渭河下游垂向潜流通量动态特征研究

Dynamic Characteristics of Vertical Hyporheic Flux in the Downstream of Weihe River,China

潜流交换控制着潜流带内水量的变化及各种物质(氧气、有机质)的滞留时间,对地下水的水量和水质变化具有重要的影响。精确计算潜流带内的潜流通量及其动态变化特征,对河流的综合治理及生态恢复具有十分重要的意义。采用热量运移解析模型求解潜流通量,利用温度示踪技术,重点研究潜流交换过程的空间非均质特征和动态变化特征;以渭河下游草滩段为研究区,进行河床浅层沉积物潜流通量的计算。结果表明:监测时段内研究区地下水流为河水补给地下水,河道内不同位置的浅层潜流带内呈现出不同的潜流通量动态特征,其变化范围在0.873~8.900μm/s之间,潜流带厚度约为0.75 m,呈现比较复杂的动态变化特征。监测时段内各深度间潜流通量总体变化趋势为上升趋势,在垂向分布上存在差异,而且这种差异随时间变化。温度示踪方法简单易行,在潜流通量的计算中具有较好的准确性,适用于潜流带内水动力交换量的精确计算。

Hyporheic exchange has significant impact on the changes of water quantity in the hyporheic zone and residence time of various substances(oxygen and organic matters).Accurate calculation of hyporheic exchange flux and its dynamic change is of crucial importance for the integrated management and ecological restoration of rivers.In the present paper,the hyporheic flux in the hyporheic zone of the Caotan section of Weihe River is calculated by using heat transfer model as a case study.The spatial heterogeneity and dynamic change of hyporheic exchange are examined through temperature tracing.Results show that in the monitoring period,groundwater in the study area was recharged by river flow.Hyporheic flux varied in a range of 8.73×10-7-8.90×10-6 m/s in shallow hyporheic zones of about 0.75 m thick at different locations,displaying complex dynamic feature.In the monitoring period,the overall trend of hyporheic flux at different depths was increasing,yet with some differences in vertical distribution varying with time.The results prove that temperature tracing method is simple and accurate in the calculation of hyporheic flux,and is suitable for the calculation of hydrodynamic exchange capacity in hyporheic zone.