Abstract: Abstract:The summer low-flow response to forest cover change in the small-sized Yulingou watershed of Northeast China was analyzed using two graphical methods (the double mass curve (DMC)and the low-flow duration curve (LFDC)).The low-flow data is obtained from the 32 summer periods (June-August)of 1973-2004 and used for deriving the flow duration curve (FDC).Compared to the baseline the period 1973-1982,there is a 15% increase in forest covers during the period 1983-2004.The latter is the result of reforestation activates.Although,the average of summer low-flow discharges has gone up by 11.84% during the latter period,the annual rate of discharge increases has been in steady decline since 1983.The reforestation had the most impact on the increase of summer low-flow discharges for percentiles between 0 to 50 on the LFDC,which demonstrates the important role of northeastern forests in enhancing summer low-flow discharges.The strength of enhancement began to decrease after the forest cover reaching 70%.Thus,a 70% forest cover should be maintained on the Yulingou watershed for the sustainable development of forest industry and water resources.The LFDC method could be applied for analyzing the effect of forest cover change on specific percentiles of summer low-flow discharges.