This document summarizes a study that used GIS to develop a groundwater vulnerability index for the Tuul River Basin in Mongolia. The study area is located in north central Mongolia and covers an area of 49,744 square kilometers. The researchers used the DRASTIC method from the US EPA to analyze parameters like depth to water, recharge rate, aquifer media, soil texture, topography, vadose zone, and conductivity to create vulnerability maps for the region and determine areas with high, moderate, and low vulnerability.