Based on flow records of Yichang gauge station between 1978-1991 and the yearly yielding data of aquatic product industries in Jiangxi,Hubei,Hunan between 1978-1995,this research has studied the relationship between the natural flow regime in Upper Yangtze River and the midstream ecosystem of Yangtze River by Principal Component Analysis (PCA) and Regression Analysis (RA).

Discussion and application of natural runoff consistency correction method;

Rebuilding the natural runoff series in the nearly 500 years at the Lanzhou Station in up stream of Yellow River;

Discuss on the natural runoff change and Its calculation method at the Lanzhou station of Yellow River;

Based on the relationships between the natural runoff at the Tangnaihai Station and the temperature and precipitation at each gauging station, a natural runoff calculation formula was established.

As a case,the model was satisfactorily structured and effectively used in computation of annual natural runoff with precipitation and evaporation at Huaibin Station on the upstream of the Huai River.

Based on the relationship between the recorded natural runoff in flood season from Lanzhou Station and the runoff data of the rivers nearby, the rings of the ancient trees and the magnitude of drought and flood therein, a 522-year runoff series at Lanzhou Station is reconstructed; for which the characteristics and variation trend of this series are analyzed herein.

This dissertation makes a systematic detailed study on the natural yearly runoff approximate cycle and low water period on the Yellow River baisn by means of the theory of hydrology and statistics on the base of the predecessors studies.