Simulation of non-point sources of pollution in a heterogeneous media by using 2D regional groundwater flow model

Abstract

Shallow unconfined aquifer is one of the major sources for drinking and irrigation in many countries of the world. Unsustainable agricultural activities disperse nitrate into groundwater, and jeopardize human’s health and socioeconomic growth in groundwater dependent regions. A two-dimensional steady-state solute transport model has been developed in the present research to simulate movement of non-point sources of Nitrate pollution in heterogeneous porous media. The migration of chemicals dissolved in groundwater is governed by advective-dispersive processes which are also affected by the velocity of the flowing groundwater. Therefore, Darcy equation is solved for hydraulic head and hydraulic conductivity to approximate the average linear velocity of the fluid. The advection-dispersion is used to approximate the spatial and temporal distribution of nonreactive dissolved chemical in a flowing groundwater. A Matlab code has been developed to solve the groundwater flow and solute transport equations by using finite difference methods. The developed program is verified by sand tank experimental data. Finally, the proposed solute transport model is used to simulate non-point source of nitrate pollution in an agriculture-intensive region of Northwest Bangladesh. Analysis of groundwater simulation results show that the aquifer in the region is very sensitive to pollution and Nitrate can travel up to 5 km horizontally and 25 m vertically in one single year. Geology, groundwater velocity, pollution concentration and type of pollution, and grid size are the factors that control pollution transportation in the area.