South Florida Water Management District Vertical Datum Upgrade

July 2024 FloridAgriculture eNewsletter

To enhance the accuracy of their data, the South Florida Water Management District (SFWMD) is upgrading the reference system used to measure water elevations in our monitoring network. SFWMD is currently in the process of shifting from reporting water elevations in the National Geodetic Vertical Datum of 1929 (NGVD 29) to the North American Vertical Datum of 1988 (NAVD 88). This includes data within the SFWMD’s environmental database for hydrologic, meteorologic, hydrogeologic and water quality data. 

The upgrade will provide the public and stakeholders with more accurate information about levels for waterbodies in the region. 

Depending on the location within the SFWMD, water levels in the newer NAVD 88 measurement system will be about 0.6 feet to 1.6 feet lower than in the older NGVD 29 measurement system. 

For example, the difference between the two measuring standards in Lake Okeechobee is 1.25 feet, so a water level of 11.25 feet NAVD 88 is 12.5 feet NGVD 29. 

Water elevations are reported as the height of the water surface compared to sea level. Water depth, on the other hand, is the height of the water surface as measured from the bottom of the water body. When NAVD 88 is fully implemented in 2024, water measurements will be published exclusively in NAVD 88. 

As of now, the U.S. Army Corps of Engineers has not stated that they will be transitioning as well, so for the time being, water levels will have to be reviewed through two different reference systems.