Abstract: In this study, the sequential clustering method was used to discriminate the significant sharp change of human activities in the mainstream area of the Tarim River during the period of 1957-2006. The lowest and suitable monthly ecological water requirements at the Xinquman, Usuman and Qara hydrological sections were calculated. The results showed that the disturbance of human activities on water resources in the mainstream area of the Tarim River was increased in recent 50 years. Runoff of the mainstream of the Tarim River was basically natural before the year of 1976, but a sharp increase of human activities occurred in 1976. The lowest annual ecological water requirements at the Xinquman, Usuman and Qara hydrological sections were 17.68×10⁸ m³, 10.02×10⁸ m³ and 3.29×10⁸ m³, and the suitable ones were 35.65×10⁸ m³, 18.23×10⁸ m³ and 7.00×10⁸ m³, respectively. The health of ecosystems in the mainstream area of the Tarim River could be ensured if the lowest ecological water requirements at these hydrological sections could be maintained at 5.33×10⁸ m³, 3.77×10⁸ m³ and 1.32×10⁸ m³ during the general water consumption period from October to next March and at 28.99×10⁸ m^3, 13.70×10⁸ m³ and 5.09×10⁸ m³ during the sensitive water consumption period from April to September.

Key words: water resources, channel, ecology, ecological water requirement, human activities, mainstream of the Tarim River