DETERMINE THE VULNERABILITY OF URBAN SURFACE WATER RESOURCES IN RACH GIA CITY, VIETNAM USING GEOGRAPHIC INFORMATION SYSTEM

Rach Gia city is located on the west coast of Mekong Delta, Vietnam. Due to the high salinity intrusion of underground aquifers, urban surface water is the main source of mining Water retention consists of reservoirs with around 600,000 m3 and 3.2 km length of a canal. These resources are taken from rivers and canals in the area. However, urban surface water in the area is contaminated by human activities such as wastewater discharge and waterway traffic. Furthermore, in dry seasons when water levels in rivers and canals reach low salinity intrusion infiltrate into rivers, affecting water supplies. Therefore, it is necessary to identify the vulnerabilities of pollution on reservoirs and canals This study employs a spatial analysis model integrating several previously defined parameters such as slope, land use, drainage network density, runoff and salinity levels. They will be prioritized and weighted and then integrated into a geographic information system (GIS). Results indicated drainage network density and land use are majors to cause vulnerability of pollution on an urban surface water resource. Despite the subjectivity involved in the weighing of analytic hierarchy process (AHP), the study determined vulnerability levels as well as factors that cause pollution. These results will support to protect urban surface water resources.