UNIVERSIDAD RICARDO PALMA
FACULTAD DE INGENIERIA
ESCUELA DE INGENIERIA CIVIL
CURSO: Ingeniería Hidráulica
TITULO DE INFORME: Watersupply
ALUMNO: CONTRERAS LAVADO VANESSA
GRUPO: 02
SUBGRUPO: 04
PROFESOR: Ing. Manuel Casas Villalobos
FECHA DE ENTREGA: 18/09/2013
Lima
2013-II
Watersupply
Water supply is the provision of water by public utilities, commercial organisations,
community endeavours or by individuals, usually via a system of pumps and pipes.
Irrigation is covered separately.
Global access to clean wáter
In 2010 about 85% of the global
population (6.74 billion people)
had access to piped water supply
through house connections or to
an improved water source through
other means than house, including
standpipes, "water kiosks",
protected springs and protected
wells. However, about 14% (884
million people) did not have
access to an improved water
source and had to use unprotected
wells or springs, canals, lakes or
rivers for their water needs.
A clean water supply, especially so with regard to sewage, is the single most important
determinant of public health. Destruction of water supply and/or sewage disposal
infrastructure after major catastrophes (earthquakes, floods, war, etc.) poses the
immediate threat of severe epidemics of waterborne diseases, several of which can be life-
threatening.
Use
In the U.S, the typical single family home uses about 69,3 gallons (262 litres) of water per
day (2008 estimate). This includes (in decreasing order) toilet use, washing machine use,
showers, baths, faucet use, and leaks.
Technical overview
Water supply systems get water from a variety of locations, including groundwater
(aquifers), surface water (lakes and rivers), conservation and the sea through desalination.
The water is then, in most cases, purified, disinfected through chlorination and sometimes
fluoridated. 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 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,
irrigation or industrial use (see also sanitation).
Service quality
Many of the 3.5 billion people having access to piped water receive a poor or very poor
quality of service, especially in developing countries where about 80% of the world
population lives. Water supply service quality has many dimensions: continuity; water
quality; pressure; and the degree of responsiveness of service providers to customer
complaints.
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. 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
ultra violet light—or it may need to undergo treatment, especially in the case of surface
water. For more details, please see the separate entries on water quality, water treatment
and drinking water.
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 pressurized water tank serving an urban area, by pumping the water up into a
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 for an urban supply.[citation needed] However, some
people can get over eight bars or below one bar. 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 (about 1 bar/10 m height). So people at the
bottom of a 100-foot (30 m) hill will get about 3 bars more than those at the top.
The effective pressure also varies because of the supply resistance even for the same
static pressure. An urban consumer may have 5 metres of ½-inch lead pipe running from
the iron main, so the kitchen tap flow will be fairly unrestricted, so high flow. A rural
consumer may have a kilometre of rusted and limed ¾" 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 a ½" lead pipe,
plus ball valve, and then supply the house on 22 or 28 mm pipes. Gravity water has a
small pressure (say ¼ bar in the bathroom) but needs wide pipes allow higher flows. This
is fine for baths and toilets but is frequently inadequate for showers. People install shower
booster pumps to increase the pressure. For this reason urban houses are increasingly
using mains pressure boilers (combies) which take a long time to fill a bath but suit the
high back pressure of a shower.
Comparing the performance of water and sanitation service providers
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 a sustained improvement track, but many others keep falling further behind best
practice. Benchmarking the performance of utilities allows to simulate 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.
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 (such as in Mexico and Colombia), to a Ministry of Health (such as in
Panama, Honduras and Uruguay), 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 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
(OFWAT) 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.
Service provision
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.
Geographical coverage
Many water utilities provide
services in 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, a utility serving Washington, DC 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 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 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.
Sector coverage
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 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
the option to cross-subsidize water services with revenues from electricity sales, if
permitted by law.
Ownership and governance arrangements
Water supply providers can be either publi, 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-subsidisation between richer and poorer consumers is
an essential governance reform in order to reduce the high levels of Unaccounted or
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.
Private sector participation
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 arrangements 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 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 "remunicipalisation”.
Public water service provision
90% of urban water supply and sanitation services are currently in 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 labour productivity. Ironically, the main losers
from this institutional arrangement are the urban poor in these countries. Because they are
not connected to the network, they end up paying far more per litre 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. 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 the best
forms of public management. As Ryutaro Hashimoto, former Japanese Prime Minister,
notes: “Public water services currently provide more than 90 per cent of water supply in
the world. Modest improvement in public water operators will have immense impact on
global provision of services.
Governance arrangements
Governance arrangements for both public and private utilities can take many forms.
Governance arrangements define 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
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 is also a risk
that staff are appointed mainly on political grounds rather than based on their professional
credentials.
Metering
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 a utility to better
locate distribution losses (technical objective). Fourth,
it allows 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 the
tendency is increasing.
Water meters are read by one of several methods:
the water customer writes down the meter
reading and mails in a postcard with this info
to the water department;
the water customer writes down the meter reading and uses a phone dial-in system
to transfer this info to the water department;
the water customer logs in to the website of the water supply company, enters the
address, meter ID and meter readings [6]
a meter reader comes to the premise and enters the meter reading into a handheld
computer;
the meter reading is echoed on a display unit mounted to the outside of the
premise, where a meter reader records them;
a small radio is hooked up to the meter to automatically transmit readings to
corresponding receivers in handheld computers, utility vehicles or distributed
collectors
a small computer is hooked up to the meter that can either dial out or receive
automated phone calls that give the reading to a central computer system.
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.
Costs and financing
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). 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) 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 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).
Women in the developing world
Water supply issues have specific adverse effects on women in developing nations.
Women are often the primary family member responsible for providing water as well as
collecting it. Inclusion of women in the design and implementation of water supply projects
is an area of concern currently being addressed by multiple world organizations.
History
Throughout history people
have devised systems to
make getting and using
water more convenient.
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. 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.
Water towers appeared around the late 19th century, as building height rose, and steam,
electric and diesel-powered water pumps became available. As skyscrapers appeared,
they needed rooftop water towers.
The technique of purification of drinking water by use of compressed liquefied chlorine gas
was developed in 1910 by U.S. Army Major (later Brig. Gen.) Carl Rogers Darnall (1867–
1941), Professor of Chemistry at the Army Medical School. Shortly thereafter, Major (later
Col.) William J. L. Lyster (1869–1947) of the Army Medical Department used a solution of
calcium hypochlorite in a linen bag to treat water. For many decades, Lyster's method
remained the standard for U.S. ground forces in the field and in camps, implemented in the
form of the familiar Lyster Bag (also spelled Lister Bag). Darnall's work became the basis
for present day systems of municipal water 'purification'.
Desalination appeared during the late 20th century, and is still limited to a few areas.
During the beginning of the 21st Century, especially in areas of urban and suburban
population centres, 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".
