Abstract: Under natural geological environment, a homogeneous geological unit is hardly existed. During the process of building a numerical model of groundwater system, it is difficult to accurately determine the hydrogeological parameters of each geological unit, which can truly depict an aquifer. The uncertain factors in groundwater modeling caused by the model uncertainties can affect the numerical model simulation process. Combing with the research of the hydrogeological parameter uncertainty and the development of geostatistics, the MODFLOW-Gslib software was developed based on the MODFLOW, which is the commonly used deterministic groundwater flow numerical software. Compared with the traditional numerical simulation method, this method of combining geostatistics with numerical simulation can simulate the parameter variability in heterogeneous aquifers. An example is given to quantitatively demonstrate the practicability of the software through choosing the hydraulic conductivity as the uncertain hydrogeological parameter to make a statistical analysis on the simulation results. It suggested that the parameters in the software are in accordance with the relevant characteristics of the uncertainty of the hydrogeological parameters. Compared with the MODFLOW simulation results, the software can describe the characteristics of hydrogeological parameter variability in an aquifer more accurately.

Key words: uncertainty, MODFLOW, geostatistics, hydrogeological parameters