Doppler Automated Flow Meter

On 7/21/05 a Starflow ultrasonic Doppler flowmeter and micrologger were installed by watershed summer interns Michael Yunker (Geology '07) and Mitchell Robinson (Env Studies: Nat Resources '07) in a creek within the town of Sewanee. The automated flow meter system will be used to monitor stream flow, and flow data from the creek (Abbo's Alley) will be used to compare hydrology and nutrient export of the urban creek to that of the relatively undisturbed forested watershed (Split Creek). The instrument at Abbos's Alley will measure and record stream stage, discharge, and temperature inside the culvert through which the stream flows. The culvert is located beneath North Carolina Avenue.

The Starflow unit and its corresponding electronics are solar powered by a solar panel that faces SW at a 45-degree angle to the horizon. The solar panel sits atop a ten-foot post, which is sunk three feet underground and back-filled with sand. The solar panel charges the battery in the control box, which is positioned below the solar panel on the same post.

According to the Unidata Starflow Ultrasonic Doppler Instrument user’s manual:

The STARFLOW contains a 128K data logger which controls the instrument’s operation and logs the measurements
Water Velocity in the vicinity of the STARFLOW is measured acoustically by recording the Doppler shift from particles and microscopic air bubbles carried in the water.
Water Depth above the STARFLOW is measured by a pressure transducer recording the hydrostatic pressure of water above the instrument.
Temperature is measured to refine the acoustic recordings. These are related to the speed of sound in water, which is significantly affected by temperature.
Battery Voltage is measured to allow the STARFLOW to stop operating if the supply voltage is below defined limits.

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