Abstract: Ecological structure of fish fauna in the Dachuan river at Lushan county of Sichuan province was studied with the method of ecological overlap coefficient. The studies are from three aspects, i.e., spatia structure, food structure and breeding structure. Both overlap and separation are found in the ecological structure of fish fauna. The ecological pressure resulted from serious overlap in one ecological aspect may be lightened by the ecological separation in other aspects. The result has significant meaning for the theory and practice of fish bleeding.

Key words: mulched drip irrigation, soil water distribution, irrigation frequency, irrigation amount