The estimating of hydraulic conductivity using 1-D electrical resistivity measurement - a case study of the shallow aquifer in the Zhuoshui River Alluvial Fan

Hydraulic conductivity (K) is an important aquifer parameter and is usually obtained using conventional pumping test. However, only limited amount of data can be collected, because pumping test is time consuming and expensive. In recent years, some studies estimated K by using pumping test data and surface electrical resistivity survey. These studies cost less because less pumping tests are required. However, majority of these studies don't consider the effects caused by layers of clay. In fact, clay layers are commonly distributed in middle-fan and distal-fan. Therefore, this study divides Zhuoshui River Alluvial Fan into several zones based on the sediment distribution. A linear regression equation is derived from the pumping test data and formation factors for each zone. This study applied these equations to develop the distribution of K in the shallow aquifer of major fan, which is bounded by the Old Zhuoshui River at the north side and by New Hu-Wei River at the south side. The result shows that the shallow aquifer of the major fan of Zhuoshui River can be divided into two zones, which are top-fan and non-top-fan areas. The regression results show good correlation between K and the formation factor in each zone. These regression equations are then used to estimate K in the study area. The results are compared between the field measurement and the results obtained from Khalil's equations. The results indicate that the estimation error, between 11 m/day and 58 m/day, is much smaller than the estimation error obtained using Khalil's equation. The developed methodology for estimating K can contribute to related groundwater research and can be applied to other alluvial fans with similar sediment distribution to this study area.