Strategies to increase water supply to include catchment, diversion,…

The idea

To combat water insecurity, various strategies are employed to increase supply. Catchment involves collecting precipitation directly, often through rooftop harvesting or land contouring. Diversion redirects surface water from rivers to agricultural or urban areas, while storage utilises dams and reservoirs to hold water during surplus periods for use during deficits. Water transfers operate on a larger scale, moving water from basins with a surplus to those with a deficit, such as China's South-North Water Transfer Project. Desalination removes dissolved salts from seawater using reverse osmosis, providing a climate-independent freshwater source for arid, coastal nations, though it requires significant energy inputs and produces hypersaline brine.

What earns the marks

• Describe catchment strategies, such as rainwater harvesting, which collect precipitation before it becomes surface runoff.
• Explain how diversion and storage systems, including dams and reservoirs, manage seasonal variations in water availability.
• Evaluate the socio-economic and environmental impacts of large-scale water transfer schemes moving water from surplus to deficit basins.
• Analyse the process of desalination, highlighting its role in providing climate-independent water supplies alongside its high energy costs.

Common mistakes and how to put them right

• Confusing water diversion with water transfer.

  Put it right: Diversion typically redirects water locally for immediate use, whereas transfers move water between entirely different drainage basins.

• Assuming desalination is a universal solution; failing to acknowledge that its high energy cost and coastal requirement limit its viability for landlocked or low-income countries.

• Overlooking the environmental impacts of storage; students often forget that dams disrupt sediment transport and aquatic ecosystems.

Exam tips

• Memorise a specific, named example for a large-scale water transfer scheme, such as the Lesotho Highlands Water Project, to support your evaluation.
• When discussing desalination, explicitly mention reverse osmosis and the environmental challenge of disposing of hypersaline brine.
• Compare the sustainability of different strategies, contrasting the low environmental impact of local catchment with the high ecological footprint of mega-dams.