Abstract: Kaidu River is the source of Bosten Lake, the largest inland fresh water lake in China. The regulation of water resources in Kaidu River plays a key role in the production, living, and ecology of the Yanqi Basin and also in the watersystem connection between Bosten Lake and other water body in the basin. Ensuring the ecological basic flow and stable ecological function in Kaidu River is important for the effective management of water resources in the basin. We first improved Tennant Method by dividing the runoff data into different periods and improving the corresponding base flow standard. With the observed runoff data from Dashankou hydrological station in 1971-2016, we analyzed the ecological base flow and corresponding minimum ecological water demand of different periods at high and low flow period. The results showed that the minimum ecological water demand of Kaidu River in each year could be basically satisfied under the conditions of considering river water loss and the government’s surface water usage controlling rules of “Three Red Lines”. However, in the semidry and extremely dry years, the remaining water in the river is little, and thus the situation to guarantee the basic ecological water demand of the river would be severe. After ensuring the minimum ecological water demand, river water loss and surface water consumption, the surplus water of Kaidu River could serve for the ecological water demand of Bosten Lake and its watersystem connection in both wet and normal years. However, it could not satisfy the ecological water supply to Bosten Lake in the semidry and extremely dry years. Our results provide important guidance for maintaining ecological health and sustainable utilization of water resources in Kaidu River Basin.

Key words: ecological basic flow, Kaidu River, water-system connection, water resource management.