Abstract Two main processes of runoff are commonly thought to take place in a drainage basin: infiltration-excess overland flow, known also as Hortonian overland flow (HOF), and saturation overland flow (SOF). While HOF mainly takes place in arid and semiarid regions once the infiltration capacity of the upper skin of the soil (usually ~1 mm thick) is surpassed, SOF may takes place in wet humid and subhumid climates. SOF takes place once the groundwater table reaches the surface (mainly close to the stream channel), or due to an impermeable subsurface soil layer. Despite the low precipitation in semiarid regions, a number of publications advocated the occurrence of SOF also in semiarid regions, subsequently underplaying the centrality of biocrusts to effectively generate runoff. These publications are mainly based on moisture measurements that were conducted with dielectric-based sensors. In the present work, it will be argued that: (a) the amount and duration of the rain cannot possibly result in SOF, (b) the location of the alleged SOF, as reported by some publications (at the up- or mid-slope), is unlikely to facilitate SOF, (c) the likelihood that the electrical pulses produced by the dielectric-based sensors will distinguish between completely saturated and nearly saturated conditions is low, (d) in certain occasions even when the moisture content, as detected by these sensors, was slightly below saturation, the authors tended to assume that the soil was saturated, (e) while claiming that the subsurface soil layer reached saturation, the upper layer of the soil (where overland flow takes place) was occasionally reported to remain below saturation, (f) no supportive evidence for the occurrence of SOF or even subsurface flow was provided, such as visible wet belts with dense vegetation. It is therefore concluded that the occurrence of SOF in semiarid regions should be cautiously considered and re-examined.

中文翻译：

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比较半干旱和湿润地区的地表水流过程：饱和地表水流发生在半干旱地区吗？

摘要 通常认为流域内发生两个主要径流过程：入渗-过量地表流，也称为霍顿地表流（HOF）和饱和地表流（SOF）。虽然 HOF 主要发生在干旱和半干旱地区，一旦超过土壤表层（通常约 1 毫米厚）的渗透能力，SOF 可能发生在潮湿和半湿润气候中。一旦地下水位到达地表（主要靠近河道），或由于不透水的地下土壤层，SOF 就会发生。尽管半干旱地区降水量低，但一些出版物主张在半干旱地区也发生 SOF，随后淡化了生物结皮的中心性以有效产生径流。这些出版物主要基于使用基于电介质的传感器进行的湿度测量。在目前的工作中，将争论的是：（a）降雨的数量和持续时间不可能导致 SOF，（b）一些出版物报道的所谓 SOF 的位置（在上游或中期）斜率)，不太可能促进 SOF，(c) 由基于电介质的传感器产生的电脉冲区分完全饱和和接近饱和条件的可能性很低，(d) 在某些情况下，即使水分含量，如这些传感器检测到，略低于饱和，作者倾向于假设土壤已经饱和，（e）同时声称地下土壤层达到饱和，据报道，土壤上层（发生地表流的地方）偶尔会保持在饱和度以下，(f) 没有提供 SOF 甚至地下流发生的支持性证据，例如可见的带有茂密植被的湿带。因此得出的结论是，应谨慎考虑和重新审视半干旱地区发生 SOF。