Performance Evaluation of Profile Probe for Continuous Monitoring of Volumetric Water Content in Multilayered Cover System

Abstract

A profile probe (PP) is a handy instrument for simultaneously measuring volumetric water content (θ) at shallow multiple depths in the field. The accuracy of the θ measurement is important for moisture migration and water balance studies associated with the multilayered cover system (MLCS) provided over nonoperational landfills. There are no guidelines or controlled procedure for evaluating the accuracy of a PP for varying layers of an MLCS. A simple laboratory setup is developed in this study to evaluate all six sensors of a PP simultaneously for a particular soil type and compaction state. The results obtained from this study were used to improve the accuracy of PP measurements for the type of soils generally used in MLCSs. The validity of the proposed procedure was further evaluated based on a new set of PP measurements. The procedure adopted in this study improved the accuracy of PP measurement from ±6% to ±1%. The most interesting observation is the parity in sensor readings by following the proposed procedure, which was initially found to be different. The results from this study indicated that improper θ measurements can result in an error as high as 18% in the determination of change in soil water storage for different layers of a trial MLCS. Adopting the procedure proposed in this study ensures reliable and precise θ measurements for the materials used in MLCS for all the sensors of PP. In the absence of soil-specific calibration for PP, the equations proposed in this study can be used for the type of soils used in MLCSs.