In order to reveal the trend of water chemistry change in the Yarlung Tsangpo River (Yajiang River) under the background of climate change and provide scientific and technological support for water resources and water environment management in the basin, based on the study of hydrochemical characteristics of the Yajiang River in 2016, 2017 and 2018, combined with the research results of existing research teams on hydrochemistry, this paper studies the trend of 11 hydrochemical components change of the upper, middle and lower reaches of the Yajiang River over the past 60 years by comprehensive use of linear tendency estimation, climate change model output and BP neural network model. The results show that the annual average temperature in the upper, middle and lower reaches of the Yajiang River Basin has been increasing obviously in the past 60 years. The average temperature warming rate was 0.38°C/10a. The precipitation in the Yajiang River Basin fluctuated obviously and showed an overall rising trend, with a rising rate of 7.34 mm/10a. pH value of the water in Yajiang River was weakly alkaline and showd an upward trend. TDS was higher than the average level of the world river (120 mg/L) and showed a trend of gradual increase. Based on the climate change model RCP4.5 scenario, the artificial neural network prediction shows that the TDS flux in the upper, middle and lower reaches of the Yajiang River Basin presents a gradually increasing trend, and the downstream will have a certain impact on the production and life of the downstream residents. 

Based on the principles of ecology and design, the general method framework of designed ecosystem was put forward. The framework is guided by the provision of integrated ecosystem services and based on the basic laws of the ecosystem, which aims to create a balanced habitat of soil and water, configure a stable and orderly local biological network, and design recreation facilities with minimum intervention. At the same time, according to the practice of ecological restoration design and the classical ecological engineering design guides, this study summarized the key design parameters of the designed ecosystem from three aspects: structure, materials and auxiliary measures, a total of 31 items. On this basis, to engineer the traditional ecological wisdom, specific design methods and quantitative parameters of terrace, impounding-pond, dike-pond and stacking-fields habitat creation modes in the aspects of basic model characteristics, habitat unit shaping, water cycle regulation, soil environment regulation, biological community allocation and recreation facilities construction were put forward. This result provides an engineering and replicable method for the practice of large area ecosystem restoration engineering in China.

The existing landscape performance evaluation research has problems such as the lack of ecological theory support in the evaluation system, the lack of comprehensive performance evaluation of water landscape according to the scale of site design, the completeness of the selection of framework or indicators, and the lack of typicality and availability. Therefore, the authors fully combed the four existing systems of landscape performance evaluation. At the same time, the related theories of water ecosystem services were studied, the types and elements of water ecosystem services were identified, and then the logical relationship between water ecosystem services and landscape performance evaluation were clarified. Based on the water ecosystem service theory, combined with the relevant international landscape performance evaluation system and indicators, the authors built a scientific and operable comprehensive performance evaluation index system for water landscapes, including 5 types of project layers, 10 types of criteria layers and 28 indicators. The relevant results are expected to provide a basis for the 

optimization of design strategies for water landscape designers.