Abstract:
The presence of highly vulnerable karstic systems in areas of intense human
activities often results in the degradation of existing surface- and groundwater quality
status. Water quality protection and improvement, as required by the Water Framework
Directive (WFD), depends on correct identification and prioritisation of the most
relevant pollution sources within complex multi-stressor conditions. This paper presents
a methodology that combines the use of hydrogeology, water quality and
quantity data, and electrical resistivity tomography methods to access different anthropogenic
impacts upon the water cycle, focusing on the water quality of a section of
the Portuguese karstic Querença-Silves aquifer. During this study an interpretation of
the possible interconnections between pollutant sources, their pathways and local
surface-groundwater connections was made, based on data obtained from field campaigns.
As a result of this study, the areas with more interconnection between surfaceand
groundwater were identified, namely the influent sites from the local stream into
the aquifer. The impact of the diffuse pollution sources was verified at the monitoring
points, especially those located downstream of large farming plots. Pollution in this
karst aquifer results from seepage through agricultural areas and infiltration at the
influent points of the stream. This aspect of stream influence upon the aquifer means
that pollution sources located upstream of the area of the aquifer (e.g., a WWTP—
Wastewater Treatment Plant) can also contribute to the aquifer pollution.
