Water supply network
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[[Image:Nanzenji aqueduct channel.jpg|thumb|right|[[Kyoto]] water channel]]
[[Image:Goldfields Pipeline SMC.JPG|thumb|right|A pipeline in the [[Goldfields Water Supply Scheme]] near [[Perth, Western Australia]].]]
A '''water supply network''' is a system of engineered [[hydrologic]] and [[hydraulic]] components, including:
# the [[drainage basin|watershed]] or geographic area that collects the water, see [[Water purification#Sources of drinking water|water purification - sources of drinking water]];
# a raw (untreated) water reservoir (above or below ground) where the water gathers, such as a [[lake]], a [[river]], or [[groundwater]] from an underground [[aquifer]];
# a means for delivery from the source to a point of treatment, such as (underground) [[piping]], uncovered ground level [[aqueducts]] and/or [[tunnel]]s;
# [[water purification]], such as a water treatment plant;
# transmission from treatment, through [[piping|pipes]] to treated water storage, that may be either elevated or ground level; and
# distribution through [[piping]]/[[Water pipe|watermains]] from storage to consumption (at houses, [[fire hydrant|fire hydrants]], industrial use points, etc).
The product, delivered to the point of consumption is [[fresh water]] or [[drinking water]].
==Water treatment==
{{Main|Water treatment}}
Virtually all large systems must treat 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 purification usually occurs close to the final delivery points to reduce pumping costs and 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 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.
Once treated, chlorine is added to the water and it is distributed by the local supply network. Today, water supply systems are typically constructed of plastic, ferrous, or concrete circular pipe. However, other "pipe" shapes and material may be used, such as square or rectangular [[concrete]] boxes, arched [[brick]] pipe, or [[wood]]. Near the end point, the network of pipes through which the water is delivered is often referred to as the ''water mains''.
Shallow dams and reservoirs are susceptible to outbreaks of toxic [[algae]], especially if the water is warmed by a hot sun. The bacteria grow from stormwater runoff carrying [[fertilizer]] into the river where it acts a nutrient for the algae. Such outbreaks render the water unfit for human consumption.
==Distribution==
The energy that the system needs to deliver the water is called [[pressure]]. That energy is transferred to the water, therefore becoming water [[pressure]], in a number of ways: by a [[pump]], by gravity feed from a water source (such as a reservoir or a [[water tower]]) at a higher elevation, or, in smaller systems, by compressed air.
[[Image:Arizona cap canal.jpg|thumb|right|The [[Central Arizona Project Aqueduct]].]]
These systems are usually owned and maintained by [[local government]]s, 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 [[urban planner|city planners]] and [[civil engineering|civil engineers]], who must consider many factors, such as location, current demand, future growth, leakage, pressure, pipe size, pressure loss, fire fighting flows, etc.
[[Construction]] occurs using the expertise of builders, called contractors, with expertise in building hydraulic facilities.
The advent of these systems, along with comparable [[sewage]] systems, was one of the great [[engineering]] advances that made [[urbanization]] possible. Improvement in the quality of the water has been one of the great advances in [[public health]].
As water passes through 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 [[domestic water system|copper pipes]] can result in customer reports of "blue water" and/or 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 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 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]].
==Topologies==
Like electric power lines, roads, and microwave radio networks, water systems may have a [[Loop (graph theory)|loop]] or [[Graph theory|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 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.
==Maintenance==
Water supply networks usually represent the majority of assets of a water utility. Systematic documentation of maintenance works using a [[Computerized Maintenance Management System]] is a key to a successful operation of a water utility.
==See also==
{{Portal|Water}}
* [[Aqueduct]]
* [[Domestic water system]]
* [[Goldfields Water Supply Scheme]]
* [[Hardy Cross]]
* [[Hosepipe ban]]
* [[Hydrology]]
* [[Plumbing]]
* [[Tap water]]
* [[Water supply in Hong Kong]]
* [[Water]]
** [[Water pipes]]
** [[Water Meter]]s
*** [[Automatic meter reading]]
**[[Backflow prevention device]]
** [[Fire hydrant]]
** [[Strainers]]
** [[Valve]]
** [[Water tower]]
** [[Water quality]]
** [[Water resources]]
** [[Water supply]]
==External links==
* [http://dcmms.sourceforge.net DCMMS: A web-based GIS application to record maintenance activities for water and wastewater networks.]
[[Category:Water industry]]
[[Category:Physical infrastructure]]
[[Category:Environmental engineering]]
[[Category:Hydraulics]]
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[[pt:Rede de abastecimento de água]]
[[zh:供水系統]]