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

Abstract

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.