The temporal and spatial environmental flow requirements (EFRs) for the river ecosystem of the Haihe River Basin were analyzed based mainly on the eco-functional regionalization of available water resources. The annual EFRs for the river ecosystem of the Haihe River Basin were 47.71 × 10(8) m(3), which accounted for 18% of the average annual flow (263.9 × 10(8) m(3)). The EFRs for river reaches, wetlands, and estuaries were 22.67, 15.32 and 9.72 × 10(8) m(3), respectively. Moreover, the EFRs for the river ecosystem during the wet (June to October), normal (April, May, November), and dry (December to March) periods were 29.99, 9.51 and 8.21 × 10(8) m(3), respectively. Thus, toward a more integrated water resource allocation in the Haihe River Basin, the primary effort should focus on meeting the EFRs for river systems located in protected areas during the dry period.