Scenario Modelling of Climate Change's Impact on Salinization of Coastal Water Resources in Reclaimed Lands

Abstract A numerical model accounting for variable density flow and transport was built up to quantify the actual and future (2050) salinization trends of a coastal aquifer in the Po delta (Northern Italy). SEAWAT 4.0 was employed to model the interaction between the surface drainage system and the underlying aquifer. PEST was employed for inverse parameter calibration using hydraulic heads and groundwater salinities as constraints. The calibrated model was used to predict the behavior of the coastal aquifer using a multiple scenario approach: increase in evapotranspiration induced by temperature increase; increase in the frequency of extreme high rainfall events; extreme drought conditions; and irrigation canals dewatering due to salinization of the Po River branches. For each scenario, two sub-scenarios were established to account for the projected local sea level rise. The first three scenarios have only minimal effects on the aquifer salinization, while the fourth forecasts a severe aquifer salinization due to enhanced upward fluxes of saline and hypersaline groundwater. The scenarios quantified the possible future salinization trends of groundwater and could be useful to identify adaptation strategies which allow to better manage water resources of this and similar areas. Results show that the Po delta will experience a significant salinization by 2050 and that the major cause is autonomous salinization via seepage of saline groundwater rather than enhanced salt-water intrusion due to sea level rise. The enhanced autonomous salinization will increase the salt export into the drainage canals that are also employed for irrigation, posing serious treats to the local flourishing agricultural economy