Refining the Calibration Process for Heat Dissipation Sensors.

Heat dissipation sensors (HDS), used to measure soil water matric potential, were used in long-term field studies designed to evaluate net infiltration of water into reclaimed mine tailing and waste rock facilities.  The mine waste facilities were reclaimed by placing a store and release soil cover over the mine waste.  HDS were employed as part of a vadose zone monitoring program to characterize the unsaturated flow through the reclaimed soil profile (soil cover and mine waste).  The primary goal of the vadose zone monitoring program is to calibrate existing soil water balance models (UNSAT-H) for the mine facilities and to predict long-term performance of the soil cover based on data collected during the cover performance period.  Thus, it is imperative that the vadose zone instrumentation be carefully calibrated.  Campbell Scientific 229 sensors (HDS) are the primary instrument used to calibrate the model in this study.  Prior to installation, the HDS were calibrated over a range of matric potentials and fit to the van Genucthen equation.  Using the initial laboratory calibration points and field data, the sensor calibration coefficients were refined over a period of 6 years to correct for variances in field and laboratory conditions.  This presentation discusses the specific methods used to refine the HDS calibration process.