Station Sensors and Equipment

Each station in the Puerto Rico Landslide Forecast Network includes monitoring stations that are equipped with below-ground sensors that measure volumetric water content, soil suction pressure, soil temperature, and soil groundwater pressure. Sensors are installed in a hand-excavated pit that is dug to the base of the soil, where weathered bedrock material is encountered. The sensor array is installed at intervals of 0.25d, 0.5d, 0.75d, and 1d, where "d" is the total depth of the soil profile. The sensor distribution is shown in the diagram here.

Above ground sensors measure air temperature, barometric pressure, and rainfall. The stations are each controlled by a datalogger that collects data every 5 minutes and transmits data hourly via cellular modem to our local server between 7:00-20:00 AST. Because the stations are powered by solar energy and battery, data is usually not transmitted overnight to save power.

Station Data

Data measured include volumetric water content, soil suction, soil groundwater level, soil temperature, air temperature, barometric pressure, and rainfall.

Volumetric water content (VWC) is the ratio of water volume to total soil volume. Values typically do not exceed 0.5 cm3/cm3. Volumetric water content can be used to calculate soil saturation.

Soil suction is the negative pore pressure inside the soil. When soil pore pressure is positive, there is no suction. Our sensors only measure negative pressures up to 0 kPa. When the sensors read ~0 kPa, soil pore pressure could be positive.

Soil groundwater level is measured with a vibrating wire piezometer. The piezometer measures the pressure of groundwater above its position. Units reported are in centimeters of water. The readings of the piezometer are corrected for atmospheric pressure variations from the above-ground barometer.

Soil temperature is also measured by our piezometer instrument. The units reported are degrees Celsius.

Air temperature is measured by an above-ground thermometer. The units reported are degress Celsius. Air temperature values reported may be excessively high if the sensor is directly exposed to the sun.

Atmospheric pressure is measured by an above-ground barometer.

Rainfall rate and amount is measured by a tipping-bucket pluviometer. The units reported are millimeters.