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examBoard: Cambridge
examType: IGCSE
lessonTitle: Water Supply Enhancement Strategies
Water is essential for all life on Earth, yet many regions face water scarcity due to growing populations, climate change and pollution. Water supply enhancement strategies are methods used to increase the availability of freshwater for human use, agriculture and industry.
Key Definitions:
Over 2 billion people live in countries experiencing high water stress. By 2025, half of the world's population will be living in water-stressed areas. This makes water supply enhancement crucial for human survival and development.
While 71% of Earth is covered in water, only 2.5% is freshwater. Of this freshwater, 68.7% is frozen in ice caps, 30.1% is groundwater and only 1.2% is surface water in lakes, rivers and swamps.
Dams and reservoirs are among the oldest and most widely used methods of enhancing water supply. They store water during rainy seasons for use during dry periods and can also generate hydroelectric power.
A dam is a barrier built across a river to hold back water, creating a reservoir or artificial lake behind it. Water from the reservoir can be released in a controlled manner for various purposes including drinking water supply, irrigation and power generation.
Built across the Nile River in 1970, the Aswan High Dam created Lake Nasser, one of the largest artificial lakes in the world. It provides water for irrigating 2.1 million hectares of farmland and generates about 10% of Egypt's electricity. However, the dam has trapped nutrient-rich silt that once fertilised farmland naturally, leading to increased use of chemical fertilisers. It has also caused coastal erosion in the Nile Delta and displaced over 100,000 people during construction.
Groundwater is water found underground in the cracks and spaces in soil, sand and rock. It is stored in and moves slowly through geologic formations called aquifers.
Humans access groundwater through wells, boreholes and springs. Modern extraction often involves drilling deep wells and using pumps to bring water to the surface.
Overextraction of groundwater can lead to serious problems including:
The Ogallala Aquifer underlies eight states in the Great Plains of the USA and supplies water for about 30% of all irrigation in the United States. Since large-scale pumping began in the 1950s, water levels have declined by more than 30 metres in some areas. The aquifer is being depleted at a rate of approximately 12 billion cubic metres per year, with recharge rates far below extraction rates. This has led to concerns about the long-term viability of agriculture in the region.
Rainwater harvesting is the collection and storage of rainwater for reuse on-site, rather than allowing it to run off. It is one of the simplest and oldest methods of self-supply of water for households and communities.
These systems can range from simple rain barrels to complex arrangements with filters, pumps and treatment systems.
Small-scale systems for individual homes typically include:
Larger systems for communities or agriculture may include:
Desalination is the process of removing salt and other minerals from seawater or brackish water to make it suitable for human consumption or irrigation.
There are two main approaches to desalination:
Uses heat to evaporate water, leaving salt behind. The water vapour is then condensed to produce freshwater. Methods include:
Uses semipermeable membranes to separate salt from water. The main method is:
While desalination provides a reliable source of freshwater independent of rainfall, it comes with significant challenges:
Singapore has developed an innovative water recycling system called NEWater, which purifies treated wastewater using advanced membrane technologies. The process includes microfiltration, reverse osmosis and UV disinfection. NEWater now meets about 40% of Singapore's water needs and is primarily used for industrial purposes and indirect potable use (by adding it to reservoirs). This approach, combined with desalination, rainwater harvesting and imported water, has helped Singapore reduce its dependence on water imports from Malaysia.
Water transfer schemes move water from areas of abundance to areas of scarcity through canals, pipelines, or aqueducts. These can operate on small local scales or as massive inter-basin transfers.
Water transfer projects vary greatly in scale and complexity:
China's South-North Water Transfer Project is the largest water transfer scheme in the world. It diverts water from the Yangtze River in southern China to the more arid northern regions through three canal routes spanning thousands of kilometres. The eastern and central routes are already operational, delivering water to Beijing and other northern cities. The project has cost over $62 billion so far and has required the relocation of hundreds of thousands of people. While it has helped address severe water shortages in northern China, it has also raised concerns about ecological impacts on the Yangtze River basin and the long-term sustainability of such massive engineering solutions.
Modern water management increasingly focuses on combining multiple strategies and considering the entire water cycle rather than implementing single solutions.
Effective water supply enhancement should consider:
There is no single "best" water supply enhancement strategy. The most appropriate approach depends on local conditions including climate, geography, available resources and social factors. Sustainable water management requires balancing human needs with environmental protection and considering both short-term demands and long-term sustainability. As climate change alters rainfall patterns and increases water stress in many regions, adaptive and integrated approaches to water management will become increasingly important.
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