NOAA's National Water Level Observation Network: Advancements in Observations, Infrastructure, and Applications

In 1807 Thomas Jefferson established the U.S. Government’s first science agency, the Survey of the Coast, with the mission of making accurate nautical charts and products to ensure safe marine navigation.  The advent of automated water level gauge technology at many locations around the country in the mid 1800’s replaced laborious manual readings of tide staffs and this eventually grew into the National Water Level Observation Network (NWLON).  The Survey of the Coast is now part of NOAA and the NWLON network now consists of 210 permanent real-time stations throughout the U.S. and its territories, which observe and transmit coastal water levels every 6 minutes.  The original intent of the network was to provide tidal datum control to support nautical charting, along with the tide predictions needed by mariners to adjust chart soundings for current water level depth, but both advances in observing system technologies and the arrival of the internet and real-time communications have greatly expanded the applications for these data providing many societal benefits.  Today the system provides real-time water level information to support a wide range of applications including commercial and recreational navigation, observations of storm tide and nuisance flooding, tsunami warnings, long-term trends in sea level rise and validation, coastal resilience planning, assimilation for operational coastal hydrodynamic forecast models, and many other applications.  The NWLON was recognized as one of 15 high impact, high benefit US government earth observing systems out of over 300 surveyed in a 2014 White House Office of Science and Technology Report.   As with any long-term observational network, there are constant challenges with ensuring the provision of high quality data gathered in widely varying and highly dynamic environmental conditions, and system maintenance, infrastructure enhancements and technology improvements are critical to ensure measurement quality and continuity.  Recent and planned upgrades include, establishing a tiered data system based on data uncertainty to better inform users and partners, working with partners to incorporate their data into the NWLON, transitioning to microwave radar systems as primary sensor technology, dual purposing the radar systems to also observe wave amplitude and period, and investigating the use of GPS to ensure understanding of land motion contribution to the long term data records.  These advancements will enable the NWLON to continue delivering accurate, timely and reliable water level measurements in an efficient manner to the widest spectrum of users for years into the future.