For the needs of the whole region’s emergency regulation of the nullah sudden water pollution event, the emergency regulation strategy of the accident section and upstream and downstream of the sudden water pollution event is studied. For the accident section, the duration of the whole emergency event is calculated using the parameter quantification method; for the upstream of the accident section, the NSGA-II is used to adjust the gate opening to ensure the water level stability of the upstream pools; for the downstream section, the optimized partition method is used to identify the unfavorable pools and close the unfavorable pool to extend the water supply time. Based on the example of an emergency event in the section of the Liyanghe gate–Guyunhe gate of the middle line project, the research results are as follows: the accident section is identified as the Xiaohe gate–Hutuohe gate, the upstream of the accident section is the Liyanghe gate–Xiaohe gate, and the downstream of the accident section is the Hutuohe gate–Gangtou Tunnel gate. The duration of the emergency event in the accident section is 7.9 h; the maximum average water level deviation before the gate upstream of the accident section is 0.05 m; two unfavorable canal pools are identified in the stream of the accident section, and the water supply time of the unfavorable pools is extended by 6.13 and 5.61 d.
The current calculation method of breakthrough time calculates the concentration value of the measuring point at different times based on the model solution, which is determined by approaching the concentration value corresponding to the breakthrough standard through trial calculations. However, it is necessary to research the breakthrough standard with practical applications of mathematical and physical significance, especially a one-dimensional mathematical model of contaminant migration under Dirichlet boundary conditions. A general algorithm for directly calculating the breakthrough time was established in this research. Moreover, the calculation standard of the breakthrough time was also discussed based on the similarity between the analytical solution and the mathematical law of thermal conduction. This research considered parameters of the seepage velocity, dispersion coefficient and characteristics of the impervious layer, and the sensitivity analysis of these factors were investigated. The results show that the proposed algorithm was basically consistent with the current method, and the concept of thermal penetration depth is also feasible for the calculation standard. This is not only suitable for different breakthrough standards, but also simple and convenient. This study can provide a reference for the design, management and subsequent remediation of actual sites. INDEX TERMSBreakthrough time, mathematical model, convection dispersion, analytical solution, general algorithm. I.
Due to the temperature of shallow aquifers being affected by atmospheric temperature, groundwater source heat pumps (GWSHPs) become unstable and the operation efficiency of GWSHP is constrained. In the study, the coupling numerical simulation model of the groundwater flow field and temperature field is established based on the continuous monitoring results in an actual experimental site, and the water and thermal migration of shallow aquifer is simulated under the influence of the atmospheric environment. The influence of the dynamic change in ground temperature is analyzed on a GWSHP. The results indicated that the temperature of the shallow aquifer is affected by the external temperature, and the recharge temperature in the summer cooling period was 33°C, and that in the winter heating period was 6°C in the actual site, to avoid the occurrence of thermal penetration when there is a gap between the actual situation and the design situation, the single cooler can balance the insufficient cooling capacity in summer under the most unfavorable situation. The research results can also provide a reference for the development and utilization of geothermal energy resources in shallow aquifers.
In recent years, many research methods have been developed for the traceability of groundwater contamination source, in which the numerical simulation and analytical methods are the most common methods to study on groundwater flow and solute transport. However, the establishment and solution of an optimization model is a very complex inverse problem. Given that many decision variables are needed to be identified, two relatively simple analytical and numerical methods are applied for the prediction of chloride migration range and duration process in source area, then the geophysical prospecting and drilling sampling analysis are also used for the verification, moreover, the source center is determined based on the difference between predicted results and measured results. In addition, the influence of the observation points layout, hydrodynamic dispersion parameters and groundwater flow rate on the traceability effect are also analyzed. The results show that located observation points can reflect the chloride distribution accurately, hydrodynamic dispersion parameters and groundwater flow rate have more significant impacts on the traceability effect compared with other factors. Lastly, the proposed model application process is also discussed in the limited scale site, and it provides the reference for source traceability and subsequent remediation design under the similar hydrogeological conditions.
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