Extreme precipitation events (EPE) often cause catastrophic floods accompanied by serious economic losses and casualties. The latest version (V06) of the Integrated Multi-satellite Retrievals for Global Precipitation Measurement (GPM IMERG) provides global satellite precipitation data from 2000 at a higher spatiotemporal resolution with improved quality. It is scientifically and practically important to assess the accuracy of the IMERG V06 in capturing extreme precipitation. This study evaluates the two widely used products of IMERG during 2000–2018, i.e., IMERG late run (IMERG-L) and IMERG final run (IMERG-F), in the densely populated and flood-prone North China Plain. The accuracy of the IMERG V06 is evaluated with ground measurements from rain gauge stations at multiple scales (hourly, daily, and seasonally). A novel target tracking method is introduced to extract three-dimensional (3D) extreme precipitation events, and the near-real-time uncalibrated PERSIANN-CCS (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks Cloud Classification System) and GSMAP (Global Satellite Mapping of Precipitation) satellite data are added to further evaluate IMERG’s performance during extreme precipitation. Finally, for flash flood events induced by extreme rainfall in the Hebei Province from 15 to 23 July 2016, the accuracy of capturing the event with IMERG-F and IMERG-L was verified. Results reveal that IMERG-F is better than IMERG-L at all investigated scales (hourly, daily, and seasonally), but the difference between the two products is less at higher time resolutions. Both products manifest decreased performance when capturing 3D extreme precipitation events, and comparatively, IMERG-F performs better than IMERG-L. IMERG-F exhibits a distinct discontinuity in extreme precipitation thresholds between land and ocean, which is a limitation of IMERG-F not documented in previous studies. Moreover, IMERG-L and IMERG-F are comparable at an hourly scale for some metrics, which is beyond the expectation that IMERG-F is notably better than IMERG-L. This study provides a scientific basis for the performance of satellite precipitation products and contributes to guiding users when applying global precipitation products.

In water resources management on a global scale, it is important to reconcile the conflicting interests of different regions and actors regarding water use. To solve this issue more effectively, an optimal allocation model of water resources that coordinates the interests of regional multi-level water resource managers and balances the benefits acquired by regional multi-level water resource managers was proposed. The model consisted of three components, including option generation, option selection, and fallback bargaining. The Hybrid Strategy Whale Optimization Algorithm (HSWOA) was created to generate the initial alternative set throughout the alternative generation process. In the alternative screening process, quick non-dominated sorting was used to choose Pareto alternatives from the initial alternative set. Through many rounds of negotiations, water resource managers at all levels reached a consensual water resource allocation plan during fallback bargaining. This model was used to reconcile the conflicting water interests of municipal and county water managers in Handan, China, in terms of economic, social, and ecological benefits. It was also compared with the Pareto solution set obtained from NSGA-III. In terms of convergence speed and accuracy, the results demonstrated that HSWOA outperformed the Whale Optimization Algorithm (WOA). The results show that several rounds of discussions between municipal and county water management eventually resulted in Nash equilibrium. In normal flow year, the recommended scheme could yield economic benefit of 315.08×10⁸ Yuan, social benefit of 0.1700, and ecological benefit of 5.70 × 10⁶ m³, whereas in low flow year, the recommended scheme could yield economic benefit of 354.85×10⁸ Yuan, social benefit of 0.2103, and ecological benefit of 57.82 × 10⁶ m³. Compared to existing studies, the recommended scheme has clear advantages in terms of social and ecological benefits. The proposed optimal water resource allocation was Pareto optimal. This paper presented a new way of thinking about reconciling the conflicting interests of different levels of water resource managers in the process of water allocation.

The spatial and temporal distributions, contamination evaluation, and source apportionment of Cu, Zn, As, Pb, Cd, and Cr in the sediments of Hulun Lake were explored in this work. The pollution characteristics of six heavy metals were assessed by single factor pollution index (PI) and geo-accumulation index (Igeo). The sources of heavy metals in the surface sediments were analyzed by the positive definite matrix factorization (PMF) and Pearson correlation analysis. The sedimentary records of heavy metals in core sediments were reproduced by radioisotopes. The average concentrations of 6 heavy metals except Cd were lower than the corresponding background values. The spatial distributions of Cu, Zn, Cr, Cd and As were generally similar and showed higher abundances in the southwestern part of the lake. With the use and import of heavy metals, the concentration of heavy metals in core sediments increased with the fluctuation of years. The peak of heavy metal concentration was related to the high growth rate of gross domestic product in 2003-2008. The single factor pollution index and geo accumulation index results showed that the surface sediment was mainly polluted by Cd, followed by Zn and As. Natural parent material, agricultural activities and industrial activities were the main sources of heavy metal pollution in the sediments, accounting for 17.03%, 26.34%, and 56.63% of the total heavy metal accumulation, respectively. Pb was derived mainly from natural parent material. Cd and As were closely associated with agricultural activities. Cu and Zn were mainly attributed to industrial mining activities. Source apportionment of the ecological risks of heavy metals illustrated that industrial sources were the primary ecosystem risk sources (66.1%), followed by agricultural sources (23.75%) and natural sources (10.15%). The results will also provide reference data for future studies of heavy metals pollution in sediments from Hulun Lake and other lakes.

The rational utilization of unconventional water sources is of great significance to areas where conventional water resources are scarce, and water resource allocation is an important way to realize the rational distribution of multiple water sources. This paper constructs a water resources allocation system integrating model data parameter database, water resources supply and demand prediction module, groundwater numerical simulation module and water resources allocation module. Taking brackish water as the main research object and final goal of achieving the best comprehensive optimization of social, economic and ecological benefits. The brackish water is incorporated as an independent water source into the water resource allocation model, and the stratum structure model and groundwater numerical model are constructed to simulate the brackish water level in the planning target year. The water resources allocation system is applied to Guantao County, China. The results show that increasing the development and utilization of brackish water under the recommended scheme can significantly reduce the water supply pressure of local fresh water resources in agriculture and industry. Compared with the current year, the overall water shortage in the region will be reduced by 4.493 × 10⁶ m³ in 2030, and meanwhile, the brackish water level will be decreased by 12.69 m in 2035, which plays a positive role in improving soil salinization.

Accurate estimation of terrestrial water storage anomalies (TWSA) is crucial for the sustainable management of water resources and human living. In this study, long-term TWSA estimates are reconstructed by integration of multiple meteorological products and the water balance (WB) method at 0.5° × 0.5° resolution, generating a total of 12 combinations of different meteorological data. This scheme is applied to 10 river basins (RBs) within China and validated against GRACE observations and GLDAS simulations from 2003 to 2020. Results indicate that similar seasonal characteristics can be observed between different precipitation and evapotranspiration products with the average correlation coefficient and Nash–Sutcliffe efficiency coefficient metrics larger than 0.96 and 0.90, respectively. Three GRACE solutions indicate similar seasonal variations and long-term trends of TWSA over 10 RBs, with the correlation above 0.90. Similar performance can also be observed concerning the root mean square error and mean absolute error metrics. Nevertheless, WB-based TWSA estimates represent larger discrepancies compared to GRACE observations and GLDAS simulations. Specifically, the variation amplitude and long-term trend of WB-based results are much larger than that of the GRACE observations, which is mainly caused by the inaccuracy of remote sensing products and the neglect of anthropogenic activities. Comparable TWSA estimates independently computed from the WB method can only be achieved in 4 out of 10 RBs. This study can provide insightful suggestions for an enhanced understanding of TWSA estimates and improving the performance of the water balance method.