Usefulness of a groundwater temperature baseline monitoring network for the identification of thermal interferences between shallow geothermal exploitation systems in urban environments

Congress on Groundwater and Global Change in the Western Mediterranean (2017. Granada)The growing demand for renewable energy in urban environments has triggered the implementation of numerous geothermal exploitation systems. In the case of groundwater heat pump systems, an injection of pumped groundwater with different energy properties from those of the aquifer extracted occurs. Consequently, a thermal impact within the urban groundwater body develops. Moreover, high density of installations in the same area entails a risk of thermal interference between them. In order to control the qualitative state of the water bodies and to guarantee a minimum of rights for groundwater users, a geothermal monitoring network has been established in the city of Zaragoza. The Geological Survey of Spain (IGME), in collaboration with the Ebro Hydrographic Confederation (CHE), operates such monitoring network composed of 45 points covering the whole metropolitan area. A total number of 37 monitoring points are being continuously monitored using automatic data loggers, with 17 of them corresponding to totally penetrating new construction piezometers. Uninterruptedly data collection for more than 10 years has proved its utility, allowing to: (1) characterize the aquifer background temperature, (2) identify the urban heat island effect, (3) observe heat plumes of different geothermal systems, (4) monitor the thermal interferences between systems, and (5) monitor the chemical quality of the urban aquifer. The use of high resolution data obtained from this control network, together with data of the exploitation regime of geothermal utilization and the use of numerical models of flow and heat transport have allowed to reproduce the thermal regime of the aquifer. All of this is serving as a basis for informing and assisting the local water authority during the administrative procedure for authorization of thermal discharges, for its monitoring and control.Unidad de Zaragoza, Instituto Geológico y Minero de España, EspañaConfederación Hidrográfica del Ebro, EspañaDepartamento de Ciencias de la Tierra, Universidad de Zaragoza, EspañaPeer reviewe