Rt. James et al., A SEDIMENT RESUSPENSION AND WATER-QUALITY MODEL OF LAKE-OKEECHOBEE, Journal of the american water resources association, 33(3), 1997, pp. 661-680
The influence of sediment resuspension on the water quality of shallow
labs is well documented. However, a search of the literature reveals
no deterministic mass-balance eutrophication models that explicitly in
clude resuspension. We modified the Lake Okeechobee water quality mode
l - which uses the Water Analysis Simulation Package (WASP) to simulat
e algal dynamics and phosphorus, nitrogen, and oxygen cycles - to incl
ude inorganic suspended solids and algorithms that: (1) define changes
in depth with changes in volume; (2) compute sediment resuspension ba
sed on bottom sheer stress; (3) compute partition coefficients for amm
onia and ortho-phosphorus to solids; and (4) relate light attenuation
to solids concentrations. The model calibration and validation were su
ccessful with the exception of dissolved inorganic nitrogen species wh
ich did not correspond well to observed data in the validation phase.
This could be attributed to an inaccurate formulation of algal nitroge
n preference and/or the absence of nitrogen fixation in the model. The
model correctly predicted that the lake is light-limited from resuspe
nded solids, and algae are primarily nitrogen limited. The model simul
ation suggested that biological fluxes greatly exceed external loads o
f dissolved nutrients; and sediment-water interactions of organic nitr
ogen and phosphorus far exceed external loads. A sensitivity analysis
demonstrated that parameters affecting resuspension, settling sediment
nutrient and solids concentrations, mineralization, algal productivit
y, and algal stoichiometry are factors requiring further study to impr
ove our understanding of the Lake Okeechobee ecosystem.