基于热追踪方法的河道垂向潜流通量的非均质性研究

Study on the heterogeneity of vertical hyporheic flux using a heat tracing method

提出以河床温度作为示踪变量,基于一维稳态垂向热量运移问题的解析解,结合曲线拟合的热追踪方法推求潜流通量和地表水温度等参数。以山东省汶上境内大汶河为例,对3个不同剖面的潜流通量进行实例分析,并通过地下水温度和潜流带深度的关系曲线揭示潜流带深度的分布规律。结果表明:热追踪方法可以定量刻画河道垂向潜流通量的非均质性。本次试验测温剖面上潜流通量变化范围为99.61～356.25L(/m2·d);在夏季,实测河床温度剖面低温区为潜流通量高值区;河道剖面上潜流通量服从正态分布,同一剖面不同位置处数值差异较大,没有明显变化趋势,存在多个集中排泄区,约62%的总潜流通量来自于50%的总剖面长度,呈显著空间非均质性,证实了通过热追踪方法研究潜流通量非均质特征的有效性;潜流带深度与潜流通量大小呈反比关系,通过此方法说明潜流带深度也呈现空间非均质性。

The temperature of streambed was used as a tracer to capture the hyporheic flow. Based on the analytical solution of onedimensional steadystate heat transport equation under the vertical groundwater dis charge conditions, the hyporheic flux and surface water temperature were obtained via curve fitting method. The temperature data were monitored at three crosssections of the Dawen River, in Wenshang County, Shandong Province during 4h to 7 June, 2012. Distribution regularity of the depth of the hyporheic zone was revealed by the relation curve of groundwater temperature and the depth of the hyporheic zone. The re suits show that the heterogeneity of vertical hyporheic flux could be obtained quantitatively by heat tracing method. The range of hyporheic flux variation was 99.6-356.25L/（m2. d） and the amplitude of variation was 100-200L/（m2 d）. In summer, the low temperature area of measured streambed profile was the area with high value of hyporheic flux. The hyporheic flux varied significantly within the same section without ob vious variation trend and complied with normal distribution. The distribution of strong discharge zones was well agreed with the remarkable heterogeneity of streambed. Almost 62% of the hyporheic fluxes come from 50% of the total length of the three crosssections, which confirmed the validity of the study of hyporheic flux heterogeneity using the heat tracing method. The depth of the hyporheic zone is inversely proportional with the hyporheic flux. The hyporheic zone depth also has great spatial heterogeneity.