Common approaches for characterizing streambed architecture, and its influence on groundwater-surface water (GW-SW) exchanges, are generally limited by their invasiveness and low spatial sampling density, which is a particular issue in streambeds that typically have high spatial heterogeneity. Combined DC resistivity and induced polarization (DC-IP) imaging can provide rapid, non-invasive and continuous information on streambed lithology; however, its full potential remains unrealized, leading to its underutilization for streambed investigations. The objective of this study is to demonstrate the value of DC-IP imaging, in both 3D and high-resolution, for characterizing streambed architecture and interpretating GW-SW exchange patterns. The study focused on a 50 m long stream reach located in Kintore, Ontario, Canada. Traditional methods – streambed temperature mapping, vertical head gradient measurements, streambed porewater quality, and sediment cores – were used to qualitatively identify spatial GW-SW exchanges. Underwater 3D DC-IP surveying was then conducted across the stream reach to obtain high-resolution distributions of resistivity and chargeability. Resistivity first identified three distinct zones along the stream reach: Zone 1 (0–12 m) and Zone 3 (38–50 m) exhibits high resistivity (>100 ohm-m), while Zone 2 (12–38 m) exhibits relatively low resistivity (<40 ohm-m). Chargeability highly complements resistivity by confirming that the shallow streambed contains only non-clayey materials; therefore, the more resistive Zones 1 and 3 is attributed to more permeable coarse sand and gravel, while the more conductive Zone 2 is attributed to less permeable finer sand, and consequently, increased porewater EC due to longer residence times and hyporheic exchanges. This geoelectrical interpretation is well-supported by information from traditional methods (e.g., higher temperature and hydraulic gradients correspond to the more permeable Zone 1 and Zone 3). This study demonstrates the unrealized value of spatially continuous, high-resolution DC-IP information for mapping streambed architecture and its control on GW-SW exchange patterns.

表征河床结构及其对地下水-地表水 (GW-SW) 交换的影响的常用方法通常受到其侵入性和低空间采样密度的限制，这在通常具有高空间异质性的河床中是一个特殊问题。结合直流电阻率和诱导极化 (DC-IP) 成像可以提供有关河床岩性的快速、非侵入性和连续信息；然而，它的全部潜力仍未实现，导致其在河床调查中的利用不足。本研究的目的是展示 DC-IP 成像在 3D 和高分辨率方面对表征河床结构和解释 GW-SW 交换模式的价值。该研究的重点是位于加拿大安大略省金托尔的 50 m 长河段。传统方法——河床温度测绘、垂直水头梯度测量、河床孔隙水质量和沉积物岩心——被用于定性识别空间 GW-SW 交换。然后在河流范围内进行水下 3D DC-IP 测量，以获得电阻率和充电能力的高分辨率分布。电阻率首先确定了河流河段的三个不同区域：1 区（0-12 m）和 3 区（38-50 m）表现出高电阻率（>100 ohm-m），而 2 区（12-38 m）表现出相对较高的电阻率。低电阻率（<40 ohm-m）。通过确认浅河床仅包含非粘土材料，可充电性高度补充了电阻率；因此，阻力更大的区域 1 和 3 归因于更具渗透性的粗砂和砾石，而导电性更强的第 2 区归因于渗透性较差的细砂，因此，由于较长的停留时间和低流交换，孔隙水 EC 增加。这种地电解释得到了来自传统方法的信息的充分支持（例如，较高的温度和水力梯度对应于更具渗透性的 1 区和 3 区）。这项研究展示了空间连续、高分辨率 DC-IP 信息在映射流床架构及其对 GW-SW 交换模式的控制方面的未实现价值。