Solute transport model for groundwater contamination in Wadi Bani Malik, Jeddah, Saudi Arabia

Groundwater is susceptible to pollutants. Contamination occurs when human products such as gasoline, oil, and sewage get into the groundwater and cause it to become unsafe for human use. In the last 15 years, Wadi Bani Malik has become a highly polluted area due to the disposal of sewage water in the Al-Musk area. This area has been subjected to environmental hazards, and the groundwater is the most vulnerable to the pollution. The degree of pollution can be determined from the analysis of arsenic (As). In this investigation, solute transport modeling is conducted using the finite difference method implicitly with the backward in time and center space (BTCS) technique. The model solution is in good agreement with the analytical solution. More importantly, when the model is compared with the observed As samples, it shows a strong correlation > 0.8. The model predicts the movement of the contaminants in the groundwater beginning from the starting day of installation of the land fill, showing that the plume will only travel about 16–20 km in 40 years. By that time, less than about 30% of the concentration in groundwater will be subjected to decay (diluted). However, it is difficult to fully explain the real concentration rate of change in the Al-Musk area towards the groundwater because between 2000 and 2011, the pollution was considered as a continuous source, but after that, the disposal of sewage in Al-Musk Lake has mainly stopped. So, the behavior of the lake is now defined as a discontinuous point source function.