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Reservoir operation is important to realize the coordination of social, economic and environmental systems. However, climate events have changed the water cycle process and the spatial-temporal distribution of the water resource system, which has brought new challenges to regional water resources management and reservoir operation. This study aims at analyzing the impacts of climate change on the multi-objective reservoir operation at the dry season, and the adaptive reservoir operation scheme for future climate change scenarios. The Jinsha River, at the upper reaches of the Yangtze River, was chosen as the research area because a large number of reservoirs have been built in the basin. Firstly, the Pettitt, MK and Moving t-test methods were used to identify the abrupt points of the hydro-meteorological data series from 1957 to 2018, and then the SWAT model was used to quantify the impacts of climate change on the runoff in the Jinsha River. Secondary, the multi-objective optimal operation model of cascade reservoirs was constructed, and then an improved PA-DDS method is developed to find the Pareto front between ecological protection and power generation. Thirdly, the impacts of climate change on reservoir operation were analyzed by comparing the scheduling results between the pre-change period (1957-1996) and the post-change period (1997-2018). Finally, using the Delta downscaling method, the GCM models chosen by suitability assessment were inputted into the SWAT model to simulate the future runoff for the reservoir operation model under different scenarios. The results showed that (1) the temperature and precipitation in the Jinsha River faced an abrupt change in 1997, while the runoff changed in 1997 and 2004. (2) the SWAT model can well simulate the daily runoff of Jinsha River (Re0.79, R2>0.8), while climate change accounts for 52.4% and 52.1% of runoff change during 1997-2004 and 2005-2018, respectively. (3) climate change can increase the ecological deviation degree and the power generation of reservoirs. In addition, compared with the traditional optimal scheduling scheme, the potential climate change brings higher requirements for water resources optimization in the future. (4) From 2021 to 2100, the temperature, precipitation and runoff of the Jinsha River are continually increased compared with the pre-changed period. It should be noted that the runoff from September and October is significantly reduced in most scenarios, increasing the insufficient storage risk of cascade reservoirs; man-made floods may be caused by the increasing runoff from April to June and the concentrated discharge of reservoirs before flood season. This study can provide theoretical support for reservoir operation and provide technical references for the impact mechanism of climate change on water resources and their management.

Forest status in natural catchment is substantially important for hydrology and water quality, but it has been increasingly altered by human activities and climatic factors. Due to recent rapid changes in forest cover, there is an urgent need for hydrological water quality models which can adapt to these changing environmental conditions. The objective of this study was to analyse the impact of rapid continuous forest decline on nitrogen losses in a temperate mountain range catchment using a dynamic setting of the HYPE (HYdrological Predictions for the Environment) model. The modified model was applied to the Große Ohe catchment, Germany, which has experienced severe forest dieback (caused by bark beetle infestations) and its recovery over the last three decades. The model was validated by using also additional 25 years data from an internal gauge station (Forellenbach) and two soil measurement sites. Three scenarios, namely, no forest change, deforestation with subsequent regeneration, and deforestation without regeneration, were compared to identify key factors influencing catchment discharge and nitrogen export due to deforestation and regeneration. Results showed that the model performed well at the Große Ohe catchment scale, with Nash-Sutcliffe Efficiency values of 0.77 and 0.57 for discharge and IN concentration, respectively, and percentage BIAS values of -11.6% and 0.5%, respectively, during the validation period. Similar good performances were also observed at other scales. The simulation results proved that the improved model was able to (1) well capture the timing of peak flows and the seasonal dynamics of inorganic nitrogen (IN) concentration, and more importantly, (2) reflect the first increasing and then decreasing trend of discharge and IN concentration, in accordance with the deforestation and forest regeneration, respectively. By comparing scenarios, after experienced forest dieback without regeneration, the discharge and IN concentration exports were 24.9% and 160%, respectively, greater than those of scenario without forest change. However, the discharge and IN concentration exports were only 3.63% and 39.6% greater, respectively, with the help of continuous regeneration, indicating that forest regeneration is important for restoring hydrological and water quality status in the catchment. Compared to non-change scenario, the deforestation scenario exhibited decreased annual plant uptake of 34.7%, and strong increase in annual denitrification and N mineralization suggesting that the increased nitrogen export was likely induced by the reduction in vegetation uptake and the increased availability of soil nitrogen from tree residues. Overall, the adapted mechanistic modelling under the changing catchment forest conditions can strongly support forest management in terms of water quality.

This study investigated the combined impacts of the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) on streamflow under four scenarios: neutral, pure ENSO, pure IOD, and a combination of ENSO and IOD. The Jinsha River Basin (JRB), at the head of the Yangtze River, was used as a case study. By using statistical methods such as coherent wavelet analysis (WTC), we are committed to studying what kind of impact the IOD will have, the difference in impact between ENSO and IOD at different stages, and the difference in impact between ENSO and IOD on the mean and extreme values of runoff, compared with traditional single ENSO event, to provide support for water resource management, especially for reservoir operation. The key results are as follows. (a) Both ENSO and IOD events affect annual and seasonal streamflow in the JRB. (b) The impact of pure IOD events on annual streamflow in the JRB was twice as great as that of pure ENSO events in developing years, whereas the opposite was true in decaying years. (c) The combined impact of ENSO and IOD led to a higher streamflow maximum than the annual or seasonal average streamflow. Conversely, their impact on the streamflow minima was less than 10% during both developing and decaying years, except at Zhimenda Station. (d) Overall, water shortages could be more serious in developing years than in neutral years, and much more attention should be given to flooding control in decaying years. These results can be used as a reference for water resource management concerning agricultural planning and ecological protection in the JRB.

To promote ecosystem protection in the Wujiang River, this paper proposes a practical approach for calculating the environmental flow. The proposed approach combines the idea of the “guarantee rate” of the flow duration curve (FDC) method and the grading idea of the Tennant method. A daily flow series of the Wujiang River was compiled from 1956 to 2019 and used to compare the effect of the proposed approach versus the traditional approaches in four selected sections along the river. The results show that the environmental flow of the Wujiang River can be divided into five levels by the T-FDC method, with a level-by-level disparity, and all levels can capture the temporal and spatial variability of river flow. Additionally, the calculated basic environmental flow process ranges between the historical minimum and second minimum monthly average flow, and the threshold width of the optimal flow is more reasonable than the Tennant method. The T-FDC method can provide technical support for Wujiang River ecosystem management and sustainable development.

With the in-depth development of online tourism platforms, the online review of products in scenic spots has become an important basis for tourism consumption decisions. Through data mining and analysis of the online review of products in scenic spots, the tourism image perceived by tourists has become an important way to study the tourism image of scenic spots. Taking the Yearning Tea Plantation as an example, the word frequency and the content of tourism image attributes were analyzed by using the ROST CM6 content mining system software to comment on the online tourism platform for the sample of tourists, to understand the tourists’ perception of the tourism image of the Yearning Tea Plantation, and to provide the basis for the improvement and improvement of the tourism image of the leisure agriculture scenic spot.