长江三角洲水害特点与成因分析

结合长江三角洲区域特点,对长江三角洲洪涝、河网水污染、太湖蓝藻水华以及长江口咸潮入侵四类水害特点进行分析,识别区域水害的主要因素和水害成因。结果表明:当前长江三角州洪涝灾害以涝灾为主,具有频发性,影响范围广,损失巨大等特点。河网水污染已为常态,贯穿全年,具有雨污同期性,汛期水污染问题加剧。太湖蓝藻水华表现出明显的时空变异性,长江口咸潮入侵也形成了北支咸潮倒灌进入南支,南支外海咸潮上溯的入侵路径,形成“两边高,中间低”的空间分布特征。水文条件是水害形成的自然因素,人类活动则是导致水害问题不断严重的根本原因。区域下垫面变化加剧了洪涝灾害,而不合理的闸坝调度方式导致汛期河网水污染加剧。区域内污染物过量排放,加重了太湖富营养化程度,使蓝藻水华问题恶化。水利工程的调度运行影响着入海径流,对咸潮入侵产生影响。此外,社会财富的增值亦使水害损失持续上升。

Study on characteristics and causes of water-induced disaster in Yangtze Delta

The Yangtze Delta is suffering from the water-induced disasters, like the flood, the river pollution in the plain, the outbreak of the cyanobacteria in Taihu Lake and the seawater intrusion in the estuary, which lead to dramatic losses every year. The aim of this paper is to analyze the characteristics of above four types of the water-induced disasters and identify the main causes. The result shows that water logging is the majority in the region with frequent occurrence, wide range and huge damage. The default state of the river pollution runs through the whole year with the synchronization in precipitation, which cause a water quality deterioration when the flood season comes. The outbreak of the cyanobacteria in Taihu Lake has a temporal and spatial regularity. The seawater intrusion in the estuary also has its own special path, i.e. seawater backward flowing into the southern branch from the northern branch as well as the sea region. This fixes a spatial distribution in a lower salinity in the middle and a higher salinity at the both sides. Obviously, the hydrological factors in nature cause the disaster. However, the interaction with the human activity exacerbates the disaster damages. For instance, the variations of land use and cover intensify the flood; the inappropriate operations on the dams and sluices worsen the water quality; the eutrophication in Tailhu Lake could be further deteriorated due to the the excess contaminant discharges;the operations in the water facilities lead to the changes in runoff into the sea, which would influences the sea water intrusion. In addition, the enlargements of social wealth is a force to be reckoned which results in a continuous growth in the losses by the water-induced disasters.