大坝对下游景观格局及生态系统服务的影响

The influence of dam on downstream landscape pattern and ecosystem services

大坝是水资源利用和调控的有效手段,为社会经济发展做出了重要贡献。大坝改变了河流的自然属性,是下游景观格局及生态系统服务变化的重要驱动力。大坝改变了区域水资源的时空配置,在不同尺度和不同层面产生相应的水分效应:(1)大坝引发了整个下游物理、化学和生物的变化,这种变化主要发生在流域水文、河道和物种流动等方面;(2)大坝改变地表水和地下水的动态,从而影响到河岸带、灌溉区、洪泛区及更远的横向区域。下游水源补给能力下降,使地下含水层和沿河湿地无法及时补充,干流与支流、湖泊间的互动关系被阻断,影响区域水资源的输送与交换;(3)水环境的变化影响社会经济发展的方向和程度,使下游土地利用和土地覆被发生相应的改变。生态系统服务在地理过程、生物过程和社会经济发展过程中产生和利用,大坝改变了水分、能量和物质的循环过程,对区域生态系统服务的维持带来深远的影响。河流是区域生态系统服务网络的核心和重要通道,大坝通过河流对下游产生初级和次级影响,强烈地改变了区域生态系统服务网络的稳定和发展。

Dam is an effective utilization and regulation method for water resource,which has made an important contribution to social and economic development. Dam changed river natural attributes,being the important driving force for the downstream landscape and its ecological system services. Dam changed the spatial and temporal distribution of regional water resources,which generated the corresponding water effects at different scales and different levels：（ 1） Dam caused physical,chemical,and biological changes of the river,from downstream to estuary.These changes mainly took place in river channel,hydrological and species flow,etc.（ 2） The changes of the surface water and groundwater affected the riparian zone,irrigated area,flood plain and horizontal region. Reduced water supply ability had great influence on the underground aquifer and the wetland. The interaction between the main stream and tributaries and lakes was blocked,influencing the transmission and exchange of water.（ 3） The change of water environment influenced the degree and direction of social and economic development,and the downstream land use and land cover changed correspondingly. Ecosystem services had been realized by cooperation of geographic process,biological process and social economic development. Dam changed the water,energy and material cycling process,which would have long-term and farreaching influence on the maintenance of regional ecosystem services. Dam strongly changed regional ecosystem services network’s stability and development through affecting the downstream primary and secondary effects.