The land surface model (LSM) is extensively utilized to simulate terrestrial processes between land surface and atmosphere in the Earth system. Hydrology simulation is the key component of the model, which can directly reflect the capability of LSM. In this study, three offline LSM simulations were conducted over China using the Community Land Model version 5.0 (CLM5) driven by different meteorological forcing datasets, namely China Meteorological Forcing Dataset (CMFD), Global Soil Wetness Project Phase 3 (GSWP3), and bias-adjusted ERA5 reanalysis (WFDE5), respectively. Both gridded and in situ reference data, including evapotranspiration (ET), soil moisture (SM), and runoff, were employed to evaluate the performance levels of three CLM5-based simulations across China and its ten basins. In general, all simulations realistically replicate the magnitudes, spatial patterns, and seasonal cycles of ET over China when compared with remote-sensing-based ET observations. Among ten basins, Yellow River Basin (YRB) is the basin where simulations are the best, supported by the higher KGE value of 0.79. However, substantial biases occur in Northwest Rivers Basin (NWRB) with significant overestimation for CMFD and WFDE5 and underestimation for GSWP3. In addition, both grid-based or site-based evaluations of SM indicate that systematic wet biases exist in all three CLM5 simulations for shallower soil layer over nine basins of China. Comparatively, the performance levels in simulating SM for deeper soil layer are slightly better. Moreover, all three types of CLM5 simulate reasonable runoff spatial patterns, among which CMFD can capture more detailed information, but GSWP3 presents more comparable change trends of runoff when compared to the reference data. In summary, this study explored the capacity of CLM5 driven by different meteorological forcing data, and the assessment results may provide important insights for the future developments and applications of LSM.

The construction of water-saving renovation projects can bring substantial benefits to the development of agriculture, but it may also be accompanied by negative impacts, especially in a large-scale irrigation district. Hence, there is always controversy, and it is vital and necessary to investigate the effectiveness of water-saving renovation. In this study, the Yahekou irrigation district, one of the largest districts in China, is selected as the case to explore the beneficial influence and adverse impact. Kriging interpolation, Pearson correlation analysis, and linear regression analysis are employed to study the temporal evolution, spatial distribution, and domain influencing factors. The results show that the water-saving renovation project in the Yahekou irrigation district had significant water-saving benefits during the period of 1998–2021, and the average annual water use of the irrigation district decreased by 61%. Canal lining is an important influencing factor for the decrease in irrigation water use, with a correlation coefficient of −0.538, B of −18.669, and R² of 0.290. Furthermore, the water-saving renovation of irrigation districts is not the dominant reason for changes in groundwater depth. Meanwhile, the groundwater depth below ground level (the level DBGL) in the irrigation district increased by 82%. The combined effects of atmospheric precipitation, canal lining, river sand mining, and groundwater exploitation have led to a sustained increase in groundwater depth in the study area. The results obtained from this study can provide valuable and scientific reference for agricultural water resource management over the large-scale irrigation district. This article focuses on the impact of water-saving renovation on ecological and technical indicators such as water use and the groundwater DBGL. However, the impact of water-saving renovation in irrigation districts is multifaceted; subsequent research can explore the impact of water-saving renovation projects on society and the economy.

Terrestrial evapotranspiration (ET) is a critical component of water and energy cycles, and improving global land evapotranspiration is one of the challenging works in the development of land surface models (LSMs). In this study, we apply a bias correction approach into the Community Land Model version 5.0 (CLM5) globally by utilizing the remote sensing-based ET dataset. Results reveal that the correction approach can alleviate both overestimation and underestimation of ET by CLM5 over the globe. The adjustment to overestimation is generally effective, whereas the effectiveness for underestimation is determined by the ET regime, namely water-limited or energy-limited. In the areas with abundant precipitation, the underestimation is effectively corrected by increasing ET without the water supply limit. In areas with rare precipitation, however, increasing ET is limited by water supply, which leads to an undesirable correction effect. Compared with the ET simulated by CLM5, the bias correction approach can reduce the global-averaged relative bias (RB) and the root mean square error (RMSE) by 51.8% and 65.9% against Global Land Evaporation Amsterdam Model (GLEAM) ET data, respectively. Meanwhile, the correlation coefficient (CC) can also be improved from 0.93 to 0.98. Continentally, the most substantial ET improvement occurs in Asia, with the RB and RMSE decreased by 69.7% (from 7.04% to 2.14%) and 70.2% (from 0.312 mm day⁻¹ to 0.093 mm day⁻¹, equivalent to from 114 mm year⁻¹ to 34 mm year⁻¹), and the CC increased from 0.92 to 0.99, respectively. Consequently, benefiting from the improvement of ET, the simulations of runoff and soil moisture are also improved over the globe and each of the six continents, and the improvement varies with region. This study demonstrates that the use of satellite-based ET products is beneficial to hydrological simulations in land surface models over the globe.

Rural domestic sewage, originating from human activities that involve the extraction and utilization of natural resources, is an inherent component of the ecological cycle in nature. Therefore, its disposal methods should align and harmonize with the laws governing nature’s evolutionary processes. This study conducted a comprehensive investigation on the domestic sewage facilities in representative villages located within the water source protection area of the middle route of the South-to-North Water Diversion Project. Taking Village A’s domestic sewage treatment station as a case study, an analysis was performed to assess its operational status and identify existing issues. The consideration of rural domestic sewage treatment should encompass factors such as the generation and discharge of household wastewater, the characteristics of water quality, discharge regulations, the natural and social environment, as well as post-completion operations and maintenance modes. We also proposed source reduction measures for the reuse of gray water in domestic sewage treatment in Village A, along with integrated treatment approaches involving biochemical treatment, landscape integration, and farmland irrigation for black water. These measures not only achieve effective treatment outcomes but also foster harmonious coexistence between humans and nature. Moreover, they align with the principles of ecological civilization while considering rural revitalization and promoting green agricultural development.

The quartz sand-enhanced coagulation (QSEC) is an improved coagulation method for treating water, which uses quartz sand as a heavy medium to accelerate the sedimentation rate of flocs and reduce the sedimentation time. The factors that influence the QSEC effect and can be controlled manually include the quartz sand dosage, coagulant dosage, sewage pH, stirring time, settling time, etc., and their reasonable setting is critical to the result of water treatment. This paper aimed to study the optimal conditions of QSEC; first, single-factor tests were conducted to explore the optimal range of influencing factors, followed by response surface methodology (RSM) tests to accurately determine the optimum values of significant factors. The results show that the addition of quartz sand did not improve the water quality of the coagulation treatment, it took only 140 s for the floc to sink to the bottom, and the sediment volume only accounted for 12.2% of the total sewage. The quartz sand dosage, the coagulant dosage, and sewage pH all had a significant impact on the coagulation effect, and resulted in inflection points. A QSEC-guiding model was derived through RSM tests, and subsequent model optimization and experimental validation revealed the optimal conditions for treating domestic sewage as follows: the polyaluminum chloride (PAC) dosage, cationic polyacrylamide (CPAM) dosage, the sewage pH, quartz sand dosage, stirring time, and settling time were 0.97 g/L, 2.25 mg/L, 7.22, 2 g/L, 5 min, and 30 min, respectively, and the turbidity of the treated sewage was reduced to 1.15 NTU.

In the process of sewage coagulation treatment, quartz sand is often used as a heavy medium to accelerate the settling rate of flocs, but it will adversely affect the removal efficiency of pollutants. The factors that affect the coagulation effect and can be controlled manually include the quartz sand dosage, coagulant dosage, sewage pH, stirring time, settling time, etc, their reasonable setting is critical to. This paper was to study the optimal conditions of quartz sand enhanced coagulation(QSEC), first, single-factor tests were conducted to preliminarily explore the optimal range of influencing factors, and then response surface methodology（RSM）tests were performed to accurately determine the optimums of significant factors. The results showed that the addition of quartz sand can’t improve the water quality of coagulation treatment, but it can significantly accelerate the coagulation settlement process, the quartz sand dosage, the coagulant dosage and sewage pH all impacted significantly on its coagulation effect, and existed inflection points. A model that could guide QSEC was obtained by RSM tests. The model optimization and experimental validation showed that the optimal QSEC conditions for treating domestic sewage were as follows: the polyaluminum chloride(PAC) dosage, cationic polyacrylamide(CPAM) dosage, the sewage pH, quartz sand dosage, stirring time and settling time were 0.97 g·L-1, 2.25 mg·L-1, 7.22, 2 g·L-1, 5 minutes and 30 minutes, respectively, and the turbidity of treated sewage was reduced to 1.15 NTU.