Thirsty planet: understanding water demand, supply and scarcity in the 21st century
- Tom McAndrew
- 13 minutes ago
- 9 min read
Water is ordinary until it isn’t. For most of human history, rivers, springs and rain felt inexhaustible: they shaped where we settled, fed our crops, and powered early industry. Today those assumptions no longer hold. Rising demand, changing climates, ageing infrastructure and deep inequalities mean that water is now one of the defining environmental and social challenges of our time. This article explains, in plain, exam-friendly language, how water is used, why shortages happen, and what that means for people, farms and cities. I’ll draw on the latest global evidence so you can connect ideas to real-world numbers and case studies.
How much water do we actually use?
When we talk about 'water demand' we mean the water people, businesses and ecosystems need for different purposes, drinking and washing, growing food, cooling factories and producing electricity. Not all uses are equal. Agriculture is by far the biggest user worldwide: roughly seven out of every ten litres withdrawn from rivers, lakes and aquifers are used to grow crops and feed livestock. Industry accounts for just under one fifth of withdrawals, while domestic or municipal use — homes, schools and hospitals, is around 10–12%. These global averages hide large differences: in dry, agricultural countries the share for farming can be far higher, while industrialised nations often show larger industrial shares. UNESCO+1
Understanding those proportions is important. If agriculture uses 70% of freshwater on average, even modest gains in irrigation efficiency can free up water for towns, ecosystems and industry. But efficiency gains can be complicated: sometimes they reduce waste, sometimes they enable farmers to expand irrigated area, which can negate the savings, a phenomenon known as the rebound effect.
Where does our water supply come from?
Freshwater for people and farms comes from several sources: surface water (rivers and lakes), groundwater (aquifers beneath the ground), and increasingly non-conventional sources such as desalinated seawater and reclaimed wastewater. Groundwater is especially important for household water supplies: in many regions it supplies roughly half of domestic demand. In agriculture, groundwater irrigation accounts for about a quarter of global irrigation water, though again this varies hugely by country and region. Aquifers are the unsung reservoirs, they buffer droughts and supply millions of wells — but many are being pumped faster than they are recharged. UNESCO+1
The balance between supply and demand is not static. Rainfall, snowpack and glacier melt control how much water enters rivers and aquifers each year; humans control how much is withdrawn. In places that rely on seasonal snow and glacial melt, warming winters and shrinking glaciers are changing the timing and amount of runoff, creating shortages at the times when water was previously dependable.
Who is affected: scale and inequality
You might be surprised to learn just how many people face poor water access. Globally, billions of people still lack safely managed drinking water and basic sanitation. Recent UN/WHO estimates suggest that more than two billion people do not have safely managed drinking-water services, and progress remains uneven, gains in some regions are offset by stagnation or regress elsewhere. At the same time, studies find that roughly half of the global population experiences severe water scarcity for at least one month each year. That means water shortages are not confined to a handful of desert nations; they affect people in cities, farming regions and industrial heartlands across the world. United Nations+1
Water scarcity often maps onto inequality. Households in wealthy neighbourhoods can tap into reliable piped networks and bottled supplies; poorer communities may rely on distant wells, contaminated sources, or expensive water delivered by truck. Women and girls disproportionately shoulder the burden of water collection where services are lacking, with consequences for education and health. Rural communities depending on rainfall or small rivers are particularly vulnerable to seasonal drought, while many urban systems struggle with leaks and underinvestment even when water is theoretically available in the basin.
Why scarcity is growing: demand up, supply uncertain
Several interacting forces are pushing water scarcity to the top of the political agenda.
First, demand keeps rising. Growing populations, urbanisation and changes in diets (more meat and processed food) increase the water needed for food production. Economic development and industrial growth raise municipal and industrial water use per person. Globally, freshwater demand has grown at just under 1% per year over recent decades, and that steady growth compounds into significant increases over time. UNESCO
Second, climate change is altering water supplies. Warmer temperatures increase evaporation and change precipitation patterns; some regions get wetter, others drier. The World Meteorological Organization reported that 2023 was among the driest years for many of the world’s rivers in the past three decades, driven by record-high temperatures and widespread droughts. That kind of variability undermines river flows, dries reservoirs, and stresses irrigation systems that were designed for the climate of the past. Melting glaciers, which act like slow-release reservoirs feeding rivers in summer — are retreating fast, threatening water supplies for regions that currently rely on seasonal meltwater. AP News+1
Third, groundwater depletion is a hidden crisis. In many farming regions, intensive irrigation has caused water tables to fall as aquifers are pumped faster than they recharge. Unlike a drained reservoir which you can see, falling groundwater is invisible until wells begin to run dry or require deeper drilling, a costly adaptation that favours wealthier farmers and leaves smallholders vulnerable.
Finally, human mismanagement and policy failure are major contributors. Water is often underpriced, leading to wasteful use; infrastructure is neglected; water rights and allocations can be poorly enforced. Competing users, farmers, cities, industries and ecosystems, often lack transparent rules for sharing limited supplies, which fuels conflict and inefficiency.
Types of scarcity: physical, economic and quality-related
Water scarcity is not a single thing. Physical scarcity occurs when natural water resources are insufficient to meet demand, arid regions with low rainfall or basins over-allocated to irrigation typify this. Economic scarcity happens when water is available but people lack the infrastructure, institutions or money to access it, think of rural villages with abundant groundwater that remains untapped because there is no well or pump. Finally, water quality scarcity arises when pollution makes water unsafe for drinking, irrigation or wildlife, industrial discharge, untreated sewage and agricultural runoff can all degrade usable supplies.
Understanding these distinctions matters for solutions. Building a desalination plant might help in a physically scarce coastal city, but it won’t solve the needs of a landlocked rural community suffering economic scarcity. Cleaning polluted rivers requires stronger regulation and investment in wastewater treatment.
The food–water–energy nexus
Water doesn’t exist in isolation: it is linked to food and energy. Irrigation uses most freshwater globally, so food security depends on water availability. At the same time, energy production, through hydropower, cooling for thermal power plants, or pumping and treating water, consumes large quantities of water. Policies that ignore these links can create perverse outcomes: promoting biofuels, for instance, increases water demand in already stressed basins; intensive hydropower development can alter river flows needed for downstream agriculture.
These interconnections mean that decisions in one sector ripple into the others. Smart policy needs integrated planning, not siloed targets.
Examples that illustrate the problem
Some of the clearest examples are striking because they reveal conflicts between rising demand and shrinking reliability. The Colorado River basin in the western United States, once seen as an abundant source for multiple states and Mexico, now faces years of drought and long-term declines in snowpack that have cut inflows to reservoirs. Major cities and farms that rely on the Colorado have had to negotiate unprecedented cuts and rethink their water use.
In parts of South Asia and the Middle East, intensive groundwater pumping for high-value crops has led to falling water tables, forcing farmers to drill deeper wells. In several countries, groundwater decline is so severe it threatens future agricultural productivity.
At the global scale, the World Resources Institute’s Aqueduct tool shows that around two dozen countries experience extremely high water stress each year, that’s groups of nations where human use approaches the limit of available supply and where any additional drought or infrastructure failure can have cascading effects. Meanwhile, studies and UN reports estimate that roughly half of the world’s people experience severe water scarcity for at least one month a year, and that billions still lack safely managed drinking-water services. Those statistics make clear why water is a security, development and humanitarian issue. wri.org+1
Coping strategies: supply-side and demand-side measures
Responses to water scarcity can broadly be grouped into supply-side and demand-side measures, though the best solutions usually combine both.
Supply-side interventions expand or stabilise available water. They include building reservoirs, inter-basin transfers, desalination, and wastewater reuse. Desalination has become a lifeline for some coastal cities and countries, but it is energy-intensive and costly, with environmental trade-offs from brine discharge. Reusing treated wastewater, for industry, irrigation or even indirect potable use, is gaining traction as a circular approach that reduces the pressure on freshwater sources.
Demand-side measures aim to reduce or reshape water use. Smarter irrigation techniques (drip irrigation, precision scheduling), improved crop choices, and reducing leaks in urban distribution networks can radically lower demand. Pricing that reflects the real cost of water, combined with social protections for the poorest, can reduce wasteful consumption without denying basic services. Behavioural change campaigns and technological innovation (soil moisture sensors, satellite irrigation monitoring) also play a role.
Importantly, nature-based solutions are increasingly promoted: restoring wetlands, reforesting catchments, and protecting soils can improve natural water storage, slow runoff and enhance groundwater recharge. These measures often bring co-benefits for biodiversity and climate adaptation.
Governance, institutions and the politics of water
Technical fixes alone are rarely enough. Water governance, the rules, organisations and social arrangements that determine how water is allocated and managed, is central. Clear allocation systems that define who can use what water, when and under what conditions reduce conflicts. Effective monitoring (of river flows, groundwater levels and water quality), transparent data, and accountable institutions allow societies to make evidence-based decisions.
Transboundary basins, rivers and aquifers shared by more than one country, pose particular challenges. Cooperative treaties (like those managing parts of the Nile, Mekong or Rhine) can facilitate joint management, but politics can derail agreements when water becomes scarce. Many experts now argue for ‘water diplomacy’ that links basin management with climate adaptation and development planning.
Looking ahead: risks, opportunities and responsibilities
Projections vary, but many analyses warn that without major changes, freshwater demand will increasingly outstrip reliable local supply in several regions. Some reports predict that by 2030–2050 the gap between freshwater demand and supply could be wide in many basins, putting food production and urban supplies at risk. The combination of climate change, population growth and changing diets makes this a credible worst-case scenario unless policy, technology and behaviour change.
Yet there are opportunities. Improved irrigation techniques, wastewater recycling, stronger governance and investments in resilient infrastructure could blunt the worst impacts. Cities can become water-smart through leak reduction, stormwater harvesting and reuse. Agricultural systems can shift towards less water-intensive crops or adopt water-sharing schemes that reward conservation. International cooperation and finance can help poorer countries invest in safe supplies and sanitation.
For you as an A-level student, this is a powerful and practical topic: it connects physical geography (hydrology, climate) with human geography (policy, inequality, development). It also offers rich case-study material for exam essays: contrast a water-rich country with a water-stressed basin, discuss the trade-offs of desalination, or analyse how climate change might alter water availability in a mountain-fed river system.
The future is not predetermined
Water scarcity is a test of human adaptability and fairness. The physical drivers are real, climate change, glacier melt, and variability in rainfall, but how societies respond will determine outcomes. Investments in infrastructure, smarter agricultural practices, equitable allocation rules and international cooperation can avert the most damaging impacts. Conversely, ignoring the links between food, energy and water, or failing to address inequality, risks locking in deeper scarcity and social stress.
Water is a connector, between ecosystems and economies, between cities and farms, and between present needs and future resilience. Understanding the numbers (how much water agriculture uses, how many people lack safe services) is essential, but so is analysing the social and political choices that decide who gets water and who doesn’t.
Selected sources and further reading
United Nations World Water Development Report 2024 — statistics and findings on global water demand, withdrawals by sector, and access. UNESCO+1
FAO AQUASTAT — global data on water use by sector, sources, and country-level databases for irrigation and withdrawal statistics. FAOHome+1
World Resources Institute — Aqueduct Water Risk Atlas and analysis of countries facing extremely high water stress. wri.org+1
Intergovernmental Panel on Climate Change (IPCC) AR6 synthesis — assessments of climate impacts on water systems and risks to water security. IPCC+1
World Meteorological Organization / news reporting (WMO, AP) — reports on river flows and drought in 2023 and projections for water access under climate change. AP News+1
World Health Organization / UNICEF / UN webpages — statistics on access to safely managed drinking water and sanitation services. World Health Organization+1
The Guardian — reporting and analysis on global water risks, food production and glacier melt (useful for accessible summaries and case examples). The Guardian+1
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