Impacts of Sea Level Rise on Seawater Intrusion in Cubatão River, Brazil

Estuarine systems are very sensitive environments to sea level rise as a consequence of climate changes, which can enhance seawater intrusion and affect multiple water uses. The seawater intrusion under sea level scenarios in an estuarine river by applying the one-dimensional hydrodynamic and water quality model HEC-RAS 5.0.5 was studied. The study was carried out at the estuarine reach of Cubatão River, in São Paulo, Brazil. Considering sea level rise scenarios of Δ H = 0.25 m, 0.50 m, and 1.0 m combined with constant freshwater discharge conditions for Cubatão River (16 m 3 /s, mean annual discharge and 8 m 3 /s, dry season discharge), the model results showed that seawater intrusion moves significantly upstream the river in all cases and the maximum seawater intrusion length may reach 10 km in the worst scenario (Δ H = 1.0 m and 8 m 3 /s freshwater discharge), 70% higher than the current sea level and the mean discharge. At the local water abstraction point for urban supply, salinity concentration may reach 12 g/kg, making conventional water treatment unfeasible. Sea level rise may threaten water supply facilities and require water resource management solutions, such as water abstraction restricted times when salinity concentration is low; higher freshwater reservation; new water abstraction locations, farther the present ones; or higher water discharges in Cubatão River from a local hydroelectric power plant, which can cause water resource management conflicts.