Characteristics of spatial and temporal distribution of heavy rainfall and surface runoff generating process in the mountainous areas of northern China
Abstract. The intensity and duration of precipitation play an important role in surface runoff processes. A hilly area may have more complicated runoff processes. In this study, the characteristics of annual rainfall from 1987 to 2023 in the Taihang Mountain were obtained by the Pearson-III frequency curve, homogeneity and MK test. Four surface runoff generation processes during 2014 to 2023 were monitored. The contribution of rainfall to changes in runoff were quantified based on the double cumulative curve method. Results showed that for the last decade, a significant upward trend in the frequency of moderate and heavy rainfall events. The spatial variability of rainfall in the Taihang Mountain and the influence of elevation are both smaller when the rainfall during 24 h is lower than 50 mm. The two surface runoff processes in 2016 and 2023 were typical runoff resulted from excess rain, which belonged to the storm runoff. The two surface runoff processes in 2021 were runoff generation under saturated condition. For runoff generation under saturated condition, the contribution of rainfall was only 58.17 %. While when the runoff coefficient was greater than 0.5, the surface runoff generating processes were entirely determined by rainfall. This study suggested that for semi-arid regions, where rainfall is unevenly distributed over the seasons, more soil water is needed to maintain local and downstream water demand during the non-rainy season.
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