1. General Model Information
Main medium: aquatic
Main subject: biogeochemistry, hydrology
Organization level: ecosystem
Type of model: ordinary differential equations, partial differential equations
Keywords: water quality, lakes, sediment, phosphorus dynamics, carbon dynamics
Dr. J. Trösch
Lab. of Hydraulics, Hydrology and Glaciology
Eldgenössische Technische Hochschule
LIMNOD is a one-dimensional vertical lake model which considers coupled physical,
biochemical and sedimentation processes. For the physical description
(state variables are temperature and conductivity), the lake is divided into fully
mixed epilimnion and a hypolimnion with a sharp thermocline between these layers.
The thermocline depth is calculated daily by means of an energy-balance considering
heat and radiation exchange with the atmosphere and energy input by the wind. In the
hypolimnon the turbulent mixing processes are expressed by the concept of a time and
depth dependent eddy diffusion.
Based on the physical processes a cycle of nutrients
is calculated with phosphorus as limiting nutrient (state variables are the concentrations
of particular organic carbon (biomass), dissolved oxygen and dissolved and particular phosphorus).
In the sediment two types of organic phosphorus, inorganic phosphorus and organic carbon are
considered. In this coupled system, transport of chemical species is governed by the physical
model. Inversely, biochemical processes influence the stability of the water column due to light
extinction by biomass reducing the penetration depth of the incoming short wave radiation and due
to dissolution of settling particles from the epilimnion, enhancing the concentration of dissolved
species in the hypolimnion.
LIMNOD is a physical-biochemical model
for long-term prediction of water quality in lakes. The effects of restoration measures such as
oxygenation, deep water drainage and artificial mixing can also be studied. The model is adaptable
to most lakes by adjusting some lake specific parameters or by adding new state variables.
Source of the Abstract:
Joergensen S.E., B. Halling-Soerensen and S.N Nielsen
(Edts.) 1996: Handbook of Environmental and Ecological Modelling. CRC Press Boca Raton et al. 672 pp.
II. Technical Information
Operating System(s): DOS
Programming Language(s): FORTRAN 77
III. Mathematical Information
Karagounis, I., 1992. Ein physikalisch- biochemisches Seemodell; Anwendung auf das Nordbecken des Luganersees. Communications Nr. 116 of the Laboratory of Hydraulics, Hydrology and Glaciology, Federal Institute of Technology, Zürich, Switzerland.
Karagounis, I., Trösch, J., and Zamboni, F., 1993. A coupled physical- biochemical lake model for forecasting water quality. Aquatic Sciences, Vol. 2: pp.87-102.
V. Further information in the World-Wide-Web
VI. Additional remarks
Last review of this document by: T. Gabele: 15. 10. 1998
Status of the document: -
last modified by
Tobias Gabele Wed Aug 21 21:44:45 CEST 2002