Hybrid sensor networks for hydrological monitoring

"Accurate knowledge of the composition of soil properties is important to many domains, including agriculture, water supply management, and contamination control. Existing hydrological monitoring systems have numerous drawbacks, the most important of which are their cost and lack of autonomy, and the low temporal and spatial resolution of the data they collect.The research described in this thesis proposes to alleviate these problems by pairing high-resolution in situ measurement with remote data collection and software maintenance. The proposed system is a hybrid sensor network composed of wired and wireless connections. The sensor nodes, which perform the measurements at different depths of the soil, are wired together to form a sensor string. This string is buried in the ground, with the top-most node, designated as the cap node, above the surface. The cap node is connected wirelessly to other cap nodes and a base station that is used as a gateway between the sensor network and the external world.The sensor network has the ability to measure not only the conditions of the surface soil, but the condition of the soil at different depths below the surface. This feature, coupled with the ability to have all sensors measure concurrently over the entire site, facilitates real-time collection of accurate data on hydrological processes in the soil. The capabilities of the proposed system far exceed those of any instrumentation currently available. This system enables the collection of data at a scale and resolution that is orders of magnitude greater than any existing method, while dramatically reducing the cost of monitoring. The quality and sheer volume of data collected as a result will enable previously infeasible research in hydrology"--Abstract, page iii.