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The assessment to vulnerability of the water supply system needs several modeling tools and cases to simulate. A decision-support tool which integrates the common procedures of impact assessment of climate change, downscaling, weather generation, hydrological model, and interface for linking system dynamics model is proposed here. In this study, the impact of climatic change and growing water demand to the water supply system in Touchien river basin in Taiwan was derived. The vulnerability for the current water supply system was estimated for present and future conditions. The result demonstrated that the water supply system could meet the water demand in Touchien river basin but might be subjected to serious water shortage due to climatic change and expanded water demand. Results are expected to give the authorized government sectors a hint for instituting water policy and implementing allocation measures for irrigational water.

The study presents a numerical infiltration model of a hysteretic flow coupled with general mass conservation for practical application to unsaturated soil. In unsaturated soil, hysteresis is an important phenomenon in the complicated hydrological processes, and it is usually ignored when simulating the relationship of soil water content. The governing equation of unsaturated flow is the Richards equation, and it is difficult to obtain the analytic solutions because of the variation of temporal boundary conditions and the dynamics of change of soil water content in the vadose zone. The numerical solution is solved by the finite difference method technique with the Picard iteration scheme combined with the hysteresis model derived by Huang et al.

Abstract:In recent years, many approaches have been developed using the artificial neural networks (ANN) model incorporated with the Theis analytical solution to estimate the effective hydrological parameters for homogeneous and isotropic porous media, such as the Lin and Chen approach (ANN approach) and the principal component analysis (PCA)-ANN approach. The above methods assume a full superimposition of the type curve and the observed drawdown and try to use the first time-drawdown data as a match point to make a fine approximation of the effective parameters. However, using first time-drawdown data or early time-drawdown data does not always allow for an accurate estimation of the hydrological parameters, especially for heterogeneous and anisotropic aquifers. Therefore, this article corrects the concept of the superimposed plot by modifying the ANN approach and the PCA-ANN approach, as well as incorporating the Papadopoulos analytical solution, to estimate the transmissivities and storage coefficient for anisotropic, homogeneous aquifers. The ANN model is trained with 4000 training sets of the well function, and tested with 1000 sets and 300 sets of synthetic time-drawdown generated from the homogeneous and heterogeneous parameters, respectively. In situ observation data from the time-drawdown at station Shi-Chou on the Choushui River alluvial fan, Taiwan, is further adopted to test the applicability and reliability of the proposed methods, as well as provide a basis for comparison with the Straight-line method and the Type-curve method. Results suggest that both of the modified methods perform better than the original ones, and using late time-drawdown to optimize the effective parameters is shown to be better than using early time-drawdown. Additionally, results indicate that the modified ANN approach is better than the modified PCA-ANN approach in terms of precision, while the efficiency of the modified PCA-ANN approach is approximately three times better than that of the modified ANN approach.

This research proposes a combination of SWAT and MODFLOW, MD‐SWAT‐MODFLOW, to address the multi‐aquifers condition in Choushui River alluvial fan, Taiwan. The natural recharge and unidentified pumping/recharge are separately estimated. The model identifies the monthly pumping/recharge rates in multi‐aquifers so that the daily streamflow can be simulated correctly. A multi‐aquifers condition means a subsurface formation composed of at least the unconfined aquifer, the confined aquifer, and an in‐between aquitard. In such a case, the variation of groundwater level is related to pumping/recharge activities in vertically adjacent aquifer and the river‐aquifer interaction. Both factors in turn affect the streamflow performance. Results show that MD‐SWAT‐MODFLOW performs better than SWAT alone in terms of simulated streamflow, especially during low flow period, when pumping/recharge rates are properly estimated. A sensitivity analysis of individual parameter suggests that the vertical leakance may be the most sensitive among all investigated MODFLOW parameters in terms of the estimated pumping/recharge among aquifers, and the Latin‐Hypercube‐One‐factor‐At‐a‐Time sensitivity analysis indicates that the hydraulic conductivity of channel is the most sensitive to the model performance. It also points out the necessity to simultaneously estimate pumping/recharge rates in multi‐aquifers. The estimated net pumping rate can be treated as a lower bound of the actual local pumping rate. As a whole, the model provides the spatio‐temporal groundwater use, which gives the authorities insights to manage groundwater resources. Copyright © 2012 John Wiley & Sons, Ltd.