Assessment of groundwater vulnerability by applying the improved DRASTIC model: a case in Guyuan City, Ningxia, China.

Groundwater is the main source of production and living in most arid and semi-arid areas, and it plays an increasingly critical role in achieving local urban development. There is a serious issue regarding the contradiction between urban development and groundwater protection. In this study, we used three different models to assess the groundwater vulnerability of Guyuan City, including DRASTIC model, analytical hierarchy process-DRASTIC model (AHP-DRASTIC) and variable weight theory-DRASTIC model (VW-DRASTIC). The groundwater vulnerability index (GVI) of the study area was calculated in ArcGIS. Based on the magnitude of GVI, the groundwater vulnerability was classified into five classes: very high, high, medium, low, and very low using the natural breakpoint method, and the groundwater vulnerability map (GVM) of the study area was drawn. In order to validate the accuracy of groundwater vulnerability, the Spearman correlation coefficient was used, and the results showed that the VW-DRASTIC model performed best among the three models (ρ=0.83). The improved VW-DRASTIC model shows that the variable weight model effectively improves the accuracy of the DRASTIC model, which is more suitable for the study area. Finally, based on the results of GVM combined with the distribution of F- and urban development planning, suggestions were proposed for further sustainable groundwater management. This study provides a scientific basis for groundwater management in Guyuan City, which can be an example for similar areas, particularly in arid and semi-arid areas.

[Territorially ecological restoration zoning and optimization strategy in Guyuan City of Ningxia, China: Based on the balance of ecosystem service supply and demand]. / 基于生态系统服务供需平衡的宁夏固原生态修复分区与优化策略.

Scientifically identifying the territorially ecological restoration zoning is a vital prerequisite for implementing ecological restoration projects and enhancing environmental quality. Based on remote sensing data, we syste-matically assessed supply and demand for ecosystem service and their relationship in Guyuan City, China by using the InVEST model, coordination degree model, and spatial autocorrelation analysis. We carried out territorially ecological restoration zoning by coupling the ecosystem service supply and demand. Furthermore, the corresponding optimization strategies were put forward according to the regional characteristics of natural resources and socio-economic development. The results showed that the areas with high water yield, carbon storage, soil conservation and habitat quality were mainly located in the southern part of Guyuan City. The areas with high population density, economic development level and high ecological demand were mainly located in the central urban area and the location towns of the county government. The spatial mismatch of supply and demand for ecosystem services in Guyuan City was dominant, as indicated by the fact that the areas with high ecological supply having low ecological demand and low ecological supply having high ecological demand. The average coordination index was 0.5, indicating that the relationship between ecological supply and ecological demand was basically coordinated. Based on the diffe-rences between supply and demand of ecosystem services and regional natural geographical pattern, the administrative township units in Guyuan could be classified into six ecological restoration zonings: key ecological restoration area, potential ecological restoration area, ecological economic reconstruction area, characteristic agricultural development area, ecological core protection area, and ecological industry construction area. Different management strategies were proposed to provide scientific support for ecological restoration.