Abstract: Based on emergy theory and its analysis approach, and by using statistical and field survey data, the eco-economic system in Wenchuan County of Sichuan Province in 1982-2002 was analyzed. The results showed that this County had a poorer economic level and a smaller economic size. The input of emergy mainly came from renewable resources; while the output of emergy mainly came from un-renewable resources, and fossil and cement products took the main parts. Wenchuan exported huge amount of emergy, with the items including fossil and wood resources. The export of emergy, especially of wood emergy, had brought ecological problems due to vulnerable ecosystem. In the County, the emergy consumption per capita was small and the living standard was low, and thus, much attention should be paid to the harmonious development of economy and ecology.

Key words: Ceratophyllum demersum, Physiological response, Eutrophication, Stress