Characterization of soil water content variability at the catchment scale using sensor network and stochastic modelling

Wireless sensor network technology has recently been used for high spatial and temporal resolution soil water content measurements to facilitate better understanding of hydrological processes in catchment scale. Its performance strongly depends on the quality of the sensors and the number of sensor nodes. In the first paper, the newly developed SPADE soil water content sensor was calibrated using a two-step laboratory-based procedure using dielectric reference liquids. The sensor accuracy was evaluated in terms of sensor-to-sensor variability and temperature effect. Using sensor-specific calibration significantly improved the estimation of apparent dielectric permittivity as compared to using a universal calibration function. The transferability of the temperature correction function from reference liquids to soils was successful and has been verified with undisturbed soil samples. A site-specific petrophysical model (complex refraction index model, CRIM) was used to convert apparent dielectric permittivity into soil water content using 15 soil samples from the Rollesbroich catchment, with RMSE values of 0.028, 0.025, and 0.022 cm3cm-3 for 5, 20, and 50 cm, respectively.