Characteristics of Multi-Scale Variability of Water Discharge and Sediment Load in the Hanjiang River During 1955-2012

Based on daily precipitation, water discharge and sediment runoff recorded at 12 meteorological stations in the Hanjiang river and hydrological date gathered from Chaoan station from 1955—2012, the characteristics of multi-scale variations in flow discharge and sediment load are analyzed by Mann-Kendall trend test and wavelet analysis. The results indicate that there is no obvious variation in runoff and the sediment load from 1955-2012, a significant descendent trend in sediment load while the amount of runoff has no obvious variation during 1982-2012.There are three significant periodic variations at scales of 25~30a, 9~14a, 3~8a for runoff and sediment discharge, but the 25~30a scale is the most significant. The periodic of runoff and sediment discharge in Hanjiang river is consistent, but the periodic of sediment discharge slightly lags the periodic of runoff. At the 4-year scale, not only the positive and negative phases about the curves of runoff and sediment discharge have appeared frequently and sharply but there are so many mutation points, while at the 12-year and 30-year scales have appeared normally, human activity has a great power influence on short scales. Construction of a large number of hydropower stations, the improvement of forest vegetation coverage and an increase in water consumption are the main factors for the reduction of runoff and sediment yield in Hanjiang basin.