The natural support capacity (NSC) of water resources is a key aspect of the regional carrying capacity of water resources, and it can reflect the quality and quantity of water resources in a region. This paper aims to evaluate the NSC of water resources using a model based on the principal component analysis (PCA) to benefit the development and utilization of regional water resources. A case study in the Fuyang district, Zhejiang Province, China, was carried out. First, water resources, as dependent variables, were assumed to be linearly influenced by the indicators affecting the NSC of water resources. These indicators were regarded as independent variables for multivariate analysis in this study. Then, the available water resources data for the Fuyang district between 1995 and 2003 were inputted to the model to analyze NSC levels of water resources. The results indicated that the most important parameters influencing the NSC of water resources could be shortlisted to water resources availability, surface water resources, groundwater resources, allowable withdrawal of water resources, and emission intensity of chemical oxygen demanding. Our findings revealed that the NSC of water resources in the Fuyang district fluctuated between 1995 and 1999 and generally declined after 2000, indicating that the issue of water pollution has worsened since 2000. These results are consistent with the field observations and thus shall provide new potential applications of a PCA-based model in evaluating the NSC of water resources and the relevant water resource carrying capacity for similar areas.

Mountain creek areas are a type of flood-prone area, and the flood control in these areas has not been well understood. This study aims to evaluate the impact of rain patterns on the water level and the establishment of flood control standard in mountain creek areas by conducting a case study. The case study was performed on a typical mountain creek area, called Shiliqu watershed in Hangzhou, China. A MIKE11 model was first established to analyze the required flood control standard through investigating the river level impacted by two rain patterns (the designed rainstorm and the typhoon Fitow). The results show that the designed rainstorm pattern and the typhoon Fitow rain pattern have the single-peak and multi-peak profile, respectively. The peak rainfall value of the designed rainstorm pattern is much higher than that of the typhoon Fitow. However, the large fluctuations under the typhoon Fitow rain pattern causes multi-level overtopping which threats the safety of the flood control. Also, the typhoon Fitow could have a greater influence on the water level of the tributaries of the river than that of the mainstream. The selection of rain pattern on the design of flood control standard in mountain creek areas is discussed.