佳芦河流域生态治理影响下的水沙关系变化

Change of the runoff-sediment relationship and its response to ecological management in Jialu River Basin

河流水沙关系是反映流域水文循环及土壤侵蚀过程的主要指标。以黄土丘陵沟壑区佳芦河流域为研究区,基于水文方法在年尺度和小时间(次洪水)尺度上分析流域综合治理前后径流和输沙关系变化特征以及对流域治理的响应。结果表明:1)1972年为佳芦河流域径流输沙发生明显突变的转折年。2)与基准期(1957—1972年)相比,治理期(1973—2014年)的径流与输沙之间关系在年尺度和次洪水尺度上均发生了显著变化,且径流输沙均显著减少。3)次洪水尺度上,流域临界径流深为6 mm,低于该值,水沙关系离散,反之水沙关系相对稳定;当降雨量<50 mm、降雨强度<4 mm/h或历时>3 h时,治理期的水沙关系与基准期相比发生显著变化。该流域在年尺度和次洪水尺度上水沙关系变化显著的主要原因是水土流失综合治理造成的,并且对中低降雨量、中低降雨强度和中长历时降雨的次洪水过程产流产沙有显著减少的效果。

[Background]The runoff-sediment relationship is the main indicator that reflects the hydrological cycle and soil erosion.In this study,we investigated the variation of flow-sediment relationship under the influence of ecological management in Jialu River Basin in typical hilly and gully loess region,aiming to provide some theoretical basis for the benefit evaluation of soil and water conservation and the prediction of soil and water loss.[Methods]Based on Tyson polygon method and multiple hydrological methods(Mann-Kendall trend test,ordered clustering analysis,and double mass curve method),we analyzed the characteristics of runoff-sediment relationship before and after comprehensive management and its response to the management on the yearly and small time(event)scale in Jialu River Basin on the Loess Plateau.[Results]1972 was the transition year of runoff and sediment load in Jialu River Basin.Thus,the whole period was divided into two sub-periods,the baseline period(1957—1972)and the management period(1973—2014).Compared with the baseline period,the runoff-sediment relationship in the management period significantly changed at the yearly and event scale,and the sediment discharge at unit runoff depth was significantly declined.At event scale,the critical runoff depth of the basin was 6 mm.When the runoff depth was lower than this value,and the runoff-sediment relationship was discrete,otherwise,the runoff-sediment relationship tended to be stable.If rainfall amount was<50 mm,rainfall intensity was<4 mm/h or rainfall duration was>3 h,the runoff-sediment relationship in the management period changed significantly compared with the baseline period.[Conclusions]The main reason for the change is the comprehensive management of soil and water conservation,and the significant reduction of the runoff and sediment yield of medium-low precipitation,medium-low rainfall intensity and medium-long rainfall duration.