Integrating water-related disaster and environment risks for evaluating spatial-temporal dynamics of water security in urban agglomeration.

Water security is a compound concept coupling multi-dimensional perspectives, such as resource utilization, environmental protection, and disaster prevention. With this concern, this study focuses on the spatial-temporal dynamics of water security with considering water disaster risk index (WDRI), water environment risk index (WERI), and water supply-demand. WERI centers on risk source's hazard, control effectiveness, and risk receptor's vulnerability. Indices related to hazard, exposure, and vulnerability are used for evaluating WDRI. A multi-objective fuzzy membership function is presented for determining the indices' weight, and the distribution pattern of water security is illustrated based on cluster analysis. A real-world case study of Beijing-Tianjin-Hebei urban agglomeration (BTHUA) is given for verifying availability of the evaluation framework. Results indicate the general water security in BTHUA with a critical safe state yet a downward trend. Opposite change characteristics of water security exist between its southern and northern cities. WDRI and WERI show the trends of increasing (with a growth rate of 0.48%) and decline (with an average decrement rate of 0.56%), respectively. Beijing has high-value WDRI and WERI, and the order of WDRI and WERI is presented as follows: Beijing (0.67) > Tianjin (0.54) > Hebei (0.33) and Beijing (0.69) > Tianjin (0.58) > Hebei (0.16), respectively. Cluster analysis reveals a poor match relation between water security and regional socio-economic development. Areas with high-level economic development (e.g., Beijing and Tianjin) have poor environmental performances, with WDRI and WERI of 0.54 ~ 0.68 and 0.57 ~ 0.70, respectively. Additionally, water resources overload index of BTHUA is 8.513, which is higher than Chengdu-Chongqing urban agglomeration (1.431), Triangle of Central China (0.228), and Yangtze River Delta urban agglomeration (0.742). Findings can provide a theoretical reference for promoting sustainable utilization of water resources in BTHUA and the other areas with prominent water problems.