Population growth will in many regions increase the pressure on water resources and likely increase the number of people affected by water scarcity. In parallel, global warming causes hydrological changes which regionally also impact human water supply. This study estimates the increase in pressure on global water resources due to population growth and adverse hydrological effects at different levels of global mean temperature rise above pre-industrial level (∆<i>T</i><sub>glob</sub>), including reduced mean water availability, growing prevalence of hydrological droughts, and increased frequency of flooding hazards. The study analyses the results in the context of success and failure of implementing the Paris Agreement, and evaluates how climate mitigation can reduce the future number of people affected by severe hydrological change, assessed for the population as a whole, as well as for vulnerable population groups already projected to experience water scarcity in the absence of climate change. The results show that without climate mitigation efforts, in 2100 more than 5.1 billion people in the SSP2 population scenario would more likely than not be affected by severe hydrological change, and about 1.9 billion of them would already be affected by water scarcity in the absence of climate change. Limiting warming to 2 °C or 1.5 °C by a successful implementation of the Paris Agreement would strongly limit the number of people affected by severe hydrological changes and water scarcity to 274 million or 104 million, respectively. At the regional scale, substantial water related risks remain at 2 °C, with more than 10 % of the population affected in Latin America and the Middle East and North Africa region. Constraining ∆<i>T</i><sub>glob</sub> to 1.5 °C would limit this share to about 5 % in these regions.