Development of a Lake Eutrophication model

Abstract

This paper presents the development and critical testing of the Lake Eutrophication, Effect, Dose, Sensitivity (LEEDS)-model—an extensive dynamic compartmental model for predicting phosphorus concentrations and eutrophication effects in lake ecosystems, driven by easily accessible lake variables. Earlier model versions have been presented before, and the focus here is on the novelties. Several parts and processes in the model have been altered and the results of these changes are described and evaluated. Changes that provided significant differences and improved predictions have been adopted. These changes include addition of two compartments for colloidal phosphorus, a seasonal moderator for the lake outflow, higher settling velocity for resuspended material, new algorithms for mixing between deep water and surface water and for phosphorus diffusion from areas of sediment accumulation. Algorithms to calculate the water content and organic content of accumulation sediments and a sub-model for suspended particulate matter (SPM) are also introduced. The model predictions are in good agreement with empirical data from several lakes in a wide limnological domain. The main results presented in this paper are: (1) Various model equations, constants and structures have been critically tested and evaluated. (2) Based on these critical model tests, the model has been improved without additional driving variables. The complete description of the new model is given in Appendix A. The novelties include a seasonal moderator for the lake outflow, inclusion of phosphorus bound in phytoplankton in the fluxes from the lake, new algorithms for mixing and diffusion, introduction of two compartments for colloidal phosphorus, algorithms for water content and organic content in A-sediments and a sub-model for SPM. (3) The new model has been validated, showing good agreement against empirical data from different types of lakes. The new model should be considered as a useful tool for lake management as well as for explanatory purposes.