Development and Test of an Infrastructure Free Real-Time Water Level Measurement System

NOAA's Center for Operational Oceanographic Products and Services (CO-OPS) is responsible for developing and maintaining the National Water Level Observation Network (NWLON). NWLON consists of over 200 long term observatories that provide near real-time, 6 minute average, water level observations from locations throughout all U.S. coasts. CO-OPS continually analyzes state-of-the-art and emerging technologies to identify potential improvements in data quality and operating efficiency. NOAA, recognizing the changing conditions, anticipates a critical need for real time oceanographic and meteorological observations where traditional approaches are less feasible. CO-OPS is working on the design, development and testing of a real-time tidal measurement system, "The Hermit," for use in coastal regions. The latest prototype has recently completed a successful 3 month field test deployment in the St Andrews Sound region of Georgia, a location where relatively few long term water level records have been collected to date. The test location provided unique challenges such as having a very limited coastal infrastructure and experiencing a 7-8 foot tidal range. The Hermit consists of a bottom mounted pressure/conductivity/temperature sensor (Seabird SBE 26+) and a surface communications buoy which are linked via acoustic modems (Link Quest). The surface buoy relays data back to the CO-OPS database in near-real time using an Iridium satellite based communication system. Additionally, the buoy includes an AirMar all-in-one meteorological sensor. In addition to The Hermit deployment, three test GPS bench marks and a tide staff were installed on a nearby coastline to vertically reference water level measurements. During this deployment, The Hermit successfully provided near real-time measurements of bottom pressure, water conductivity and temperature, wind speed and direction, air temperature, and barometric pressure over the 3 month deployment. During the test period, several high wind storm surge events were captured, along with a perigean spring tide. Details of these data along with the system design will be presented along with CO-OPS plans for future operational applications.