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St. Petersburg Coastal and Marine Science Center

St. Petersburg Coastal and Marine Science Center > Research and Support Capabilities

Research and Support Capabilities at the St. Petersburg Coastal and Marine Science Center

Shipboard Operations

Electromagnetic Seepage Meter

   control panels for the data collection of seepage
Two orange cases in photo are the control panels for the data collection of seepage. Each control panel provides power to an electromagnetic flow meter mounted inside a 1-m-diameter dome. [larger version]
Quantifying the flux of water across the seafloor is very difficult and tools are limited. Tools that do exist are subjected to forces that can influence the quality of data. One tool that is used is a seepage meter. Typical seepage meters are constructed of end-sections cut from standard 55-gallon steel drums. The dome is placed on the bottom and acts like a funnel, forcing water to move through a hole in the EM flow meter. The resulting flow through the flow meter causes a secondary voltage which is sent back to the control panel. The discharge or recharge into the bottom can be calculated based on the flow and area of the dome. More sophisticated seepage meters utilize heat-thermistors or electromagnetic flow meters. The USGS in St. Petersburg uses two electromagnetic (EM) flow meters, 1 inch and 1/2 inch throat size, attached to the underside of a 1m3 dome. The 1 inch throat size is used when larger flow is expected and the 1/2 inch size for greater resolution at low-flow conditions.

The EM flow meter is connected to a control panel powered by a 12VDC marine battery. The control panel contains an internal logger programmed to log a data point every 1 minute, providing detailed information on seepage flux. The data are measured as changes in voltage, calibrated, and converted into a flux measurement (liters per minute). Based on the size of the dome, seepage flux is calculated and output as volume per time (cm/d or L/m2/day).

http://coastal.er.usgs.gov/sgd/html/em_meter.html
http://sofia.usgs.gov/publications/ofr/2004-1369/
http://sofia.usgs.gov/publications/fs/2004-3117/
http://soundwaves.usgs.gov/2006/03/fieldwork2.html

 

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Page Last Modified: April 29, 2014 @ 12:48 PM (JSS)