High-frequency time series analysis and cross-correlation identified the relationship between precipitation and water-level responses at 16 sandstone wells in southern California, USA. The time series analysis suggested that the water table rises only when a threshold value of precipitation is reached during the rainy season that likely represents the water content deficit from the previous 7-month dry season being replenished before generating a water-table response. The cross-correlation indicates two statistically significant lag-times: 0–3 and 20–50 days. Confidence in these results was augmented by unprecedented and exceptionally high-resolution sampling frequency. Water pressure readings were collected every second and then analyzed to identify and remove the effects of barometric pressure changes, Earth tides and earthquakes on water levels. These effects are usually considered “noise” in recharge studies, but their accurate quantification helped assess the unconfined nature of the wells, minimize uncertainties of the results, and isolate the groundwater responses to precipitation. Diffusivity values for the thick unsaturated zone, based on the time lags, suggest quick responses are related to flow through fractures and longer time lags are associated with piston-type movement in the matrix. Fast responses were more likely for shallow water tables in response to high-intensity precipitation events and vice versa. These findings are consistent with those found, using lower resolution data, for the Chalk aquifer in England (UK), despite the contrasting fracture and matrix properties, hydrogeological setting and climatic conditions. Thus, the same style of response to precipitation is expected globally where similar fractured porous media are present.

高频时间序列分析和互相关确定了美国南加州 16 口砂岩井的降水与水位响应之间的关系。时间序列分析表明，只有在雨季达到降水阈值时，地下水位才会上升，这可能代表前 7 个月旱季的含水量不足在产生地下水位响应之前得到补充。互相关表明两个具有统计学意义的滞后时间：0-3 天和 20-50 天。前所未有的高分辨率采样频率增强了对这些结果的信心。每秒收集一次水压读数，然后对其进行分析，以识别和消除气压变化、地球潮汐和地震对水位的影响。这些影响在补给研究中通常被认为是“噪音”，但它们的准确量化有助于评估井的无侧限性质，最大限度地减少结果的不确定性，并隔离地下水对降水的响应。基于时间滞后的厚非饱和带的扩散率值表明，快速响应与通过裂缝的流动有关，而较长的时间滞后与基质中的活塞式运动有关。响应高强度降水事件的浅水位更有可能快速响应，反之亦然。这些发现与使用较低分辨率数据发现的英格兰（英国）白垩含水层的结果一致，尽管裂缝和基质特性、水文地质环境和气候条件存在差异。因此，