The additional acceleration of geothermal water flow in the discharge section by the geothermal driving force

Abstract

The rise of geothermal water level can be observed in the discharge section in a convective hydrothermal system. It is hard to explain in terms of gravity-driven groundwater systems, suggesting the existence of an additional driving force. This geothermal driving force is closely related to the changes in density, salinity, and viscosity caused by the increase in groundwater temperature. It is significant to quantitatively characterize the geothermal driving force for the interpretation of geothermal water level and flow. A case study is carried out in a convective geothermal system in Huangshadong, South China. The recharged groundwater migrated to a position with an average depth of 2.09 km and was heated to 100-130 ℃. The geothermal driving force produced by the increase in temperature and in salinity is +125.33 m and −2.62 m, respectively. The actual pressure head produced by the geothermal driving force is +122.71 m. The migration speed of geothermal water under the action of geothermal driving force from the heating position to the discharge area increased from 2.14×10 -3 m/d to 3.09×10 -3 m/d. The results indicate the presence of a geothermal driving force accelerates the groundwater migration in the discharge section of convective hydrothermal system.