Urban water demand will increase by 80% by 2050, while climate change will alter the timing and distribution of water. Here we quantify the magnitude of these twin challenges to urban water security, combining a dataset of urban water sources of 482 of the world’s largest cities with estimates of future water demand, based on the Intergovernmental Panel on Climate Change (IPCC)’s Fifth Assessment scenarios, and predictions of future water availability, using the WaterGAP3 modelling framework. We project an urban surface-water deficit of 1,386–6,764 million m³.

To chalk out the future course of action in view of the disputes regarding the use of Mahanadi river water, a well-rounded strategy that includes both the people and policymakers is needed. The strategy must allow for dialogue by rebuilding trust and should look at arbitration and negotiation as methods of conflict resolution.

Water scarcity is rapidly increasing in many regions. In a novel, multi-model assessment, we examine how human interventions (HI: land use and land cover change, man-made reservoirs and human water use) affected monthly river water availability and water scarcity over the period 1971–2010. Here we show that HI drastically change the critical dimensions of water scarcity, aggravating water scarcity for 8.8% (7.4–16.5%) of the global population but alleviating it for another 8.3% (6.4–15.8%).

It is often purported that unusually dry weather conditions provoke small-scale social conflict—riots—by intensifying the competition for water. The present paper explores this hypothesis, using data from Sub-Saharan Africa. We rely on monthly data at the cell level (0.5×0.5 degrees), an approach that is tailored to the short-lived and local nature of the phenomenon. Using a drought index to proxy for weather shocks, we find that a one-standard-deviation fall in the index (signaling drier conditions) raises the likelihood of riots in a given cell and month by 8.3%.