Landfills are one of the groundwater pollution sources in Gaza Strip. This study focuses on two landfills operating in Gaza Strip; the first is Dear Al Balah landfill which has a lining system and the second landfill is Gaza landfill which does not have a lining system. The main objective of the present study is to assess the effect of landfill components on percolated leachate to groundwater aquifer using the Hydrologic Evaluation of Landfill Performance (HELP) model. A comprehensive analysis of landfill components affecting the generated leachate was conducted. The results showed that the landfill components were ordered in priority according to their effects on percolated leachate through clay layer as follows: (1) existing of lining system enhances the percolation reduction up to 87%, (2) 30% reduction of rainfall level enhances the percolation reduction up to 50%, (3) 50% reduction of existing landfill area enhances
