The eastern zone of Terceira Island (Azores) is divided by normal faults oriented NW-SE that defines the Lajes graben. The subterranean hydrology of this depression is characterized by the occurrence of ten perched aquifers, differentiated by local faults, and by a basal aquifer, which is presumed to be unique at island.
The recharge of these water systems takes place the central sectors of the island, while the discharge occurs in the submarine platform that surrounds the island, in the intertidal zone and in a series of wetlands and lagoons located in the coastal bay (e.g. Praia da Vitoria’s, Belo Jardim’s and Pedreira do Cabo Praia’s wetlands). The groundwater flow of the Lajes graben presents in some places situations where the circulation is atypical, without the expected radial characteristics, explainable by the presence of faults with a differential hydraulic behavior.
In this work, a qualitative analysis of the water in the southern sector of the Lajes graben is carried out, where fuel spills were referenced, based on analytical data wells for water supply and coastal wetlands.