The Florida Department of Environmental Protections Answers
TCPalm’s Questions
About Record Amounts of Phosphorus Flowing into Lake
Okeechobee
TCPalm’s questions::
The Florida Statewide Annual Report on Total Maximum Daily Loads, Basin
Management Action Plans, Minimum Flows or Minimum Water Levels, and
Recovery or Prevention Strategies" released by the DEP in June states total
phosphorus loads to Lake Okeechobee in 2017 were 812,623 pounds, down
from a starting load of 988,404 pounds. (Page 18 of 68)
But data from the South Florida Water Management District shows the total
phosphorus load to Lake O in 2017 was 2.3 million pounds, the highest level
ever recorded.
Questions:
-- Is the DEP's lower number an estimate based on computer modeling and
assuming full compliance with best management practices? If not, who was it
generated?
-- Why does DEP use numbers from computer models when the actual
numbers are available?
-- Why does DEP contend phosphorus loading to Lake Okeechobee is going
down when, in fact, it's going up the BMAP was established for the lake in
Dec. 2014? (See the Lake O chart on page 16 of the SFWMD board
presentation that's attached.)
-- Why isn't it disingenuous for the DEP to say the BMAP system is working
when these numbers indicate it isn't?
DEP’s reply, via spokeswoman Dee Ann Miller:
DEP relies on both computer modeling and measured data to evaluate
existing conditions in basins and BMAP progress. Computer models are used
to establish a target, or TMDL, for a healthy water body, because sufficient
empirical data is not always available to reveal what the nutrient levels were
when the water body was healthy and meeting its designated uses.
Generally, TMDLs represent an average of multiple years and not loading
from one year. Where modeling is done to predict expected nutrient levels
and set these targets, the same modeling is used to determine necessary
reductions, assign those reductions (allocate), and track progress towards
reaching those targets.
In many waterbodies including the Lake Okeechobee Watershed, computer
modeling was necessary to develop the TMDL which represents multi-year
loading and determine a starting multi-year load, assign reductions to
subwatersheds, and track progress. Nutrient reduction benefits of projects

 (once implemented and functioning) are estimated using modeled multi-year
loads for the Lake Okeechobee Watershed and methods applied in BMAPs
statewide. That is the number published with the 2017 Annual Report, a
modeled long-term expectation associated with implemented projects. The
measured load specific to 2017 was not finalized when the Annual Report
was submitted, but will be included in the South Florida Environmental
Report.
In addition to tracking estimated loads based on models and best
management practice efficiencies, the BMAP process includes periodic
evaluations of empirical data included in the plan’s monitoring network.
Some watersheds do not have sufficient long-term data available, and part of
the iterative process of BMAPs involves establishing monitoring at
appropriate sites and collecting sufficient data to evaluate progress over
time. The Lake Okeechobee watershed has a lot of available data which is
currently being evaluated as part of the 5-Year Review.
The BMAP tracks project benefits as compared to a snapshot of modeled load
from a specific time period using the model so that we can understand how
investments and changed practices are credited against the starting multiyear load. Information presented in the statewide report is based on those
modeled multi-year estimates, and will be reviewed alongside an evaluation
of data from the BMAP monitoring plan during the first 5-Year Review in 2019.
Measured loading and concentration data is critical to evaluating water
quality improvements. Year to year loading is primarily driven by the amount
of rainfall such as Hurricane Irma, which is why looking at long-term loads
and concentrations is also important. Concentrations of phosphorus can be
driven by rainfall as well, but also management practices and projects can
improve phosphorus concentrations in runoff. The Department has seen
improvement in concentrations over time, but there are still a lot of actions
necessary to ultimately achieve the TMDL. That is why the BMAP recognizes
the importance of going beyond Best Management Practices across the Lake
Okeechobee Watershed, implementing treatments projects like Istapoga
Marsh & Nicodemus Slough among others, and implementing the
Comprehensive Everglades Restoration Plan for the watershed.