Spatial Patterns of Soil Salinity in the Gediz Delta Revealed by Multispectral Satellite Data and Field Observations

Soil salinity in coastal deltas is a significant environmental problem that threatens both the continuity of agricultural production and the balance of sensitive ecosystems. Recognized as one of the 14 Ramsar sites in Türkiye, the Gediz Delta Wetland is one of the two main breeding grounds for flamingos in the country and is home to many other bird species, including herons and Dalmatian pelicans. These areas in the Mediterranean basin are currently affected by climate change, with decreasing rainfall and increasing temperatures. In this study, soil salinity in the Gediz Delta, located on the western Anatolian coast of Türkiye and designated as a Ramsar site, was analyzed using remote sensing methods. During the field studies, soil samples were collected from areas within the delta exhibiting significant salinity, and electrical conductivity (EC) values were measured on site. Six different salinity indices (NDSI, SI, SAVI, NDCI, NDWI, BSI) were calculated for the same areas using Sentinel-2 satellite images, and regional averages were determined with ArcGIS Pro software. The relationships between the field data and satellite-based indices were evaluated using correlation analysis and multiple linear regression models. The analysis showed that the NDWI and SAVI indices had a high correlation with field measurements (r = -0.83 and r = 0.74, respectively) and made significant contributions to explaining EC values. With the multiple regression model, field data were predicted with an accuracy of over 98% (R² = 0.98, RMSE = 2.03 mS/cm). These findings indicate that remote sensing indices can be a reliable tool for salinity monitoring and can contribute to the development of sustainable management strategies, especially in areas with conservation priorities.