Abstract:
The presence of high vulnerable karstic systems in areas of intense human activities often results in the degradation of
existing groundwater quality status. The water quality (WQ) protection and improvement, as required by the WFD (Water
Framework Directive), depends on a correct prioritisation of the most relevant impact pollution sources to be identified within
complex multi-stressor conditions. This paper presents a methodology that combines the use of hydrogeology, WQ and quantity data,
and geophysical methods to access the human activities’ impacts upon the water cycle, focusing on the WQ of a karstic system.
The procedure was applied to a section of the Portuguese karstic Querença-Silves aquifer, under FCT PROWATERMAN project
PTDC/AAC-AMB/105061/2008 (http://www.lnec.pt/organizacao/dha/organizacao/dha/nas/estudos_id/PROWATERMAN). During
this study an interpretation of the possible interconnections between pollutant sources, their pathways and local surface-groundwater
connections was analysed, based on data obtained from field campaigns.
As a result of this study, the most relevant recharge areas and the identification of influent sites of the local stream to the aquifer were
acknowledged. The areal distribution of the diffuse pollution sources was verified in the monitoring points, especially those located
in the near downstream of the larger farming plots. Pollution in this karst aquifer results from seepage through agricultural areas and
infiltration in the influent points of the stream. This aspect of stream influence upon the aquifer means that pollution sources located
upstream the area of the aquifer (e.g. WWTP (Wastewater Treatment Plant)) can contribute to the aquifer pollution.
