The Investigation of Basin Scale Hydraulic Tomography in Chou-Shui River Alluvial Fan in Taiwan.

Controlling of aquifer hydraulic parameters is the main factor influencing the future groundwater resources management and recharge evaluation. However, the hydraulic parameters can only be obtained from few wells which have been implemented water tests or from models calibration, existing hydraulic parameters were used to acquire parameters of other areas by kriging method. There are several differences between hydraulic parameters obtained from the method stated above and from in-situ tests. In order to improve the accuracy of hydraulic parameters, the study cited advanced hydraulic tomography and river stage tomography technologies from foreign counties and operated in coordination with the monitoring function of present groundwater observed wells network to apply to Chou-shui river alluvial fan. In order to improve the accuracy of hydraulic characteristics estimation, and plan future development of hydraulic tomography and river stage tomography technologies, the study estimated data by hydraulic tomography and river stage tomography using numerical simulation methods which considering the hydraulic parameters obtained from the large-scale pumping tests, determining observation wells which had high correlation among groundwater levels, and considering correlation between river water level and groundwater level changes.

The results of the study are: (1) using current artificial pumping behaviors to estimate hydraulic conductivity of a large-scale aquifer is feasible, (2) according to the results of correlation analysis between river stage and groundwater level, correlation coefficient distribution are similar in upstream, middle stream and downstream of Chou-shui river, and there are high correlation between river stage and groundwater level in southeast and northwest alluvial fan of Chou-shui river, (3) the influence of Chou-shui river and Beigang river on the groundwater level of this area are the similar, (4) according to the results of groundwater recharges potential, high potential recharge regions are along the Chou-shui river, (5) average yearly recharge depth of Tu-ku bridge watershed and Beigang(2) watershed are 87.4cm and 65.06cm respectively, (6) leakage of soil layers is decreasing in Chou-shui river alluvial fan from upstream to downstream.