Why is it necessary to protect reservoirs and rivers and conserve water?

Each settlement has its own water sources. Even in the Sahara there is water, which the tenacious cacti extract with the help of a powerful root system. Even a tiny bacterium, which can hardly be seen through a microscope, needs water. What can we say about a person who, with a slight loss of fluid in the body, can lose consciousness or even die! Without water resources, we are doomed to perish soon. If heat can be obtained with the help of solar energy or wind, then there is no substitute for water.