Abstract: In this paper, the time and volume of 8 times of ecological water conveyance to lower reaches of the Tarim River was analyzed based on the data of ecological water conveyance and the field investigation on natural vegetation. The change of water volume from the Bosten Lake and the Tarim River to the lower reaches was summarized. The correlation between the seed falling time of 32 plants species and the watering time of the river course in the lower reaches of the Tarim River was analyzed, and the beginning time of ecological water conveyance was discussed. Furthermore, the feasible and rational beginning time of ecological water conveyance was put forward for conserving and regenerating natural vegetation in the study area. The results are as follows: (1) Because of the serious water consumption along the river channel, conveyed water for the ecology is mainly relied on stream flow of the Tarim River instead of the Bosten Lake. So it is a precondition that whether water resources in the mainstream area of the Tarim River are enough or not; (2) The 8 times of ecological water conveyance were mainly implemented during the periods from April to June and from August to October, because 49.73% water flows into the Bosten Lake and 82.33% water flows into the Tarim River during these periods; (3) The correlation between the watering time of the river course and the regeneration of natural vegetation was low, because the seed falling time of natural vegetation was not considered previously. Therefore, it is more rational to convey water from the Tarim River than from the Bosten Lake; (4) Judged from the seed falling time, the period from July to September is the most rational, however, that from midAugust to the end of September is the most reasonable if judged from stream flow of the Tarim River.

Key words:  ecological water conveyance, time of ecological water conveyance, plant seed falling, utilization of water resources, Bosten Lake, lower reaches , of the Tarim River