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Public Information Statement
National Weather Service Tampa Bay Ruskin FL
119 PM EDT Mon Jul 14 2025

...Withlacoochee River Vertical Datum Change Postponed Until
Tuesday, July 22, 2025..

To: Emergency Management Officials, News Media, and other users.

Due to the potential for heavy rainfall this week, changes to the
vertical datum used for river forecasts and data points within
the Withlacoochee River Basin in West Central Florida will be
delayed by one week.

Effective Tuesday, July 22, 2025 at 8 am EDT (1200 UTC) the
National Weather Service in Tampa Bay will change the vertical
datum used for river forecasts and data points within the
Withlacoochee River Basin in West Central Florida. These changes
include the following rivers within the Withlacoochee River Basin
in NWS Tampas Area of Responsibility:

- Withlacoochee River
- Little Withlacoochee River

Currently, river observations and the forecasts for points on
these rivers are reported in a stage height, or a level above a
specified benchmark at each river site. Through survey data from
the US Geological Survey, conversion of these stations to the
North American Vertical Datum of 1988 (NAVD88) is now possible.
Use of this datum not only provides more accurate reporting of
water level height throughout the Withlacoochee River Basin, but
it will also allow for the reporting of observed and forecast
water level height above NAVD88 at each river forecast point along
the river.

Flood stages for the river forecast points will be converted to
the NAVD88 equivalent and rounded to the nearest tenth of a foot.
As a result, the impacts that occur when water levels reach the
updated flood stage categories have not changed. Instead, this
adjustment will allow for better communication of the water
surface level throughout the basin as well as integration of
additional data points to monitor water levels in between the
established river forecast points.

These updates are a direct result of collaboration between the Southwest
Florida Water Management District, between emergency management
directors in West Central Florida, the Florida Division of
Emergency Management, and the US Geological Survey in Florida.

The following river forecast points are included in this service change:

- Withlacoochee River at Trilby (TRBF1)
- Withlacoochee River at Croom (CRMF1)
- Withlacoochee River at SR-200 near Holder (HLDF1)
- Withlacoochee River at US-41 at Dunnellon (DNLF1)
- Little Withlacoochee River at Rerdell (RERF1)

In addition to these river forecast points, 11 additional data
points will be added to the National Water Prediction Service.
These points are located from near the source of the Withlacoochee
River, in between the river forecast points, and downstream of
Dunnellon to the Bypass Channel near Inglis. You can learn more
information about these changes by visiting the NWS Tampa Bay
website and checking the news headline section referencing the
Withlacoochee Basin Datum Change.

The data for these forecast and observation points are provided through
our partner, the US Geological Survey. Without these observations,
the forecasts and increased services provided in the Withlacoochee
River Basin would not be possible. Further, the Southwest Florida
Water Management District is also providing considerable impact
data throughout the Withlacoochee River system to enhance this
service as well. You can learn more about these partner agencies
through the following websites:

- https://fl.water.usgs.gov
- https://swfwmd.state.fl.us/

To get the latest information on these and other river points in
the Tampa Bay area of responsibility, please visit our website at:

- https://water.noaa.gov/

River forecast and warning services for these forecast points are
supported by the National Weather Service in Tampa Bay Florida.
You can learn more about the office by visiting our homepage at:

- https://www.weather.gov/tbw

For further information regarding this change, please contact:

Matt Anderson                           Jennifer Hubbard
Acting Meteorologist in Charge          Warning Coordination Meteorologist
NWS Tampa Bay Florida                   NWS Tampa Bay Florida
2525 14th Ave. SE                       2525 14th Ave. SE
Ruskin, FL 33570                        Ruskin, FL 33570
(813) 645-2323 ext 224                  (813) 645 2323 ext 223
Matt.Anderson@noaa.gov                  Jennifer.Hubbard@noaa.gov

$$