Assignment of the Groundwater Level at the Leachate Collection Pipe for the Waste Landfill Groundwater Simulation: Combination of the Two Dimensional Saturated - Unsaturated Vertical and Horizontal Groundwater Flow Model

The landfill construction has caused many negative impacts on the surrounding environment, particularly groundwater. Evaluation of the function of the leachate collection pipe at the landfill site is indispensable for managing the landfill operation. 3D groundwater flow simulation may be applicable but it requires much capacity of computer and time consumption comparing with 2D groundwater flow simulation due to the huge calculations. Therefore, the 2D horizontal groundwater flow simulation (2Dh) was carried out. However, the most difficulty is the assignment of the groundwater head at the leachate collection pipe buried for leachate drainage. Therefore, in the present paper the 2D vertical model (2Dv) was applied to calculate the change of groundwater table above the leachate collection pipe. This paper paid attention to examine the validation of the assignment of the leachate collection pipe boundary by applying the results of the 2Dv. The 2Dh was coupled with the rainwater recharge model to solve the partial differential equation of groundwater flow. Finite difference method and iterative successive over relaxation were applied. The drainage volume of leachate collection was summed up in the whole landfill site and compared with the average volume of treated waste water. The study demonstrated that the groundwater level at the vicinity of the drainage pipe in the 2Dv analysis is reasonably assigned for the 2Dh.