Ecological water requirements in the lower reaches of Luanhe Basin

Based on the methods of the ecological water requirements (EWRs) at home and abroad, this paper takes the area from Panjiakou reservoir to Luanhe estuary of Luanhe Basin as the typical area to determine the water allocations of the river ecological restoration in reservoirs' downstream. EWRs are calculated with the month-by-month frequency method and eco-hydraulics method. The methods can describe EWRs according to seasons and grades, meanwhile emphasize the relationship between hydrology and ecology. Through the analysis of the ecological, hydrological and hydraulic data from the studied area from 1956 to 2000, the results indicate that: (1) The month-by-month frequency method and eco-hydraulics method are both reasonable in calculating EWRs in the Lower reaches of Luanhe Basin; (2) The minimum, medium and ideal level of annual EWRs are 4.29×10⁸,8.93×10⁸ and 16.29×10⁸m³, about 10.18%, 21.21% and 38.68% of the natural river discharge respectively; And (3) the ratio of the monthly ecological flows should be 33.5% in the flood period (August) and 11.5% in the biological propagation period in spring (April-June).