The interaction between geothermal power plants and the surrounding environment can be divided into the impacts of the power plants on the environment and the impacts of the environment on the power plants. Kristmannsdottir and Armannsson have classified the former into the following categories:
1. Surface disturbances
2. Physical effects of fluid withdrawal
4. Thermal effects
5. Chemical pollution
6. Biological effects
7. Impact on (protected) natural features
Surface disturbances include the clearing of land, changes in landscape and the introduction of man-made structures where none existed before. Physical effects of fluid withdrawal include subsidence, lowering of the groundwater table and induced seismicity as earth layers consolidate due to the removal of fluids from matrix pore spaces or when increased pressure due to injection causes the relief of accumulated geological stresses. Thermal effects include elevated temperatures of rivers, lakes and groundwater due to thermal fluid discharges and changes in cloud formation and local weather due to steam emissions. Chemical pollution can be caused by steam and non-condensible gas emissions to the atmosphere and the discharge of brine to surface or subsurface water bodies. All of these have the potential of impacting wildlife, vegetation and the socio-economic sphere around a geothermal power plant, as well as altering natural features for the short-term or permanently. Monitoring and controlling sources and their impacts is therefore of utmost importance.
On the other hand, the impacts of the environment on geothermal power plants include:
1. The application of external dynamic forces to power plant structures. These include seismic forces changing over short time scales and deforming forces that may change over much longer time scales due to subsidence. Wind (hurricanes), floods, snow and ice are also examples of dynamic environmental forces that may follow a seasonal pattern and affect power plant structures.
2. Degradation of equipment and materials due to environmental chemistry. These effects include corrosion and scaling.
All of these effects need to be monitored to maintain and sustain the power plant and its environment.