Anthropogenic Droughts and Chronic Water Scarcity.

Water shortages around the world can no longer be described as seasonal or exceptional. Around 4 billion people already live with severe water scarcity for at least one month every year. In many regions, water scarcity is increasingly driven by persistent long-term over-extraction and quality degradation rather than only by climatic variability. In many systems, water scarcity is therefore defined not only by how much water is available, but by how much of that water meets basicquality standards for human use, food production, and ecosystem health; polluted water or saline water may still appear in volumetric accounts, yet functionally it behaves as if it were not there. 

Over 1.8 billion people—nearly one in four humans—were living under drought conditions in 2022–2023, with the vast majority of them in low- and middle-income countries. Drought-related damages, intensified by land degradation, groundwater depletion, and climate change rather than by rainfall deficits alone, already cost over US$307 billion per year worldwide, more than the yearly economic output of four-fifths of UN Member States. These losses are likely underestimates, as they rarely capture indirect impacts on health, energy, migration, or social stability. 

Across many river basins, water shortage conditions are increasingly shaped not by meteorological anomalies but by cumulative human impacts— declining soil water, deforestation, disrupted evapotranspiration cycles, intensive irrigation, and shrinking surface water bodies—producing the chronic water deficits described as “Anthropogenic droughts”. In regions such as the Mediterranean, the Middle East, South Asia, the Horn of Africa, and western North America, these human-driven processes now exceed natural variability in determining drought severity and duration, with multiple assessments showing that anthropogenic factors dominate the observed intensification of droughts in these areas. Anthropogenic droughts also interact with other hazards and climate extremes to create compound risks. Prolonged dryness and heat reduce soil and vegetation moisture, increasing the likelihood and intensity of wildfires, while at the same time degraded, desiccated soils are more prone to sudden runoff and flash floods when intense rainfall events occur. These compound extremes—megadroughts followed by fires and flash floods—are increasingly observed in drying regions and are difficult to manage within traditional crisis-response frameworks that assume hazards occur one at a time and within a stable baseline.

Overall water risk across different regions around the world. The overall risk score reflects the aggregate value of physical water quantity, water quality, and regulatory and reputational risks, with higher values indicating greater water-related risks. Map produced based on Aqueduct 4.0 data

Day Zero crises in cities represent the urban face of the world’s new water reality. The term “Day Zero” has been used to describe moments when municipal systems are on the verge of being unable to supply piped water to most residents, as seen in widely publicized emergencies in cities such as Cape Town, Chennai, São Paulo, Tehran, and others. In each case, headline-grabbing shortages were triggered by drought, but made possible by years of overallocation, unchecked demand growth, and delayed investment in diversified water sources. Emergency measures—severe restrictions, tariff changes, rapid drilling of new wells, reliance on tanker supplies, and behavioral campaigns—helped some cities narrowly avoid a complete shutdown of taps. Yet in many of these places, the underlying aquifers, reservoirs and catchments remain degraded, and poorer neighborhoods continue to live with intermittent service, tanker dependence, and high water costs long after the media attention has moved on. From a water management perspective, Day Zero must not be treated as a one-off crisis to be “survived”, but a symptom that urban systems are already operating beyond their hydrological carrying capacity. The fact that a formal shutdown of the network is narrowly averted does not mean the system has rebounded; it often means that hidden forms of rationing, informal coping mechanisms, and unequal access have become the new normal. Urban Day Zero events therefore sit on the same continuum as collapsing aquifers, drying rivers and failing rainfed agriculture: all are manifestations of human–water systems that in addition to reaching insolvency, can no longer return to their previous state and must be reorganized under permanently tighter constraints