Abstract

rotective effectiveness or natural protection against contamination or intrinsic vulnerability of aquifers is natural ability of aquifers to protect themselves from contamination regardless to the characteristics of the contaminants. Through the analysis of application conditions, advantages and disadvantages of aquifer vulnerability assessment methods available worldwide, characteristics of karst aquifers as well as the specific conditions in Việt Nam, the "two factor" method was selected. The experimental application of this method in the area of Lạng Sơn city, where the fissure- karst aquifer in carbonate rocks, belonging the Bac Son Formation aged the late Carbon-early Triassic (C₂-P₁ bs), is the main groundwater source exploited for domestic water supply, has given reliable results.