COMPARISON OF HYDRAULIC PARAMETER ESTIMATES BY GRAIN SIZE ANALYSES AND AQUIFER TESTS AT A RIVERBANK FILTRATION SITE

When developing groundwater resources, one encounters difficulty to determine hydraulic parameters (transmissivity, hydraulic conductivity and storativity). Aquifer tests, laboratory permeability tests and empirical equations based on grain size analysis can be used for estimating hydraulic conductivity. Aquifer tests are commonly used as better methods than laboratory permeability tests because the aquifer tests reflect more reliable field situation than the laboratory permeability tests. The third method is using empirical relationships between grain size and hydraulic conductivity. To develop optimal riverbank filtrate, hydraulic conductivity of the riverbank deposit should be determined accurately. This study aims to compare hydraulic conductivity estimates determined by grain size analysis and pumping and slug tests. Grain size measurements were done for 184 soil samples collected from eight boreholes at the riverbank filtration site in Daesan-Myeon. Slug tests were conducted in nine boreholes and pumping tests were carried out four pumping wells at the riverbank filtration site. From the hydraulic conductivity determination by the empirical relationships using Hazen, Beyer, Kozeny, Sauerbrei and Slichter equations show approximately same values. Arithmetic mean of hydraulic conductivity of the sand/gravel layer is 1.27×10-2 ms-1 whereas that of remaining sand layers ranges from 2.68×10-4 to 4.55×10-4 ms-1. The hydraulic conductivity estimates determined by slug tests using Hvorslev and Bouwer-Rice methods range from 6.46×10-7 to 4.75×10-5 ms-1. On the other hand, the hydraulic conductivity estimates obtained from the pumping tests ranges from 4.55×10-4 to 7.40×10-4 ms-1. Thus, the hydraulic conductivity estimates of fine and medium sands obtained from grain size distribution are similar to those by pumping tests, and are higher than those by slug tests. The authors wish to acknowledge the financial support of the Sustainable Water Resources Research Center under the program of the 21st Century Frontier R&D Program (project no: 3-4-1).