Laboratory Investigation of the Effect of Gabion Spur Dikes Storage Zones on the Numerical Simulation of Pollution Transport in Rivers

Articles in Press

Document Type : Original Article

Authors

1 Water Engineering Department, agricultural engineering faculty, sari agricultural sciences and natural resources university.

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

3 Water engineering department, Agricultural engineering Faculty, Sari University.

Abstract

Ensuring the health and sustainability of the environment is one of the secondary goals of hydraulic structures. Water pollution and the reduction of its quality are serious threats to the health of the earth and will turn rivers into channels for polluted industrial wastewater. Increasing the residence time of flow in rivers by constructing hydraulic structures such as gabion spur dikes can increase the self-purification capacity. In this research, a laboratory investigation of pollution transport using NaCl tracer material in a laboratory channel with a sediment bed with a medium diameter (D50) of 11.85 mm, thickness of 12 cm, and length of 12 meters in a different number of fine-grained or coarse-grained gabion spur dikes from 1 to 4 were performed. Analytical solutions of Advection-Dispersion equation (ADE), OTIS model, and solution of Transient Storage Model (TSM) were used for numerical simulation. Laboratory results showed that gabion spur dikes with fine-grained materials reduce the peak concentration of pollution (Cmax) compared to coarse-grained materials. The results showed that the gabion spur dikes in the flow path increase the residence time of the pollutant by increasing hyporheic exchanges. The advection-dispersion equation (ADE) has low accuracy in the simulations due to the lack of attention to the role of the storage zone exchanges, with a determination coefficient (R2) of 0.71 to 0.83. On the other hand, the OTIS model, which is based on the transient storage model (TSM), considering the role of the porous zones of spur dikes in the transient storage of solute, has high accuracy with a determination coefficient (R2) of 0.91 to 0.98. The estimated coefficients of longitudinal dispersion (Dx) and storage zone exchange (α) by the temporal moment analysis were evaluated lower than the estimates of OTIS model in most of the simulations.

Keywords

Iranian Journal of Irrigation & Drainage

Articles in Press, Accepted Manuscript
Available Online from 03 January 2024

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