The groundwater pressure response to the ubiquitous Earth and atmospheric tides provides a largely untapped opportunity to passively characterize and quantify subsurface hydro-geomechanical properties. However, this requires reliable extraction of closely spaced harmonic components with relatively subtle amplitudes but well-known tidal periods from noisy measurements. The minimum requirements for the suitability of existing groundwater records for analysis are unknown. This work systematically tests and compares the ability of two common signal processing methods, the discrete Fourier transform (DFT) and harmonic least squares (HALS), to extract harmonic component properties. First, realistic conditions are simulated by analyzing a large number of synthetic data sets with variable sampling frequencies, record durations, sensor resolutions, noise levels and data gaps. Second, a model of two real-world data sets with different characteristics is validated. The results reveal that HALS outperforms the DFT in all aspects, including the ability to handle data gaps. While there is a clear trade-off between sampling frequency and record duration, sampling rates should not be less than six samples per day and records should not be shorter than 20 days when simultaneously extracting tidal constituents. The accuracy of detection is degraded by increasing noise levels and decreasing sensor resolution. However, a resolution of the same magnitude as the expected component amplitude is sufficient in the absence of excessive noise. The results provide a practical framework to determine the suitability of existing groundwater level records and can optimize future groundwater monitoring strategies to improve passive characterization using tidal signatures.

地下水对无处不在的地球和大气潮的响应为被动地表征和量化地下水文地质力学特性提供了一个未开发的机会。然而，这需要从噪声测量中可靠地提取出幅度相对较小但具有众所周知的潮汐周期的，间隔很小的谐波分量。现有地下水记录是否适合分析的最低要求尚不清楚。这项工作系统地测试和比较了两种常见的信号处理方法（离散傅里叶变换（DFT）和谐波最小二乘（HALS））提取谐波分量特性的能力。首先，通过分析大量具有可变采样频率，记录持续时间，传感器分辨率，噪声水平和数据差距。其次，验证了两个具有不同特征的真实世界数据集的模型。结果表明，HALS在所有方面都优于DFT，包括处理数据缺口的能力。虽然在采样频率和记录持续时间之间存在明显的权衡，但是在同时提取潮汐成分时，采样率应不少于每天六次，记录不应短于20天。增加噪声水平和降低传感器分辨率会降低检测精度。然而，在没有过多噪声的情况下，具有与期望分量幅度相同大小的分辨率就足够了。