The big picture

Rainfall is not equal across the world, leading to unequal supply of water. Many other factors also affect access to an adequate and safe water supply ranging from cost of water to pollution of supplies.

To be suitable for drinking, water needs to be safe and free of pathogens and contaminants. With limited supplies, water shortages may occur. In rural areas people may need to walk further for supplies and may only have access to contaminated waters.

Water related diseases are responsible for millions of deaths each year. Many water related diseases like cholera infect the digestive system and cause diarrhoea that leads to dehydration and can result in death. UNICEF estimates that diarrhoea leads to 1.8 million deaths each year of which 1.6 million are children under the age of five years.This means on average 4,384 children die every day from diarrhoea. Do your own calculations to work out how many that is per day or per minute.

Contamination of water with arsenic is a major problem is some countries. Arsenic occurs naturally in the Earth’s crust and this leads to contamination of groundwater in some regions.

Figure 1. Distribution of groundwater contaminated with arsenic.

More people are affected in Bangladesh than any other country. Over 45 million people in Bangladesh are exposed to Arsenic levels above the World Health Organization (WHO) guidelines of 10 µg/L.

Figure 2. Distribution of arsenic within groundwater in Bangladesh.

Use of groundwater contaminated with arsenic can lead to long term exposure. Effects include changes to the pigmentation of the skin, development of skin lesions, cancers of the skin, bladder and lung.

Figure 3. Water shortage can lead to conflict.

Over abstraction can lead to depletion of water resources. With limited water supplies the risk of conflict over this resource increases. Disputes over ownership and water rights may occur:

• Between individuals or groups within a country.
• Between countries where river systems are shared.

It is important to manage water supplies sustainably to ensure sufficient future supplies. Groundwater and lakes need time to replenish. We need to control demand through water conservation strategies and also increase supplies.

Distribution of water

Freshwater is not distributed equally around the world. Some regions have little if any rainfall, whereas other areas may have rainfall of several meters a year.

Figure 1. Average global rainfall distribution.

Comparison of rainfall in the Atacama Desert and in Cherrapunji

The Atacama Desert in Northern Chile and Cherrapunji in India illustrates the unequal distribution of freshwater. The Atacama Desert is considered to be one of the driest places on the planet, with average annual rainfall of about 1mm and with no rainfall being recorded in some parts of the region at all. In contrast, Cherrapunji has a sub-tropical climate with an average annual rainfall of more than 11,700mm. Extreme rainfall events for Cherrapunji have included 2,6470mm of rain over the 12 month period August 1860 to July 1861 and 2,493mm of rain over 48 hours during June 1985.

Figure 2. Atacama Desert, Chile.

Figure 3. Climate graph for Cherrapunji, India.

Precipitation is not usually consistent throughout the year. Hence, water supplies need to be carefully managed to ensure a continual supply which meets demand. Despite the high levels of rainfall, even the village of Cherrapunji, has experienced water supply shortages during the drier winter months of November to February.

Be Aware

High annual precipitation does not guarantee an adequate supply of water throughout the year. Water may need to be collected and stored during wet spells for use during drier periods.

Access to water issues

The World Health Organization (WHO) estimates that 750 million people around the world to not have access to safe drinking water. Poor infrastructure and inadequate management of water services is often to blame. This may be due to:

• Lack of knowledge and skills.
• Lack of finances.
• Lack of political will to make water a priority.

Inequalities of access to safe water occur:

• Between urban and rural areas. People living in urban areas are more likely to be connected to piped water. Some rural areas are remote and can be difficult to access. In 2014, 82% of people without access to water lived in rural areas.
• Between the rich and poor. Those with wealth are most likely to have a reliable water supply. The poor in urban areas may live in slums and shanty towns that often have poor water access.
• Between social groups. Some groups within society may be marginalized e.g. based on ethnicity, language or religion.

The development and building of a water supply infrastructure takes time and substantial resources. An intermediate solution is the use of public water points and water vendors. People in the poorest areas can pay substantially more for water than wealthier people living in the same city. This further exacerbates the inequities between rich and poor.

Figure 4. Examples of variation in cost of water within a city. Paid per m³ of drinking water, in US¢.

Climate Change

Climate change is contributing to changes in regional precipitation patterns which directly affect water availability. Climate scientists have made the following predictions:

• Some already water stressed areas in the mid latitudes and dry tropics will receive less precipitation.
• High latitudes and equatorial Pacific may experience more precipitation.
• Weather patterns are likely to be more extreme with:
  • Greater periods of dry spells resulting in drought conditions.
  • Increases in intense precipitation potentially leading to flooding.
• An increase in the melting rates of glaciers and snow will contribute to the risk of flooding.
• Along coastal areas, a rise in sea level could lead to seawater contaminating surface and aquifer water supplies.
• Overall more regions around the world are likely to experience water stress.

Figure 5. Time spent collecting water reduces the ability of women to earn money and of children to go to school. This situation could get worse in areas that have less rainfall and people have to walk further for water supplies.

Open up this document. Analyse the patterns seen in each graph or table.

Increase demand for water

Agriculture is globally the largest user of water, followed by industrial use and domestic use (for drinking and maintaining health and hygiene). The amount of water used by each sector varies from one country to another. Although the average global value for agriculture is 70%, in more economically developed countries (MEDCs) this is often lower with more water being used for industry. Conversely, in less economically developed countries (LEDCs) more water is often used for agriculture and less in the industrial sector.

(Source: Water for people, water for life. United Nation World Development Report UNESCO, 2003.)

Figure 1. Water use by sector in different countries.

Figure 2. Comparison of water withdrawal per capita.

Why is there such variation between the above countries for the amount of water withdrawn per capita?

Water demand is expected to continue to rise due to:

• Growth in population. The population is expected to increase to 9 billion by 2050. More water will be required for domestic use and for agriculture to produce more food.
• Increase in affluence and standard of living results in higher water consumption. More water is used for washing, cleaning, gardening and recreational purposes.
• Change to a more meat based diet. The production of meat requires more water than producing only fruit and vegetables.
• Growth of industry. UNESCO estimates that global industrial use of water will increase to 24% by 2025.
• Increase in urbanization. The world’s urban population is expected to grow to 6.3 billion by 2050. This will require further investment into the development of infrastructure to provide water resources.

Water stress and scarcity

Water stress occurs when there is either an insufficient amount of available water to meet demand or when the quality of water limits its uses.

A population is considered to be water stressed when supply is less than 1,700 cubic meters per person per year (m3/person/year). Water stress can develop into water scarcity when water supplies fall to below 1000 m3/person/year. Water scarcity effects economic development and human health.

Definition

Water stress is when demand exceeds the available supply over a certain time period or when the quality of water restricts its use.

There are many regions which are experiencing water stress and scarcity. The UN estimates that by 2025 two thirds of the global population will live in water stressed areas and about a fifth will suffer from water scarcity.

Figure 3. World map of water stress and scarcity.

Economic water scarcity occurs due to the lack of finances e.g. the cost of treating water to make it safe to drink. Physical water scarcity occurs when there is not enough water to meet demand.

Issues contributing to water stress include:

• Over abstraction of groundwater, in which water is being used at a faster rate than it is being replenished. In coastal areas this is leading to contamination of aquifers by seawater referred to as saline intrusion.
• Excessive abstraction of surface waters lowering water levels and the area covered by water. The Aral Sea in Asia was the fourth largest freshwater lake in the world but following high levels of abstraction has shrunk to less than 10% of its original size.
• Pollution of surface and groundwater resources. E.g. sewage effluent, toxic industrial waste and agricultural run-off. Contamination of water resources increases the cost of clean-up.
• Inefficient use of water resulting from:
  • Poor irrigation e.g. resulting in high levels of run-off and evaporation. Drip irrigation systems are used to release water directly to the roots of the plant.
  • Leakages within the water distribution system. Repairing leakages within the distribution system is an on-going battle. In some countries the water distribution is deliberately broken to "steal" the water.
  • Inefficient use of water by industry. Changes in industrial processes can reduce the amount of water used.
  • Inefficient use of water by individuals.
• Climate change which will alter rainfall patterns as discussed in subtopic 7.2

Watch the following video which examines water shortage in Murcia, Spain resulting in conflict within the country, 'Global Water Shortage Part 2' by BBC World News America: video removed for copyrighting. Find new source?

Theory of Knowledge

Global water resources are not shared equally. To what extent can this be ethically justified?

Rivers without borders

Many river systems are shared by countries resulting in some nations being dependent on sources of water that originate outside their borders. Countries upstream can control the flow to downstream neighbours. Throughout history disputes have arisen over the ownership of water resources. With increasing pressure on limited water sources, conflicts continue to arise throughout the world today.

Figure 4. Regulation of Tigris & Euphrates Rivers.

Using the information within Figure 2, the following observations can be made:

• Dams along the Tigris and Euphrates Rivers in Syria and Turkey can hold water and restrict the flow of water into Iraq.
• Iraq is probably dependent on extracting large volumes of water from the Tigris and Euphrates for irrigation.
• Farming practices may contribute to fertilizers and pesticides entering both river courses.

Examiner Tip

Take time to carefully examine figures. The ability to interpret the information provided is an important skill. You should be able to apply your knowledge and understanding to different scenarios and make appropriate conclusions or suggestions such as identifying potential environmental issues.

Conflict over the Ethiopian Grand Renaissance Dam

Watch the following video ‘Egypt, Ethiopia and Sudan sign deal on Nile dam’ by Euronews 2015:It covers an agreement in which Ethiopia accepted not to let a hydro-electric dam significantly affect the flow of the Blue Nile into Sudan. The Blue Nile originates in Lake Tana in Ethiopia and is the major tributary to the River Nile. The Blue Nile merges with the White Nile in Khartoum forming the River Nile that flows into Egypt.

The Ethiopian Grand Renaissance Dam due to be completed in 2017 will be the biggest in Africa. Downstream neighbours were concerned over its potential to threaten their supply of water. The River Nile provides Egypt with its main source of water. Egypt initially perceived the construction of the dam as a threat to its national security and prior to the agreement had threatened military action. Negotiations are aimed at reducing disruption to the flow downstream. For example, Ethiopia has agreed to fill the dam gradually which will lessen the impact on flow.

Figure 5. Location of the Ethiopian Grand Renaissance Dam.

International-mindedness

Water is a finite resources and its management requires a holistic approach.

Managing water resources I

To address increasing demand for water, we need to increase water supply and reduce demand.

Increasing water resources

Water supplies can be enhanced by increasing storage of water during periods of rainfall through the use of reservoirs, artificial recharge of aquifers and rainfall harvesting schemes.

Reservoirs

Reservoirs can be either natural or artificially created lakes used to collect and store water. Reservoirs are built by damming rivers and flooding suitable valleys. The aim of the reservoir is to store water during periods of high rainfall to provide a plentiful supply throughout the year.

What additional benefits are there to a reservoir?

• Generation of hydropower. Some reservoirs also incorporate hydropower schemes to generate electricity.

Figure 1. Hydropower relies on the energy of water falling through the penstock to turn turbines linked to an electrical generator.

• Flood control. In some regions, reservoirs are also used to capture floodwater and reduce the risk of flooding in downstream areas.
• Navigation. The reservoir can provide transport route from one site along the shore to another.
• Fisheries. Commercial fisheries have been developed in some reservoirs.
• Recreational, aesthetic and scenic value. Reservoirs can be used for many recreational activities e.g. water sports such as canoeing and water skiing. Picnic spots are often located along the shores of the lake for their aesthetic and scenic value.
• Control of water quality. Sediment load of the water can be reduced in standing water. The particles in the water precipitate out, improving the water quality.

What are the potential impacts of building reservoirs?

• Change of habitat. When an area is flooded to become a reservoir, there is a change from a terrestrial to an aquatic ecosystem. The establishment of a lake ecosystems introduces new freshwater habitats to the area. However, scarce terrestrial habitats and species may be lost.
• Relocation of people. People may need to be moved out of an area that is to be flooded and relocated elsewhere. Whole towns and villages may be affected. It has been estimated that China’s Three Gorges Dam on the Yangtze River led to the displacement of about 1.3 million people.
• Change to the flow of the water. Much of the water from the reservoir is diverted elsewhere e.g. to urban areas for industrial and domestic use. Some of the water may re-join the river further downstream as waste water, potentially polluting the river.
• Loss of fish and mammal migratory routes. Dam walls can block the migratory route of some fish and dolphins. In an effort to alleviate the loss of fish, fish ladders (concrete steps filled with water) are incorporated into the dam wall. Some fish are able to find and use the ladder allowing them to travel through the wall and continue along their way.

Figure 2. Example of fish ladder with salmon moving via a series of steps incorporated into the dam wall.

• Sedimentation in the reservoir and loss of capacity. The sedimentation of particles from the water behind the dam wall reduces the holding capacity of the reservoir. In addition, this may not always be desirable for farmers downstream who rely on the nutrients in the sediments to fertilize their fields.

Artificial recharge

Artificial recharge is used to increase the amount of water stored in aquifers. It is a widely used in some countries to enhance water supplied e.g. Netherlands, Germany and USA. Methods can include:

• Building a ditch or trench above an aquifer zone to intercept and collect run-off. The water collected gradually seeps into the ground and percolates through permeable strata into the aquifer. Although a simple method, the acquisition of sufficient land can be expensive.
• Alternatively water can be pumped directly from rivers or reservoirs into the aquifer via a borehole (a hole drilled into the ground). Pumping directly from a river with high sediment loads can cause clogging of boreholes. Using reservoirs to store the water prior to pumping into the aquifer has the advantage of allowing the sediments to settle out reducing the sediment load.

Figure 3. Artificial recharge of groundwater using a ditch.

Rainfall harvesting schemes

Rainwater harvesting involves collection of precipitation which falls on the roof of buildings. The rainwater is stored in tanks and can be used for domestic purposes e.g. cleaning and gardening. Rainwater collection reduces the risk of flooding and soil erosion. It is also a relatively cheap and easy to maintain method. The water is relatively clean but should be filtered and disinfected if used for drinking.

Figure 4. Use of water tanks to collect rainwater is a simple and effective method.

Managing water resources II

This section considers how water resources can be managed by:

• Enhancing water supplies using desalination, water transfer schemes and greywater.
• Reducing water demand.

Increasing water resources

Desalination

This is the production of freshwater suitable for drinking from seawater. It is an energy intensive process and therefore usually expensive. Historically desalination has been used in arid regions with access to a cheap supply of energy such as Saudi Arabia. With improvements in technology, desalination is becoming more common in regions where historic water supplies are either declining or not able to keep up with an increase in demand.

Reverse osmosis is the most common method used. You are probably already familiar with osmosis (the movement of water through a semipermeable membrane from a low concentrated solution to a high concentrated solution). Reverse osmosis is the opposite in which the external pressure applied is greater than the osmotic pressure and water molecules move from a high concentrated solution into a low concentrated solution.

In desalination, seawater is placed under pressure, which forces water molecules to move through a semi-permeable membrane leaving behind the salt molecules.

Figure 1. Process of osmosis and reverse osmosis.

Watch the following video which explains the process of desalination: ‘Drinking from the sea’ by SUEZ environment.

Water redistribution: water transfer schemes

These schemes often transport water from one river basin to another using pipes or canals. Water is taken from where it may be considered as surplus to where there is a water deficit. They are often expensive grand projects. This redistribution may address water demand in one area but can have adverse effects on the region of the donor river:

• Abstraction of water may lower water levels affecting habitats e.g. wetlands and associated species.
• The disruption in the flow can affect fish and other biota living in the river.
• The reduced amount of water may not be sufficient to meet the needs of local people.

The South-North water transfer project in China is one of the biggest redistribution schemes in the world. The project consists of over 14,000km of canals and has so far taken more than 12 years to construct. The aim is to take water from the Yangtze River in Southern China to the industrial north via three canal systems; the eastern, western and central route. The later carries water to Beijing and Tianjin.

Watch the following video Water diversion project: Water starts to arrive in Beijing by CCTV News

Figure 2. World heritage monument Pond du Gard aqueduct built by the Romans to transport water from Uzés to Nemausus in France.

Use of greywater

Greywater is used water that is clean enough to be used again. It includes water from baths, showers, wash basins and washing machines but not discharge from toilets (this is known as black water). Greywater can be collected and used for toilet flushing and gardening. It is not suitable for drinking due to presence of some pathogens and contaminants. Benefits of greywater:

• Reduces the amount of wastewater produced and requiring treatment.
• Reduces the amount of water that needs to be abstracted.

Figure 3. Greywater collection system.

Communal systems for the collection and treatment of greywater are often more cost effective than greywater use by individual households. These systems can incorporate:

• Physical treatment – filtration to remove large particles and disinfection to kill pathogens.
• Biological treatment – involving either bacteria or wetland systems to utilize nutrients and filter particles from the water.

Figure 4. Communal systems can use wetlands to treat greywater.

Reducing demand

Water conservation often requires a change in attitude to water and can be achieved by:

• Increasing water efficiency through improved technology and processes use e.g.:
  • In agriculture, water use can be reduced which can include the use of more efficient watering systems such as drip irrigation.
  • In industry changes to processes and reuse of water can reduce amount of water used.
  • In the home we can use aeration taps, low flush toilets, more water efficient washing machines and the use of greywater recycling.
• Public awareness campaigns. This may include promoting:
  • Use of showers instead of baths.
  • Purchase of water efficient washing machine and dishwashers.
  • More efficient use of water i.e. prevent taps running unnecessarily and fixing leaks and dripping taps immediately.
  • Use of rainwater butt and effective watering of gardens.
• Education in schools to change long term behaviour that encourages water conservation.
• Economic incentives e.g.:
  • Increasing the cost of water.
  • Installation of water meters which often reduces the amount of water used.
  • Fines for wasting water.