桐梓河流域输沙量变化及其对气候和人类活动的响应

Sediment transport variation and its response to climate and human activities in Tongzi River Basin

基于桐梓河流域二郎坝水文站1975-2015年长时间序列降水、蒸散量及输沙量数据,通过累积距平法、Morlet小波分析和Hurst指数等数理统计方法;定量分析了流域40年以来输沙量的演变过程以及未来变化趋势,并应用累积量斜率变化率比较法定量评估了研究区降雨量变化和人类活动对流域输沙量变化的影响和贡献率。研究结果表明:(1)40年来流域降水量介于608.10~1132.70 mm之间,其平均值为829.00 mm,呈不显著减小趋势,年均减小量为-3.10 mm/a。(2)流域年输沙量介于0.44万~478.01万t,其平均值为64.68万t,呈极显著减少趋势,减少速率为-4.13万t/a。未来流域输沙量呈持续递减趋势,但10年后将呈现出增加趋势。(3)1989年为流域输沙量的突变年份,1989年以前呈现上升趋势,1989年之后呈显著下降趋势,且突变年份后输沙量较突变年份前减少了76.82%。(4)输沙量存在12年左右的年代际震荡周期,形成了两个高震荡周期和一个低震荡中心,高震荡周期位于1976-1979年以及1986-1992年,低震荡周期位于1979-1985年。(5)多年季节输沙量呈持续性减少趋势,夏季输沙量在8年之后可能呈现出增加趋势,而其他季节则不存在持续性周期。(6)以1975-1989为基准期,降水量和人类活动对流域输沙量的贡献在1990-2015年分别达到4.87%和95.14%;如果考虑蒸发量对流域输沙量的影响,则人类活动对桐梓河流域径流量变化的贡献率在2003-2015年会增加到98.65%。流域输沙量在1990-2015年的减少主要由人类活动控制,人类活动每年导致输沙量减少1.57万t。

Based on the long time series data of annual precipitation,evapotranspiration and sediment transport of Erlangba Hydrological Station in Tongzi River Basin from 1975 to 2015,the evolution process and future trend of sediment transport in the past 40 years were quantitatively analyzed by the methods of cumulative anomaly,Morlet wavelet analysis and Hurst index,and the contribution rates of climate change and human activities to sediment transport in the study area were quantitatively assessed by the cumulative slope rate change comparison method.The results indicated that:(1)In the past 40 years,the precipitation in the basin ranged from 608.10 mm to 1132.70 mm,with an average of 829.00 mm.And the precipitation showed no significant decreasing trend,with an average annual decrease of-3.10 mm/a.(2)The annual sediment transport in the basin ranged from 0.44 to 478.01 million tons,with an average of 646.8 million tons.And it showed a very significant decreasing trend,with a reduction rate of-413000 t/a.In the future,sediment transport in the basin will continue to decrease,but it is likely to increase after 10 years.(3)In 1989,the sediment discharge in the basin changed abruptly.Before 1989,it showed an upward trend.After 1989,it showed a significant downward trend.The sediment discharge after the abrupt year decreased by 76.82%compared with that before the abrupt year.(4)The sediment discharge had a 12-year interdecadal oscillation period,forming two high oscillation periods and a low oscillation center.The high oscillation period was observed in 1976-1979 and 1986-1992,and the low oscillation period was found in 1979-1985.(5)The sediment transport in summer showed an increasing trend after 8 years,while there was no continuous cycle in other seasons.(6)Based on the period from 1975 to 1989,the contributions of precipitation and human activities to the sediment transport of Tongzi River Basin reached 4.8651%and 95.1385%,respectively in the period from 1989 to 2015.If the influence of evaporation on the sediment transport of the study area was taken into account,the contribution of human activities to the change of runoff of this basin would increase to 98.65%from 1989 to 2015.The decrease of sediment transport in the basin from 1990 to 2015 was mainly controlled by human activities,which reduced sediment transport by 157 thousand tons annually.