Calibrating WAM/WASP for Dissolved Oxygen in S-191

SWET has calibrated and validated Watershed Assessment Model (WAM) for the S-191 basin (i.e., Taylor Creek and Nubbin Slough). This was done as part of the Lake Okeechobee Watershed Assessment Report for the Comprehensive Everglades Restoration Plan. The modeling included simulating the water and constituents for the period 1991-2000 for 20 basins north of Lake Okeechobee. The results were calibrated and validated with flow and concentration data measured in the basins.

Florida Department of Environmental Protection (FDEP) collected hourly dissolved oxygen (DO) data at 2 sites (S191 and S213; see Figure 1) for a 3 week period. Hourly dissolved oxygen data are not commonly collected in the watershed.

Figure 1. Monitoring Station Locations for S-191

As part of the "Modifications to the Watershed Assessment Model" Project for FDEP, Water Quality Analysis Simulation Program (WASP) was incorporated into WAM to enhance the robustness of in-stream process simulations. The ability to accurately simulate DO is one of the key reasons for this enhancement.

The objective of this effort was for SWET to calibrate WAM / WASP for S-191 using the hourly DO data collected by FDEP.

Setting up WAM / WASP for S-191

In order to simulate DO levels in the streams, WAM was first used to simulate land source loads of phosphorus, nitrogen, and biological oxygen demand. The previous WAM modeling effort for S-191 was focused on phosphorus, so the input parameters affecting DO were reexamined and BOD and nitrogen constituents were added and calibrated.

Calibrating WAM / WASP

The WAM/WASP linked model was successfully calibrated using the measured hourly DO data from FDEP and other constituent data. The WAM/WASP was then run for ten years and results compared favorably with DO grab samples taken over the period of record. The model performed well within the constraints of the available data.