Vertical Datum

Water Level Measuring Standard Undergoing Upgrade

Reducing the risk of flooding and protecting South Florida's water supply depend on knowing how much water must be moved from one elevation to another. This requires a precise measurement of elevations in lakes, canals and other water bodies connected to the water control system.

To improve data accuracy, the SFWMD is upgrading the standard used to measure water levels. Elevations determined using the North American Vertical Datum 88 (NAVD 88) standard are replacing measurements based on the National Geodetic Vertical Datum 29 (NGVD 29).

The upgrade to NAVD 88 means that the values we associate with the height of water – what many people think of as mean sea level – will change. Within the SFWMD boundaries, measurements of water levels in NAVD 88 will be approximately -0.6 feet to -1.8 feet lower than they are in NGVD 29, as elevation difference varies by geographic location. For example, the difference between the two measuring standards in Lake Okeechobee is 1.3 feet, so a water level of 12.5 feet NGVD 29 is 11.2 feet NAVD 88.

During the transition period from NGVD 29 to NAVD 88, water levels and other data will be published in both standards. When NAVD 88 is fully implemented, the District will stop publishing measurements in NGVD 29.