Abstract
Droughts reduce freshwater availability and have negative environmental, economic, and social impacts. In estuaries, the dynamics between the saltwater and the freshwater can be affected during droughts, which can impact several natural resources and economic sectors negatively. The Tagus estuary is one of the largest estuaries in Europe and supports diverse uses and activities that can be affected by the saltwater intrusion (e.g., agriculture). This study assesses the saltwater intrusion in the upper reaches of the Tagus estuary using a process-based model to explore different scenarios of freshwater discharge and sea level rise. For the river discharge and mean sea level rise scenarios analyzed, salinity can reach concentrations that are inadequate for irrigation when the mean Tagus river discharge is similar or lower than the ones observed during recent droughts (22–44 m3/s). Lower river discharges aggravate the consequences. Results also show that the salinity increases with the duration of the droughts. In contrast, the impact of a moderate sea level rise on salinity intrusion is modest when compared with the impact of low river discharges. These findings contribute to support the management of the agricultural activities in the upper Tagus estuary and the water resources in the Tagus river basin.
Highlights
Extreme weather events, such as droughts, can have negative environmental, economic, and social impacts
Since tides and the freshwater discharge are the main drivers of this dynamics, during low river discharge periods the saltwater can propagate further upstream
For the analyzed river discharge and mean sea level rise scenarios, salinity reaches concentrations that are inadequate for irrigation during some periods when the mean Tagus river discharge is similar or lower than the ones observed during recent droughts (22–44 m3/s)
Summary
Extreme weather events, such as droughts, can have negative environmental, economic, and social impacts. Some studies addressed the salinity dynamics in the Tagus estuary, but the scenarios of freshwater discharge anddynamics sea level rise and assess the saltwater present knowledge of the salinity in the upper estuary remains limited. The previous implementation of SCHISM [18] is extended and applied to provide a better understanding of the salinity dynamics and its drivers in the upper Tagus estuary, in particular during droughts. This knowledge can support the definition of management and adaptation measures during droughts and help the end-users coping with future changes.
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