HYDRAULIC CONDUCTIVITY MEASUREMENT FOR SUBSURFACE DRAINAGE SYSTEM

Hydraulic conductivity is an important parameter in the design of subsurface drainage system. The measurement of hydraulic conductivity is complicated by sampling size, distance between sampling points and methods of measurement. The objective of this study was to compare drainage system (Ks), Porchet (Kp), and saturated Porchet (Kps) for measuring hydraulic conductivity. Furthermore, the sampling distance and size for Porchet method was examined. The results indicated that the distance between measurement points should not be less than 300 m due to inter-dependency of the observations. The total number of observations for a 25% error tolerance was 138. The equation Kps = 0.46 + 0.39 Kp described the relationship between hydraulic conductivity measured by Porchet and saturated Porchet methods. The K value from the drainage system, Porchet, and saturated Porchet methods (previous equation) were 2.73, 4.48 and 2.2 m d^-1, respectively. Thus, for practical purposes in the study area, hydraulic conductivity can be measured by Porchet procedure and then the result can be converted to the saturated Porchet K value, which is nearly similar to the K value obtained from the drainage system.