In view of the short water hammer control distance of a single air valve in long-distance and low lift water delivery projects, which can not effectively suppress the vacuum in the pipe, a new water hammer control scheme of combined protection of air-valve surge tank and air valve was proposed. Taking a practical project as an example, a comparative analysis of the hydraulic transient process was carried out for the air valve protection and the combined protection scheme of air-valve surge tank and air valve. The results show that the water column separation occurs in the main pipe when the air valve is used for protection, and a large impact water hammer is caused by the rapid exhaust. The combined protection scheme of air-valve surge tank and air valve can not only effectively suppress the vacuum in the main pipe, but also effectively alleviate the impact water hammer caused by exhaust. It is an economic and effective water hammer protection scheme, and can provide a reference for the water hammer protection of other long-distance and low-lift water delivery projects.

To investigate the spatial and temporal variation of terrestrial water storage in the Yellow River Basin, the inversion of terrestrial water storage in the Yellow River Basin was performed based on the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) gravity satellite data from 2003 to 2020. Besides, the Variable Infiltration Capacity (VIC) hydrological model was used to simulate the soil water changes. The groundwater storage changes between 2003 and 2014 were calculated through the water balance equation. The results show that the overall terrestrial water storage in the Yellow River Basin is in deficit during the study period, with a significant decreasing trend temporally. Spatially, the water storage is reducing from the river source to the downstream. The inversion results show that the spatial and temporal variation of terrestrial water storage in the Yellow River basin is highly correlated with the topography, climate and human activities. The results can provide a scientific basis for water resources planning and allocation in the Yellow River Basin.

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.

In order to qualitatively and quantitatively grasp the influence of the installation elevation of horizontal water stops at transverse joints on the structural stress of the bulb tubular power house, taking a certain engineering project as an example, a three-dimensional finite element model of the powerhouse was established to analyze the stress of the structure on the condition of the horizontal water stops changing within a certain range. The results show that the installation height of horizontal waterstops has a significant impact on the stress of structure, and an appropriate installation height of horizontal waterstops can improve stress of structure. Taking into account various factors, the optimal horizontal water stop installation height is 70% of the installable height, which can provide a reference for the design of the transverse joint water stop of the bulb tubular power house.

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.

Based on the runoff data of Buha River Basin and Shaliu River Basin in Qinghai Lake Basin, the annual base-flow index was obtained by using the filter smoothing minimum method. The temporal and spatial variation of precipitation and the evolution law of base flow in this basin were analyzed by TFPW-MK method, and the influencing factors of base flow were analyzed. The results show that the base-flow index of Buha River Basin first increases, then decreases and increases, reaching the maximum in May and the minimum in August; The base flow index of Shaliu River Basin fluctuates and reaches the minimum in April. The annual average runoff in the Buha River Basin and the Shaliu River Basin showed a significant increasing trend, and both the annual average base flow and base flow index showed an insignificant increasing trend; The base flow inclination rate of the Buha River Basin is twice that of the Shaliu River Basin. The base flow sequence of the Buha River Basin and the Shaliu River Basin is greatly affected by precipitation, flow, drought index and evaporation, and the Shaliu River Basin is more significantly affected by evaporation.

It has great guiding significance of studying the hydrodynamic distribution strong tide for Shenzhen River estuary management. The physical model of Shenzhen River was established to analyze the hydrodynamic distribution characteristics of beach and trough and the neap tide. The spring tide in dry season and typhoon "Hato" were selected as the boundary conditions in tidal optimal estuary. The results show that the tidal power of the main trough of the Shenzhen Estuary is obviously better than that of the middle beach, the flow velocity tends to increase from the downstream to Shenzhen River for the discharge section is narrower in upstream during rising tidal, the power of spring tide and ebb tide in dry season is basically the same, the power of spring tide in dry season is stronger than that of ebb tide, the estuary flow pattern is mostly affected by riverbed morphology during the low water level with a large area of open beach which made the south trough flow only. During the storm surge, the hydrodynamic force of the estuary is strong, the flow velocity of the middle beach is significantly greater than that of the dry season, the middle beach water is not flowing back to the trough for the high water level and the mangroves in the middle beach has a great influence on the flow pattern. According to the hydrodynamic characteristics and flood discharge requirements, the countermeasures for ecological beach consolidation and main channel widening in Shenzhen Estuary were put forward.

The study of the effect of water vapour on soil heat and moisture migration patterns at different heat source temperatures is of great significance for the application of soil heat storage and ground source heat pump technology. In this paper, a numerical model of one-dimensional unsaturated soil water-vapour-thermal coupling migration was constructed by Hydrus-1D software, and the numerical simulation study of sandy soils with and without water vapour migration at different heat source temperatures was carried out. The results show that for soil heat migration, taking into account water vapour migration increases the radius of influence of the heat source from 60 cm to 78 cm, an increase of 30%; For soil moisture migration, the radius of influence of the heat source increases from 78 cm to 100 cm, an increase of 28.21%. Compared with not considering water vapor migration, considering water vapor migration can reduce the temperature loss during soil heat storage, and the decrease of temperature loss increases with the increase of heat source temperature. When the temperature of the heat source is above 70 ℃, the temperature and moisture fields of the soil change unsteadily and dryness may occur in the vicinity of the heat source.

At present, in the region of China Southern Power Grid, there is a case that the actual load adjustment amount of primary frequency control of some hydropower units cannot reach the theoretical value under certain working conditions, resulting in the assessment of primary frequency regulation. This paper processed the original operation data of a unit, and calculated the actual load adjustment amount and actual adjustment rate of primary frequency regulation. Compared with the theoretical value, the qualified working condition area of the primary frequency regulation process was found out. The characteristic operating points were selected in the qualified working condition area, and the multi-objective particle swarm optimization algorithm based on Pareto optimization criterion was used to find the optimal PID parameters. The simulation results show that the optimized PID parameters can make the unit have better primary frequency regulation performance index than the actual parameters of the governor.

Taking the self- and cross-correlation of the multi-station streamflow series of the main and tributary of the basin as the starting point, a multi-site flood series simulation method based on the conditional resampling theory was proposed, and simulate the flood series of Pingshan, Cuntan and Yichang station on the main stream of Changjiang River. The simulation results were compared with the results of the multi-station seasonal autoregressive model (MSAR) for verification and analysis. The results show that compared with the traditional model, the proposed method can not only satisfy the basic statistical characteristics of the runoff series and the higher-order self- and cross-correlation structures of the series, but also further consider the historical extreme flood characteristic, and could generate multi-station simulated flood scenarios with different design frequency.