The spatial and temporal variations of water quality in Wuxi water area of Taihu Lake are important for regional eutrophication control and water pollution control. Based on the monthly water quality data of Wuxi water area of Taihu Lake and the water quantity data of rivers entering the lake from 2010 to 2020, the spatial and temporal variation characteristics of water quality and eutrophication status of the lake were evaluated using the integrated pollution index and integrated nutrient status index. The inter-annual variation pattern and spatial pattern of major water quality indicators were analyzed, and the correlation between the water quality of the lake and the concentration and flux of pollutants in rivers entering the lake was investigated. The results show that the water quality of Wuxi water area of Taihu Lake improved significantly from 2010 to 2020, and the integrated pollution index and integrated nutrient status index of the whole lake decreased by 25% and 10%, respectively. Except for the concentration of total phosphorus concentration with no obvious change trend, the concentration of other water quality factors in the lake area all showed a downward trend. In terms of seasonal changes, permanganate index, total phosphorus, and chlorophyll-a concentrations maintained higher values in summer and autumn, while total nitrogen and ammonia nitrogen concentrations maintained higher values in winter and spring. Spatially, nutrient concentrations decreased from the northwestern and northern lakes to the southeastern and eastern lakes. The changes in water quality of rivers entering the lake from 2013 to 2020 are basically consistent with the trends of water quality in the lake area. The concentration of total nitrogen and ammonia nitrogen in the lake area are significantly positively correlated with the concentration of total nitrogen in inflow river and the flux of ammonia nitrogen into the lake, respectively. The spatial pattern response is consistent, and the exogenous input of the inflow river is an important factor affecting the spatial and temporal changes of water quality in the lake area.

Lakes are highly susceptible to eutrophication due to their long-term closed or semi-closed status and poor hydrodynamic conditions. This paper constructed a hydrodynamic-convective diffusion model with MIKE21 software by considering the influence of rainfall on the spatial and temporal distribution of TN concentration in the Yilong Lake. The model simulated the hydrodynamic conditions under different inlet opening and closing conditions and different flow diversion schemes. The improvement of TN concentration based on the flow velocity distribution of the lake flow field was discussed. The results show that the hydrodynamic conditions and the water quality of the lake can be effectively improved by setting up water diversion inlets and increasing water diversion flow. The overall effect of diverting water from the Chenghe alone is better than diverting water from the Chenghe and Longgang River together. Under the scheme of separate diversion from the Chenghe, when the water diversion flow was double, the overall flow rate of the lake was increased by 44.04% and the TN concentration decreased by 52.78%, with the best effect of hydrodynamic optimization and water quality improvement, but the efficiency of water quality improvement per unit of water recharge is reduced. This research could provide some references for similar projects.

Urban water bodies play a vital role in maintaining the urban environment and development. In order to solve the problem of low transparency of its water body, taking Yaojiang River as the research object, the effects of solar radiation, turbidity, suspended solids concentration and particle size on water transparency were analyzed by means of comparative ratio, Pearson correlation analysis, and curve fitting calculation. The results show that the light intensity, solar elevation angle and azimuth angle affect the transparency monitoring. The stronger the light is, the greater the monitoring result of transparency is. Transparency (SD) is negatively correlated with turbidity (TUB) and suspended solids concentration (SS). Pearson correlation coefficients are -0.880, -0.570. After monitoring and calculation, the median particle size (d_50%) of Yaojiang River is between 15.5 and 61.3 μm. Filtration through a filter with a pore size of 10 μm can control the turbidity of the water body within 9.7 NTU and the concentration of suspended solids within 13.4 mg/L. The transparency of the Yaojiang River can reach 80 cm, which is the minimum requirement to maintain a normal aquatic environment.

In order to explore the water quality and pollution characteristics of the main water system in Chengde area, the monitoring data of 29 sections of Chengde surface water quality monitoring station from 2017 to 2020 were selected, and the water environment quality of the main water system in Chengde area was comprehensively evaluated by single factor evaluation, comprehensive pollution index and principal component analysis. The evaluation results show that generally speaking, the overall water quality of the main water system in Chengde is good from 2017 to 2020; From the perspective of time, the water quality of the main water system in Chengde in 2019 and 2020 was significantly improved compared with 2017 and 2018; From the perspective of space, the section pollution of Gonghou and Chenggang bridges is relatively serious. The water quality of the main water system in Chengde is mainly affected by the total phosphorus, COD and permanganate index.

In order to research the growth adaptability and engineering applicability plants in the floodplain ecological restoration area in the lower reaches of the Three Gorges dam area under flooded environment, four kinds of shrub plants such as distylium chinense, myricaria laxiflora, salix variegata and rosa sp were planted and observed in the floodplain area at the same water level in the lower reaches of the Three Gorges dam area. Four shrub plants experienced a certain degree of flooding period. The results show that the survival rates of the four shrub plants were different under flooding conditions, and the plant preservation rates from high to low were as follows: salix variegata, distylium chinense, myricaria laxiflora and rosa sp. The morphological changes, plant height growth and recovery growth were observed. Among them, salix variegata, distylium chinense and myricaria laxiflora showed better flooding adaptability under flooding stress. The applicability of ecological restoration engineering of 4 Shrub plants was evaluated by weighted scoring method. The scores from high to low are distylium chinense, myricaria laxiflora, rosa sp and myricaria laxiflora. It is determined that distylium chinense can be used as the main shrub plant in the floodplain ecological restoration project.

Based on the runoff duration data of the basin in the past 50 years, the spatial-temporal evolution and ecological effects of hydrological variation in the Zuli River basin in arid and semi-arid region were studied by using cumulative anomaly analysis, M-K nonparametric mutation test, and runoff ecological index analysis with flow duration curve. The results show that since 1970, the surface runoff of the study basin was strongly affected by climate, and its runoff appeared sudden change in 1995. After studying the variation of runoff in the basin, the surface runoff decreased significantly, and the runoff in flood season and annual runoff decreased 36.9 million m³ and 32.12 million m³, respectively. After runoff variation, the ecological deficit in the study basin was obvious, and the annual proportion of runoff ecological indexes in non-flood season increased.

This paper aims at the complex flow response relationship in the short-term joint operation of Jindong-Guandi cascade hydropower stations in Yalong River basin. In order to predict the inflow response process of the Guandi hydropower station, the random forest (RF) model and support vector regression (SVR) model were combined to mine the nonlinear relationship, and compared with the traditional lag-time model and the Muskingum model. On this basis, two simulation dispatching models were established to test the applicability of each model in the short-term operation of cascade hydropower stations. The result shows that the RF-SVR model has a higher fitting ability for the flow response relationship between hydropower stations, which can reduce the errors in the formulation of short-term dispatching plan, and effectively reduce the deviation of daily generation and the risk of water level violation. The research results can provide a reference for making short-term dispatching schemes of cascade power stations under complex hydraulic connections.

As a large number of water conservancy projects have been put into use in recent years, water conservancy departments have accumulated a large amount of information about reservoir scheduling regulations. This paper analyzed the existing reservoir scheduling regulations, and proposed a construction method of reservoir scheduling regulations knowledge graph based on DataG. In the design of the ontology model, the top-down method of disassembling the ontology twice was adopted on the reservoir scheduling mode. The differentiated knowledge extraction was performed on the structured and unstructured data. In the knowledge reasoning, the reasoning path of preconditions, scheduling measures and scheduling objectives were analyzed and defined. Finally, the visualization of the reservoir scheduling regulation knowledge graph was introduced for the Three Gorges Reservoir. The knowledge graph of reservoir scheduling regulation meets the needs of spatiotemporal dimension, solves the problem of multi-source heterogeneous data extraction, and realizes intelligent retrieval and recommendation in the field of reservoir operation.

In order to improve the search efficiency of the NSGA-Ⅱ algorithm, this paper introduced an arithmetic crossover operator with stronger global search ability and faster convergence speed to replace the simulated binary crossover operator used in the original NSGA-Ⅱ algorithm. Based on this, an improved NSGA-Ⅱ algorithm was proposed, the G_D index was used to evaluate the convergence capability of the multi-objective Pareto solution set. The method was applied to the research of Fenhe Reservoir water supply and ecological collaborative optimal scheduling to verify its effectiveness. By comparing the Pareto solution sets generated by different algorithms and various indicators of reservoir operation, and compared with the traditional algorithm, the number of iterations to reach the convergence state after the improved algorithm was reduced by 100 generations and the convergence time is shortened by 7.76%. The water shortage rate of each department under the condition of non-optimization was decreased, of which the effect of agricultural water shortage rate is the most significant, decreasing by 13.20% to 14.52%, and the total water supply increased by 0.268 to 0.303 million cubic meters. This paper verified the effectiveness of the improved algorithm and optimized scheduling, and provides an optional new idea for multi-objective optimal scheduling of reservoirs.

Xiangjiaba Hydropower Station has six functions: power generation, navigation, flood control, irrigation, reverse regulation, sediment retaining. Since the project was put into operation in 2012, all other benefits except irrigation have begun to show gradually. With the completion of the first water intaking tunnel project of the north and south main canal of Xiangjiaba, and the comprehensive construction of the first phase project of the north general irrigation area, the research on the impact of irrigation water intaking on the power generation of Xiangjiaba hydropower station is an urgent work. Based on the adjustment calculation of 43 years series runoff during 1970-2013, inflow variation of Xiangjiaba hydropower station was calculated by considering the impact of the six large reservoirs regulation and storage in the upstream and water diversion in the Yunnan province. On this basis, the impact of water intaking after the first phase of north irrigation area, north second phase of irrigation area, and irrigation district being completed on the power generation of the Xiangjiaba Hydropower Station was analyzed. The research shows that irrigation water intaking reduces the power generation of Xiangjiaba, which is 1.78×10⁸ kW·h, 2.84×10⁸ kW·h and 3.78×10⁸ kW·h, respectively, compared with that before water intaking, and mainly in the dry season. After the intake of water in each period, the water discharge can be reduced by 109 m³/s at most, the annual average output can be reduced by 105 MW at most, and the number of installed hours can be reduced by 63 h at most.