A Method of Simulating Regional Groundwater level Distribution Based on Digital Elevation Model

Abstract

It is very important to use the measured data to obtain the regional groundwater level distribution in groundwater flow modeling, which can provide the initial flow field or boundary condition for modeling, and can be used as the verification basis for the simulation results. Traditional methods are usually interpolated using existing water level data, and the accuracy of the results is greatly influenced by the number of boreholes and the rationality of distribution, so it is not applicable in ungauged region of northwest China. Actually, the flow of groundwater in most areas is affected by the topography at the regional scale, and the terrain and groundwater flow path are correlated. In this paper, a method based on digital elevation model to simulate the regional groundwater level distribution is presented. The selection of the trend surface equation and parameter calibration are the key points and difficulties, because low order polynomial may lead the trend surface equation cannot fit the measured data well, and high order polynomial maybe lead the instability of the solution to the equation. Therefore, this paper established the high order polynomial as the initial trend surface equation, then the correlation between each parameter in the trend surface equation and the elevation of the measured groundwater level was analyzed, and the parameters with obvious correlation with the elevation of groundwater level compose the trend surface equation, and then using the measured data realized the optimal estimation of the average trend level of groundwater, to ensure the best trend surface equation, finally, according to Lanczos singular value decomposition theory, the trend surface equation solution were obtained, and an unbiased and optimal estimation of the residual using the method of universal kriging interpolation was presented. This method was applied in a certain area of northwest China, and the error of the calculation results was much less than that of the kriging interpolation method, which was more consistent with the measured values and could be used to extrapolate. This method has a good prospect in the simulation of groundwater flow field in ungauged region of northwest China.