草被覆盖、雨强和坡度对黄土坡面径流含沙量的影响

Influence of Grass Coverage,Rain Intensity and Slope on Sediment Concentration of Runoff on Loess Slope

径流含沙量的大小体现水沙关系的消长和演变,可以作为评价植被影响下径流和产沙的交互演变过程特征的重要指标。通过人工降雨试验,研究不同草被覆盖度变化在不同雨强和不同坡度条件下对黄土坡面径流含沙量的综合影响特征。结果表明:(1)草被盖度越大,坡面径流的初始产流时间越滞后。有草被覆盖坡面的径流含沙量随降雨历时变化为降雨前15 min有波动,但总体上呈降低趋势,之后达到稳定,且有草被覆盖坡面的径流含沙量显著低于裸地。(2)径流平均含沙量均随雨强和坡度的增大而增大,平均含沙量对雨强和坡度的响应均可用幂函数方程描述,R^(2)分别为0.823~0.974和0.880~0.971。随着盖度的增加,平均含沙量降低,且雨强对平均含沙量的影响随盖度的增加而减弱。平均含沙量对盖度的响应可用线性方程描述,R^(2)为0.732~0.979。(3)径流平均含沙量对盖度和雨强(R^(2)=0.822,NE=0.921,p<0.01)及对盖度和坡度(R^(2)=0.975,NE=0.697,p<0.01)的响应关系皆可用二元幂函数方程描述,径流平均含沙量对盖度、雨强和坡度(R^(2)=0.771,NE=0.774,p<0.01)的综合响应可用三元线性方程描述,其中基于盖度和雨强,以及基于盖度、雨强和坡度的模型拟合效果最佳,对于含沙量的影响程度为盖度>雨强>坡度。研究结果可为黄土坡面含沙量的变化特征及机理提供参考,对黄土高原水土流失治理和生态系统可持续发展具有重要意义。

The sediment concentration of runoff reflects the fluctuation and evolution of the runoff-sediment relationship,and can be used as an important index to evaluate the characteristics of the interactive evolution process of runoff and sediment yield under the influence of vegetation.The influence of different grass covers on sediment concentration of runoff on loess slope under different rainfall intensities and slopes were studied through artificial rainfall experiment.The results showed that:(1)The greater the grass cover,the more delayed the initial time of slope runoff production.The sediment concentration of runoff on slopes covered with grass fluctuated in the beginning 15 min of rainfall,but showed a decreasing trend on the whole,and then reached a stable state,and the sediment concentration of runoff on the slope covered with grass was significantly lower than that on the bare land.(2)The average sediment concentration of runoff increased with the increasing of both rainfall intensity and slope,and the responses of average sediment concentration to both rainfall intensity and slope could be described by power function equations,with R^(2)ranging from 0.823 to 0.974 and 0.880 to 0.971,respectively.The average sediment concentration decreased with the increasing of coverage,and the influence of rainfall intensity on the average sediment concentration weakened with the increasing of coverage.The response of average sediment concentration to coverage could be described by linear equation with R^(2)ranging from 0.732 to 0.979.(3)The response of average sediment concentration to coverage and rainfall intensity(R^(2)=0.822,NE=0.921,p<0.01),coverage and slope(R^(2)=0.975,NE=0.697,p<0.01)could be described by binary power function equation.And the comprehensive response of average sediment concentration to coverage,rainfall intensity and slope could be described by a ternary linear equation(R^(2)=0.771,NE=0.774,p<0.01).Among them,the model based on coverage and rain intensity and the model based on coverage,rain intensity and slope had the best fitting effect.The degree of influence on sediment concentration followed the order of coverage>rain intensity>slope.The results could provide references for the research of change characteristics and mechanisms of sediment concentration on loess slope,and have important significance for soil and water loss control and sustainable development of ecosystem on the Loess Plateau.