Apparatus and method for monitoring snow water equivalent and soil moisture content using natural gamma radiation

A gamma monitoring apparatus for measuring water equivalent of a snowpack over a selected ground area, comprising:

• a detector unit installable at a given height above the selected ground area, the detector unit having a collimator defining a field of view to be directed on the selected ground area, and a scintillator coupled to a photomultiplier tube for detecting gamma rays emitted by naturally radioactive elements present in soil under the snowpack and absorbed by the snowpack in the field of view defined by the collimator, the photomultiplier tube having an output for producing a signal having pulses indicative of the gamma rays;
• and
• a circuit arrangement having:
• measuring means for measuring the pulses in the signal;
• registering means for registering the pulses exceeding threshold energy levels in a number of energy windows as gamma counts;
• computing means for periodically computing the water equivalent of the snowpack as functions of the gamma counts in the energy windows and the height of the detector unit with respect to ground level;
• memory means for storing data representing the computed water equivalent;
• transmission means for transmitting the data;
• and
• power supply means for providing power to the circuit arrangement and the detector unit.