Effects Of Construction Land Use Changes On Ecosystem Water Purification Service In Miyun Reservoir Watershed

Ecosystem Water Purification Service plays a decisive role in the reduction of non-point source pollution, it protect the watershed water quality. However, as the expansion of construction land, ecosystem water purification servicehas changed a lot. It’s very important to clear that how the process of urbanization, impervious construction land expansion influence the watershed ecosystem water purification service.In this study, using the Miyun Reservoir watershed as an object,which is the Beijing city’s only surface water source upstream, applicating predicted scenario simulation, InVEST model,assess Miyun Reservoir Basin water purification service in different contexts changes from land use scenario in1990to land use scenarios in2009. The results show that:(1) During the1990to2009, a254%expansion of construction area has changed in the basin, The increase of construction land area from croplands and grasslands, Construction land expansion around the outward of the original town and on both sides of the river spread expansion;(2) Construction land expansion cuts ecosystem water purification service, made a significant increase of Miyun Reservoir nitrogen input. During the1990to2009, the basin internal construction land expansion led to a56%increase in Miyun Reservoir nitrogen input;(3) In the scenarios of the future expansion, construction land increased270%, ecosystems water purification service will further degradation, watershed due to land expansion will result in the Miyun Reservoir nitrogen input in2009on the basis of an increase of4.2times;(4) Based on80m shore-based protection scenarios, strengthen the construction of shore protection zone can effectively slow down the expansion of construction land damage to the ecosystem water purification function; Expansion in2009on the basis of270%of the construction land, construction of a80m shore protection with Miyun Reservoir nitrogen input can be maintained at the2009level,80m shore protection with the construction of scenarios and enter the Miyun Reservoir in2009the nitrogen ratio of1:1.3.The results show that by setting the riparian buffers can effectively control the urban expansion caused by non-point source pollution, provide important information for policy and decision making basis.