Heat has consequences for the demand for water (water quantity) and water quality. During a prolonged hot period, there is an increased demand for drinking and cooling water, as well as water for irrigation. An example of this is the heavily attended and tropically hot prologue of the Tour de France in July 2015 in Utrecht, the Netherlands. On that day, water company Vitens pumped twice the usual amount of water into the city compared to a normal day. Across various water users, water demand increases during hot periods (agriculture, livestock, households, industry, electricity generation).

Heat also affects the quality of drinking water and surface water. For instance, if drinking water pipes are not deep enough in the ground, the temperature of drinking water gradually rises. This can lead to the growth of microorganisms and pathogens. The quality of surface water can also deteriorate due to higher temperatures, such as the growth of blue-green algae. Finally, problems can arise because companies, especially electricity companies, may no longer be allowed to discharge cooling water, as it would otherwise raise the surface water temperature. This can have cascade effects on energy supply, industry, and agriculture.

The mind map further elaborates on four consequences of heat on water quality and quantity: