In the US and Europe, more than half of water use goes to power generation. This is because most of that power is generated by thermoelectric power plants which use coal, natural gas and nuclear fuel to create steam that turns turbines. The process takes massive amounts of water to cool the steam, after which the water is returned to its source much warmer than before it was withdrawn. This is why so many power plants are located next to water bodies.
This year’s heatwave has forced some of those power plants to shut down because the receiving water bodies typically have temperature limits above which they cannot receive the hot cooling water without risking ecosystem impacts. This article about the heat wave explains this issue in more detail. [Quartz]