nd
Session S2.3 - Aqua 2015 - 42
IAH Congress
200 - ASSESSMENT OF MINERAL AND THERMAL GROUNDWATER SYSTEMS: THE "EYES" OF
GEOSCIENCES
José Manuel Marques
Instituto Superior Técnico, Centro de Recursos Naturais e Ambiente (CERENA), Instituto Superior Técnico, University of Lisbon.,
Lisboa, Portugal
Paula Maria Carreira
Instituto Superior Técnico, Centro de Ciências e Tecnologias Nucleares (C2TN), Instituto Superior Técnico, University of Lisbon,
Lisbon, Portugal
At the Portuguese mainland, mineral and thermal groundwater resources (used in the local Spa's) are faced as
the main source of local/regional development/income. Therefore, the increasing knowledge on such type of
groundwater systems is extremely important to achieve the sustainable use of these georesources, known since
Roman times in the region. The aim of this work is to review the results of the assessment of mineral and thermal
groundwater resources (issue temperatures between 17ºC and 77ºC) occurring in Portuguese mainland.
A multidisciplinary approach, including geologic, tectonic, geochemical, geophysical and isotopic (2H, 18O, 13C, 3
H and 14C) techniques, was used in order to update local and/or regional conceptual circulation models. The results
were obtained in progressive stages, which frequently overlapped. These studies embraced many activities,
including investigation and exploration, and were carried out within the framework of a conceptual model of a
given system, which was improved as more and more information was collected. The results obtained indicate
rather similar hydrogeological conceptual models ascribed to mineral and thermal groundwaters with different
geochemical signatures (e.g., HCO3/Na/CO2-rich with pH = 7; HCO3-Na with 8 < pH < 9, and Na-Cl/Ca-OH with pH =
11.5, type waters).
This multidisciplinary approach has provided important data to answer the most usual addressed questions
associated with the investigation of mineral (medicinal) and thermal groundwater systems, namely: i) what is the
origin of the waters? ii) where the recharge areas are located? iii) which are the main water-rock interaction
processes occurring at depth? Local/regional high altitude sites associated with high fractured rocks play an
important role in conducting the infiltrated meteoric waters towards the discharge zones near the Spas. The
discharge zones are mainly related to the intersection of the main local/regional fault lineaments (and conjugate
structures), responsible for promoting the mineral and thermal groundwaters ascent.
1