Aspectos ambientais associados à utilização dos recursos geotérmicos: altas vs. baixas entalpias

Catarina Pontes Fernandes Carmelo de

Key information

Authors:

Catarina Pontes Fernandes Carmelo de (Catarina Pontes Fernandes Carmelo de Matos)

Supervisors:

Paula Maria Mimo Carreira Paquete (Paula Maria Mimo Carreira Paquete); José Manuel Vaz Velho Barbosa Marques (José Manuel Vaz Velho Barbosa Marques)

Published in

12/12/2011

Abstract

In this thesis the main environmental aspects associated with the use of low and high enthalpy geothermal resources are characterized, and two case studies associated whit low enthalpy geothermal systems are presented: Caldas de Moledo (North Portugal) and Caldas da Rainha (Central Portugal). In both case studies the existence of mixing processes between thermal waters and shallow cold waters, with different recharge altitudes, are investigated through the use of isotope ratios (18O/16O) and geochemical signatures of the sampled waters. The hydrothermal system of Caldas de Moledo is located in the so called "Douro Region", characterized by a large area dedicated to the development of vineyards. The SO4 and Ca concentrations (main constituents of the agrochemicals used in the area) found in some of the Caldas de Moledo thermal spring waters show evidences of mixing between deep geothermal and shallow cold groundwater systems. However, until now, thermal waters from boreholes do not show evidences of anthropogenic contamination from the spreading of agrochemicals. In the Caldas da Rainha thermal waters case study there is a clear separation between the thermal waters and shallow cold waters. The absence of mixing trends between these two groups of waters is due to the presence of clay levels in the geological formations located on top of the thermal aquifer.