This work aims to investigate the hydrochemical characteristics and formation mechanisms of shallow groundwater in a part of the Nanchang section of Ganfu plain. The hydrochemical data from 90 groundwater samples were interpreted by the methods of mathematical statistics, Piper diagrams, Gibbs plots, ratio graphs of ions, and geochemical modeling. The results show that shallow groundwater is weakly acidic, the average concentration of cation in groundwater decrease in Ca²⁺ > Na⁺ > Mg²⁺ > K⁺, and the abundance is in the order HCO₃⁻ > NO₃⁻ > SO₄²⁻ > Cl⁻ for anions. The hydrochemical type of groundwater was dominated by HCO₃-Na·Ca·Mg, HCO₃·Cl-Na·Ca·Mg, and HCO₃-Na·Ca. Moreover, the main controlling factor of groundwater hydrochemistry is water-rock interactions. Na⁺ and K⁺ mainly originate from the dissolution of halite. Ca²⁺ and Mg²⁺ are mainly controlled by carbonate dissolution, while the main anions come from the dissolution of evaporite and carbonate. The groundwater chemical evolution is affected by the dissolution and precipitation of the mineral phase and cation exchange.

To address the issue of seasonal water resource shortages in Nanchang City, a multi-system coupling socio-hydrology simulation method was proposed. This approach involves dynamically integrating a centralized socio-economic model with a distributed surface water groundwater numerical model to explore the intricate relationships between the socio-economic system, the surface water–groundwater integrated system, and the outcomes related to seasonal water resource shortages. Taking Nanchang City as an example, this study conducted research on the water resource supply and demand balance, as well as the groundwater emergency supply, using the multi-system coupling model. Three scenarios were established: status quo, developing, and water-saving. The results show that with the increasing total water demand of social and economic development, the severity of the water resource shortage will be most pronounced in 2030. The minimum water resources supply and demand ratios for the status quo, developing, and water-saving scenarios are projected to be 0.68, 0.52, and 0.77, respectively. To meet residents’ water needs during drought conditions, emergency groundwater supply efforts are investigated. According to the simulation results, groundwater emergency supply would increase the total population by 24.0 thousand, 49.4 thousand, and 11.2 thousand people, respectively, in the status quo, developing, and water-saving scenarios. In the water-saving scenario, the Youkou and Xiebu water sources can serve as suitable emergency water sources. In the status quo scenario, the Youkou water source is the most viable emergency water source. However, in the developing scenario, relying solely on any single water source for emergency supply could have an irreversible impact on the aquifer. Therefore, considering the simultaneous use of multiple water sources is recommended, as it can fulfill water demands while ensuring the sustainable utilization of groundwater resources.

To investigate the failure mode and strength characteristics of rock-like materials containing two non-coplanar closed discontinues, and the influence of crack attitude on the shear failure of rock mass, a series of direct shear tests are carried out on rock-like materials containing two pre-existing cracks of different attitudes, one of them is horizontal crack, and the other is inclined crack. The specimens containing pre-existing cracks of four inclinations (0°, 45°, 135°, and 180°) and three dip angles (30°, 60°, and 90°) are prepared, and the failure form and stress-displacement curve are recorded during the tests. The results show that the attitude of the crack has a significant effect on the failure form and strength characteristics. In positive shear, the shear stress increases slowly and the crack initiation of the crack occurs relatively late, and in negative shear, the shear stress increases rapidly and the crack initiation stage appears earlier. Under the normal stress of 1 MPa, the fracture surface fluctuates along the pre-existing cracks, and the difference in shear strength of each specimen is less than 1.0 MPa. Under the normal stress of 5 MPa, the fracture surface mostly distributes along the horizontal direction, and the difference in shear strength of each specimen is about 2.0 MPa. Under the same level of normal stress, the crack initiation and peak stress vary with the attitude of pre-existing crack, and the variation trend of peak stress is changed when the normal stress increased due to the difference in failure form. It is calculated that the ratio of crack initiation stress to peak stress ranges from 0.61 to 0.80.

Plain farmland areas without significant topographic slope exhibit microtopographic features of different scales. Quantitative assessment of the effects of microtopography at different scales on runoff generation in typical farmland areas is of great significance for regional water resources management and flood disaster forecasting. The main objective of the study was to develop an event-based rainfall–runoff model based on the layered Green–Ampt model (LGAM) with the consideration of plot-scale microtopographic features in plain farmland areas. Our experimental field, located in Taihu Lake Basin, was classified into three types of topographic subunits (i.e., main field, rill, and ditch) according to the average elevation. To simplify the concentration process for three topographic subunits, the average concentration time method was employed. Here, various experimental scenarios were simulated, including two classical unsteady rainfall events in homogeneous soil, one ponding infiltration experiment, and two typical rainfall–runoff events in the experimental field. We found that the multilayered setting showed higher accuracy than the homogeneous setting for simulating infiltration in the ponding infiltration experiment in the field. The RMSE of simulated ponding water depth reduced from 0.166 cm to 0.035 cm and NSE rose from 0.988 to 0.999. The simulated hydrograph considering microtopography effects proved higher accuracy than that under unified topography assumption. After classifying topography, the RMSE and NSE of simulated hydrographs decreased and increased, respectively. The lower the topographic subunit, the earlier the outflow occurred. At the early stage, the runoff mostly originated from the relatively low topographic subunits. Infiltration-excess regime under saturated condition may initially dominate in the low-lying ditch under intense rainfall, with extremely high runoff coefficient. Concentration process in the plain farmland area was affected by both rainfall intensity and microtopography. The greater the rainfall intensity, the shorter the average concentration time. The concentration velocity under heavy rainfall was four times faster than that under light rainfall. The lower topographic subunit was characterized by shorter concentration pathway and average concentration time. Ditches reduced the peak flow and advanced the time to peak. This quantitative study provides new insights into effects of microtopography on runoff generation in plain farmland area as well as an effective alternative for plot-scale rainfall–runoff modeling.

The source of water supply in Nanchang City is relatively single, and the safety of urban water supply is difficult to guarantee. According to the hydrogeological conditions of the study area, a threedimensional visualization numerical model of groundwater system was established. After the model identification and verification, combined with the target of emergency water supply in Nanchang city, the emergency exploitation of groundwater in Youkou emergency water source was simulated by using the model under different emergency exploitation schemes, respectively. The prediction results show that compared with scheme I and scheme II, scheme III is most suitable for the requirements of well layout, which has the advantages with the minimum drawdown of groundwater level, and the maximum exploitation. For scheme III, under the conditions that the dewatered aquifers are no more than 1/2 and 2/3 of the original aquifer, the emergency exploitation of 36.55×10⁴m³/d and 49.45×10⁴m³/d can be provided, which could meet the emergency water demands of 54.9% and 74.3% of the local residents, respectively.