Intelligent Calibration of the Transient Storage Model by Integrating Genetic Algorithm and Finite Difference Method for Solute Transport Simulation

Articles in Press

Document Type : Research Paper

Authors

1 Assistant professor of water engineering department, Faculty of agricultural engineering, Sari agricultural sciences and natural resources university.

2 Department of Environmental Engineering, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran.

3 Water Engineering Department, Faculty of Agricultural Engineering, Sari Agricultural Sciences and Natural Resources University, Sari. Iran.

10.22059/ijswr.2025.401515.670002

Abstract

Simulating solute transport in rivers is significantly challenged by the complex phenomenon of transient storage. This study develops an integrated numerical model that couples an explicit Finite Difference Method (FDM) with a Genetic Algorithm (GA) to automate the calibration of key parameters in the one-dimensional Transient Storage Model (TSM). The governing advection-dispersion equations for the main channel and storage zones were discretized using an Upwind-Central scheme. A GA-based optimization framework was implemented to estimate four critical parameters—longitudinal dispersion coefficient (D), storage exchange coefficient (α), main channel cross-sectional area (A), and storage zone area (Aₛ)—by minimizing the Root Mean Square Error (RMSE) between simulated and experimental concentration data. The model incorporates flexible boundary conditions, including constant concentration, time-varying input, and mass flux at the upstream end, and zero-gradient or advective flux at the downstream end. Advanced numerical stability mechanisms (CFL, diffusion, and exchange criteria) ensure robust performance. Validation against experimental data from a simulated flume demonstrated the model's superior performance (R² > 0.90, NSE > 0.90) over the standard OTIS-P software. Beyond high accuracy, the model offers novel capabilities: 3D concentration output visualization, systematic parameter sensitivity analysis via the Morris method, and uncertainty assessment based on the Damköhler number (Da). This approach provides a powerful, automated tool for realistically simulating solute transport in river systems, effectively incorporating transient storage dynamics.

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Iranian Journal of Soil and Water Research

Articles in Press, Accepted Manuscript
Available Online from 10 December 2025

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