关键词: 大通站, 含沙量, 绳套曲线, 长江中下游干流, 长江干流, 流量相关曲线, 水沙关系, 针型, 长江上游, 汉江

Abstract: Owing to the different physiographical conditions, flood season of southern tributaries of the Changjiang occurs in April-June, but July-August is flood season in the upper Changjiang and Hanjiang. The sediment concentration of the upper reaches and northern tributaries is higher than that of southern tributaries but the latter have more discharges.A series of discharge-sediment concentration correlation diagrams of key stations on the Changjiang have been prepared (Fig. 6). The most outstanding feature is that curves of Luoshan. Haukou and Datong all show a counterclockwise pattern, different from other major rives in the world. This is chiefly due to the fact that in the middle and lower Changjiang discharge and sediment from rivers of different hydrological regimes are brought together. The correlation curves of these stations for the first six months (Jan.-June) largely reflect the influence of southern tributaries which have considerable discharge but low silt content but in curves of the second six mouths (July-December), the effect of highly silt-laden water from the upper Changjiang is marked. The characteristic counter-clockwise pattern of curves of the middle and lower Changjiang is the result of combination of two sections of curves of different hydro-logical regime.A comparison is made with the Huanghe which has correlation curves with usual clockwise pattern (Fig. 8), because the hydrological regime of its whole drainage basin is similar. Therefore, it is concluded that the counter clockwise pattern of correlation curves of the Changjiang is the result of particular climatic-hydrological-physical conditions of its drainage basin.