近代洞庭湖沉积与孕灾环境研究

通过对洞庭湖区不同沉积部位的22个钻孔取样和^210Pb放射性同位素测年分析，洞庭湖有较高的沉积速率，最高可达2．33cm／a，不同的沉积部位沉积速率也有较大的差异。由于19世纪以来四口分流形成，大量长江的泥沙进入洞庭湖，近50年的水文资料表明，洞庭湖83％的泥沙淤积来源于长江。由于人类围垦、上游森林砍伐和洲滩堤坝的逐年加高，洞庭湖水面减少了2／3，洞庭湖对长江洪水的调蓄能力已迅速减弱。洞庭湖的演变变化过程直接影响到长江中游的生态安全。

Study on the Dongting Lake's Sedimentation and Flood Disaster Environment Gestation in Decades

The evolution of the Dongting Lake affected by both natural process and human activity, and it also influence the eco-environmental safety of the middle Yangtze River region. Sedimentation makes lake change to shallow and capacity decreased. Sediment was recovered by 22 vibrocores in different lake sectors, high sedimentation rates revealed by ~(210)Pb measurement in different subfacies of the lake, the highest up to 2.33 cm/a. primarily due to siltation by Yangtze sediment. In the late 19~(th) century, a major flood induced channel avulsion resulted in the coupling of the Four-Tributary' sub-basin to Dongting Lake, causing a massive increase in sediment supply into the lake since then. Hydrological data demonstrate that about 83% of the lake's annual sediment influx is derived from the Yangtze. In addition, pressures from a growing population and associated human activities, such as reclamation, embanking, aquaculture, forming on slope and deforestation, the Dongting Lake has lost almost two thirds of its total area in the past century, and loss the storage capacity of the Yangtze floods.