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Interpretable machine learning for river salinity dynamics in arid basins

Amini, Hossein, Shakeri, Reza, Ghaderi, Narjes, Fakheri, Farshid, Morovati, Khosro, Zahraie, Banafsheh and Ahmadian, Reza ORCID: https://orcid.org/0000-0003-2665-4734 2026. Interpretable machine learning for river salinity dynamics in arid basins. Scientific Reports 16 , 18310. 10.1038/s41598-026-49042-9

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Abstract

Managing salinity in arid rivers is impeded by sparse monitoring, relying on low-frequency grab samples that miss hydrological event dynamics. Here, interpretable machine learning is applied to a 50-year monthly archive (1968-2018; Discharge, major ions, pH) from three stations on Iran's Karkheh River. Gradient Boosting Regression achieves high predictive skill for Total Dissolved Solids (TDS)/Electrical Conductivity (EC) (test-set R  = 0.94/0.97; RMSE = 55 mg L /56 µS cm ), validated via time-aware cross-validation. SHAP-based feature attribution reveals that Na and SO are the strongest contributors to TDS, while Na and Cl dominate EC, consistent with conservative salinity sources under baseflow conditions. A reduced-input decision tree (four predictors) retains R  = 0.81-0.87, enabling minimal-sensor monitoring. Flow-regime partitioning and STL (Seasonal-Trend decomposition using Locally estimated scatterplot smoothing)-detrended event composites reveal low-flow salinization and ion-specific post-flood recovery (Cl : 1-2 months; Na : 2-3 months), guiding targeted sampling. This framework extracts predictive power, process associations, and operational guidance from legacy grab-sample archives, scalable to data-limited basins worldwide. [Abstract copyright: © 2026. The Author(s).]

Item Type: Article
Date Type: Publication
Status: Published
Schools: Schools > Engineering
Publisher: Nature Research
ISSN: 2045-2322
Date of First Compliant Deposit: 8 May 2026
Date of Acceptance: 13 April 2026
Last Modified: 13 Jul 2026 12:45
URI: https://orca.cardiff.ac.uk/id/eprint/186878

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