Good Practices of Quality Control in the Area Surrounding of Natural Mineral Water Abstraction of São Pedro Do Sul Medical Spa (Portugal)
Authors: Ferreira Gomes Luís M. , Jorge Ana , Rodrigues Liliana 
Published: December 2021

São Pedro do Sul medical spa is a space with a millenary tradition in providing health services from the natural hot groundwater. The main source of supply of this thermal unit, was along the time, the Traditional Spring, which in the last decades has been controlled, and shows to have constancy in the flow rate, with about 10 L/s, with a temperature of 68.6°C in the origin. From 1999 onwards, with the construction of new abstraction, Well AC1, with 500m deep, with a maximum flow rate of 12.2 L/s, at 67°C, the exploitation potential of this resource increased. Due to the fabulous characteristics of the resource’s potential (hot natural mineral water), there has been over time a great development in the spa medical activity, having already frequented these spa 25450 users per year, reflecting a maximum annual turnover of 5.4 million euros, coming from thermalism alone. Currently, there are two Bathhouses in operation and the resource is used, not only for therapeutic and wellness thermalism but also for geothermal uses and yet in the cosmetic area. This situation becomes the perfect scenario for attracting investment, increasing the circulation of people and goods, but also in the interest of building new bathhouses, hotels and restaurants and subsequently new roads, gardens, public drinking water and sanitation networks. All this pressure causes a lot of potential damage to the environment, including the underground water environment, and could eventually lead to the closure of the medical spa, if the natural mineral water from the abstractions become contaminated. In Portugal, there are several legally imposed defensive mechanisms of the mineral aquifer system, namely the implementation of the Protection Perimeter, but also the analytical control of the natural mineral water, at the abstraction head, both in chemical and microbiological terms, in addition to the orientation to have an automatic, on-line, record system associated to the abstractions, monitoring parameters such as: water level, flow rate, temperature, pH and conductivity of the water captured. However, the Sao Pedro do Sul medical spa go further, implementing an external monitoring system, consisting of: i) double piezometers (to sample groundwater at different depths), ii) street rainwater samplers, and iii) records precipitation and respective quality. Thus, in this paper, after a brief presentation of the importance of the resource and the physical aspects of the place (geology, hydrogeology and quality of the resource), the fundamental elements of the implemented external monitoring system and its main results are presented, showing that precipitation itself is already contaminated, that street rainwater sample presents chemical elements that are highly harmful to public health, and that groundwater sometimes presents very worrying results. Finally, some actions are mentioned that have been implemented to minimize the potential for contamination of natural mineral water from abstractions and the mineral aquifer system.