• Only 2.5% of all water on Earth is freshwater — the rest (97.5%) is salty ocean water.
• Most freshwater is locked away in glaciers/ice (68.7%) and groundwater (30%) — only 1.3% is in rivers, lakes, soil and the air, i.e. the water we can actually reach easily.
• We get our water from three main sources: lakes & rivers, aquifers (groundwater), and reservoirs — plus desalination and rainwater harvesting.
• Globally, 70% of water goes to agriculture, 20% to industry, 10% to domestic use — but this split flips in rich countries (MEDCs use more for industry) versus poor countries (LEDCs use more for farming).
• Global water demand has quadrupled since 1934, driven by population growth, rising living standards, and industrialisation.
• Water stress = below 1700 m³ per person/year. Water scarcity = below 1000 m³ per person/year.
• Scarcity comes in two flavours: physical (there just isn't enough water there) and economic (the water exists, but people can't afford to access it).
• Water shortages cause disease, conflict, lost schooling, food shortages, and slower development — the impacts ripple through everything.
• Solutions range from small-scale appropriate technology (wells, drip irrigation) in LEDCs to huge engineering projects like Spain's Tagus–Segura transfer in MEDCs.

🌍Why water feels abundant but actually isn't

Here's the thing that trips people up: Earth is called the "blue planet," 71% of its surface is water, and yet water shortage is one of the biggest global issues of our time. How does that make sense? The answer is that almost none of that water is drinkable or usable.

Think of it like being handed a giant swimming pool full of water but told you can only scoop out one small cup — and even that cup is mostly frozen solid or buried underground. That's essentially the situation with global water.

So of that already-tiny 2.5% freshwater slice, most is either frozen in glaciers or hidden underground as groundwater. The water in rivers, lakes and the air — the stuff we actually see, drink, and irrigate crops with most easily — is a sliver of a sliver: about 1.3% of freshwater, which works out to roughly 0.03% of all water on Earth.

🚰Where humans actually get their water from

The three main sources humans rely on are:

• Lakes and rivers — surface water, relatively easy to access but vulnerable to pollution and seasonal changes.
• Aquifers (groundwater) — water stored underground after filtering through soil and rock. When the rock is fully saturated, it's called an aquifer. Accessed via boreholes, wells, or natural springs.
• Reservoirs — artificial lakes created by building dams, used to store water for controlled release.

Other, less common sources include:

• Desalination — removing salt from seawater to make it usable.
• Rainwater harvesting — collecting precipitation directly, often on roofs, for storage and later use.

⚠️The problems each source faces

🏭Who uses all the water?

Globally, water use splits roughly like this: 70% agriculture, 20% industry, 10% domestic. That's the world average — but it hides a really important pattern that examiners love to test: the split looks completely different depending on how developed a country is.

Notice the flip: in MEDCs, industry dominates because these economies manufacture goods and generate energy at huge scale — both very water-hungry processes. In LEDCs, agriculture dominates because so many people still depend directly on farming for food and income, and there's simply much less heavy industry to compete for water.

📈Why demand for water keeps climbing

Between 1934 and 2014, global water demand quadrupled — from about 1 trillion m³ to 4 trillion m³ per year. That's not a small rise; it's a massive, sustained increase, and it hasn't leveled off. In MEDCs, this demand is pushed up by several forces acting together:

• Rising living standards — more households have appliances (washing machines, dishwashers) and better sanitation, all of which use water.
• Leisure and tourism — water parks, golf courses, and swimming pools consume large volumes purely for recreation.
• Urbanisation — more people concentrated in cities means more piped water demand.
• Growing industry — manufacturing and energy production both need water as an input.
• Agricultural intensification — more water needed for livestock and irrigated crops.

📊Getting the thresholds straight

This is one of the most commonly mixed-up parts of the topic, so let's nail the exact numbers. Water shortage isn't just one category — geographers use two specific thresholds, measured in cubic metres (m³) of water available per person, per year:

Think of it as two doors you pass through as things get worse: first you cross into "stress" (below 1700), and if the situation deteriorates further, you cross into full "scarcity" (below 1000). Scarcity is the more serious, more dangerous stage.

🔀Physical vs economic water scarcity

This distinction is a favourite exam question because it forces you to think about why water is scarce, not just that it's scarce. Two places can both be "water scarce" for completely different reasons:

• Physical water scarcity — the water genuinely isn't there. It's caused by the climate of the area: low rainfall, high evaporation, drought. Example: much of North Africa and the Middle East, where deserts simply don't receive enough precipitation.
• Economic water scarcity — the water actually exists nearby, but the population lacks the money, infrastructure, or technology to extract, treat, and distribute it. Example: parts of Sub-Saharan Africa where rivers or groundwater are present, but there's no funding for pumps, pipes, or treatment plants.

🗺️Where in the world is the water deficit worst?

Areas with the greatest water deficit include:

• Australia
• North, East and Southern Africa
• The Middle East
• Southwest USA
• East Brazil, parts of Argentina and Chile
• India

Notice the pattern: these areas tend to cluster around the Tropic of Cancer and Tropic of Capricorn. This isn't a coincidence — these latitudes coincide with the world's major desert belts (the Sahara, Arabian, Kalahari, Australian deserts), where high pressure systems suppress rainfall and evaporation rates are very high.

🔍What causes a water deficit?

Water deficit boils down to an imbalance between supply and demand. It happens through:

Beyond this basic supply/demand imbalance, a few extra factors make things worse in specific places:

• Transboundary rivers — when a river flows through multiple countries, the upstream country can take large amounts of water, build dams that alter downstream flow, or pollute the river, leaving less (and lower quality) water for countries downstream. This is a major source of international tension.
• Higher temperatures — increase evaporation and transpiration, reducing the amount of water actually available even where rainfall hasn't changed.
• Land use — agriculture in particular drives up consumption significantly.
• Uneven distribution within a country — for example, China has severe shortages in the north but relative abundance in the south.
• Conflict — many LEDCs that failed to meet international water access targets are also experiencing conflict, which disrupts infrastructure and management.

💥The knock-on impacts of water shortage

Water shortage isn't just an inconvenience — it triggers a chain reaction across health, education, food, environment and economy:

• Health: Death and illness from waterborne diseases such as cholera and dysentery, often caused by using contaminated water when clean supplies aren't available.
• Conflict: Potential for disputes over shared water supplies, especially in transboundary river basins.
• Education: In rural LEDCs, children (often girls) are frequently responsible for collecting water and may walk miles daily, missing out on school as a result.
• Food security: Crops can't be irrigated so yields fall, and livestock die from lack of water — leading to food shortages.
• Environment: Damaged ecosystems and loss of habitats as water bodies shrink or dry up.
• Economy: Delayed economic development because industry can't function without a reliable water supply.

🛠️Managing water sector by sector

Water management strategies differ depending on the sector using the water — and, crucially, on whether the country can afford them.

• Industry: Recycling water within industrial processes so it's reused rather than discharged after a single use, cutting overall consumption.
• Agriculture: Drip irrigation delivers water directly to plant roots through small tubes, rather than spraying or flooding fields. Regular irrigation loses around 40% of water to evaporation and poor management — drip irrigation cuts this loss dramatically.
• Domestic: Water-efficient appliances, rainwater collection, reusing "grey water" (used household water) for washing cars or watering plants, low-flush toilets, water-saving shower heads, and water companies actively fixing leaks in the distribution network.

🌍The MEDC–LEDC funding gap

Here's the reality check that ties this whole topic together: managing water well costs money. MEDCs can afford large-scale engineering — reservoirs, pipelines, desalination plants, leak-detection technology. LEDCs often can't, so water management there relies much more heavily on NGOs (Non-Governmental Organisations, such as Water Aid) providing funding, and on appropriate technology — solutions that are cheap, simple to maintain, and suited to local conditions.

Examples of appropriate technology in LEDCs include:

• Wells — simple dug or drilled access points to groundwater.
• Gravity-fed systems — water is piped from a spring or river higher up a valley, using gravity rather than expensive pumps to move it downhill to communities.
• Boreholes with hand pumps — bring groundwater to the surface without needing electricity.
• Rainwater collection from roofs — a cheap, low-tech way to capture and store rainfall.
• Drip irrigation — even in LEDCs, this can be implemented cheaply using simple tubing.
• Drought-resistant crops — reduce the amount of water agriculture needs in the first place.

🇪🇸The problem: southeast Spain's water deficit

Southeast Spain is one of the driest regions in Europe, receiving an average of only about 365 mm of rainfall a year, most of which falls in winter. This creates a serious mismatch:

• Agriculture uses 80% of the water available in the region, with 147,000 hectares of farmland requiring irrigation.
• Regular droughts reduce supply even further on top of the already-low baseline rainfall.
• The result is a clear water deficit — demand consistently exceeds supply.
• Tourism makes it worse: water parks and golf courses consume huge quantities of water. An average tourist uses between 450–800 litres per day, compared to just 127 litres per day for an average Spanish resident — meaning tourists can use up to six times more water daily than locals.

🚧The solution: the Tagus–Segura Project

Spain's answer to this deficit was a major inter-basin water transfer scheme:

• Completed in 1978.
• A 286 km pipeline connecting four Spanish river basins: the Tagus, Jucar, Segura, and Guadiana.
• Over 60% of the water flowing into the Tagus river is transferred elsewhere.
• The goal was to supply the drier southeast — specifically Alicante, Murcia, and Cartagena — to reduce their water deficit.

⚠️But the scheme created new problems

Transferring water didn't just solve the shortage cleanly — it introduced fresh issues:

• Much of the transferred water went to tourist and leisure users rather than small-scale farmers who needed it most.
• Ironically, water consumption in the southeast increased simply because supply increased — people used more because more was available (a classic case of supply driving demand rather than the other way round).
• An estimated 15% of the transferred water is used illegally by leisure users such as golf courses.
• Large commercial farms benefited more than small-scale farmers, worsening inequality in water access.

🛑The Ebro Project — a scheme that never happened

In 2001, a second water transfer project was proposed to bring water from the River Ebro. It was ultimately abandoned for three main reasons:

• The visible failure and controversies surrounding the Tagus–Segura project (illegal use, benefiting the wrong users) made planners cautious.
• The cost of another large transfer scheme was very high.
• It posed a threat to the Ebro Delta, since the scheme would have disrupted the natural sediment flow that sustains the delta ecosystem.

Since then, Spain has shifted strategy towards desalination plants to help meet water demand — a technologically different approach that doesn't rely on taking water away from one river basin to give to another, though it comes with its own high energy costs.

• I can state what % of Earth's water is freshwater, and where most of that freshwater is stored.
• I can name the three main sources humans get water from (lakes/rivers, aquifers, reservoirs) plus two extra sources.
• I can explain the problems associated with groundwater use (over-abstraction, pollution).
• I can explain the problems associated with surface water and desalination.
• I know the global water use split (70/20/10) and how it differs between MEDCs and LEDCs.
• I can explain why water demand is higher in MEDCs than LEDCs.
• I know the exact thresholds for water stress (1700 m³) and water scarcity (1000 m³) per person/year.
• I can distinguish physical water scarcity from economic water scarcity, with an example of each.
• I can name regions of the world with the greatest water deficit and explain the latitude pattern.
• I can explain how transboundary rivers cause water supply conflicts.
• I can describe at least four different impacts of water shortage across different categories (health, education, food, economy, environment).
• I can describe management strategies for industry, agriculture, and domestic water use.
• I can explain what "appropriate technology" means and give examples used in LEDCs.
• I can describe the causes of Spain's water deficit, including the role of tourism.
• I can describe the Tagus–Segura Project (key facts, figures, and route).
• I can evaluate the Tagus–Segura Project, including its problems (illegal use, benefiting wrong users, increased consumption).
• I can explain why the Ebro Project was abandoned.