Cosmic rays probe soil moisture

The CosmOz Site Hamilton

Beginning in October 2010, CSIRO Land and Water installed cosmic-ray probes at several locations around Australia to form the inaugural CosmOz network. These sites were established at instrumented research sites operated by CSIRO and University collaborators to test and validate the operation of this new technology.

These novel probes use cosmic rays originating from outer space to measure average soil moisture over an area of about 30 hectares to depths in the soil of between 10 to 50 cm. This constitutes a quantum leap over conventional on-ground soil moisture sensing technology that can only measure soil moisture content within small volumes of soil.

The system measures fast neutrons that are produced from interactions of cosmic rays with the atmosphere and top few metres of soil. The intensity of these neutrons is moderated largely by water molecules in the soil. The number of neutrons counted over time is inversely proportional to the amount of water in the soil.

To estimate volumetric water content, each system is calibrated against soil samples that are collected from dry and wet moisture regimes using a standard protocol.

The system comprises of a data logger, neutron detector, satellite telemetry, tipping bucket rain gauge, temperature humidity, pressure sensors and three surface moisture (TDR) probes. The entire system is installed on a single mast and powered by a solar charging system. Data is logged and transmitted every 60 minutes to the Cosm0z database.

The cosmos database is located at: https://cosmoz.csiro.au/sites.