VLDA model and its application in assessing phreatic groundwater vulnerability: a case study of phreatic groundwater in the plain area of Yanji County, Xinjiang, China

Based on the GOD method and DRASTIC model for groundwater vulnerability assessment, in this paper, VLDA model for assessing phreatic groundwater vulnerability is proposed, where V is lithology of vadose zone, L is the pattern of land use, D is groundwater depth, and A is the aquifer characteristics. As a case study, the paper assesses the vulnerability of phreatic groundwater in Yanji County of Xinjiang by using the VLDA model as the tool and GIS as the platform, and matches the vulnerability with nitrate content of the phreatic groundwater in September 2009. The results indicate that areas with highly vulnerable pore phreatic groundwater account for 40.83% of the total inland area of Yanji County, including most of the northwestern area (such as the groundwater wellfield in Korla City) and Yanji Town. It is also discovered that areas with phreatic groundwater of higher vulnerability essentially coincide with areas with higher nitrate content, indicating the feasibility of using VLDA model to assess groundwater vulnerability.