The understanding of the hydrological processes in transitional zones between semi-arid and temperate ecosystems is essential since these areas are particularly sensitive to changes in precipitation and land cover. The objectives were to (1) determine the most critical factors in the generation of surface runoff during one rainy season; and (2) analyze the effect of different rainfall variables and soil moisture on the amount of surface runoff. The study area is in a semi-dry forest in the state of Chihuahua, Mexico. Vegetation, soil, and precipitation variables were monitored on three micro-catchments (0.19–0.27 ha) in 2018. Maximum 30-min rainfall intensity, rainfall depth, and soil moisture were the main variables controlling surface runoff. Rainfall intensity was better related to the amount of surface runoff, with an increase in runoff when rainfall intensities were greater than 25 mm h⁻¹. The highest runoff coefficients (10%) occurred only when rainfall intensity exceeded 30 mm h⁻¹. Similarly, surface runoff was only activated when rainfall depth exceeded 20 mm, or when the maximum volumetric water content by rainfall event exceeded 30%. Only 10% of storms exceeded these thresholds, indicating the difficulty of runoff generation in transitional zones. The interception (36%; s.d. = 30.7%), and the drastic decrease in soil moisture after each storm, suggest that more than 90% of the rainfall was lost by evapotranspiration. Our findings suggest that the groundwater recharge in a given year in these transitional zones is highly related to the number of low intensity and long duration rainfall events.

了解半干旱和温带生态系统之间过渡带的水文过程至关重要，因为这些地区对降水和土地覆盖的变化特别敏感。目的是（1）确定一个雨季地表径流产生的最关键因素；（2）分析了不同的降雨变量和土壤水分对地表径流量的影响。研究区域位于墨西哥奇瓦瓦州的半干林中。2018年在三个微流域（0.19-0.27公顷）上监测了植被，土壤和降水变量。最大的30分钟降雨强度，降雨深度和土壤湿度是控制地表径流的主要变量。降雨强度与地表径流量更好地相关，^-1。仅当降雨强度超过30 mm h ^-1时才出现最高径流系数（10％）。同样，只有在降雨深度超过20 mm或降雨事件引起的最大体积水含量超过30％时才激活地表径流。只有10％的暴风雨超过了这些阈值，表明在过渡带中产生径流的难度很大。拦截（36％；标准差= 30.7％）以及每次暴风雨后土壤水分急剧下降，表明超过90％的降雨是由蒸散损失的。我们的发现表明，在这些过渡带中，给定年份的地下水补给与低强度和长时间降雨事件的数量高度相关。