Groundwater vulnerability assessment and sensitivity analysis in Nong Rua, Khon Kaen, Thailand, using a GIS-based SINTACS model

The SINTACS approach was used to evaluate intrinsic groundwater vulnerability within Nong Rua District, Khon Kaen Province, Thailand. The approach is based on seven environmental variables prepared in the form of GIS data layers. These variables are depth to water level, infiltration capacity, unsaturated zone, soil type, aquifer media, hydraulic conductivity, and slope. The resulting vulnerability map depicts the spatial extent of six classes of vulnerability ranging from very low to extremely high. High and moderate level classes of vulnerability dominated most of the study area. The northwestern, southwestern and central parts of the study area fell under the very high and extremely high vulnerability levels according to this approach. These regions displayed characteristics that indicated their vulnerability such as a high infiltration rate, coarse-texture soil, and shallow depth to groundwater. The statistical correlation coefficient between the nitrate concentration in 87 wells and the SINTACS vulnerability levels was 0.51. Both map removal and single variable sensitivity analyses were performed to observe the influence of specific variables on the model result. The result of this study is useful for guiding strategic planning of groundwater quality management.