Analyzing the dynamic evolution and current situation of development and utilization of water resources is of great significance to the sustainable development and protection of water resources. The data of 1997-2020 water resources bulletins of 10 water resources zones, including Songhua River, Liao River, Hai River, Yellow River, Huai River, Yangtze River, Southeast China, Pearl River, Southwest China, and Northwest China, were selected to analyze the dynamic evolution of water resources and the current situation of development and utilization in these zones by using Kendall rank test. The results show that there are spatial differences in the dynamic evolution of water resources in China with the Yellow River region showing a highly significant increasing trend, the Songhua River basin showing a significant increasing trend, the Huai River basin showing a non-significant decreasing trend, and the rest of the basin showing a non-significant increasing trend. The Songhua River and Yangtze River basin show a weakly significant increasing trend, while the Liao River, Hai, Huai and Southeast rivers basin show a non-significant decreasing trend; The other water resources basin all show a non-significant increasing trend. The proportion of surface water is the largest, groundwater is the second largest and other water uses is the smallest. The water consumption of agriculture and industry in China's water use structure is on a highly significant downward trend after 2013, which corresponds to an increase in the efficiency of water use in agriculture and industry, a stable level of water use in domestic use and an increase in ecological water use year by year.

In order to explore the calculation method of water demand of water-reduced river landscape under hydropower development, combined with the data of hydrology and social economy in the region, this paper compared the changes of landscape characteristics after water reduction in similar projects. Taking the water reduction channel caused by Danba Hydropower Station as an example, the landscape evaluation factors were chosen comprehensively. Considering human visual effects, the landscape water demand evaluation system was established. A calculation method for the landscape water demand of the water-reduced reaches caused by the construction of hydropower stations was proposed. Based on the hydraulic model, the landscape indicators of each river section were calculated according to the determined index system, and the water volume required for the wide valley section, canyon section and county river section to meet the landscape requirements of water-reduced river channels is 70.4 m³/s, 64.8 m³/s, 50.7 m³/s. The 70.4 m³/s is taken as the landscape water demand of the whole reach of the reduced water.

The contradiction between the supply and demand of water resources becomes increasingly acute, so it is particularly important to optimize the allocation and efficiently utilize the limited water resources in the region. Water resources allocation in Hengshui city was taken as a case study. The demand of optimal allocation of Hengshui city water resources was considered comprehensively. The multi-objective optimal allocation of water resources model was established by taking the social benefit, economic benefit and ecological benefit as the objective function. The scheme of optimal allocation of water resources based on MOEA/D algorithm was given, and comparison experiments between the proposed scheme and the scheme based on NSGA-Ⅲ algorithm was done. The experimental results show that proposed scheme is superior to the scheme reported by literature, which can provide relevant support for the rational allocation of water resources in Hengshui city.

In order to explore the spatial and temporal distribution of water quality in the Yellow River basin and the causes of pollution, the monthly monitoring data of 7 basic water quality indicators at 8 provincial boundary stations of the Yellow River from 2015 to 2019 were systematically collected, and the spatial and temporal distribution characteristics and trend changes of water quality of the Yellow River were systematically analyzed by seasonal Kendall trend test method. Based on the surface water quality standard, the status of water quality was evaluated and the main pollution indicators were determined. The linear regression model was used to discuss the causes of pollution. The results show that the spatial distribution characteristics of most water quality indicators are middle reaches > lower reaches > upper reaches. The concentration values of water quality indicators at Tongguan station are significantly higher than those at other stations. TP concentration values at some stations in the middle and lower reaches of the river show a significant upward trend, especially at Gaocun and Lijin stations. From the perspective of spatial variability, the poor water quality of Tongguan station is related to the convergence of several seriously polluted tributaries in this section. From the perspective of seasonal variability, the seasonal distribution characteristics of TP concentration show that the non-flood season is less than the flood season. Under the effect of rainfall erosion in the flood season, agricultural phosphorus carried by tributaries flow into the river with the surface runoff formed by rainfall, resulting in the increase of TP concentration. The seasonal variation of NH3-N concentration in flood season is less than that in non-flood season, which is strongly correlated with air temperature. Higher flow rate and air temperature in flood season contribute to the dilution and degradation of NH3-N.

In order to comprehensively evaluate the water environment health status of Poyang Lake, a quantitative evaluation index system was established from three aspects of water quality, hydrology and aquatic organisms. The comprehensive weighting method combining analytic hierarchy process and coefficient of variation method was used to determine the comprehensive weights of indicators. The TOPSIS method was applied to construct the evaluation model, which determine the score of evaluation objects by combining the weights of indicators. The results show that there are seasonal changes in the water environment health status of Poyang Lake, and the two indicators of hydrology and aquatic organisms in summer are obviously better than other periods, so that water environment health grade is the highest and belongs to grade Ⅰ, with better coordination; The water environment health grade in autumn and winter is the worst and belongs to grade Ⅲ, among which hydrological condition is the main influencing indicator. This study can provide reference for water environment protection and construction of Poyang Lake.

In order to understand how the South-to-North Water Diversion Project has influenced the groundwater depth across the southern plains area of Beijing, this study collected the groundwater depth and water consumption measurements over the period of 2010-2020 in Daxing District. The geostatistical methods was carried out to analyze the spatial-temporal variability of the groundwater depth, and a principal component analysis (PCA) was used to evaluate the groundwater exploitation intensity over the period. The results show that the water diversion project has been putting the groundwater depth on a decline, reducing the average from 19.13 m over 2010-2014 to 17.67 m in 2015-2020, indicating a significantly constructive influence toward the groundwater depth recovery in the region. The nugget effect values of the groundwater depth, as calculated using the geostatistical semi-variogram model, dropped from 55.92% in 2010-2014 to 39.05% in 2015-2020. This decline indicates the weakening influence of human factors toward the groundwater depth. The PCA calculations show that the effect of regional water consumption on groundwater extraction intensity decreased from 2010 to 2020. Water consumption in industries, tertiary industries, and agriculture contributed to this tendency, while domestic water consumption stimulated groundwater extraction intensity. The findings turn out to be reliable theoretical and methodological references for groundwater resource management toward the regions along the water diversion routes.

With the development of the city, the contradiction between urban water supply and spring protection has become increasingly prominent, and the groundwater resources must be developed reasonably under the premise of ensuring that the spring water is not affected. Monthly rainfall and water level data of Botu Spring Group from 1990 to 2005 in Jinan area were selected to analyze the characteristics of rainfall recharge and the lagging response of water level in spring area to precipitation by statistical method. When the average of three-point movement of precipitation starts to correlate with water level in spring area, the average of ten-point movement of precipitation has the strongest correlation with water level in spring area. The current spring water level is closely related to the comprehensive rainfall in the first ten months. After ten-point moving average treatment of precipitation, through comparative analysis of groundwater exploitation data in urban area, east of Jinan and west of Jinan, it is proved that water level in spring area is closely related to groundwater hydrology unit in urban area and west of Jinan, and there is no hydraulic connection with groundwater hydrology unit in east of Jinan, so groundwater unit in east of Jinan can be reasonably exploited.

In order to study the applicability and error sources of reasoning formula method in design flood calculation in complex hilly areas, Morris screening method was used to analyze the sensitivity of reasoning formula method parameters. The applicability of reasoning formula method in different watershed areas was analyzed by comparing with hydrological comparison method and historical flood survey results. The results show that the area average rainfall is the main error source of the reasoning formula method, and the error tends to increase with the area of the basin. The reasoning formula method can still be applied to the basin with an area of 500-1 000 km² by reasonable selection of parameters. Taking Pujiang River Basin as an example, using the traditional area rainfall calculation method (without reduction), when the control section catchment area is about 100 km², 100-500 km² and more than 500 km², the error is 5.1%-5.3%, 11.2%-16.0% and 25.2%-25.5%, respectively. When the basin area is larger than 500 km², the calculated result is only about 0.2% smaller than the historical survey data after reasonable reduction of area rainfall.

In order to improve the accuracy of real-time flood forecasting in Jinhua River basin, the basin flood forecasting model coupled with Mike 11 Nam and Mike 11 HD and the real-time correction model based on Ensemble Kalman filter were established, and the real-time correction of flood forecasting in Jinhua River basin was realized. The simulation effect of the basin flood forecasting model on the main stations in the basin is good, and the simulation accuracy of flood discharge and flood level is high. When the real-time correction model is within 10h of the forecast period, the correction effect decreases with the increase of the forecast period, and the prediction error can be effectively reduced in the early stage of the forecast period. On the whole, the established basin flood forecasting model and the real-time correction model based on Ensemble Kalman filter can meet the application requirements of flood forecasting in Jinhua River basin.

In order to study the sponge urban transformation scheme of existing communities, taking an existing community in Hongshan District of Wuhan as an example, a SWMM rainfall-runoff model was established. Different LID combination schemes were determined according to the feasibility analysis of site conditions, space requirements and underlying surface characteristics. The runoff control and pollution load of each combination scheme under different recurrence periods in the study area were simulated. The simulation results of each combination scheme were analyzed from the ecological, social and economic aspects. The results show that the ecological and social benefits of biological retention facilities were high. The combination of LID facilities for laying infiltration trench, vegetative swale and biological detention facility has the best effect on runoff control, flood peak and pollutant reduction in the study area, and has good social and economic benefits, which is the best scheme.