Snow pillows work by measuring the hydrostatic pressure exerted by the weight of the snowpack above them, which allows for the calculation of the snow's water equivalent. Essentially, they "weigh" the snow.
Here's a breakdown of the process:
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The Pillow: A snow pillow is a large, flat, fluid-filled bladder, typically made of rubber or a similar durable material. These pillows are usually circular or rectangular and range in size.
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Fluid-Filled: The pillow is filled with a non-freezing fluid, such as antifreeze and water. This fluid transmits the pressure exerted by the snowpack.
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Pressure Transducer: The pillow is connected to a pressure transducer. This device measures the pressure of the fluid inside the pillow. The pressure is directly proportional to the weight of the snow above it.
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Data Conversion: The pressure transducer converts the pressure reading into an electrical signal. This signal is then processed by a data logger in a nearby shelter.
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Water Equivalent Calculation: The data logger uses the pressure reading to calculate the snow water equivalent (SWE). SWE is the depth of water that would result if the entire snowpack were melted. The weight of the snow directly corresponds to the amount of water it contains. This value is critical for understanding water resources, predicting floods, and managing reservoirs.
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Automated Reporting: The data is often transmitted remotely via satellite or radio telemetry to agencies that monitor water resources and snow conditions.
In summary, a snow pillow acts as a large scale measuring device. The weight of the snow pressing down on the fluid inside the pillow translates into a pressure reading, which is then converted into an estimate of the water content within the snowpack. This data is crucial for water resource management.
