Soil water content plays a key role in partitioning water and energy fluxes, in providing water to the atmosphere for precipitation, and controlling the pattern of groundwater recharge. Despite the importance of soil water content, it is not yet measured in an operational way, e.g. for a better prediction of hydrological fluxes (e.g. runoff, latent heat) at larger scales and in the framework of the development of early warning systems (e.g. flood forecasting) and the management of irrigation systems.
A promising new technology for environmental monitoring is the wireless sensor network. Wireless sensor network technology allows real-time soil water content monitoring with a high spatial and temporal resolution for observing hydrological processes in small watersheds (0.1-80 km²) and they are able to bridge the gap between local (e.g. lysimeter) and regional scale measurements (e.g. remote sensing). Although wireless sensor networks can still be considered as an emerging research field, the supporting communication technology for low cost, low power wireless networks has matured greatly in the past decade.
In the framework of TERENO the sensor network SoilNet for the near real-time monitoring of soil moisture and temperature has been developed, tested, and deployed (Bogena et al., 2007; Bogena et al., 2009; Bogena et al., 2010; Rosenbaum et al., 2010; Rosenbaum et al., 2011). Elements of the system (wireless modules, multi sensor boards, environmental monitoring boards, Ethernet interface board) have been developed and manufactured in great quantities by external companies. A detailed description concerning the SoilNet technology was provided by Bogena et al. (2010).