| The lake is an important national resource and a place on which human beings depend,and plays a vital role in water supply,flood regulation,water quality improvement and biodiversity conservation.As a highland lake,Dianchi faces problems such as strong lake closure,low water recharge,high water evaporation,long water exchange cycles,and difficulty in recovering from pollution.In order to solve the environmental problems faced by Dianchi,the relevant departments have adopted "six major projects" for the management of Dianchi.Among them,the Outer Basin Diversion Project has been the most effective and has played a vital role in solving the environmental problems of Dianchi.This paper takes the Niulanjiang-Dianchi water replenishment project as an example and examines the effect of changes in the water environment,water ecology,economic and social environment,and the value of ecosystem service functions on the improvement of the Dianchi environment in the Dianchi basin before and after the replenishment project.Problems in the Dianchi basin are pointed out,and measures and suggestions are made for the protection and restoration of the river and lake systems.The main conclusions of the thesis are as follows:(1)Four water quality evaluation methods and water nutrient status evaluation methods were used to calculate the water quality categories and nutrient status of Dianchi before and after the water replenishment project.The results show that the water quality of Dianchi has improved significantly after the water replenishment compared with that before the replenishment,and Dianchi is free from the plague of poor V water.(2)The changes in the species and abundance of fauna,flora and plankton in Dianchi before and after the recharge project were compared.The results show that the water bloom covered the whole lake before the recharge,especially in the north and southeast of Dianchi.The species and abundance of fauna,flora and plankton in Dianchi increased after recharge compared to the pre-recharge period,and the reappearance of disappeared species marked the improvement of the water environment in Dianchi.(3)The social environment and economic aspects compared the impact of property prices around the Panlong River and Dianchi before and after the opening of the water replenishment project,people’s evaluation of Dianchi,national reports on Dianchi,and changes in tourism revenue and the number of people received at Dianchi National Tourism Resort.The results show that after the opening of the water replenishment project,the property prices in and around Dianchi have increased significantly,from RMB 6,000/m2 to RMB 12,000/m2.It is clear from the questionnaire that people are very satisfied with Dianchi after the water replenishment.The state attaches great importance to the water replenishment project and gives high recognition to the results achieved by the water replenishment project.The tourism revenue and the number of visitors to the Dianchi National Tourism Resort have increased significantly compared to the pre-recharge period,with an average annual increase of 2.23% in tourism revenue and 0.92% in tourism visits after the recharge.(4)The value of ecosystem service functions was calculated using the market value method,the shadow engineering method,the travel cost method and the alternative cost method to calculate the value of material products,the value of regulating services and the value of cultural services in Dianchi before and after the water replenishment project.The results showed that the value of the ecosystem service function of Dianchi increased by 71.2% after the opening of the water replenishment project compared with that before the replenishment,and the ecological environment of Dianchi is developing for the better.(5)The problems in the Dianchi basin are analysed,such as the low replenishment of Dianchi during the dry season,the incompatibility between the water environment and economic development,the decline in water quality in the Panlong River section,and the high level of sediment in the flood season of the replenishment project.Suggestions are made for the protection and restoration of China’s river and lake systems,such as strengthening the work of water resources demonstration,carrying out water resources science and education,combining ecological restoration and landscape enhancement of rivers and lakes,strengthening scientific and technological support and improving supervision,establishing and improving the unified scheduling and centralised management system and mechanism,vigorously improving the river and lake manager system,and accelerating river and lake water system connectivity and promoting recreational management. |
