Basin tendency on flood and drought occurrence for two major rivers in China

Abstract

River basins play a key role in modulating precipitation variability and manifesting the diversified variability response by runoff or soil moisture. These responses are basin-dependent and frequency dependent controlled by many catchment-related characteristics. The fundamental idea of flood/drought tendency evaluation is to examine the basin response in keeping the high-frequency precipitation variability and memorizing the long-term precipitation variability. This study presents the uses of (1) the Variable Infiltration Capacity (VIC) model and (2) continuous wavelet transform for the tendency evaluation in the sub-basin basis for two major river basins in China, namely the Yangtze River basin and the Pearl River basin. The terrestrial hydrological processes over the two basins are simulated by using the macro-scale hydrological VIC model over the period of 1951-2000. The variability properties of hydrological variable for different sub-basins in time-frequency domain, ranged from 1/6 - 9 years, are revealed by the wavelet transform. With inspection on the wavelet power ratios of runoff and soil moisture to precipitation across different timescales, the flood or drought tendency is then investigated in associated with the effects of basin geomorphologic factors. The results obtained provide valuable information in devising adaptation and mitigation strategies in humid and semi-humid regions, especially in the context of possible climate change.