Characteristics of runoff and sediment and regularity of alluviation and siltation in east and south Dongting Lake

Abstract

Listen

Translate article

通过实地调查并对1957年以来水文、泥沙观测资料做系统分析和计算,探讨东、南洞庭湖出、入湖水量、沙量的年际和年内变化特征,以及长江下荆江段裁弯对湖区径流和泥沙的影响。提出了湖区泥沙汛淤枯冲的变化规律及水位升降与湖区泥沙冲淤的关系;论证了丰、平、枯年湖区淤积严重,面积日益缩小对径流的调节作用正在减弱。;1.The inflow of East and South Dongting Lake mainly comes from West Dongting Lake and the Xiang-jiang River, making up about 78.3% of the total inflow.However.the hydrological regime is affected to a larger extent by the inflows of the Ouchi.Songzi and Taiping mouthes of the Changjiang River rather than by the Xiang, Zi, Yuan and Li rivers.The lake regulating function between flood and drought years is weak, since the correlation coefficient between inflow and outflow is 0.98.2.In flood season the inflow and outflow in the lake are concetrated in the period from May to Oct.Because the lake is charged by the inflow of the Xiang and Zi rivers before flood water of the Changjiang River comes, the regulating effect for flood of the Changjiang River is getting reduced.3.The suspended sediments of the lake mainly come from the three inlets.Their accumulation is dominant in the silt-abundant years, producing about 67 000 000 tons of sediments per year and 2.09 cm thick in average.4.The sediments of the lake are characterized by siltation during flood seasons and alluviation during drought seasons.Generally, the fomier occurs during the period of Jan.-Apr.and Nov.-Dec.and the latter between June and Sep..The maximum intensity values appear in Apr.and July to Aug., respectively.The total amount of yearly alluviation is much less than that of yearly siltation, so the lake is always in the serious silting situation whenever in flood year, average year or drought year.5.the curve cut-off on the part of the Jingjiang River obviously shows a decrease in the inflows from three inlets.Among these, the Ouchikou has a decrease of more than 60%.It also makes the sediment discharge decrease to some extent.The Ouchikou has a decrease of more than 50%, the Chenglingji about 40%, and the net sediment discharge only 16%.6.The lake is mainly in the silting status in case of high-water level.The alluviation intensity is much less than the silting intensity at any water level.The alluviation and siltation can be distinguished from the variation of water level.