A new study warns that water shortages are imminent in major cities worldwide, especially in the Mediterranean, African, and North American regions, with some areas facing the risk of Day Zero Drought (DZD) within the next decade due to climate change and rising water consumption.

Using advanced climate models under emission scenarios SSP3-7.0 and SSP2-4.5, researchers predict that up to 35% of vulnerable regions could experience DZD within the next 15 years, putting as many as 750 million people at risk by the end of the century, including both urban and rural populations.

The study emphasizes that these projections are probabilistic and not definitive, highlighting the importance of regional planning for emergency responses and long-term water management.

Researchers also note that the models do not account for groundwater resources, which are crucial during droughts, suggesting that actual risks could be higher than projected.

A significant limitation of the research is its exclusion of groundwater data, although efforts have been made to partially account for this in the models.

Experts acknowledge the urgency of this research in understanding water scarcity risks, emphasizing that more data and analysis are needed for conclusive results, but agree that the increasing threat requires immediate action.

The findings underscore the growing threat to global water resources from climate change and human activity, calling for urgent measures to prevent catastrophic shortages.

The study stresses that Day Zero Droughts are already occurring in some regions, and immediate adaptation and sustainable water management are critical to avoiding severe crises.

In drought hotspots like the Mediterranean and southern Africa, the recovery periods between droughts are shrinking, reducing water reservoir refill times and complicating future water management strategies.

Research based on 100 climate model simulations indicates that extreme drought events, termed 'hour-zero,' are likely to become more frequent, with some regions experiencing these events more than 99% of the time.

The concept of 'hour-zero drought' was first introduced in 2018 after Cape Town's water crisis, and scientists warn such events are inevitable in drought-prone areas due to ongoing climate change.

Even if global warming is limited to 1.5°C, hundreds of millions will still face severe water shortages, with existing reservoirs in Mediterranean countries at risk of drying during initial DZD events.

Urban areas, particularly in the Mediterranean, are highly vulnerable, with estimates suggesting that about 14% of major water reservoirs could dry out during their first DZD, severely impacting local livelihoods.