On wireless sensing networks in hydrology: from observation to prediction

Abstract:

The use of wireless sensor networks (WSN) has gained increasing attention in the field of hydrology, because WSNs offer a unique potential to monitor the spatial and temporal dynamics of soil moisture at scales beyond the field scale. In addition, they provide unique opportunities for the validation of numerical models, hydrogeophysical measurement techniques, as well as for the calibration and validation of remotely sensed soil moisture data. In this presentation, we will discuss results of temporal and spatially resolved measurements of soil moisture using WSNs installed in two different small-scale catchments under forest (Wüstebach, Germany) and grassland (Rollesbroich, Germany). In combination with measurements of hydrological fluxes, we were able to close the water balance of the Wüstebach catchment up to 3% of the yearly rainfall. In addition, changes between wet and dry states of the catchment could be observed and related to a critical soil moisture content. Using stochastic analysis of water flow in the unsaturated zone and pedotransfer functions, we were able to predict subgrid variability of soil moisture. This framework also allowed deriving the spatial variability of soil hydraulic parameters using the relationship between the variance of soil moisture and its mean soil water content. Finally, soil moisture data from the WSN in the Wüstebach catchment were used to validate a detailed hydrologic model of the catchment using empirical orthogonal functions and coherence wavelet analysis. Further development of wireless sensing technologies will include the monitoring of soil moisture potential and biogeochemical properties such as redox potential.