关键词: 洪涝灾害, 生态系统, 流域管理, 洞庭湖

Abstract: Dongting Lake drainage basin embraces Xiangjiang,Zishui,Yuanshui,Lishu i rivers and a part of the Yangtze River.Due to neglection of environmental mana gement,soil erosion in the upper and middle reaches of the Yangtze,lake sediment ation,large scale reclamation of marshes,irrational distribution of agriculture and improper cropping system in high water level zone,the flood regulation capa city of the lake was descending,and flood stage was risen and prolonged.Conseque ntly more and more river levees and lake dikes were reinforced almost every year to prevent the disasters,which made flood level go up and flood period last for more days.The frequency of flood and waterlogging disasters rose and their dama ge was enlarged. The countermeasures of watershed ecosystem management were presented as fo llows: (a)In order to publicize knowledge of territory safety, ecological disas ter relief strategy should be placed as an important part of state security system and on the agend a.(b)The reclamation without storing floodwater should be readjusted into new la nd use system with flood storage project.Cultivation and planning can be carried out in normal years.The relaimed land can be used for storing water while a cat astrophic flood takes place.Certain fields acting as a hindrance for flood flow should be merged properly with lakes for fish culture.(c)Environmental migration should be placed in towns so that the tremendous population pressure on land an d lakes can be relieved.(d) To readjust allocation,cropping system and build up high efficiency,multi ecosystem engineering projects which are suitable to the shallow waters,of shores lakes and rivers as well as paddy fields.(e)The adjust ment of hilly land use structure and reconstruction of mountain vegetation wil l serve as fundamental measures for disaster relief.Soil erosion in hilly areas is much more serious,so to set up ecological land use patterns in hilly areas of the upper and middle reaches of the Yangtze is the key project for water and so il conservation.

Key words: watershed ecosystem management, flood and waterlogging, Dongtin lake