近50年钦江水沙变化研究

【目的】分析钦江近50年来河流水沙变化特征,以及河床演变对水沙变化的响应。【方法】以钦江为研究对象,收集长时间序列的水沙和河床断面资料,基于小波分析、"3S"和Mann-Kendall非参数秩次相关检验等方法,分析水沙变化及其影响因素。【结果】20世纪60年代以来钦江水沙均呈现下降趋势,其中含沙量下降趋势尤为明显,水沙变化突变年份是1979年和1995年;夏半年的平均流量与平均输沙量分别占全年的58.62%和61.77%,年平均流量和年平均含沙量存在4~6年和15年的周期振荡特征;中游河床枯季先冲刷后淤积,下游则以冲刷为主;流量主要受降雨控制,而含沙量则主要受控于水土流失、森林保育和人口增长等多种因素。【结论】钦江水沙总体呈下降趋势,水土流失、水利工程和耗水量等人类活动是泥沙减少的重要影响因素。

Variations of Runoff and Sediment in Qinjiang River in the Past 50 Years

Objective] The characteristics of runoff and sediment variations in Qinjiang River in the past 50 years and the response of riverbed evolution to water and sediment variations are analyzed.Methods] Taking Qinjiang River as the research object, the long-term sequence of water discharge, sediment flux and riverbed sections were collected, and the variations of water discharge and sediment flow and their influencing factors were analyzed based on wavelet analysis, "3S" method and Mann-Kendall nonparametric rank test.Results] The results indicated that:(1) Since 1960s, the water discharges and sediment fluxes in the Qinjiang River had shown a downward trend, especially the decline of sediment concentration was particularly obvious. The years of sudden changes in water discharges and sediment fluxes was 1979 and 1995; (2) The average water discharge and sediment flux in summer half year accounted for 58.62% and 61.77% of annual total, respectively. The annual mean water discharge and sediment flux showed oscillating periods of 4-6 and 15 years, respectively; (3) The middle reaches of riverbed showed erosions and accretions in sequence, while the lower reaches were dominated by erosions; (4) The water discharge was mainly controlled by rainfall, while the sediment flux was influenced by many factors including soil erosion, forest conservation and population growth.Conclusion] Therefore, it is considered that the water and sediment in Qinjiang River generally show a downward trend, and human activities such as soil erosion, water conservancy projects and water consumption are the important influencing factors of sediment reduction.