Development and Application of Regional Groundwater Numerical Model Calibration Methodology, A Case Study of Chou-Shui River Alluvial Fan
Date Issued
2016
Date
2016
Author(s)
Shiu, Fu-Jian
Abstract
This study is aimed to develop a regional groundwater numerical model calibration method, which applies empirical orthogonal function (EOF) with simulated error hydrograph of groundwater level to quickly and accurately catch and calibrate the temporal-spatial distribuation of surface water recharge and hydrogeological parameters. The established method was applied on the groundwater system of Chou-Shui River Alluvial Fan. The proposed groundwater parameters calibration method is based on an optimization model which the objective function is minimizing the the root mean square error (RMSE) of the simulated and observed average error in groundwater storage. The decision variables are horizontal hydraulic conductivity, vertical leakance and surface water recharge. There are three constraints of the optimization model: (1) the surface water recharge of groundwater system in every iteration of calibrating process must obey the mass balance; (2) the simulated groundwater level must follow the governing equation of groundwater flow; (3) the value of horizontal hydraulic conductivity and vertical leakance are restricted to a reasonable limits. The process of the optimization model sets the initial value of decision variables first, and inputs the variables to groundwater model. Thus, the groundwater level can be simulated and the objective function will be estimated. If the objective function doesn’t satisfy the stop condition, the simulated error hydrograph of groundwater level will be calculated and analyzed with EOF. Then, the modified decision variables is calculater according to the simulated error hydrograph of groundwater level end the result of EOF analysis. From iterations, the optimal temporal-spatial distribuation of surface water recharge and hydrogeological parameters can be obtain. This study applied the optimization model on the calibration of the groundwater system in Chou-Shui River Alluvial Fan. The simulated period is from January 2012 to December 2014 monthly. The total variables of hydraulic conductivity in four acquifers are 126, of vertical leakance are 96. There are 1302 the surface water recharge temporal-spatial distribuation in all stress period. The result show that the RMSE is decreased dramatically in early iteration of the calibration and become smoothly after 5th iteration and finally stop at 24th iteration. The calibrated hydraulic conductivity and vertical leakence are mostly in reasonable limits. The simulated groundwater level can reflect the approximately trendance in all acquifer and can capture the peak of the observed value in first acquifer. Hence, the established method of this study can effectively and accurately calibrate temporal-spatial distribution of surface water recharge and hydrogeological parameters.
Subjects
Chou-Shui River Alluvial Fan
Empirical orthogonal function
Optimization model
Parameters calibration
Type
thesis
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