Ecological Safety Evaluation for Water Resources of China Based on Pressure-State-Response Model: A Case from Zhoushan Archipelago

Water resource ecological safety is a key factor in regional economic and social development. The comprehensive evaluation of water resource ecological safety is an important precondition for realizing regional sustainable development with the increasingly serious water ecological crisis. Zhoushan City of China was taken as an example, and the pressure–state–response model (PSR) was used to evaluate the ecological safety status of regional water resources, improve deficiencies in the existing evaluation index system and evaluation method effectively, and put forward three evaluation subsets (18 evaluation indexes). An evaluation index system was established based on these indexes to evaluate the water resource ecological safety. Combined weights of indexes were calculated using the analytic hierarchy process (AHP) and entropy weight method, and water-resource ecological safety indexes were used to evaluate the water-resource ecological safety status in Zhoushan City during 2010–2019. Results show that the water-resource ecological safety level in Zhoushan City during 2010–2019 presents a rising trend and transformed from a serious warning state into a medium warning state as well as a relatively safe state and safe state. This transformation indicates that the ecological safety status in Zhoushan City gradually improves. The comprehensive evaluation value is the minimum (0.15) under the serious warning state in 2013 and the maximum (0.85) under the safe state in 2019. Ammonia nitrogen and chemical oxygen demand (COD) emissions in industrial wastewater, total water supply throughout the year, and governance area of water and soil loss are the main factors that influence the water resource ecological safety in the city. The ecological safety level of regional water resources can be effectively elevated through key measures, such as increasing the water resource supply throughout the year, reducing the application of pesticides and chemical fertilizers, and reducing the discharge of pollutants, including COD and ammonia nitrogen in industrial wastewater. The water resource ecological safety evaluation model based on the PSR model and AHP–entropy weight method that demonstrates a certain application value can provide a novel idea and method to support the ecological safety evaluation of regional water resources.