Study shows India’s deltas sinking due to human activity, PgII

Key Highlights:

• A study reveals that India's river deltas are sinking due to human activities like groundwater extraction and urbanization.
• Six Indian deltas, including Ganges-Brahmaputra, Brahmani, Mahanadi, Godavari, Cauvery, and Kabani, are experiencing land subsidence.
• Over 90% of the Ganges-Brahmaputra, Brahmani, and Mahanadi deltas are affected by sinking.
• In some deltas, the rate of land subsidence exceeds the rate of regional sea-level rise.
• Ganges-Brahmaputra and Cauvery deltas are significantly impacted by unsustainable groundwater extraction, while the Brahmani delta is affected by rapid urbanization.

Detailed Insights:

• The study used interferometric synthetic aperture radar data from the European Space Agency’s Sentinel-1 satellite (2014-2023) to assess subsidence rates in 40 major deltas globally.
• A random forest machine learning model correlated subsidence rates with stressors like groundwater storage, sediment flux, and urban expansion.
• Land subsidence leads to increased coastal and river flooding, permanent land loss, saltwater intrusion, agricultural land degradation, and damage to infrastructure.
• The Ganges-Brahmaputra delta has transitioned from a "latent threat" to an "unprepared diver," indicating increased risk and stagnant institutional capacity.
• The study acknowledges limitations in GRACE data for smaller deltas and the need for updated sediment flux data.

Scientific/Technical Concepts Involved:

• Interferometric Synthetic Aperture Radar (InSAR): A remote sensing technique using radar to detect ground deformation.
• Sentinel-1: An ESA satellite mission providing radar data for various applications, including monitoring land subsidence.
• Random Forest: A machine learning algorithm used for classification and regression tasks, here used to correlate subsidence with stressors.
• GRACE Satellites: A joint NASA-German mission measuring variations in Earth's gravity field, used to estimate groundwater storage.