Abstract: The distribution of ecological water demand of Yitong River within a year was investigated using flow duration curve method according to the historical flow data at Nong’an station and Yitong station. Nong’an Station is located in the mid-lower reaches of Yitong River, and Yitong station is in the upstream of Yitong river. Calculation results showed that the minimum ecological water demand at Nong’an station was 46.94 million m³, which accounts for 15.46% of the annual runoff; and the minimum ecological water demand at Yitong station was 3.04 million m³, taking up 4.80% of the annual runoff. Furthermore, the Tennant method and the average value of minimum monthly flow were used to estimate and verify the ecological water demand. The result obtained by Tennant method is close to the result by the flow duration curve method. The results indicate that the distribution of ecological water demand of Yitong River within a year is in correspondence with the practical water allocation, which means that the water demand is large in high flow period and small in low flow period. Through the ecological water demand, the aquatic habitats at Nong’an segment could be protected; whereas the aquatic habitats of Yitong segment have already degenerated and impoverished, and protective measures should be taken.

Key words: ecological water demand of rivers, minimum ecological water demand, flow duration curve method, Yitong River, annual distribution