Global Water Distribution, Consumption and Insecurity

Water availability is about supply, demand and quality

Water is needed for drinking, cooking, washing and sanitation, but also for growing food, manufacturing goods and generating energy. Only about 2.5% of Earth's water is freshwater, and freshwater supplies are unevenly distributed.

A water surplus occurs where available supply exceeds demand. A water deficit occurs where demand exceeds available supply. These are relative measures: a place with considerable rainfall can still experience a deficit if its population, farms and industries need more water than can be supplied.

Water security means reliable access to sufficient clean water. Quantity alone is not enough. A river may contain plenty of water, but pollution or a lack of pipes and treatment facilities can prevent people from using it safely. Water insecurity therefore involves problems with quantity, quality or access.

The global pattern of surplus and deficit

Water surplus is common in wet regions and in places where demand is relatively low. The Amazon rainforest region of Brazil has abundant rainfall. Canada and parts of the northern USA, together with Russia, also contain extensive areas of surplus. Cooler conditions reduce evaporation, while relatively low population densities in many areas limit demand.

Deficits are common in dry regions with low rainfall and high evaporation, including the Middle East, North Africa, western USA and parts of Australia. Parts of East and southern Africa, India and South America also experience deficits. Here, shortages can reflect a combination of limited supply, high demand and difficulties accessing water.

These are broad regional patterns, not descriptions of every place within a country. Availability can also change through the year: a wet season may replenish stores, whereas a long dry season reduces river flows and groundwater recharge. The important comparison is between usable supply and demand in a particular place and period.

Why water consumption is increasing

Population growth increases domestic demand because more people need water for drinking, cooking, washing and sanitation. Its effects extend beyond households: feeding a larger population requires more agricultural production, while supplying goods and energy increases industrial water use.

Economic development also increases consumption. As incomes rise, more households can afford showers, flushing toilets, washing machines and dishwashers. Expanding factories use water in production, and electricity generation may require water for cooling. More intensive farming and irrigation increase agricultural demand. Urban growth concentrates these demands in towns and cities.

Globally, approximately 70% of water use is agricultural, 20% industrial and 10% domestic. The proportions vary between countries, but the global pattern shows why rising demand for food and manufactured goods matters as well as household consumption.

Physical factors affecting availability

Climate controls how much water enters and leaves water stores. Precipitation supplies rivers and replenishes groundwater. Low rainfall limits this replenishment, while high evaporation and water loss from plants reduce the amount remaining available. Drought can therefore turn a previously adequate supply into a shortage.

Geology affects the storage and movement of groundwater. Permeable rocks allow water to enter pores or cracks and may form aquifers. The type and arrangement of rocks influence where groundwater is stored and how much can be accessed. Rainfall alone therefore does not determine whether a place has useful underground supplies.

Human factors affecting availability

Pollution of supply reduces the amount of usable water. Untreated sewage, industrial waste, pesticides and fertilisers can contaminate rivers and groundwater. Water may still be physically present but unsafe to drink without treatment.

Over-abstraction occurs when people remove water faster than it is replaced. For example, pumping groundwater for irrigation can lower underground stores if recharge cannot keep pace. This reduces the supply available for future use and for other users.

Limited infrastructure prevents available water from reaching people safely. Pipes, pumps, canals and treatment works are expensive to build and maintain. Rural and remote communities can be particularly difficult to serve. Infrastructure limitations occur in some higher-income countries as well as in lower-income countries and newly emerging economies.

Poverty restricts both public provision and household access. Communities may lack investment in water systems, while households may be unable to afford a clean supply. This explains why people can be water insecure even in a region with substantial freshwater resources.

Pollution and waterborne disease

Water insecurity can force people to rely on contaminated supplies. Where treatment, sanitation and waste disposal are inadequate, sewage and other pollutants enter water sources. Pollution is therefore both a cause of insecurity and a problem associated with inadequate water and sanitation provision.

Drinking contaminated water can spread diseases such as cholera, typhoid fever and dysentery. Diarrhoea can cause severe dehydration and may be fatal. Illness also prevents people from working, reducing household income and making it harder to pay for safe water.

These effects are often greatest in lower-income countries and newly emerging economies where treatment and healthcare resources are limited, although water insecurity is not confined to these countries.

Effects on food production and industrial output

When water is scarce, farmers may have to reduce irrigation or stop it altogether. Crops receive less water, so yields fall and crops may fail. Reduced harvests can create food shortages and increase prices, while farmers lose income.

Industry also depends on reliable supplies. A shortage can interrupt production and reduce industrial output, lowering business earnings and national income. Electricity supplies may be disrupted where water is needed for cooling or where reduced river flows limit hydroelectric generation. These interruptions can then affect other businesses.

Why shortages can lead to conflict

Where demand exceeds supply, households, farms, industries and regions may compete for the same water. Competition can also cross national borders because rivers and aquifers are shared.

An upstream country can reduce the amount reaching a downstream country by abstracting water or storing it behind dams. Pollution upstream can also reduce the quality of downstream supplies. The downstream country may then struggle to meet its own needs, creating tension over how the resource should be shared.

For example, dams on the Tigris and Euphrates rivers in Türkiye have affected water flows into Syria and Iraq. This illustrates why water management in one country can have consequences beyond its borders. Shortages create the potential for conflict, but do not mean that conflict must occur.

Supply, demand and access

• Surplus: available supply exceeds demand.
• Deficit: demand exceeds available supply.
• Security: sufficient clean water is reliably accessible; abundant water alone does not guarantee this.

Global patterns

• Surplus: Amazon rainforest region, Canada, parts of northern USA and Russia.
• Deficit: Middle East, North Africa, western USA and parts of Australia, East and southern Africa, India and South America.
• Patterns vary within countries and between seasons.

Rising consumption

• Population growth: more domestic use, food production, industry and energy demand.
• Economic development: more water-using appliances, factories and intensive farming.
• Global use: approximately 70% agriculture, 20% industry, 10% domestic.

Availability: six factors

• Climate: rainfall replenishes stores; evaporation and drought reduce supply.
• Geology: controls groundwater storage and movement.
• Pollution: makes supplies unsafe or costly to treat.
• Over-abstraction: withdrawals exceed replenishment.
• Limited infrastructure: restricts treatment and distribution.
• Poverty: limits investment and affordability.

Impacts of insecurity

• Contaminated supplies → waterborne disease → illness, deaths and lost income.
• Less irrigation → lower yields or crop failure → shortages and higher food prices.
• Unreliable industrial supplies → reduced output, income and possible electricity disruption.
• Demand exceeding supply → competition and potential conflict, especially over shared rivers.
• Example: Türkiye's dams on the Tigris and Euphrates affect flows into Syria and Iraq.