urban supply. However, some people can get over or below. A single iron main pipe may cross 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. So people at the bottom of a hill will get about 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 of pipe running from the iron main, so the kitchen tap flow will be fairly unrestricted. A rural consumer may have a kilometre of rusted and limed iron pipe, so their kitchen tap flow will be small.
For this reason, the UK domestic water system has traditionally 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 a pipe, plus ball valve, and then supply the house on pipes. Gravity water has a small pressure 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 which take a long time to fill a bath but suit the high back pressure of a shower.
Institutional responsibility and governance
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.Policy and regulation
Water supply policies and regulation are usually defined by one or several ministries, in consultation with 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, to a Ministry of Health, a Ministry of Public Works, a Ministry of Economy or a Ministry of Energy. 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 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.
Regulatory agencies
Dozens of countries around 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 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 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 US states they are called Public Utility Commissions. For England and Wales, a regulatory agency for water was created as part of 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.
Many countries do not have regulatory agencies for water. In these countries service providers are regulated directly by local government, or the national government. This is, for example, the case in the countries of continental Europe, in China and India.