Work

Seasonal Freshwater Inflows in Cochin Backwater Estuary Inferred from Stable Isotopes and Machine Learning

Year: 2025

Type: article

Abstract: Cochin backwater region in Southern India is one of the most dynamic estuaries, strongly influenced by seasonal river runoff and seawater intrusion. This study explores the rela-tionship between monsoonal rains, salinity, and stable isotopic composition (δ¹⁸O and δ¹³C) to estimate the contribution of freshwater fluxes at different seasonal intervals for the Cochin Backwater (CBW) estuary. Seasonal variations in oxygen isotopes and salinity re-vealed distinct trends indicative of freshwater-seawater mixing dynamics. The compari-son of Local and Global Meteoric Water Lines highlighted enriched isotope values during the pre-monsoon season, showing significant evaporation effects. Carbon (C) isotopic analysis in dissolved inorganic matter (δ¹³CDIC) at 17 stations during the pre-monsoon season revealed spatially distinct carbon dynamics zones, influenced by various sources. These characteristic zones were Zone 1, dominated by seawater, exhibited heavier δ¹³CDIC values; Zone 2 showing significant contributions of lighter terrestrial δ¹³C; while Zone 3 reflected inputs from regional and local paddy fields with a distinct C3 isotopic signature (-25‰), modified by estuarine productivity. In addition, different advanced machine learning techniques were tested to improve analysis and prediction of seasonal variations in isotopic composition and salinity. The combination of these advanced machine learn-ing models not only improved the predictive accuracy of seasonal freshwater fluxes but also provided a robust framework for understanding the estuarine ecosystem and would pave way for better management and conservation strategies.

Source: Hydrology

DOI: 10.3390/hydrology12110277

Authors: Prasanna K., Ravi Rangarajan, Fursan Thabit, Prosenjit Ghosh, Habeeb Rahman

Institutions: Birbal Sahni Institute of Palaeosciences, University of Doha for Science and Technology, University of Chinese Academy of Sciences, Indian Institute of Science Bangalore, Cochin University of Science and Technology

Language: English

Topic: Groundwater and Isotope Geochemistry

Subfield: Geochemistry and Petrology

Field: Earth and Planetary Sciences

Domain: Physical Sciences

SDGs: Clean water and sanitation, Climate action

Open Access status: gold

Estimated APC paid: $2,172