白洋淀流域湿地连通性研究

湿地在流域防洪减灾、水资源调节、缓解环境污染、保护生物多样性和维持区域生态环境方面具有重要功能和价值。作为我国北方平原湿地系统之一,白洋淀流域湿地对于保障雄安新区的水资源安全和良好生态环境等方面具有关键性作用。了解目前白洋淀流域湿地生态系统的现状对于新区建设和未来科学规划也具有重要意义。以2017年9月欧空局提供的10米分辨率的Sentinel-2B影像为主要数据源,并结合谷歌地球高分辨率卫星影像(分辨率0.23m),通过人工目视解译和机器自动分类等多种方式,绘制了白洋淀流域最新的湿地生态系统网络分布图;在此基础上,利用地理信息系统分析了白洋淀流域湿地的连通性(包括水文连通性和景观连通性)。结果显示:(1)2017年白洋淀流域湿地面积为4596.6km~2,包括沼泽、洪泛区、沟渠、湖泊、河流,主要分布在坡度为0°至2°,海拔在100m以下的平坦地区;而流域内非湿地面积约86%,以耕地和林地为主。(2)2017年白洋淀流域河道长度为2440km,面积为514 km~2,其中山区河道177 km~2,平原河道337 km~2。河道内耕地面积比例达27%,建设用地比例约为8%,河道占用明显。河道两侧1km、2km和3km距离范围内耕地比例分别占61.77%、62.53%、62.63%。随着距离的扩大,湿地面积减少,非湿地面积增加。(3)由于人类活动的直接和间接影响,河道的水文连通性下降,与河道没有受到干扰时的连通性水平相比,减少了三分之一。(4)从景观格局指数SPLIT和DIVISION指示的流域湿地连通性看,景观级别上流域内自然湿地的景观连通性最差,人工湿地次之。在类型级别上沼泽类型的连通性最差,河流、沟渠与洪泛区湿地类型的连通性较好,湖泊的景观连通性最好。为保障白洋淀流域水安全,以流域湿地网络为整体,恢复和增强流域湿地网络连通性,将有效提高雄安新区水资源安全和生态环境保护的能力。

Preliminary study on wetland connectivity in Baiyangdian basin

Wetlands have important functions and values in flood control and disaster mitigation, water resource regulation, mitigation of environmental pollution, protection of biodiversity, and maintenance of regional ecological environment. As one of the wetland systems in the northern plain of China, the Baiyangdian basin wetlands play a key role in safeguarding the water resources security and good ecological environment in Xiong''an New Area. It is of great significance to understand the current status of wetland ecosystem in the Baiyangdian basin for the construction of new area and future scientific planning. Based on the 10-meter resolution Sentinel-2B image provided by the European Space Agency in September 2017 as main data source, and combined with Google earth high-resolution satellite image (resolution 0.23m), this paper has drawn the latest wetland ecosystem network distribution map of Baiyangdian basin using manual visual interpretation and automatic machine classification. On this basis, the connectivity of Baiyangdian basin wetland (including hydrological connectivity and landscape connectivity) was analyzed with GIS (Geographic Information System). The results show that:(1) In 2017, the wetland area of Baiyangdian basin was 4596.6km², including marshes, floodplains, irrigation canals, lakes, and rivers. Those wetlands mainly distributed in flat areas with a slope of 0° to 2° and an altitude of 100m or less. The area of non-wetland in the basin accounted for about 86%, mainly cultivated land and forestland. (2) In 2017, the length of the river courses in the Baiyangdian basin was 2440 km, with an area of 514 km², including 177 km² in the mountainous area and 337 km² in the plain area. The river course was obviously occupied, in which the proportion of the cultivated land reached 27%, and the proportion of construction land was about 8%. The proportion of cultivated land within the range of 1km, 2km and 3km on both sides of the river took up 61.77%, 62.53% and 62.63%, respectively. With the increase of distance, the area of wetland decreases and the area of non-wetland increases. (3) As a result of the direct and indirect effects of human activities, the hydrological connectivity of river courses has decreased by one third compared with the level of connectivity when the river courses were undisturbed. (4) From the perspective of the wetland landscape connectivity indicated by SPLIT and DIVISION, the natural wetland in the basin had the worst landscape connectivity, followed by constructed wetlands at the landscape level. At the type level, the marsh type had the worst connectivity, and the connectivity of rivers, irrigation canals and floodplains wetlands was better, and the lake had the best landscape connectivity. In order to guarantee the water security of Baiyangdian basin, restoring and enhancing the connectivity of the wetland network in the basin as a whole will effectively improve the ability of water resources safety and ecological environment protection capacity in the Xiong''an New Area.