Detecting ground water - surface water interaction in streams with DTS

Groundwater-surface water (GW-SW) flux measurement techniques, such as reach mass-balance, seepage meters, Darcian flux and temperature sensing can be applied simultaneously to provide multiple lines of evidence (e.g., Gonzalez et al. 2015, Schmadel et al. 2014, Kennedy et al. 2009, Gilmore et al. 2016b), but challenges remain for directly linking results from different spatial and temporal scales of measurement. For smaller streams where groundwater discharge is a significant percentage of stream discharge into the reach (typically ≥10%), the integrated groundwater flux from point measurements can be compared to a larger-scale (i.e. 10^2-10^3 m reach length) approach to confirm results. But for reaches in larger stream (river) systems, the stream-groundwater discharge ratio is usually much too large to use reach mass balance as a direct point of comparison (Gilmore et al. 2016b, Schmadel et al. 2010, Jain, 2000). A promising approach for linking point measurements and testing interpolation techniques in large river systems is fiber-optic distributed temperature sensing (FO-DTS) (Briggs et al. 2012a, Briggs et al. 2012b, Tyler et al. 2009). FO-DTS uses a fiber-optic cable to detect groundwater discharge through the streambed along the length of the cable (typically ≤1km). This may be an effective way to “connect the dots” between point measurements of groundwater discharge in large systems (Krause et al. 2012), when other techniques like reach mass balance, are not feasible. The overall goal of this research is to develop an optimal approach to link point measurements of groundwater-surface water fluxes in large river systems. The specific objectives are to: (1) test the combined DTS and point-measurement approach in a small stream, where interpolated results can be confirmed using a reach mass-balance approach, and (2) apply the technique in larger river systems to characterize spatial distributions and temporal variability of groundwater fluxes at existing groundwater-surface water monitoring stations on larger rivers. This project will improve techniques for multi-scale measurement of groundwater-surface water interactions, give critical insight into temporal and spatial variability of water fluxes in larger river systems, and improve our understanding of the value of existing groundwater-surface water monitoring stations. Raw project data is available by contacting [e-mail]地下水-地表水（groundwater-surface water, GW-SW）通量测量技术，诸如河段质量平衡法（reach mass-balance）、渗压计（seepage meters）、达西通量（Darcian flux）与温度传感（temperature sensing），可同步部署以提供多重佐证依据（例如Gonzalez等2015年、Schmadel等2014年、Kennedy等2009年、Gilmore等2016b年的研究），但目前仍存在关键挑战：难以直接关联不同空间与时间尺度的测量结果。 对于地下水排泄量占河段径流比例较高（通常≥10%）的小型溪流，可将单点测量所得的综合地下水通量与尺度更大的方法（即长度为10²~10³米的河段）进行对比，以验证结果可靠性。但对于大型河流系统中的河段，河流-地下水排泄比通常过高，无法通过河段质量平衡法作为直接对比依据（Gilmore等2016b年、Schmadel等2010年、Jain 2000年）。 光纤分布式温度传感（fiber-optic distributed temperature sensing, FO-DTS）是一种在大型河流系统中关联单点测量并验证插值技术的颇具潜力的技术手段（Briggs等2012a、Briggs等2012b、Tyler等2009年的研究）。FO-DTS通过铺设于河道内的光纤电缆，沿电缆长度（通常≤1千米）检测河床的地下水排泄量。当河段质量平衡法等其他技术不可行时，该方法可有效"串联"大型系统中地下水排泄量的单点测量结果（Krause等2012年）。 本研究的总体目标是开发一套最优技术方案，以关联大型河流系统中的地下水-地表水通量单点测量数据。具体研究目标包括：（1）在小型溪流中验证DTS与单点测量结合的方法，此时可通过河段质量平衡法验证插值结果；（2）将该技术应用于大型河流系统，以表征大型河流现有GW-SW监测站点处地下水通量的空间分布与时间变异性。 本项目将完善多尺度地下水-地表水交互作用的测量技术，为大型河流系统中水通量的时空变异性提供关键认知，并深化对现有地下水-地表水监测站点价值的理解。 原始项目数据可通过联系[e-mail]获取。