Monitoring the salt regime of drained lands using radar method

This paper develops an approach to monitoring the salt regime of drained lands based on the integration of Sentinel-1 radar data, Sentinel-2 multispectral indicators, topographic factors, and the results of laboratory analysis of aqueous extracts. The environmental status of the Salavat inter-farm drainage system in the Republic of Bashkortostan, characterized by complex hydrogeological and geomorphological conditions and an increased risk of secondary salinization, is analyzed. An algorithm for generating an integral Risk01 index is proposed, taking into account soil roughness (VV/VH), chronic soil dryness (NDMI), topography (TPI), climatic anomalies (CHIRPS), textural features of the SAR signal, and the brightness of bare soil. Results of aqueous extracts from soil samples collected at depths of 0–25 and 25–50 cm, followed by determination of their electrical conductivity, are presented for verification. A high level of agreement between satellite estimates and actual measurements was established: R² = 0.93 for the 0–25 cm layer and R² = 0.88–0.91 for the 25–50 cm layer. It was revealed that, over the period 2002–2025, the area of land with moderate and severe salinity increased from 195 to 603 hectares, indicating intensified degradation processes. A methodology is proposed that enables rapid differentiation of salinity levels, stability under vegetation cover and cloud cover, and enables the generation of cartographic recommendations for land reclamation management and field survey planning.