How Climate Change Threatens Global Water Security and Management

Water is arguably the most vital natural resource on Earth. Every living organism depends on it, every economy runs on it, and yet, it remains one of the most unevenly distributed and increasingly scarce resources globally. As the climate continues to warm, the systems that supply and regulate water – rainfall, rivers, glaciers, and groundwater – are being disrupted in ways that threaten billions of people. Understanding how climate change affects water resources is no longer an academic exercise; it’s a survival imperative.

Why water is a contested and critical resource 🔗

Water underpins agriculture, industry, energy production, sanitation, and human health. Despite its importance, access to clean and adequate water is deeply unequal. According to Water.org, around 342 million people in India alone lack access to safe water, while 539 million lack access to a safe toilet. Globally, the picture is similarly grim. The gap between water demand and water supply is widening, driven by population growth, urbanisation, and economic development – all compounded by a rapidly changing climate.

The disparity in water access between wealthy and poor communities is stark. Those with financial resources can invest in borewells, filtration systems, and private water tankers. Meanwhile, low-income households, particularly in rural areas, often rely on untreated surface water or walk long distances to fetch water from shared sources. Climate change intensifies these inequalities because its worst effects – prolonged droughts, erratic monsoons, and flooding – disproportionately impact the most vulnerable populations.

The five sources of water and growing scarcity 🔗

The world relies on five main categories of water: surface water (rivers and lakes), underground water (aquifers), glaciers, rainwater, and sea water. Of these, the first three – surface water, groundwater, and glaciers – are already under severe stress from overexploitation.

UN-Water reports that only about 0.5% of all water on Earth is usable and available freshwater, and climate change is threatening even that limited supply. Over the past two decades, terrestrial water storage including soil moisture, snow, and ice has been declining at roughly 1 centimetre per year. Glaciers are retreating at alarming rates – in 2023 alone, glaciers globally lost over 600 gigatons of water, the largest loss in five decades.

Given this stress on conventional water sources, the development of technologies to desalinate sea water and systems to harvest rainwater more effectively has become critical. Sea water, which makes up about 97% of the planet’s total water, remains largely untapped for direct human use due to the high cost and energy demands of desalination. Rainwater harvesting, while a simpler and more affordable solution, is still not practised at scale in most regions.

India’s unique water challenges 🔗

India presents one of the most pressing case studies in water insecurity. The country supports approximately 16% of the global population but has access to only about 4% of the world’s freshwater resources. This fundamental imbalance is at the heart of India’s water crisis.

The agricultural sector is the largest consumer of water in India, with irrigation accounting for roughly 83% of total water use. Groundwater alone supplies over half the country’s water needs, and about 89% of extracted groundwater goes towards irrigation. Much of this extraction relies on traditional, inefficient irrigation methods that lead to massive water loss through evaporation and seepage.

According to projections, India’s population could reach approximately 1,800 million by 2050. To meet the needs of this growing population, water availability would need to nearly triple from the current estimated 500 cubic kilometres per year. This is a monumental challenge, especially when existing resources are already stressed.

The World Economic Forum’s 2025 Global Risks Report identified water supply shortages as the most severe risk facing India over the next two years (2025-2027). India was listed alongside Mexico, Morocco, Tunisia, and Uzbekistan as the five countries most at risk. Notably, the number of countries identifying water shortages as a top-five risk jumped from seven in 2024 to 27 in 2025 – a sign of how rapidly the crisis is escalating worldwide.

The 2024 heat-water nexus 🔗

2024 was recorded as India’s warmest year since 1901. Heatwaves intensified across the country, resulting in 733 deaths from extreme heat. The water gap – the difference between renewable water availability and actual consumption – is projected to grow sharply under future warming scenarios. At 1.5°C of warming, India’s water gap could increase by 11.1 cubic kilometres per year, and at 3°C, this figure could rise to 17.2 cubic kilometres per year.

Water scarcity affected an estimated 330 million people in India in 2024, with about half the nation’s land area experiencing drought-like conditions. Major cities like Bengaluru, Chennai, Delhi, and Hyderabad have faced scenarios where water supplies came to a near-complete halt – the so-called ‘Day Zero’ events.

How climate change aggravates water problems 🔗

Climate change affects water resources through multiple, interconnected pathways. It’s not just about getting less rain – the entire water cycle is being destabilised.

Changes in rainfall patterns and runoff 🔗

Global warming alters atmospheric moisture levels and circulation patterns, leading to shifts in where and when rain falls. Some regions experience heavier rainfall compressed into shorter periods, while others face prolonged dry spells. In India, the monsoons – which deliver about 80% of annual rainfall – have become more erratic. The Grantham Research Institute notes that while total global precipitation is expected to increase because warmer air holds more moisture, the distribution will be highly uneven, with greater variability between wet and dry periods in the same location.

More frequent floods and droughts 🔗

Paradoxically, climate change causes both more flooding and more drought. Warmer temperatures increase evaporation from land and water bodies, drying out soils and reservoirs. At the same time, when rain does come, it often arrives in intense bursts that cause flooding rather than recharging groundwater. According to the United Nations, by 2050, the number of people at risk of floods is projected to grow from 1.2 billion to 1.6 billion. Meanwhile, droughts are becoming more severe in many regions, reducing agricultural yields and increasing wildfire risk.

Rising temperatures, aridity, and glacier melt 🔗

Higher temperatures directly increase evaporation rates, making arid regions even drier. For countries like India that depend on glacier-fed rivers, the accelerating melt of Himalayan glaciers is a serious concern. While increased melt may temporarily boost river flows, the long-term outlook is grim: once glaciers shrink past a critical point, the rivers they feed will see drastically reduced flows, affecting hundreds of millions of people downstream.

Sea level rise and coastal aquifer contamination 🔗

Rising sea levels push saltwater into coastal freshwater aquifers, making groundwater in these areas unfit for drinking or irrigation. This saltwater intrusion is already a problem in many coastal areas across South and Southeast Asia. Pacific island nations are particularly vulnerable, where even modest sea level rise threatens the limited freshwater supply available.

Changes in plant water use due to CO₂ levels 🔗

Elevated CO₂ concentrations affect how plants use water. Higher CO₂ can reduce the rate at which plants open their stomata (the tiny pores on leaf surfaces), which in turn reduces water loss through transpiration. While this might sound beneficial, the net effect on the water cycle is complex. Reduced transpiration can alter local rainfall recycling, potentially reducing precipitation in regions that rely on it.

Regional water impacts across Indian river basins 🔗

Climate change does not affect all regions equally. Within India, the projected impacts vary significantly across river basins.

Rivers like the Luni in Gujarat and Rajasthan are expected to experience acute physical water scarcity. The Luni is already an ephemeral river in many stretches, and reduced rainfall will further diminish its flows. River basins of Mahi, Pennar, Sabarmati, and Tapi face the prospect of constant water shortages, driven by both reduced supply and growing demand from agriculture and urbanisation.

Meanwhile, basins of major rivers like the Cauvery, Ganga, Narmada, and Krishna are likely to experience seasonal or periodic water stress. These rivers currently support massive populations and extensive agricultural systems. The Cauvery basin is already a flashpoint for inter-state disputes – the decades-long conflict between Tamil Nadu and Karnataka over Cauvery water allocation resurfaced in 2023, triggered by rainfall deficits and drought-like conditions.

These regional disparities mean that a one-size-fits-all approach to water management will not work. Strategies need to be tailored to the specific hydrological, climatic, and socioeconomic conditions of each basin.

Adaptive water management strategies 🔗

Given the scale of the challenge, both community-level and national-level adaptive measures are essential. The IPCC’s AR6 assessment underscores that while limiting warming to 1.5°C would minimise water-related risks, proactive adaptation is needed regardless, because some degree of water cycle disruption is already locked in.

Community-level initiatives 🔗

Rainwater harvesting is one of the simplest and most effective adaptive strategies. It involves collecting and storing rainwater for later use – whether for drinking, irrigation, or groundwater recharge. In India, the IPCC has listed rainwater harvesting as a specific adaptation measure to address future climate change. Tamil Nadu’s mandatory rainwater harvesting policy for buildings has shown concrete results, increasing groundwater recharge and reducing dependence on external water sources.

Improved soil moisture management is another critical measure, especially for rainfed agriculture. Techniques like mulching, cover cropping, and contour farming help retain soil moisture longer, reducing the impact of erratic rainfall. In Rajasthan, the Jal Swavlamban Abhiyan (water self-reliance campaign) has focused on building check dams, restoring ponds, and creating water-harvesting structures. This initiative has led to significant improvements in groundwater levels and agricultural productivity in arid regions.

Watershed management programmes that involve local communities in planning and maintaining water resources have also proven effective. When communities have a stake in managing their local water systems – ponds, tanks, streams – they tend to use them more sustainably.

National-level policies and frameworks 🔗

At the policy level, the most important shift required is integrating climate variability into water resource planning. Traditional water management has operated on the assumption that climate and water sources are stable over time. Climate change fundamentally undermines this assumption, making historical data an unreliable guide for future planning.

India’s National Water Mission, part of the National Action Plan on Climate Change, aims to promote integrated water resource management, minimise waste, and ensure more equitable distribution. The Jal Jeevan Mission has made progress in extending tap water connections to rural households – as of December 2024, about 154 million households had been connected.

Decentralised water management is another key principle. Rather than relying solely on large-scale infrastructure like dams and canals, a decentralised approach empowers local institutions and communities to manage water resources based on their specific needs and conditions. This makes the system more resilient to the localised and unpredictable impacts of climate change.

Investment in wastewater treatment and reuse also presents a major opportunity. The World Economic Forum highlights that every dollar invested in ecosystem restoration related to water yields an estimated $7 to $30 in economic benefits through improved water quality, reduced flood risk, and better agricultural resilience. Yet globally, water infrastructure investment needs to triple to about $1 trillion annually to ensure sustainable access in a changing climate.

The path forward 🔗

The relationship between climate change and water security is not a distant, abstract problem. It is playing out right now – in dried-up reservoirs in Rajasthan, in saltwater intrusion along India’s coasts, in the fierce disputes over river water between Indian states, and in the growing water gap that is projected to widen with every fraction of a degree of warming.

Addressing this crisis requires action at every scale: individuals conserving water in their daily lives, communities investing in local water harvesting and recharge systems, states resolving water-sharing disputes through cooperation, and nations embedding climate projections into every water policy decision. The technology and knowledge to manage water more sustainably already exist. What’s needed is the political will and public awareness to implement them before the gap between supply and demand becomes unbridgeable.

What do you think? Can decentralised water management – where communities take charge of their own water resources – really work at scale in a country as large and diverse as India? And should water-scarce nations prioritise investing in desalination technology, or is the focus better placed on conservation and harvesting of existing freshwater sources?

References

1. https://water.org/our-impact/where-we-work/india/
2. https://www.unwater.org/water-facts/water-and-climate-change
3. https://www.downtoearth.org.in/water/water-shortage-emerges-as-top-environmental-risk-for-india-and-the-world-over-next-two-years
4. https://www.downtoearth.org.in/water/unrelenting-heat-and-the-increasing-water-gap-in-india
5. https://earth.org/water-scarcity-how-climate-crisis-is-unfolding-in-india/
6. https://www.lse.ac.uk/granthaminstitute/explainers/what-is-water-security-and-how-is-it-impacted-by-climate-change/
7. https://www.un.org/en/climatechange/science/climate-issues/water
8. https://www.statista.com/topics/6988/water-accessibility-in-india/
9. https://www.ipcc.ch/report/ar6/wg2/chapter/chapter-4/
10. https://www.mdpi.com/2305-6703/5/1/4
11. https://www.weforum.org/stories/2024/11/7-facts-about-the-global-water-crisis-that-cop29-leaders-should-know/