  The contamination impact and the migration of the contaminant into the
surrounding environment due to the presence of a spilled oil pipeline will
cause significant damage to the natural ecosystem. For this reason, it is
decisive to develop a rapid response strategy that might include accurate
predictions of oil migration trajectories from numerical simulation modeling.
In this paper, a three-dimensional model based on a high-resolution
shock-capturing conservative method to resolve the nonlinear governing partial
differential equations of the migration of a spilled light nonaqueous liquid
oil contaminant in a variably saturated zone is employed to investigate the
migration of the oil pipeline leakage with great accuracy. The effects on the
oil type density, gasoline and diesel oil, the unsaturated zone depth, its
saturation, the hydraulic gradient, and the pressure oil pipeline are
investigated through the temporal evolution of the contaminant migration
following the saturation profiles of the three-phase fluids flow in the
variably saturated zone. The calculation results indicate that the leaking
oil's pressure is the parameter that significantly affects the contaminants'
arrival time to the groundwater table. Also, the water saturation of the
unsaturated zone influences the arrival time as the water saturation increases
for a fixed depth. The unsaturated zone depth significantly influences the
contaminant migration unsaturated zone. At the same time, the oil density and
the hydraulic gradient have limited effects on the contaminant migration in the
variably saturated zone.
