What is Geothermal Water?

Geothermal water is ground water that is heated by the earth’s energy. The term geothermal comes from two Greek words: geo, which means earth, and therme, which means heat. By harnessing the physical properties of steam and heat, geothermal water can be used to generate electricity. If the water is hot enough, it can be pumped straight into radiators and used as space heating. Some areas even bottle and sell it as drinking water.

Reservoirs of geothermal water are found in locations where the earth's heat is near enough to the surface so that water or steam can reach the top. There are two types of geothermal water reservoirs: low temperature reservoirs and high temperature reservoirs. Low temperature reservoirs hold water that is less than 302° F (150° C). High temperature reservoirs hold water that is greater than 302° F (150° C). The deeper the reservoir is located in the earth, the hotter the water it holds will be.

Different types of power plants have been created in order to convert geothermal water into electricity. Dry steam power plants use steam as it comes from the ground to turn blades in the power plants turbine. Flash steam power plants use high pressure piping to bring the hot water to the surface. Once at the surface, the water is then converted to steam and used to generate electricity. A binary cycle power plant uses lower temperature water to vaporize a separate fluid which is then used to produce electricity.

Geothermal water reaches the surface in a variety of ways. Hot springs are produced when the reservoir is connected to the surface by faults. Geysers are periodic eruptions of steam that can shoot up to 200 feet (60.96 m) into the air. A fumarole is an opening in the earth that emits a mixture of steam and gases. These geothermal features are usually formed around volcanic activity.

Mudpots are a type of either a hot spring or a fumarole. Mudpots are pools of bubbling mud rather than water. If the reservoir does not have much water, what little water that does reach the surface is mixed with soil filled with volcanic ash, clay, and other components. This produces mud that is usually white or gray in color. When the mud is multicolored, it is called a paint pot.