Although cosmic-ray neutron sensing (CRNS) is probably the most promising noninvasive proximal soil moisture measurement technique at the field scale, its application for hydrological simulations remains underexplored in the literature so far. This study assessed the use of CRNS to inversely calibrate soil hydraulic parameters at the intermediate field scale to simulate the groundwater recharge rates at a daily timescale. The study was conducted for two contrasting hydrological years at the Guaraíra experimental basin, Brazil, a 5.84-km², a tropical wet and rather flat landscape covered by secondary Atlantic forest. As a consequence of the low altitude and proximity to the equator low neutron count rates could be expected, reducing the precision of CRNS while constituting unexplored and challenging conditions for CRNS applications. Inverse calibration for groundwater recharge rates was used based on CRNS or point-scale soil moisture data. The CRNS-derived retention curve and saturated hydraulic conductivity were consistent with the literature and locally performed slug tests. Simulated groundwater recharge rates ranged from 60 to 470 mm yr^–1, corresponding to 5 and 29% of rainfall, and correlated well with estimates based on water table fluctuations. In contrast, the estimated results based on inversive point-scale datasets were not in alignment with measured water table fluctuations. The better performance of CRNS-based estimations of field-scale hydrological variables, especially groundwater recharge, demonstrated its clear advantages over traditional invasive point-scale techniques. Finally, the study proved the ability of CRNS as practicable in low altitude, tropical wet areas, thus encouraging its adoption for water resources monitoring and management.

中文翻译：

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基于宇宙射线中子传感的热带湿实验盆地地下水动态补给模拟

尽管宇宙射线中子传感 (CRNS) 可能是最有前途的无创近端土壤水分测量技术，但迄今为止，其在水文模拟中的应用仍未得到充分探索。本研究评估了使用 CRNS 在中场尺度上反向校准土壤水力参数以模拟每日时间尺度的地下水补给率。该研究在巴西瓜莱拉实验盆地进行了两个对比鲜明的水文年，该盆地面积为 5.84 平方公里，热带潮湿且相当平坦的景观被次生大西洋森林覆盖。由于低海拔和接近赤道，可以预期低中子计数率会降低 CRNS 的精度，同时为 CRNS 应用构成未经探索和具有挑战性的条件。基于 CRNS 或点尺度土壤水分数据，对地下水补给率进行逆校准。CRNS 导出的保留曲线和饱和导水率与文献和当地进行的段塞试验一致。模拟地下水补给率范围为 60 至 470 毫米年^–1，对应于 5% 和 29% 的降雨量，并且与基于地下水位波动的估计值密切相关。相比之下，基于逆点尺度数据集的估计结果与测量的地下水位波动不一致。基于 CRNS 的现场尺度水文变量估计的更好性能，尤其是地下水补给，证明了其优于传统侵入性点尺度技术的明显优势。最后，该研究证明了 CRNS 在低海拔、热带潮湿地区的可行性，从而鼓励将其用于水资源监测和管理。