A method for lake ecosystem health assessment: an Ecological Modeling Method (EMM) and its application

Ecosystem health is a newly proposed concept that sets new goals for enviro nmental management. Its definition, indexing and assessment methods are sti ll being perfected. An Ecological Modeling Method (EMM) for lake ecosystem health assessment is proposed in this paper. The EMM's procedures are: (1) to analyze the ecosystem structure of a lake in order to determine the stru cture and complexity of the lake's ecological model; (2) to develop a model having ecological health indicators, by designing a conceptual diagram, es tablishing model equations, estimating model parameters and being integrate d with ecological indicators; (3) to compare the simulated and observed val ues of important state variables and process rates (i.e. model calibration) in order to evaluate the applicability of the model to lake ecosystem heal th assessment; (4) to calculate ecosystem health indicators based on the de veloped model; and (5) to assess lake ecosystem health according to the val ues of the ecosystem health indicators. The EMM was applied, as a case stud y, to the ecosystem health assessment of a eutrophic Chinese lake (Lake Cha o) between April 1987 and March 1988. A relative order of health states fro m poor to good was determined as follows: August-October 1987 > April-May 1 987 > June-July 1987 > November-December 1987 > January-March 1988. These r esults compared quite favourably with the actual current conditions at Lake Chao. The EMM method, therefore, was suitable in assessing lake ecosystem health at Lake Chao.