Studying Effect of Travel Distance on Dispersion Coefficient in Layered Soil Perpendicular to Flow Direction using Numerical Model

Document Type : Original Article


1 Department of Water Science and Engineering, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran.

2 Expert of Water Engineering, Urban Green Space of Shahrood Municipality, Iran.


One of the most important measurable properties of the porous medium is dispersivity, which is used in advection-dispersion equations related to pollutant transport in the study of groundwater. In the past, the dispersivity coefficient for the entire porous medium was considered as a constant coefficient, but many studies conducted in the last few decades have shown that the dispersivity depends on many parameters, including the travel distance. Since most of these studies have been conducted in homogeneous porous media, in this research, the effect of travel distance of 20, 50 and 80 cm on the dispersivity coefficient in a porous medium corresponding to coarse, medium and fine granularity was investigated. The results obtained in this research showed that in all travel distances, the volume of pore water reached one before reaching the relative concentration of 0.5, and the pollutant travel rate decreased with increasing travel distance, which was consistent with the results of other studies. Also, the numerical modeling by Hydrus numerical model showed that this model was able to calculate the value of the diffusion coefficient for the travel distances of 20, 50 and 80 cm with the RMSE error equal to 0.065, 0.068 and 0.061, respectively, which indicates its high accuracy is in simulating and moving the contaminant in the porous medium.


Al-Tabbaa, A., Ayotamuno, J., and Martin, R., 2000. One-dimensional solute transport in stratified sands at short travel distances. Journal of hazardous materials, 73(1), pp. 1-15.
Ayotamuno, M.J., 1999. Contaminant transport and immobilisation in stratified sands, University of Birmingham.
Bazoobandi, A., Emamgholizadeh, S., and Ghorbani, H., 2022. Estimating the amount of cadmium and lead in the polluted soil using artificial intelligence models. European Journal of Environmental and Civil Engineering, 26(3), pp. 933-951.
Emamgholizadeh, S., Bahman, K., Bateni, S.M., Ghorbani, H., Marofpoor, I., and Nielson, J.R., 2017. Estimation of soil dispersivity using soft computing approaches. Neural Computing and Applications, 28, pp. 207-216.
Emamgholizadeh, S., Bahman, K., Ghorbani, H., Maroufpoor, E., and Ajdari, K., 2014. Estimating soil dispersivity coefficient by Artificial Neural Network. International Journal of Soil Science, 1(1), pp. 382-390.
Farasati, M., and Seyedian, S., 2013. Effect of Scale on NaCl Dispersivity by HYDRUS 2D. Journal water and Soil, 27(4), pp. 823-831.
Liu, Y., Liu, Y., Li, S., Zhang, Q., and Qian, J., 2023. Scale dependence of dispersion coefficient for solute transport in porous media using image analysis. Journal of Hydrologic Engineering, 28(6), pp. 04023016.
Maroufpour, A., Kashkuli , H., Moazd, H., and Mohammadouli Samani , H., 2014. Investigating the dependence of soil permeability on its thickness in saturated homogeneous sandy soils . . Journal of Science of Shahid Chamran University, 16(1), pp. 16-29.
Mehdipanah, H., Tashakkori, A., Emamgholizadeh, S., and Maroufpoor, E., 2022. Study of the Effect of Transport Distance on Dispersion Coefficient of Sodium Chloride in Horizontal Stratified Sandy Soils and its Simulation with HYDRUS-2D. Irrigation and Water Engineering, 13(2), pp. 297-311.
Ohadi, S., Hashemi Monfared, S.A., Azhdary Moghaddam, M., and Givehchi, M., 2023. Feasibility of a novel predictive model based on multilayer perceptron optimized with Harris hawk optimization for estimating of the longitudinal dispersion coefficient in rivers. Neural Computing and Applications, 35(9), pp. 7081-7105.
Parsaie, A., Emamgholizadeh, S., Azamathulla, H.M., and Haghiabi, A.H., 2018. ANFIS-based PCA to predict the longitudinal dispersion coefficient in rivers. International Journal of Hydrology Science and Technology, 8(4), pp. 410-424.
Samani, F., Tabatabaei, S., Abbasi, F., and Alaei, E., 2019. Hydraulic parameters sensitivity analysis of porous media at inverse solution of bromide transport. Journal of Water and Soil Science, 23(3).
Selim, H., Davidson, J., and Rao, P., 1977. Transport of reactive solutes through multilayered soils. Soil Science Society of America Journal, 41(1), pp. 3-10.
Shamir, U.Y., and Harleman, D.R., 1967. Dispersion in layered porous media. Journal of the Hydraulics Division, 93(5), pp. 237-260.
Shiran , H., Sayad, M., and Taghavi  , H., 2018. Modeling of bromide movement in disturbed soil columns using HYDRUS- 1D model. Watershed Researches ( Research and Development ), 24(3), pp. 21-30.
Tao, H. et al., 2022. Development of new computational machine learning models for longitudinal dispersion coefficient determination: Case study of natural streams, United States. Environmental Science and Pollution Research, 29(24), pp. 35841-35861.
Younes, A., Fahs, M., Ataie-Ashtiani, B., and Simmons, C.T., 2020. Effect of distance-dependent dispersivity on density-driven flow in porous media. Journal of Hydrology, 589, pp. 125204.