Recently, frequent water shortages and reductions in water flow have been observed in the northern segment of the Yellow River within the Beijing–Hangzhou Grand Canal. In response, a water replenishment program has been initiated. This study is focused on the section of the Grand Canal north of the Yellow River and uses the GSFLOW model to examine interaction between surface water and groundwater, as well as the effect of water replenishment. The results indicate that, after the water replenishment, the efficiency of water replenishment was highest in the Xiao Canal (64.30%), followed by the Wei Canal (39.09%), the South Canal (12.11%), and the North Canal, which exhibited the lowest efficiency (5.75%). This variation can be attributed to greater water loss with increasing distance from the replenishment source, leading to lower replenishment efficiency. Surface water recharge to groundwater was extended by 32 days, with replenishment effects persisting even after the water supply ceased. The maximum influence distance on either side of the canal reached 5.73 km, with an average impact distance of 1.48 km, resulting in a total affected area of 974.7 km², accounting for 2.2% of the study area. Water replenishment positively influenced the recovery of groundwater levels along the Grand Canal.

The experiment of loess crack development under dry–wet cycle conditions is of great significance for the study of groundwater preferential flow channels and the prevention and control of infrastructure engineering disasters in loess areas. The loess samples in Chencang District of Baoji City, Shaanxi Province, were taken as the samples in the test. The multiple humidification and dehumidification tests were used to simulate multiple rainfall evaporation, and the moisture content changes in the loess samples during the dry–wet cycle were calculated. With the help of digital image technology, the fracture parameters of the loess samples were extracted, and the variation law of crack parameters was analyzed by combining fractal dimension, Bayesian factor, and Pearson correlation coefficient. The findings indicate that variations in soil moisture content and the number of dry and wet cycles contribute to fluctuations in soil evaporation rates, resulting in varying degrees of soil cracking development. The increase in the number of dry and wet cycles leads to evident soil shrinkage, an accelerated water evaporation process, pronounced surface deterioration, and a higher degree of crack development. The rate of crack propagation varies at different locations, with a higher rate observed in the horizontal plane compared to the vertical plane. The influence of temperature and humidity varies due to the different dimensions of cracks (horizontal and vertical). Horizontal crack development is primarily influenced by temperature, while vertical crack development is primarily influenced by humidity. Temperature and humidity inhibit each other. When one factor is dominant, the other indirectly affects crack development by influencing the dominant factor. The research findings can serve as a valuable reference for effectively mitigating and minimizing the impact of crack development-induced disasters.

Groundwater is a vital water source for human survival and regulates the hydrological cycle within the uppermost strata. Through the processes of recharge and discharge, as well as solute exchange, it interacts with surface water systems in Zhengzhou, e.g., the Yellow River and the Jialu River. Therefore, systematically assessing its hydrochemical characteristics, driving factors, and health risks is crucial for ensuring the safety of public drinking water and regional development. This study focuses on shallow (45~55 m), medium-deep (80~350 m), deep (350~800 m), and ultra-deep (800~1200 m) groundwater in Zhengzhou City. A descriptive statistical analysis was employed to identify the primary chemical constituents of groundwater at various depths within the study area. Piper diagrams and the Shukarev classification method were employed to determine the hydrochemical types of the groundwater. Additionally, Gibbs diagrams, correlation coefficient methods, ion ratio coefficient methods and chlorine–alkali indices were employed to investigate the formation mechanisms of the chemical components of the groundwater, and the health risks in the study area were evaluated. Results: Ca²⁺ dominates the shallow/medium-deep groundwater, Na⁺ dominates the deep/ultra-deep groundwater; HCO₃⁻ (70~82%) is the dominant anion. Water chemistry shifts from HCO₃-Ca to HCO₃-Na with depth. Solubilisation, cation exchange, counter-cation exchange, and mixed processes primarily govern the formation of the groundwater’s chemical composition in the study area. Nitrate health risk assessments indicate significant differences in non-carcinogenic risks across four population groups (infants, children, young adults, and adults). Medium-depth groundwater poses a potential risk to all groups, while shallow and deep groundwater threaten only infants. Ultra-deep groundwater carries the lowest risk.

Groundwater is one of the main water supplies for Zhengzhou City. Changes in groundwater depth negatively affect the water supply and geological stability of the city. Based on groundwater monitoring data from 1999 to 2024, this paper investigates the spatiotemporal changes in shallow groundwater depth in Zhengzhou and their driving factors. Trend analysis, ordinary Kriging interpolation, and Pearson correlation analysis were first employed to characterize the spatiotemporal evolution patterns of groundwater depth. A principal component regression (PCR) framework was then applied to reduce multicollinearity among hydro-climatic and water-use variables and to quantify their integrated relationships with groundwater depth at individual monitoring wells. The main findings are as follows: (1) Over the past 25 years, groundwater depth in Zhengzhou has gradually increased, with an average decline rate of 0.68 m per year. The most rapid increase occurred from 1999 to 2012. (2) Spatially, groundwater depth is greatest in the central urban area (average 35.2 m) and decreases with distance from the city center, forming a depression cone in the downtown area. (3) Anthropogenic factors dominate groundwater depth variation. Groundwater extraction shows a strong positive correlation with groundwater depth, and standardized regression coefficients indicate that domestic water consumption and groundwater supply are the key drivers of groundwater deepening and recovery, respectively. Rapid urbanization has led to water table decline, while changes in precipitation have had relatively minor effects. (4) Socioeconomic factors, such as expansion of construction land, population growth, and industrialization, have also contributed to the increase in groundwater depth by raising water demand and reducing infiltration recharge. The PCR-based analysis provides a parsimonious and spatially explicit basis for understanding groundwater-depth dynamics in a rapidly urbanizing plain city and offers practical guidance for targeted groundwater management, extraction control, and ecological water replenishment in Zhengzhou and similar regions.

To evaluate the impacts of the Middle Route of the South-to-North Water Diversion Project on groundwater depth in the water-receiving areas of Henan Province, this study systematically investigated the spatiotemporal evolution of groundwater depth and its influencing factors before and after project operation, based on monitoring data from 2004 to 2024, using geostatistical methods and principal component analysis. The results indicate that following project operation, the ratio of groundwater supply to allowable groundwater withdrawal decreased from 216.50% to 175.09%, representing a reduction of 41.41 percentage points and indicating an alleviation of groundwater overexploitation pressure. After project operation, the areal proportion of the 0–8 m groundwater depth interval decreased by 14 percentage points relative to the pre-operation period, that of the 8–28 m interval increased by 14.2 percentage points, and that of the >28 m interval decreased slightly. After project operation, the spatial variability of groundwater depth changed, and the nugget-to-sill ratio exhibited fluctuating behavior: it decreased during 2015–2021, indicating a stage-wise strengthening of spatial dependence; in 2022, the nugget-to-sill ratio increased sharply and spatial autocorrelation weakened; and overall, the ratio fluctuated within the strong to moderate spatial autocorrelation range. The PLSR-VIP analysis identified surface water supply and domestic water consumption as the two highest-ranked factors associated with groundwater depth. Although diverted water volume had a full-sample VIP of 1.010, its VIP exceeded 1 in only 38.1% of leave-one-year-out refits and decreased to 0.825 after detrending, with a non-significant detrended correlation (r = −0.228, q = 0.356). These findings indicate that its statistical importance was sensitive to sample composition and temporal trends. During 2015–2024, groundwater depth exhibited a decreasing trend, indicating groundwater-level recovery, coinciding with changes in the regional water supply structure. However, the independent contribution of the diversion project to this recovery could not be established from the present analyses.

Understanding the crack development and rainfall infiltration in loess under wetting–drying cycles is crucial for assessing slope stability and promoting sustainable land management in ecologically vulnerable regions. This study employed a three-dimensional column model (Φ₂₄ × 50 cm) with 64 buried electrodes to simulate short-term heavy rainfall by changing the light duration (10 h/d and 5 h/d) and using 100 mm rainfall water. Results indicate that dry–wet cycles cause cumulative damage, significantly altering soil infiltration properties. After four cycles, the rainfall infiltration recharge coefficient increased from an initial 0.44% to 45.58%, a more than 100-fold rise. Resistivity imaging revealed a shift in water transport mode: from uniform matrix flow initially to preferential flow dominated by crack networks as cracks developed. During drying, crack zones exhibited high resistivity (ρ > 150 Ω·m), while water-filled cracks during infiltration showed low resistivity (ρ < 50 Ω·m). Resistivity is an excellent comprehensive index to quantify multi-field coupling damage, and its change (ρ∝ 1/w^1.86 × 1/(1 + 0.032 width)) synchronously responds to water content, crack development and dry–wet process. Low water content (w < 15%) and medium crack width (4–6 mm) are the most sensitive states. Longer illumination (10 h/d) promoted greater crack development and higher infiltration capacity compared to shorter cycles (5 h/d). The developed resistivity–moisture relationship provides a non-destructive monitoring tool for slope moisture dynamics, supporting not only geotechnical stability assessment but also optimized irrigation scheduling and adaptive land-use planning. These insights contribute directly to the sustainable management of soil and water resources in loess landscapes, aligning with sustainability goals in fragile ecosystems.