Tagus estuary, Portugal

Case study area

Situated near the capital city of Lisbon, the Tagus estuary comprises a protected natural reserve area and is the stopping grounds for a wide range of migratory bird species and transiting fish. Upstream waters from the Tagus river have their source in Spain, whose freshwater flows through the Tagus before outflowing into the Atlantic Ocean in large plumes near Lisbon. The outflowing waters bring a mix of nutrients into the Atlantic that increase the primary production off the Portuguese coast and foster a major European fishing industry.

The estuary's broad and shallow bay is no deeper than 10 metres at any point, and is mesotidal with semi-diurnal tides. While the Tagus Estuary has been relatively under studied for such a large estuary, an in situ monitoring programme has been running in the region since 1999, making it an ideal location for CERTO to determine long-term changes in water quality. Water quality in the Tagus is of great concern for a number of entities in Portugal due to its complex natural ecosystem and its proximity to the city of Lisbon and the upstream industrial sites, and the human footprint left upon it through a recent increase in pressure from the tourism and fishing industries.

The CERTO project is using historical water quality data from the Tagus Estuary to learn about what is needed to improve the monitoring of its waters, and is organizing new in situ data collection campaigns with new instrumentation for this purpose. Fieldwork data will also be combined with new remote-sensing techniques applied to Copernicus satellite data, in an effort to provide new and dependable data in accordance with the real needs of the Tagus' main water monitoring facilities.


Satellite image of the Tagus estuary

Satellite image of the Tagus estuary