The Establishment and Application of Model Calibration Principle Considering Hydrogeological Structure
Groundwater numerical model is an important tool for groundwater management. To obtain a reliable model, model calibration is required. Conventionally, the approaches for model calibration can be classified into two categories: automatic calibration and manual calibration. Automatic calibration is normally based on the optimization method which can decrease the value of model error with high efficiency. However, the automatic calibration, which is a black box process, is difficult to be interpreted to researchers for understanding the groundwater system. In the other hand, manual calibration requires researchers to adjust model parameters and the model structure manually. This manual process consumes a lot of time and the efficiency is low. The advantage of manual calibration is that the process can includes more physical information such as grill’s log and geophysics. The manual calibration probes can help researchers understand the features of the studied groundwater system. In this study, a set of calibration principles for manual calibration are proposed and a revision of hydrogeological structure is also made based on the principles of manual calibration. This study develops model calibration principles considering hydrological structure to incorporate the advantages of both optimization and manual calibration. This model also has a benefit of transferring the expertise of manual calibration to other researchers. In this model, the hydraulic characteristic of the groundwater flow field is used as the physical base. The calibration principles are defined to clarify hydrogeological structure and associated parameters. These principles are: 1. The sequence of parameters for calibration. 2. The principles of parameter adjustment for the simulated water level trend. 3. The principles of parameter adjustment for the simulated water level fluctuation amplitude. 4. The principles of parameter adjustment for impervious layer range and vertical permeability coefficients. 5. Pumping volume adjustment. 6. The handling of dry cells in the simulation model. The developed methodology is applied to the first-impervious layer (T1) of Neipu (1) in Pintung Plain. Neipu (1) is at the second-aquifer (F2). Xishi (1), in the first-aquifer, is located in the northwestern upstream area with about 10 km in distance. According to hydrogeological map of Central Geological Survey, there is an impervious layer with favorable extensibility between two station. This impervious layer should hinder the groundwater flow. However, the water level observation shows high correlation between two stations. Therefore, the impervious area and the extension of the impervious layer maybe different to what was assumed. This study establishes and calibrates the groundwater numerical model in Pintung Plain using the propose calibration principles. The results show more clarification and details of the hydrogeological structure of the studied area. This improved hydrogeological information can be a good reference for future groundwater management.
|Appears in Collections:||Thesis|