Assessing ecological land use and water demand of river systems: a case study in Luanhe River, North China

Economic and social development has greatly increased ecological water demand and modified land use of river systems worldwide, causing overall degradation of many of these systems. In this study, theoretical and technical frameworks for regionalization on the eco-environmental function of river systems are formulated and applied to the Luanhe River system. Based on its eco-environmental functions, this river can be regionalized into four types of first-class functional areas: ecological preservation areas, habitat restoration areas, ecological buffer areas and development and utilization areas. Considering the overall ecoenvironmental functions, we assessed the ecological land use of the Luanhe River system. The total area of basic ecological land use is 876.98 km(2); the restrictive ecological land use is 1745.52 km(2); ecological land use of the river system returned from farmland is 284.25 km(2); and that returned from construction land is 17.35 km(2). The average minimum ecological flow of mainstreams in upper and middle reaches of the Luanhe River is 4.896 m(3) s(-1) based on the habitat method. And the recommended minimum and suitable annual ecological water demand of channels in the lower reaches are 391 million m(3) and 819.5 million m(3), respectively. The evaporation and seepage consumption and vegetation consumption in riparian zones of the Luanhe River system are approximately 132.6 million m(3) and 145.3 million m(3) per year, respectively. Our results suggest that is crucial to regulate the instream ecological water use of the Luanhe River's mainstream starting from the Panjiakou-Daheiting Reservoir system. We recommend accelerating ecological land-use planning and strengthening the regulation of ecological water use on this river system focusing on important lower reaches under the condition of competitive water demand.