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Water resources are sources ofwaterthat are useful or potentially useful to humans. Uses of water include

agricultural, industrial, household, recreationaland environmentalactivities. Virtually all of these human

uses require fresh water.

97% of water on the Earth is salt water, leaving only 3% as fresh water of which slightly over two thirds is

frozen in glaciers andpolarice caps.[1] The remaining unfrozen freshwater is mainly found as groundwater,

with only a small fraction present above ground or in the air. [2]

Fresh water is a renewable resource, yet the world's supply of clean, fresh water is steadily decreasing.

Water demand alreadyexceeds supply in many parts of the world and as the world population continues to

rise, so too does the water demand. Awareness of the global importance of preserving waterforecosystem

services has only recently emerged as, during the 20th century, more than half the worlds wetlands have

been lost along with their valuable environmental services. Biodiversity-rich freshwater ecosystems are

currently declining faster than marine or land ecosystems.[3] The framework for allocating water resources

to water users (where such a framework exists) is known as water rights.

A graphical distribution of the locations of water on Earth.

Sources of fresh water

Surface water

Surface wateris water in a river, lake or fresh water wetland. Surface water is naturally replenished by

precipitation and naturally lost through discharge to the oceans, evaporation, and sub-surface seepage.

Although the only natural input to any surface water system is precipitation within its watershed, the total

quantity of water in that system at any given time is also dependent on many other factors. These factorsinclude storage capacity in lakes, wetlands and artificial reservoirs, the permeability of the soil beneath

these storage bodies, the runoffcharacteristics of the land in the watershed, the timing of the precipitation

and local evaporation rates. All of these factors also affect the proportions of water lost.

Human activities can have a large and sometimes devastating impact on these factors. Humans often

increase storage capacity by constructing reservoirs and decrease it by draining wetlands. Humans often

increase runoff quantities and velocities by paving areas and channelizing stream flow.

The total quantity of water available at any given time is an important consideration. Some human water

users have an intermittent need for water. For example, many farms require large quantities of water in the

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spring, and no water at all in the winter. To supply such a farm with water, a surface water system may

require a large storage capacity to collect water throughout the year and release it in a short period of time.

Other users have a continuous need for water, such as a power plant that requires water for cooling. To

supply such a power plant with water, a surface water system only needs enough storage capacity to fill in

when average stream flow is below the power plant's need.

Nevertheless, over the long term the average rate of precipitation within a watershed is the upper bound for

average consumption of natural surface water from that watershed.

Natural surface water can be augmented by importing surface water from another watershed through a

canalorpipeline. It can also be artificially augmented from any of the other sources listed here, however in

practice the quantities are negligible. Humans can also cause surface water to be "lost" (i.e. become

unusable) throughpollution.

Brazilis the country estimated to have the largest supply of fresh water in the world, followed by Russia

and Canada.[4]

Under river flow

Throughout the course of the river, the total volume of water transported downstream will often be a

combination of the visible free water flow together with a substantial contribution flowing through sub-surface rocks and gravels that underlie the river and its floodplain called the hyporheic zone. For many

rivers in large valleys, this unseen component of flow may greatly exceed the visible flow. The hyporheic

zone often forms a dynamic interface between surface water and true ground-water receiving water from

the ground water when aquifers are fully charged and contributing water to ground-water when ground

waters are depleted. This is especially significant in karst areas where pot-holes and underground rivers are

common.

Ground water

Sub-Surface water travel time

Shipot, a common water source in Ukrainian villages

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Sub-surface water, or groundwater, is fresh water located in the pore space of soil and rocks. It is also

water that is flowing within aquifers below the water table. Sometimes it is useful to make a distinction

between sub-surface water that is closely associated with surface water and deep sub-surface water in an

aquifer (sometimes called "fossil water").

Sub-surface water can be thought of in the same terms as surface water: inputs, outputs and storage. The

critical difference is that due to its slow rate of turnover, sub-surface water storage is generally much larger

compared to inputs than it is for surface water. This difference makes it easy for humans to use sub-surface

water unsustainably for a long time without severe consequences. Nevertheless, over the long term the

average rate of seepage above a sub-surface water source is the upper bound for average consumption of

water from that source.

Desalination

Desalination is an artificial process by which saline water(generally sea water) is converted to fresh water.

The most common desalination processes are distillation and reverse osmosis. Desalination is currently

expensive compared to most alternative sources of water, and only a very small fraction of total human use

is satisfied by desalination. It is only economically practical for high-valued uses (such as household and

industrial uses) in arid areas. The most extensive use is in the Persian Gulf.

Frozen water

Several schemes have been proposed to make use of icebergsas a water source, however to date this has

only been done for novelty purposes. Glacier runoff is considered to be surface water.

The Himalayas, which are often called "The Roof of the World", contain some of the most extensive and

rough high altitude areas on Earth as well as the greatest area of glaciers and permafrost outside of the

poles. Ten of Asias largest rivers flow from there, and more than a billion peoples livelihoods depend on

them. To complicate matters, temperatures are rising more rapidly here than the global average. In Nepal

the temperature has risen with 0.6 degree over the last decade, whereas the global warming has been

around 0.7 over the last hundred years.[5]

Uses of fresh water

Uses of fresh water can be categorized as consumptive and non-consumptive (sometimes called

"renewable"). A use of water is consumptive if that water is not immediately available for another use.

Losses to sub-surface seepage and evaporation are considered consumptive, as is water incorporated into a

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product (such as farm produce). Water that can be treatedand returned as surface water, such as sewage, is

generally considered non-consumptive if that water can be put to additional use.

Agricultural

It is estimated that 69% of worldwide water use is for irrigation, with 15-35% of irrigation withdrawals

being unsustainable.[6]

Industrial

It is estimated that 22% of worldwide water use is industrial [6]. Major industrial users include power plants,

which use water for cooling or as a power source (i.e. hydroelectric plants), ore and oil refineries, which

use water in chemical processes, and manufacturing plants, which use water as a solvent.

Water is also used in many industrial processes and machines, such as the steam turbine and heat

exchanger, in addition to its use as a chemical solvent. Discharge of untreated water from industrial uses is

pollution. Pollution includes discharged solutes (chemical pollution) and discharged coolant water (thermal

pollution). Industry requires pure water for many applications and utilizes a variety of purification

techniques both in water supply and discharge.

Household

It is estimated that 8% of worldwide water use is for household purposes [6]. These includedrinking water,

bathing, cooking, sanitation, and gardening. Basic household water requirements have been estimated by

Peter Gleickat around 50 liters per person per day, excluding water for gardens. Drinking water is water

that is of sufficiently high quality so that it can be consumed or used without risk of immediate or long

term harm. Such water is commonly called potable water. In most developed countries, the water supplied

to households, commerce and industry is all of drinking water standard even though only a very small

proportion is actually consumed or used in food preparation.

Recreation

Recreational water use is usually a very small but growing percentage of total water use. Recreational

water use is mostly tied to reservoirs. If a reservoir is kept fuller than it would otherwise be for recreation,

then the water retained could be categorized as recreational usage. Release of water from a few reservoirs

is also timed to enhance whitewaterboating, which also could be considered a recreational usage. Other

examples are anglers, water skiers, nature enthusiasts and swimmers.

Environmental

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Explicit environmental water use is also a very small but growing percentage of total water use.

Environmental water usage includes artificial wetlands, artificial lakes intended to create wildlife habitat,

fish ladders , and water releases from reservoirs timed to help fish spawn.

World water supply and distribution

Food and water are two basic human needs. However, global coverage figures from 2002 indicate that, of

every 10 people:

roughly 5 have a connection to a piped water supply at home (in their dwelling, plot or yard);

3 make use of some other sort of improved water supply, such as a protected well or public

standpipe;

2 are unserved;

In addition, 4 out of every 10 people live without improved sanitation.[6]

At Earth Summit 2002 governments approved a Plan of Action to:

Halve by 2015 the proportion of people unable to reach or afford safe drinking water. The Global

Water Supply and Sanitation Assessment 2000 Report (GWSSAR) defines "Reasonable access" to

water as at least 20 liters per person per day from a source within one kilometer of the users home.

Halve the proportion of people without access to basic sanitation. The GWSSR defines "Basic

sanitation" as private or shared but not public disposal systems that separate waste from human

contact.

As the picture shows, in 2025, water shortages will be more prevalent among poorer countries where

resources are limited and population growth is rapid, such as the Middle East,Africa, and parts ofAsia. By

2025, large urban and peri-urban areas will require new infrastructure to provide safe water and adequate

sanitation. This suggests growing conflicts with agricultural water users, who currently consume themajority of the water used by humans.

Generally speaking the more developed countries ofNorth America, Europe and Russia will not see a

serious threat to water supply by the year 2025, not only because of their relative wealth, but more

importantly their populations will be better aligned with available water resources. North Africa, the

Middle East, South Africa and northern China will face very severe water shortages due to physical

scarcity and a condition of overpopulation relative to their carrying capacity with respect to water supply.

Most ofSouth America,Sub-Saharan Africa, Southern China and India will face water supply shortages by

2025; for these latter regions the causes of scarcity will be economic constraints to developing safe

drinking water, as well as excessivepopulation growth.

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1.6 billion people have gained access to a safe water source since 1990. [2] The proportion of people in

developing countries with access to safe water is calculated to have improved from 30 percent in 1970 [18] to

71 percent in 1990, 79 percent in 2000 and 84 percent in 2004. This trend is projected to continue.[19]

Economic considerations

Water supply and sanitation require a huge amount of capital investment in infrastructure such as pipe

networks, pumping stations and water treatment works. It is estimated that Organisation for Economic Co-

operation and Development (OECD) nations need to invest at least USD 200 billion per year to replace

aging water infrastructure to guarantee supply, reduce leakage rates and protect water quality. [20]

International attention has focused upon the needs of the developing countries. To meet 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 USD 10 to USD 15 billion

would need to be roughly doubled. This does not include investments required for the maintenance of

existing infrastructure.[21]

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 the two.

But this is where the economics of water management start to become extremely complex as they intersect

with social and broader economic policy. Such policy questions are beyond the scope of this article, which

has concentrated on basic information about water availability and water use. They are, nevertheless,

highly relevant to understanding how critical water issues will affect business and industry in terms of both

risks and opportunities.

Business response

The World Business Council for Sustainable Development in its H2OScenarios engaged in a scenario

building process to:

Clarify and enhance understanding by business of the key issues and drivers of change related to

water.

Promote mutual understanding between the business community and non-business stakeholders on

water management issues.

Support effective business action as part of the solution to sustainable water management.

http://mdgs.un.org/unsd/mdg/Resources/Static/Products/Progress2008/MDG_Report_2008_En.pdf#page=44http://en.wikipedia.org/wiki/Water_resources#cite_note-17http://en.wikipedia.org/wiki/Water_resources#cite_note-18http://en.wikipedia.org/wiki/Investmenthttp://en.wikipedia.org/wiki/Organisation_for_Economic_Co-operation_and_Developmenthttp://en.wikipedia.org/wiki/Organisation_for_Economic_Co-operation_and_Developmenthttp://en.wikipedia.org/wiki/Water_resources#cite_note-19http://en.wikipedia.org/wiki/Millennium_Development_Goalshttp://en.wikipedia.org/wiki/Millennium_Development_Goalshttp://en.wikipedia.org/wiki/Water_resources#cite_note-20http://en.wikipedia.org/wiki/World_Business_Council_for_Sustainable_Developmenthttp://www.wbcsd.org/includes/getTarget.asp?type=d&id=MTk5Nzchttp://en.wikipedia.org/wiki/Scenario_buildinghttp://en.wikipedia.org/wiki/Scenario_buildinghttp://en.wikipedia.org/wiki/Scenario_buildinghttp://mdgs.un.org/unsd/mdg/Resources/Static/Products/Progress2008/MDG_Report_2008_En.pdf#page=44http://en.wikipedia.org/wiki/Water_resources#cite_note-17http://en.wikipedia.org/wiki/Water_resources#cite_note-18http://en.wikipedia.org/wiki/Investmenthttp://en.wikipedia.org/wiki/Organisation_for_Economic_Co-operation_and_Developmenthttp://en.wikipedia.org/wiki/Organisation_for_Economic_Co-operation_and_Developmenthttp://en.wikipedia.org/wiki/Water_resources#cite_note-19http://en.wikipedia.org/wiki/Millennium_Development_Goalshttp://en.wikipedia.org/wiki/Millennium_Development_Goalshttp://en.wikipedia.org/wiki/Water_resources#cite_note-20http://en.wikipedia.org/wiki/World_Business_Council_for_Sustainable_Developmenthttp://www.wbcsd.org/includes/getTarget.asp?type=d&id=MTk5Nzchttp://en.wikipedia.org/wiki/Scenario_buildinghttp://en.wikipedia.org/wiki/Scenario_building

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It concludes that:

Business cannot survive in a society that thirsts.

One does not have to be in the water business to have a water crisis.

Business is part of the solution, and its potential is driven by its engagement.

Growing water issues and complexity will drive up costs.

Hardness

Hardness in water is defined as the presence of multivalent cations. Hardness in water can cause water to

form scales and a resistance to soap. It can also be defined as water that does not produce lather with soap

solutions, but produces white precipitate (scum). For example, sodium stearate reacts with calcium:

2C17H35COONa + Ca2+ (C17H35COO)2Ca + 2Na

+

Hardness of water may also be defined as the soap-consuming capacity of water, or the capacity of

precipitation of soap as a characteristic property of water that prevents the lathering of soap.

TYPES OF HARD WATER

A distinction is made between 'temporary' and 'permanent' hard water.

Temporary hardness

Temporary hardness is caused by a combination of calcium ions and bicarbonate ions in the water. It can be

removed by boiling the water or by the addition of lime (calcium hydroxide). Boiling promotes the

formation of carbonate from the bicarbonate and precipitates calcium carbonate out of solution, leaving

water that is softer upon cooling.

The following is the equilibrium reaction when calcium carbonate (CaCO3) is dissolved in water:

CaCO3(s) + CO2(aq) + H2O Ca2+(aq) + 2HCO3

-(aq)

Upon heating, less CO2 is able to dissolve into the water (see Solubility). Since there is not enough CO2

around, the reaction cannot proceed from left to right, and therefore the CaCO3 will not dissolve as rapidly.

Instead, the reaction is forced to the left (i.e., products to reactants) to re-establish equilibrium, and solid

CaCO3 is formed. Boiling the water will remove hardness as long as the solid CaCO3 that precipitates out is

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removed. After cooling, if enough time passes, the water will pick up CO 2 from the air and the reaction will

again proceed from left to right, allowing the CaCO3 to "re-dissolve" into the water.

Permanent hardness

Permanent hardness is hardness (mineral content) that cannot be removed by boiling. It is usually caused

by the presence in the water of calcium and magnesium sulfates and/or chlorides which become more

soluble as the temperature rises. Despite the name, permanent hardness can be removed using a water

softeneror ion exchange column, where the calcium and magnesium ions are exchanged with the sodium

ions in the column.

Hard water causes scaling, which is the left-over mineral deposits that are formed after the hard water had

evaporated. This is also known as limescale. The scale can clog pipes, ruin water heaters, coat the insides

of tea and coffee pots, and decrease the life of toilet flushing units.

Similarly, insoluble salt residues that remain in hair after shampooing with hard water tend to leave hair

rougher and harder to untangle.[1]

Softening

It is often considered desirable to soften hard water. This is because the calcium and magnesium causing

hardness partly block the oil emulsifying action simple soap formulations use in the cleaning action. The

calcium and magnesium form an insoluble precipitate observed as a soap scum and extra large amounts of

soap have to be used to counteract this. Most modern soaps and detergents contain ingredients that at least

partly prevent this effect and detergents are available that are chemically completely unaffected by the

hardness. This makes hardness removal/softening an optional rather than a necessary water treatment

except possibly in the case of extremely hard water. Where softening is practiced it is often recommended

to soften only the water sent to domestic hot water systems so as to prevent or delay inefficiencies anddamage due to scale formation in water heaters. Another reason for this is to avoid adding sodium or

potassium from the softener to cold water taken for human consumption while still providing softening for

hot water used in washing and bathing.

Process

A water softener works on the principle of cation orion exchange in which ions of the hardness minerals

(mainly calcium and magnesium ions) are exchanged for sodium orpotassium ions, effectively reducing

the concentration of hardness minerals to tolerable levels and thus making the water softer and giving it a

smoother feeling.[13]

http://en.wikipedia.org/wiki/Water_softenerhttp://en.wikipedia.org/wiki/Water_softenerhttp://en.wikipedia.org/wiki/Limescalehttp://en.wikipedia.org/wiki/Hard_water#cite_note-0%23cite_note-0http://en.wikipedia.org/wiki/Cationhttp://en.wikipedia.org/wiki/Ion_exchangehttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Potassiumhttp://en.wikipedia.org/wiki/Concentrationhttp://en.wikipedia.org/wiki/Hard_water#cite_note-12%23cite_note-12http://en.wikipedia.org/wiki/Water_softenerhttp://en.wikipedia.org/wiki/Water_softenerhttp://en.wikipedia.org/wiki/Limescalehttp://en.wikipedia.org/wiki/Hard_water#cite_note-0%23cite_note-0http://en.wikipedia.org/wiki/Cationhttp://en.wikipedia.org/wiki/Ion_exchangehttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Potassiumhttp://en.wikipedia.org/wiki/Concentrationhttp://en.wikipedia.org/wiki/Hard_water#cite_note-12%23cite_note-12

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The most economical way to soften household water is with an ion exchange water softener. This unit uses

sodium chloride (table salt) to recharge beads made of the ion exchange resins that exchange hardness

mineral ions for sodium ions. Artificial or natural zeolites can also be used. As the hard water passes

through and around the beads, the hardness mineral ions are preferentially absorbed, displacing the sodium

ions. This process is called ion exchange. When the bead or sodium zeolite has a low concentration of

sodium ions left, it is exhausted, and can no longer soften water. The resin is recharged by flushing (often

back-flushing) with saltwater. The high excess concentration of sodium ions alter the equilibrium between

the ions in solution and the ions held on the surface of the resin, resulting in replacement of the hardness

mineral ions on the resin or zeolite with sodium ions. The resulting saltwater and mineral ion solution is

then rinsed away, and the resin is ready to start the process all over again. This cycle can be repeated many

times.

The discharge of brine water during this regeneration process has been banned in some jurisdictions

(notably California, USA) due to concerns about the environmental impact of the discharged sodium.

Potassium chloride (softener salt substitute) may also be used to regenerate the resin beads. It exchanges

the hardness ions for potassium. It also will exchange naturally occurring sodium for potassium resulting in

sodium-free soft water.

Some softening processes in industry use the same method, but on a much larger scale. These methods

create an enormous amount of salty water that is costly to treat and dispose of.

Temporary hardness, caused by hydrogen carbonate (orbicarbonate) ions, can be removed by boiling. For

example, calcium bicarbonate, often present in temporary hard water, may be boiled in a kettle to remove

the hardness. In the process, a scale forms on the inside of the kettle in a process known as "furring". This

scale is composed ofcalcium carbonate.

Ca(HCO3)2 CaCO3 + CO2 + H2O

Hardness can also be reduced with a lime-soda ash treatment. This process, developed by Thomas Clarkin

1841, involves the addition of slaked lime (calcium hydroxide Ca(OH)2) to a hard water supply to

convert the hydrogen carbonate hardness to carbonate, which precipitates and can be removed by filtration:

Ca(HCO3)2 + Ca(OH)2 2CaCO3 + 2H2O

The addition of sodium carbonate also permanently softens hard water containing calcium sulfate, as the

calcium ions form calcium carbonate which precipitates out and sodium sulfate is formed which is soluble.

The calcium carbonate that is formed sinks to the bottom. Sodium sulfate has no effect on the hardness of

water.

http://en.wikipedia.org/wiki/Sodium_chloridehttp://en.wikipedia.org/wiki/Ion_exchange_resinhttp://en.wikipedia.org/wiki/Zeolitehttp://en.wikipedia.org/wiki/Ion_exchangehttp://en.wikipedia.org/wiki/Potassium_chloridehttp://en.wikipedia.org/wiki/Bicarbonatehttp://en.wikipedia.org/wiki/Calcium_bicarbonatehttp://en.wikipedia.org/wiki/Calcium_carbonatehttp://en.wikipedia.org/wiki/Thomas_Clark_(chemist)http://en.wikipedia.org/wiki/Slaked_limehttp://en.wikipedia.org/wiki/Calcium_sulfatehttp://en.wikipedia.org/wiki/Sodium_sulfatehttp://en.wikipedia.org/wiki/Sodium_chloridehttp://en.wikipedia.org/wiki/Ion_exchange_resinhttp://en.wikipedia.org/wiki/Zeolitehttp://en.wikipedia.org/wiki/Ion_exchangehttp://en.wikipedia.org/wiki/Potassium_chloridehttp://en.wikipedia.org/wiki/Bicarbonatehttp://en.wikipedia.org/wiki/Calcium_bicarbonatehttp://en.wikipedia.org/wiki/Calcium_carbonatehttp://en.wikipedia.org/wiki/Thomas_Clark_(chemist)http://en.wikipedia.org/wiki/Slaked_limehttp://en.wikipedia.org/wiki/Calcium_sulfatehttp://en.wikipedia.org/wiki/Sodium_sulfate

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Na2CO3 + CaSO4 Na2SO4 + CaCO3

ADVANTAGES OF WATER HARDNESS

Hard water does have some advantages, however. It is an important source of calcium for teeth and bones,

as well as of other minerals necessary for healthy living. It also does not dissolve so many undesirable

substances, so its use to make beer and other beverages produces better results.

The World Health Organization says, "There does not appear to be any convincing evidence that water

hardness causes adverse health effects in humans."

Some studies have shown a weak inverse relationship between water hardness and cardiovascular disease

in men, up to a level of 170 mg calcium carbonate per liter of water. Other studies have shown weak

correlations between cardiovascular health and water hardness. The World Health Organization has

reviewed the evidence and concluded the data were inadequate to allow for a recommendation for a level of

hardness.

In a review by Frantisek Kozisek, M.D., Ph.D. National Institute of Public Health, Czech Republic gives a

good overview of the topic, and unlike the WHO, sets some recommendations for the maximum and

minimum levels of calcium (40-80 mg/L) and magnesium (20-30 mg/L) in drinking water, and a total

hardness expressed as the sum of the calcium and magnesium concentrations of 2-4 mmol/L.

Hard water is not a health hazard. In fact, the National Research Council (National Academy of Sciences)

states that hard drinking water generally contributes a small amount toward total calcium and magnesium

human dietary needs. They further state that in some instances, where dissolved calcium and magnesium

are very high, water could be a major contributor of calcium and magnesium to the diet.

1) It tastes better and is thought to reduce the number of heart illnesses.

2) It provides useful calcium ions for the healthy growth

of bones and teeth.

3) The formation of lime scale in pipes causes the inside of the pipe to be covered with insoluble

carbonates.

This layer of carbonate prevents the water in the pipe

from coming into contact with the metal of the pipe and so prevents pipe corrosion

and poisonous metal salts becoming dissolved in the water.

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Hard water in the US

According to the United States Geological Survey, 89.3% of US homes have hard water. The softest waters

occur in parts of the New England, South Atlantic-Gulf, Pacific Northwest, and Hawaii regions.

Moderately hard waters are common in many of the rivers of the Tennessee, Great Lakes, Pacific

Northwest, and Alaska regions. Hard and very hard waters are found in some of the streams in most of the

regions throughout the country. Hardest waters (greater than 1,000 mg/L) are in streams in Texas, New

Mexico, Kansas, Arizona, and southern California which can also cause very stubborn hard water stains.

Hard water in Canada

Prairie provinces (mainly Saskatchewan and Manitoba) contain high quantities of calcium and magnesium,

often as dolomite, which are readily soluble in the groundwater that contains high concentrations of trapped

carbon dioxide from the last glaciation. In these parts of Canada, the total hardness in mg/L calcium

carbonate equivalent frequently exceeds 200 mg/L, if groundwater is the only source of potable water.

Some typical values are: Calgary 165 mg/L, Saskatoon Hard water in England and Wales

Information from the British Drinking Water Inspectorate shows that drinking water in England is

generally considered to be 'very hard', with most areas of England, particularly the East, exhibiting above

200 mg/L as calcium carbonate equivalent. Wales, Devon, Cornwall and parts of North-West England are

softer water areas, and range from 0 to 200 mg/L. In the brewing industry in England and Wales, water is

often deliberately hardened with gypsum in the process of Burtonisation.

DISADVANTAGES OF WATER HARDNESS

It is easiest to identify water hardness by its effect on soap and other detergents. Because soaps and

detergents have an ionic nature, when they are dissolved in hard water, each soap molecule reacts with

calcium ions, to produce scum. This essentially renders the soap useless, and much more soap or detergent

is required to clean anything if used with hard water.

Another major problem with hard water is that, when it is heated, in a kettle, washing machine or hot water

pipe, it begins to deposit solid calcium carbonate. This is the cause of lime scale building up in kettles,

damaging heating elements of washing machines and blocking water pipes.

http://www.hardwaterstainstips.com/http://everyday-chemistry.suite101.com/article.cfm/surfactants_cleaning_chemicalshttp://www.hardwaterstainstips.com/http://everyday-chemistry.suite101.com/article.cfm/surfactants_cleaning_chemicals

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1) Lime scale furring of kettles and pipes.

The fur is the insoluble carbonate formed

during heating water with temporary hardness.

The deposits of lime scale can build up on the inside of the pipe

restricting the flow of water or causing a blockage.

This can happen in industry where hot water is used

or in domestic heating systems (like the hot water in your house).

Lime scale deposits can be removed using a weak acid.

Lime scale in pipes can be prevented using a water softener

or a scale inhibitor.

Lime scale in pipes can also be an advantage (see above).

2) Soap is wasted because more soap is required for washing.

Soap in hard water forms a "scum" from reacting with

the calcium or magnesium compounds in the water.

Other detergents which do not contain soap

do not form wasteful scum during washing.

ADVANTAGES OF USING DETERGENTS OVER SOAP IN HARD

WATER

Soaps and detergents behave differently in hard water. Soaps form a scum in hard water and this scum will

not rinse away easily and is known to turn laundry a grayish hue. The insoluble film it leaves can leave a

residue on your laundry much like you would see in a shower stall where hard water is present. synthetic

detergents can lather well even in hard water. This is because they are soluble sodium or potassium salts of

sulphonic acid or alkyl hydrogen sulphate and similarly form soluble calcium or magnesium salts on

reacting with the calcium ions or magnesium ions present in water. This is a major advantage of the

cleansing property of detergents over soap.

Surface Water

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Sub-Surface Water

http://upload.wikimedia.org/wikipedia/commons/4/49/Parinacota.jpg

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Frozen Water Desalination

Tap Water Hand Pump

Well

http://upload.wikimedia.org/wikipedia/commons/7/73/Wasserhahn.jpg

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Water can be found in various forms. Here are a few different pictures of the different forms of water.