Water insecurity, water stress, and water scarcity

Humans depend on freshwater for drinking, agriculture, industry, and sanitation. However, the global distribution of freshwater does not match the distribution of the world's population. This mismatch means that some regions have more water than they need, while others face serious shortages.

Key definitions

• Water insecurity - A situation in which water supply cannot meet demand, either because there is not enough water or because the water available is not of sufficient quality for use
• Water stress - Occurs when demand for water exceeds supply, or when water quality is too poor to use. It is defined as less than 1,700 m³ of water available per person per year
• Water scarcity - A more severe condition where available water falls below 1,000 m³ per person per year

Factors that determine the level of water stress in a region

• High water stress - Found in areas with low water availability and/or high demand, such as Mexico and India
• Low water stress - Found in areas with high water availability and/or low demand, such as Brazil and Russia
• Limited water stress despite low availability - Some places, such as Kenya, have low water availability but also low demand, which limits the level of stress experienced

Water stress is most likely to occur in areas that combine high population density with unreliable or low water supplies.

Physical and economic water scarcity

• Physical water scarcity - There is not enough freshwater held in rivers, streams, lakes, and groundwater to meet demand. This tends to occur in countries with low rainfall and high levels of evapotranspiration – the combined loss of water through evaporation and plant transpiration. Saudi Arabia is an example
• Economic water scarcity - Freshwater exists in rivers, streams, lakes, and groundwater but is inaccessible because there is a lack of investment in the technology needed to extract and transport it. Many developing countries in Sub-Saharan Africa experience this form of scarcity

Physical factors causing water insecurity

Several natural processes and environmental conditions influence whether a region has sufficient freshwater to meet the needs of its population.

Climate and rainfall

The climate of a region – particularly its rainfall patterns – is a key driver of water insecurity.

How climate affects water availability:

• Places that receive higher rainfall generally have greater access to freshwater and a lower risk of water insecurity
• Rapid rates of direct runoff cause river water to discharge quickly into the sea, making it harder for humans to extract and use
• High rates of evaporation from lakes and reservoirs can prevent water levels from reaching a sustainable point for human use
• Unpredictable seasonal rainfall increases vulnerability to water insecurity, as seen in the Sahel region of Africa

Water quality and warming

Where water stores such as lakes and reservoirs experience falling water levels, the remaining water is likely to be warmer because shallower water requires less energy to heat. Warmer water allows bacteria to multiply more rapidly, which can make the water harmful to human health if it is used for consumption.

Saltwater encroachment

Rising sea levels have increased the risk of saltwater encroachment on freshwater aquifers – underground layers of permeable rock that store water. This process occurs when saltwater is drawn into aquifers to replace freshwater that humans have extracted. Wells dug into these aquifers then become contaminated with salt, reducing the supply of usable freshwater. Bangladesh is a notable example of this problem.

Case study: Climate variability in California

California illustrates how physical factors can drive water insecurity even in a wealthy, developed region.

Key details:

• California has experienced a greater range of precipitation levels throughout the 21st century, while demand for water remains high – primarily for crop irrigation
• Climate change has increased atmospheric temperatures, raising the rate of evaporation from California's main reservoirs
• Shasta Lake, in the north of the state, fell to 31% capacity in 2022 – its lowest level since records began
• Of the 20 warmest years on record in California, 11 have occurred since 2000
• Low rainfall has also increased the risk of wildfires. In 2020, the August Complex wildfire stretched for over 1 million acres

Human factors causing water insecurity

Human activities can reduce both the quantity and quality of available freshwater, contributing significantly to water insecurity.

Chemical pollution of freshwater sources

Chemical pollution contaminates freshwater and reduces the supply of safe water available for use.

Common sources of chemical pollution:

• Agricultural runoff - Water running off farmland may contain pesticides or livestock waste, which can cause algal blooms in water courses
• Industrial discharge - Industries that use water as a coolant may release contaminated water back into freshwater systems
• Domestic wastewater - Homes connected to river systems can introduce pollutants directly into waterways

In countries where wastewater management has been poorly developed, pollution levels are even greater, further reducing the supply of safe freshwater.

Groundwater contamination

Groundwater supplies can become contaminated with heavy metals such as arsenic or lead. These metals tend to accumulate in groundwater when industrial waste is buried or dumped and precipitation washes through the waste material, carrying pollutants downward into the water table.

Over-abstraction

Over-abstraction occurs when populations extract too much water from rivers, lakes, and aquifers. This means that these water stores cannot be replenished quickly enough to avoid water stress. Where communities share a water source such as a river, people living downstream may find their capacity to meet water needs significantly reduced.

Hydroelectric power

Hydroelectric power plants hold water back in reservoirs to generate electricity. This can restrict the flow of water downstream, causing water stress for communities that depend on those rivers.

Case study: Over-abstraction from the Aral Sea

The Aral Sea – a former large lake on the border between Kazakhstan and Uzbekistan – provides a dramatic example of how over-abstraction can cause water insecurity.

Background:

• The Aral Sea was once the world's fourth largest inland lake, with an area of 68,000 km² in 1960
• Mountains to the east of the Aral Sea basin feed the lake with snowmelt during the summer months

Causes of shrinkage:

• In the 1960s, irrigation canals were built to divert water from the main rivers feeding the lake to surrounding cotton fields
• Most of the diverted water was lost through leaks in the canals
• In July, temperatures around the Aral Sea frequently reach around 30 °C, causing further water loss through evaporation
• The diversion of water meant the lake was no longer recharged

Result:

• Between 1960 and 2010, the Aral Sea shrunk to around 10% of its original size

Rising global demand for water

Global demand for water is increasing due to a combination of demographic, economic, and social changes. These pressures are intensifying water stress and water scarcity in many regions.

Drivers of increasing water demand

According to the UN, over 2 billion people worldwide live in countries classified as 'water-stressed'.

Additional factors driving demand

• New energy extraction methods - Processes such as fracking require large amounts of water
• Urbanisation - The growing global population is becoming increasingly urbanised. Urban areas contain dense living conditions where water demand is concentrated around a limited number of water stores

Water prices and access to water

Water has become an expensive commodity in some countries and regions, despite many people viewing clean water as a human right. In many countries, including the UK, water is supplied by private companies as a commercial product.

Factors that influence the cost of water

• Transport costs - Moving water from its source to where it is needed requires infrastructure such as pipelines and canals. In some cases, water is transferred long distances by road tanker or ship
• Market-driven pricing - In some areas, water prices rise as demand increases and supply becomes scarcer
• Source access costs - Extracting water at its source can be expensive. Digging wells and creating standpipes – vertical water pipes – can be costly for communities in developing countries
• Purification costs - The more polluted the water, the more expensive it is to purify and make suitable for use

How pricing structures vary

• Bulk purchasing can reduce the price per unit, meaning farmers may receive water at a lower price than householders
• Local governments may subsidise water costs for certain industries to encourage economic growth
• Households also face costs beyond the water itself, including investment in pipework, taps, sinks, water storage units, and toilets

The consequences of rising water costs

The growing cost of water means that poorer people in developing countries are more likely to rely on insufficient, poor-quality water supplies.

Potential benefits of treating water as a commodity:

• If people must pay for water, they are more likely to conserve it
• Water companies may compete to produce a higher quality product and have an incentive to maintain supply infrastructure to a high standard, minimising losses through leaks

The Water Poverty Index

The Water Poverty Index (WPI) is an international measure used to assess water security. It gives an overall score out of 100 based on five components, with higher scores indicating greater water security.

The five components of the WPI

WPI scores are often displayed using a radial graph, which is a chart shaped like a pentagon with each axis representing one of the five components. This allows the water security profiles of different settlements or countries to be compared visually.

Patterns in WPI scores

Developing countries tend to have lower WPI scores than developed countries. This is because developed countries usually have established water infrastructure and management networks that ensure greater access, capacity, and resource quality.