Rainfall observations derived from 76 ground rainfall gauges from January 1, 2018 to December 31, 2020 were used to evaluate the accuracy of IMERG Final Run (IMERG_FR) and IMERG Early Run (IMERG_ER) in IMERG (Integrated Multi-satellitE Retrievals for GPM) products over the small Sancha River basin in Guizhou Province. This study aimed to explore the precipitation detection capacity of IMERG_FR and IMERG_ER on different time scales. Metrics for assessment include correlation coefficient (C_CC), relative bias (R_RB), root-mean-squared error (R_RMSE), probability of detection (P_POD), false alarm ratio (F_FAR), critical success index (C_CSI). The performance of IMERG was assessed at different time scale with different precipitation thresholds. The results show that the IMERG_FR and IMERG_ER have a certain precipitation detection ability in the small basin on the whole, and it still needs to improve the accuracy of IMERG products in estimating precipitation intensity.

Flood prediction and design calculation in ungauged region are often restricted by data of rainfall and runoff. Based on the DEM data extraction of Horton geomorphologic parameters in Luoyang river basin, geomorphic units line of Luoyang river was calculated, and the basin confluence and the response relation between geomorphic parameters was established. The three layers of evaporation and saturation excess runoff were used to construct Xin’anjiang model based on geomorphic unit line. Luoyang river basin flood simulation was carried out by combination of genetic algorithm with objective optimization. Compared with Xin 'anjiang model, the results show that the Xin’anjiang model based on geomorphic unit line can obtain better simulation results, which can provide reliable technical support for hydrologic analysis and calculation of small and medium-sized rivers in ungauged region.

Naolihe National Nature Reserve is located in the hinterland of Heilongjiang Sanjiang Plain and is an important ecological function area in China. Based on remote sensing image data and hydrological data of the protected area, this paper inversed the vegetation coverage by pixel dichotomy, analyzed the spatial and temporal distribution characteristics of vegetation coverage in Naolihe Nature Reserve from 1984 to 2021, and studied the influence of precipitation and flooding frequency on vegetation coverage. Studies have shown that from 1984 to 2021, the low and middle vegetation coverage areas of Naolihe wetland first increased and then decreased, while the middle and high vegetation coverage areas showed the opposite trend. From the correlation coefficient between annual monthly precipitation and monthly vegetation coverage, the vegetation growth in Naolihe Nature Reserve is greatly affected by precipitation, which is positively correlated, and the response of vegetation coverage to precipitation is about one month behind. When the frequency of wetland flooding is between 0.45 and 0.50, the wetland vegetation grows well. The research can provide reference for Nalihe wetland ecological protection.

Analyzing the hydrological response of mining activities in the Loess Plateau will help to promote ecological protection and high-quality development in mining areas. This paper selected four typical small watersheds of Baima River, Songta River, Xinshui River and Zhouchuan River on the Loess Plateau, and conducted a study on the applicability of 8 base flow segmentation methods in the Loess Plateau. The difference of anomaly cumulative percentages (DACP) based on paired watersheds was employed to analyze the impact of mining disturbances on the base flow process in the basin. The results show that the Chapman-Maxwell filtering method and the Eckhardt filtering method have the best applicability in the typical small watersheds of the Loess Plateau, the segmented base flow is relatively stable, and the base flow hydrograph conforms to the precipitation and runoff mechanism and the water regression process of the watershed; The base flow of the four small watersheds showed significant downward trends from 1956 to 2012 as a whole; With the increase of mining disturbance intensity, the DACP index of base flow increased, and mining disturbance increased the base flow of the basin.

In order to study the adjustment characteristics and response of the important shoals in the bar area of the Yangtze River estuary under the influence of sediment discharge decreasing and human activities, this article took the Hengsha shoal, the Jiuduansha shoal and the eastern Nanhui beach as examples. The measured hydrological and topographic data were used to investigate the morphological adjustment of the shoals and the response to changed environment. The results show that in recent years, the two-dimensional geomorphology of the shoals were shrank in the bar area of the Yangtze River estuary, and the tail of the shoals stop progradation in general. The Hengsha shoal and Jiuduansha shoal had different degrees of tidal creeks development; Empirical relationships were developed between the areas of the Hengsha shoal and the previous seven-year average fluvial erosion intensity during flood seasons. This relationship can be used to reflect the change tendency of shoal’s area with the altered flow and sediment regime; The estuarine regulation project can restrain some part of the shoal’s erosion, which was caused by the variation of the flow and sediment conditions. However, the estuarine regulation project may have a slow and long-term cumulative impact on the surrounding regions.

Aiming at the problem that the evaluation and prediction of water resources carrying capacity involves multi-factor comprehensive indicators, particle swarm optimization algorithm was used to optimize the training parameter penalty factor C and kernel parameter σ in the support vector machine model, and a water resources carrying capacity prediction model was established based on PSO-SVM. According to the index grade standard, the training set data was constructed to evaluate the water resources carrying capacity of Heilongjiang Province in 2017. The results show that the water resources carrying capacity index of Heilongjiang Province in 2017 is between 0.423 4 and 0.709 2. The water resources carrying capacity in some areas is at level II, the carrying capacity is weak, and there is still much room for improvement.

In order to analyze the influencing factors and their correlations of water use efficiency, incorporate all independent variables and overcome multicollinearity, the partial least squares method was used to study the correlation factors of water use efficiency in 2019 in China. The results show that the partial least square method can describe the correlation between variables effectively. Factors that are highly correlated with water consumption per ten thousand Yuan of GDP are natural conditions, social development level, GDP proportion of added value of primary industry, and the proportion of labor force in the water industry. The overall economic water use efficiency is high in the eastern region and low in the western region. Factors that are highly correlated with actual irrigation water consumption per mu of cultivated land are natural conditions and GDP proportion of added value of primary and secondary industries. Agricultural water use efficiency is high in the central region and low in the western region. Factors highly correlated with the water consumption per ten thousand Yuan of industrial added value are natural conditions, sewage treatment rate, urbanization rate and the capital proportion of water industry. Industrial water efficiency is high in the eastern region and low in the central region. Factors highly correlated with per capita public water consumption are per capita water resources, annual precipitation, sewage treatment rate, per capita GDP and GDP proportion of added value of primary and secondary industries. There is little correlation between regional factors and public water use efficiency. The research results can provide reference for the optimal management and rational utilization of water resources.

The tidal river network area has the characteristics of criss-crossed water systems and developed cities. High intensity land use and development leads to serious hydrological pollution and degradation of ecological environment functions of urban landscape lakes. Taking the typical urban landscape lake in the river network area - Baiyun Lake in Guangzhou as the research object, this paper constructed a two-dimensional hydrodynamic and water quality coupling model to study its eco-environmental water demand and its water supplement schemes. The results show that the two-dimensional hydrodynamic and water quality coupling model in the river network area based on Mike21 can effectively simulate the temporal and spatial evolution law of water quality in urban landscape lakes, and the relative errors between the simulated values and the measured values are less than 0.20, Nash efficiency coefficients are greater than 0.75. By jointly using Baiyun Lake sluice and pump hydraulic engineering to dispatch and replenish water, the assurance rates of eco-environmental water demand of Baiyun Lake and its connected rivers are basically 100%, the contents of TN and TP meet the fourth class water quality. The research results can provide reference for ecological and environmental governance of urban landscape lake of polluted river network.

The ecological security of rivers is not only closely related to the physical, chemical and biological integrity of the river itself, but also affected by the natural, economic and social conditions of the regions through which it flows. Based on the "driving force-pressur-state-function-response" (DPSFR) framework and matter-element extension model, a river ecological security evaluation system was constructed. Taking Hongru River as an example, it was divided into 10 evaluation units according to the spatial differences such as physical geography and water conservancy projects, and the river ecological security evaluation and spatial differentiation characteristics research were carried out. The results show that the ecological safety level of the Hongru River in 2017 was in a critical safety state, and there was a tendency to develop to an unsafe level. Its spatial differentiation characteristics were that the upstream was better than the downstream, and the tributaries were better than the mainstream, especially in the functional and response layers. Among the indicators, total phosphorus, per capita comprehensive water consumption, river longitudinal connectivity, and water quality assessment cross-section compliance rate are the main factors affecting the spatial distribution of ecological security differences in Hongru River. The response is a criterion layer that is significantly related to the spatial differentiation of the ecological security of the Hongru River.

As a key point in early-warning of river system health, alert source verification is an important basis for eliminating hidden trouble and maintaining the river system health. Based on the analysis of the alarm source factors affecting the health status of Dongjiang river system, the alarm source index system was constructed, and the alert sources verification model of Dongjiang river system health was established by the partial least squares regression (PLSR) method. This model was used to verify main alarm source factors for affecting the health status of the Dongjiang river system (2015-2019), and the influence trend and degree of different alarm source factor on the health status of Dongjiang river system were analyzed. The results show that annual rainfall is the most direct and significant positive effect factor on the health status of Dongjiang River system. In addition, factors such as ecological water use, social development and river management level in this basin also play a promoting role. However, the flood disaster, sewage discharge, water for production and living, non-eco-friendly water conservancy facilities in this basin, and inter-basin water transfer have obvious negative effects on the health of Dongjiang river system.