Global water gaps are widening due to climate warming, leading to worrying water shortages in many regions of the world.

• What are water gaps? Water gaps refer to the difference between the availability of renewable water resources and water consumption in a particular region. A water gap occurs when water consumption exceeds locally available renewable water resources. These gaps indicate unsustainable water use, leading to the depletion of groundwater, rivers, lakes and environmental flows.
• Global situation: According to studies published in the journal Nature Communications, the global water gap currently represents 457.9 km3/yearProjections indicate increase by 26.5 km3/year (+5.8%) under a 1.5°C warming scenario and 67.4 km3/year (+14.7%) under a 3°C warming scenarioThese projections highlight the uneven impact of warming levels on water gaps, underscoring the need for continued climate change mitigation to ease pressure on water resources.
• Which areas are most at risk?
  • Regions that already have water gaps: Eastern USA, Chile, Mediterranean, South and East India, and North China Plain.
  • Regions that may be affected: Italy, Madagascar, and some US states on the East Coast (North Carolina and Virginia) and in the Great Lakes region (Wisconsin, Minnesota, Illinois).
  • Countries with the largest water gaps: India (124.3 km3/year), United States (53.8 km3/year), Pakistan (35.8 km3/year), Iran (35.0 km3/year) and China (27.2 km3/year).
• Why are water gaps getting bigger? Climate change is disrupting precipitation and evapotranspiration patterns. Growing demand for water, driven by population growth and urbanization, pollution, the expansion of irrigated agriculture, and greater industrial use, is exacerbating water scarcity.
• What can be done? To combat water scarcity, it is necessary a more sustainable water management strategyThis includes investments in resilient infrastructure, improving water storage capacities, desalination of seawater, reuse of treated wastewater, and physical and virtual water transfers to distribute water from areas with plenty to areas that need it.
• It is also important: Improving water management practices and policy interventions. Farmers may need to switch to less water-intensive crops, improve water productivity in crops, or invest in more efficient irrigation technologies to adapt to changing water availability.

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Glossary of key terms

• Water gap: The difference between available renewable water resources and water consumption.
• Renewable water resources: Water sources that are naturally replenished, such as rainfall and river runoff.
• CMIP6: Coupled Model Intercomparison Project Phase 6, a standardized experimental protocol for climate models.
• Baseline (climatic conditions): The reference period (in this case 2001-2010) that is used for comparison with future climate scenarios.
• Multi-model analysis: Using multiple climate models to assess the range of potential future changes and uncertainties.
• Evapotranspiration: The combined process of evaporation of water from the surface and transpiration of water from plants.
• Hydrological basin: An area from which all water drains into a common river or lake.
• Environmental flow: The amount of water needed to maintain the health and functioning of aquatic ecosystems.
• Virtual water: Water consumed in the production of goods and services that are traded in commerce.
• Sustainable water consumption: Using water resources in a way that does not compromise their availability for future generations.