Watershed Hydrologic Model Development for Loxahatchee Ecosystem
Restoration
M. Clay Brown, Yongshan Wan, Randy VanZee, and Wasantha Lal
South Florida Water Management District, West Palm Beach, FL
The Loxahatchee River and Estuary located on the East Coast of South Florida,
supports unique ecological resources and biological habitats that are greatly
impacted by both sea level rise, estuary inlet dredging and watershed hydrologic
alteration. The Loxahatchee watershed hydrologic model is one of the modeling
tools being developed by the South Florida Water Management District
(SFWMD) for Loxahatchee Ecosystem restoration. The model is built on a new
generation model, Hydrologic Simulation Engine, that simulates 2-D overland
flow, 3-D ground water flow, 1-D channel flow, and flow in and out of lakes in an
integrated manner.
A semi-implicit finite volume scheme is used for
computational engine, allowing for unconditionally stable solutions of the
simulated system. The initial step in developing the model is to design a natural
system model (NSM) that simulates the hydrologic response of the natural or predrained watershed to today’s hydrologic input (e.g., rainfall and ET from 1965 to
2001). Using unstructured triangular grids, the model domain covers the extent of
the historic watershed including the original Loxahatchee slough. The NSM
version of the Loxahatchee watershed model, using the historic ocean tide as the
downstream boundary condition, simulates what the surface and ground water
flow into the estuary would be if the watershed remained under pre-drained
conditions. This information is critical in setting up the hydrologic restoration
target, which, in turn, determines the target salinity regimes in the estuary and the
floodplain. The second step in the model development is to use todays and future
landuse and hydrography in the watershed to simulate the hydrology of the
developed watershed.
This modeling approach will provide meaningful
comparisons between the two systems, and the results will be used to formulate
alternatives to restore the hydrology for a healthy and stable Loxahatchee
Ecosystem.
Brown, Wan, Van Zee, and Lal, 3301 Gun Club Road, West Palm Beach, FL,
33406, Phone: 561-682-2256, mcbrown@sfwmd.gov