8. What are the causes of water pollution? How can we provide enough clean water?

What are the sources of water pollution?
This is a pretty good summary for an HIC

Whether water is clean enough to use, or too polluted depends on many things such as where it is, whether there is enough for everyone to use, what we do with it, and how we deal with the water we have used before we let it run back to join the rivers and lakes.

How the problems arise?

The Developing World :
In the developing world the biggest problem is the shortage of water and the lack of clean supplies. When water is very scarce people have to make good use of it. That might mean using the same source of water for drinking and cooking, a place to wash, a place to clean clothing, pots and pans and a place to let the farm animals drink as well. The same water is used by many people for many different purposes, and each time the water becomes a little more polluted.

Imagine a river that is the only source of water for a series of farming villages along its banks.
The people in the first village might be very careful and always get their drinking water from above the village, do all their washing a little further down stream, and let their animals drink in the river as it leaves their village. By being very careful and aware of basic hygiene they can try to stay healthy. They can do very little to protect themselves from dead animals decaying in the river further upstream, or from germs and parasites introduced to the water by wild animals.
As the river leaves their village the water will have been polluted by washed bodies, food scraps from washed pots and pans, and body waste from the farm animals and village dwellers. The people in the next village will have to drink this polluted water, and will suffer from the diseases that accompany dirty water.

If an animal dies and falls into the only water supply for miles around, the people still have to drink the water. If the water is thick with mud and snails, but is the only water within reach, people have to drink it.

Whether the water source is a river, a lake or a well, the problems are similar throughout the developing world; little piped and sterilised water, and not enough water to go round means that the same source has to be used for everything, and the risk of pollution and disease is very high.

The Developed World:
You might think that in developed countries with more money to spend on health care, water supplies and pollution control, water pollution wouldn't be a problem. If people in developed countries lived a life similar to that of people in the developing countries, but used all their high technology skills, the developed world might have an almost pollution free water supply. Unfortunately that's not the case. The developed world produces things in factories, people drive around in cars, and want farmers to grow disease and pest free crops. The problem is that people in the developed world create far more pollution than their counterparts in the developing world.

Factories can produce huge quantities of pollution that end up in the water supply and it's not just the waste that goes directly into the rivers that causes problems.

Smoke from chimneys can contain harmful chemicals such as those which create acid rain. When it rains, all these chemicals are brought back down to the ground in the rain drops, and then find their way into the water supply.

Chemicals sprayed onto fields and crops, such as pesticides ( to kill insects ), herbicides ( to kill weeds ) and fertilizers ( to make crops grow faster, stronger and quicker ) can all soak into the soil when it rains. Eventually the chemicals are washed into drainage ditches, streams or rivers, and thus into the drinking water.

Sometimes dangerous chemicals have been dumped in places where they can escape into the water supply. Rubbish Dumps and Toxic Waste Sites are all supposed to have a waterproof layer around them to stop chemicals escaping, but sometimes it doesn't work. There are many older dumps where the site isn't waterproof and nobody knows exactly what was dumped there!

An example of HIC Pollution - Love Canal and the U.S.A:
A good example is the Love Canal site near Niagra Falls in the United States of America. During the 1940's and 1950's the canal was used as a dump for 22,000 tonnes of chemical wastes. The site was then filled in and covered in soil, and houses built over the top. In 1978 it was noticed that many people there were ill and that children were being born with defects. It didn't take long to discover why, and the worst affected areas were evacuated. Six years later the U.S government had discovered another 17,500 similar sites, 546 of which were considered to be dangerous to the health of people living there. At many of these sites, chemicals are leaking out into the groundwater supply causing serious pollution.

Did you know that over 700 different chemicals have been found in US drinking water when it comes out of the tap! The United States Environmental Protection Agency (EPA) classifies 129 of these chemicals as being 'particularly dangerous'.

In 1982 the EPA found poisonous chemicals in the water supply of 35 different states. In 25 states the contamination was so serious that wells had to be closed.

Another example of HIC pollution: The River Rhine and Europe:
The River Rhine is regarded as being Europe's dirtiest river. Almost one fifth of all the chemical production in the world takes place along its banks. Despite the best attempt to purify the river water before it becomes drinking water, Cornelius van der Veen, the head of the Dutch water works in the Rhine catchment area, once said "Even well-thought-out purification and reprocessing systems mean that just about every substance present in untreated water is also to be found in drinking water."

On 1st November 1986, the Sandoz chemical factory in Switzerland had a warehouse fire. While the firemen were extinguishing the flames they sprayed water over drums of chemicals that were exploding due to the heat. The water and chemical mixture was washed into the Rhine, dumping 30 tonnes of pesticides, chemical dyes and fungicides into the river. As a result the river life died up to 100 miles downstream. Things could have been worse though. A nearby building contained sodium, a metal that reacts violently with water. If the fire hoses had been sprayed on the stored Sodium, the explosion could have destroyed a group of storage tanks holding the nerve gas, Phosgene!

After the fire had been put out, the German government ( West Germany at that time ) checked the water as it passed through Germany. They discovered a high level of a chemical called Atrazine ( a herbicide ) that wasn't listed as having been stored at the Sandoz site. Eventually another giant chemical company, Ciba-Geigy, admitted that they'd had an accident the day before and spilled 100 gallons of Atrazine into the river. The West German government didn't believe this figure and stated that nearer to 1500 gallons must have entered the river.

As the monitoring of the Sandoz chemicals continued, more chemicals were discovered and it emerged that many different companies were discharging chemicals unlawfully. BASF, well known for their recording tapes, admitted to spilling 1100kg of herbicide, Hoechst admitted to a major leak of chlorobenzene, and Lonza confessed that they had lost 4,500 litres of chemicals from their plant.

Despite this worrying state over 20 million people were, and still are, getting their drinking water from the Rhine.

(thanks to http://www.geography-site.co.uk/pages/environ/water.html )

What are the major problem areas?

With over 8 billion people on the planet, disposing of sewage waste is a major problem. In developing countries, many people still lack clean water and basic sanitation (hygienic toilet facilities). Sewage disposal affects people's immediate environments and leads to water-related illnesses such as diarrhoea that kills 3-4 million children each year. (According to the World Health Organization, water-related diseases could kill 135 million people by 2020.)

In developed countries, most people have flush toilets that take sewage waste quickly and hygienically away from their homes. Yet the problem of sewage disposal does not end there. When you flush the toilet, the waste has to go somewhere and, even after it leaves the sewage treatment works, there is still waste to dispose of. Sometimes sewage waste is pumped untreated into the sea. The population of Britain produces around 1200 million litres of sewage every day, some of it still pumped untreated into the sea through long pipes.

In theory, sewage is a completely natural substance that should be broken down harmlessly in the environment: 90 percent of sewage is water. In practice, sewage contains all kinds of other chemicals, from the pharmaceutical drugs people take to the paper, plastic, and other wastes they flush down their toilets. When people are sick with viruses, the sewage they produce carries those viruses into the environment. It is possible to catch illnesses such as hepatitis, typhoid, and cholera from river and sea water.

Runoff from farms, containing compost, manure and chemical fertilizers, flowinto rivers. If too much is added to a particular water source it cannot cope and algal blooms result. These take oxygen out of the water, killing the fish and other life forms.

Waste water

Virtually everyone pours chemicals of one sort or another down their drains or toilets. Even detergents used in washing machines and dishwashers eventually end up in our rivers and oceans. So do the pesticides we use on our gardens. A lot of toxic pollution also enters waste water from road runoff. Roads are typically covered with a cocktail of toxic chemicals—everything from spilled fuel and brake fluids to bits of worn tyres (themselves made from chemical additives) and exhaust emissions. When it rains, these chemicals wash into drains and rivers. It is not unusual for heavy summer rainstorms to wash toxic chemicals into rivers in such concentrations that they kill large numbers of fish overnight. It has been estimated that, in one year, the road runoff from a single large city leaks as much oil into our water environment as a typical tanker spill.

So now we know what the problems are, how do we try are sort it out?
Actually it depends where you are and who you are in terms of wealth as to how you ensure enough clean water for those that need it.
In HICs and in the better parts of towns and cities in MICs and some LICs you have a regional water system and regional sewage system, which while part of the same cycle of water use, operate separately.
In rural parts of many countries the best systems keep to the 2 systems apart.
But looking at regional systems in HICs, there is some sort of treatment of the water before it enters the home

This last picture comes from http://www.metrocouncil.org/environment/Kids/01.htm
I know it says kids but really it isn’t – on the first screen it says kids – 8 to 80! And is a good explanation of what sewage treatment does – here is the final summary from the site – by the way, you may need to use the page links at the top to get it going , but then the Go forward button begins to work
As you see the 2 systems are similar, except that sewage water is assumed to have more in it that need to be taken out!

Both these diagrams show water being taken from and put back into a river. But not everyone receives river water in their home. For example in East Anglia much of the water comes from the ground water store and is pumped up from below through boreholes. But the growing population means that more water is being taken out than is being replenished by rainfall. So, in many cases, the boreholes are up to twice as deep as they were 20 or 30 years ago – the water table has dropped 200m or more.

So one way of supplying sufficient water is to collect it in reservoirs and pipe it to where it is needed. One the earliest and most farsighted schemes was started by Birmingham City council
In the closing years of the nineteenth century the city of Birmingham, in the English midlands, was under pressure from the growing pace of industrialisation. Its population was expanding rapidly as workers and their families were attracted by the prospect of new jobs in the factories and mills, even though living conditions for many in the slum districts of the city were appalling. Similar problems existed in many other industrial cities in Britain.
Large numbers of people had to use wells polluted by sewage. The crowded and unsanitary conditions often resulted in deadly epidemics of water-borne diseases such as typhoid and cholera.

The essential need in order to combat these was an ample supply of clean water, for the amount of water used in the city had doubled between 1876 and 1891. There was little prospect of being able to meet the ever growing demand for water from existing sources. After some investigation, the Birmingham City council decided upon a sparsely populated area of mid-Wales, 75 miles to the west through which flowed the River Elan.
There were a number of reasons for the choice of the Elan Valley district as the source of supply for Birmingham. The annual rainfall was high, and the valleys of the rivers Elan and Claerwen near Rhayader were narrower downstream, making it easier to construct masonry dams. The city of Birmingham is built on relatively low ground, and the use of reservoirs constructed in the high moorlands of mid-Wales would allow the water supply to be fed by aqueduct on a suitable gradient by gravity alone, without the need for costly pumping. Further factors in favour of the area were that the local bedrock was impermeable and ideal for retaining the water held in the reservoirs, and also the relatively sparse population in what was a remote upland area. This lessened the task of securing ownership of over 70 square miles of the watershed.
Only the affected landowners, however, were to be given any financial compensation and tenant farmers and smallholders, who needed it most, were evicted without recompense. Servants and other workers employed by the two large estates in the valleys lost their income and their accommodation. It is likely that at least some of these were left with no alternative but the workhouse. The Elan Valley and the nearby Claewen Valley which was added 50 years later still supplies Birmingham with the majority of its water.
For anyone interested in the history of the dams you can find lots of personal stories and pictures collected from people over the years and also it explains some of the engineering issues involved at this site

However, these days, rarely are reservoir schemes solely built for the supply of fresh water for urban dwellers. They often combine the supply of hydroelectric power, with flood control and irrigation for farming and even recreation facilities, such as sailing and fishing.

A case study of a dam and or reservoir: The Three Gorges Dam on the Yangtze River in China

A MUST SEE Video of the Three Gorges - excellent summary of all you might need to know and more


The Yangtze is China’s largest river stretching 5,600 kms from its source in Tibet to where it enters the Yellow Sea near Shanghai. Midway through its course the river flows through a 190km section known as the Three Gorges. The river valley narrows here and there are steep limestone cliffs on either side. The river is fast flowing and hidden rocks make it dangerous for ships.
The Scheme
The dam, when completed, will be the biggest in the world, 2kms wide and 185 metres high. It will create a reservoir 600kms long behind it. It was started in 1993 and was completed in November 2008
The cost will be at least $20 billion and the hydro-electric plant will generated 18,000 megawatts of electricity, making it the biggest HEP station in the world.

Advantages of the Scheme
During the 20th Century there were 3 catastrophic floods, plus many smaller ones. Over 300,000 people have been drowned. The dam will reduce flooding from a 1 in 10 year event to a 1 in 100 year event, thereby saving thousands of lives.
The dam will provide 10% of China’s present electricity requirements. It will be a clean fuel, reducing China’s SO2 and CO2 emissions and helping to reduce global warming gases.
All year round navigation will be possible by ocean going vessels as far as Chongqing at the far end of the reservoir.
Over 20,000 medium term jobs , up to 60,000 at its height have been provided in the construction industry. This will create a positive multiplier effect to the local economy
It will provide enough water for all those in Shanghi and many other downstream cities

Disadvantages of the Scheme

1.2 million people will be relocated. This will include 13 cities, 140 towns, and 4500 villages. In addition 1600 industrial enterprises will have to be relocated.
23,000 hectares of fertile farmland and 7000 hectares of forest will be drowned.
Fertile soil will be lost to farms downstream from the dam. This is likely to lead to an increase in the use of chemical fertilisers.
Sediment will build up behind the dam over time leading to a squeezing out of the reservoir. This will have a number effects, reducing the capacity of the reservoir and the amount of electricity generated and possibly impeding the flow of river traffic
Pollution in the form of sewage and toxic metals from industry will collect and build up the reservoir.
The reservoir will create much deeper, colder water thereby changing the environment including types and numbers of fish.
The dam lies near an earthquake fault line. Although the government says they have taken this into account, any major earthquake could create a disaster on an unprecedented world scale, with a death toll of several million. (Remember the earthquake just before the Chinese Olympics in Sichuan was not THAT far away.]


World's Rivers in 'Crisis State', Report Finds: is an excellent article bringing together all the problems being suffered by river systems world wide and the implications for the humans who live along them:
The picture below was taken from the article and makes a very good summary of the issues: