Multitemporal remote sensing to investigate saltwater intrusion impact on agricultural greening in the Po River Delta (Italy)

Agriculture along the coast depends on optimal water resource management, especially in delta areas. Indeed, freshwater aquifers close to the sea are at risk of saltwater intrusion, with disastrous consequences for crops. This is a complicated process that is the result of multiple factors, both natural and man-made. Droughts are responsible for particularly severe saltwater intrusion events. Indeed, lack of rainfall leads to reduced river flow, which favors the flow of marine water inland. Climate change is aggravating this condition in diverse parts of the globe. Therefore, it is crucial to investigate the process of saltwater intrusion in river deltas deeply. Although this phenomenon has already been addressed in the literature in some areas of the world, there is still much to be done to assess the effects of saltwater intrusion on crops at the sub-regional level. In this task, multi-temporal remote sensing opens up new horizons of knowledge. New Earth observation (EO) technologies make it possible to monitor the evolution of the process over several years of observation and vast areas. The open-source big data offered by international space programmes are an excellent starting point for understanding this trend. This study aims to examine the effects of saltwater intrusion on agricultural greening in the Po Delta (Italy), an important European food production area. The main economic activity in the area is agriculture, made possible by centuries of land reclamation and co-existing with wetlands of considerable ecological importance, now threatened by the salinization of the water. In fact, during dry summers, the Po River's flow rate decreases significantly, favoring the intrusion of saltwater for tens of kilometers inland, affecting irrigation systems and causing severe impacts on production. This study's analyses are based on the correlation between Po river water salinity at 47 sampling sites and NDVI values using Landsat 5. The research results could provide a low-cost, multi-temporal tool based on remote sensing to quantify/map the effects of saltwater intrusion on agriculture at the delta scale, helping stakeholders adopt a more efficient/sustainable use of freshwater near the sea.

Acknowledgments - This study was carried out within the Agritech National Research Center and received funding from the European Union Next-GenerationEU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR) – MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.4 – D.D. 1032 17/06/2022, CN00000022). The authors also thank the Start-up funding from Inner Mongolia University (21800-5223728).