24 and a skewness of −0.51. An average of 432.9 mm, or 78.6% of the total yearly precipitation, fell in the rainy season from May to September (Supplementary Table 1). It is noted that almost all the runoff generation storms occurred in the rainy season in this region (Zhu et al., 1997). Over the SSP, LSP, and SCP monitoring periods, Forskolin clinical trial the mean annual precipitation was 522 mm, 524 mm, and 565 mm; the mean rainfall amount in the rainy season was 405 mm, 413.4 mm and 449.5 mm, which accounted for 77.6%, 78.9% and 79.5% of total annual precipitation, respectively (Fig. 4). The following are the supplementary data to this article. In this study, if a storm generated flows on any of those monitoring plots, it was referred to

as a runoff generation event. Flows selleck chemical may be present on some plots but absent on other plots in a small runoff generation rainfall event due to the difference in soil infiltration. There were 22, 25, and 59 runoff generation storm events in the SSP, LSP, and SCP monitoring periods. It is noted that the

LSP monitoring period was within the SCP monitoring period. Overall, all those runoff generation storm events ranged from 3.6 to 110 mm in event rainfall amount, 0.25–26.1 h in rainfall duration, and 1.03–62.4 mm/h in mean event intensity (Fig. 5). To determine the recurrence intervals of runoff generation storms, an empirical equation was used in this study (Eq. (1)). The equation was developed by Shanxi Bureau of Meteorology based on the long-term continuous data collected at the weather stations across the Shanxi Province. The coefficients (A, B, n) in the equation were calibrated using

the rainfall data in each region and they are varied from region to region. equation(1) logN=I×tnB24n−1Where N is recurrence interval (year); t is rainfall duration (h); I is mean rainfall intensity (mm/h); A, B and Olopatadine n are coefficients (A = 40, B = 65, and n = 0.7). The recurrence intervals of all the runoff generation storms over the study periods are shown in Fig. 5d. At slope angles of 5°, 10°, 15°, 20°, 25°, and 30°, the mean annual runoff per unit area was 42.9, 44.2, 45.4, 44.2, 44.3 and 47.2 mm on SSP, in comparison of 31.1, 24.3, 33.7, 28.8, 27.2, and 25.1 mm on LSP. Overall, the variation in runoff per unit area with slope angles was fairly limited on SSP (Fig. 6a). The highest mean annual runoff, occurring at 30°, was only 9.1% more than the lowest, occurring at 5°. On LSP, the highest mean annual runoff, occurring at 15°, was 27.8% more than the lowest, occurring at 10°. The relationship between runoff and slope angles was inconsistent between SSP and LSP. On SSP, the mean annual runoff per unit area generally showed a slight increase with slope angles. However, on LSP, the mean annual runoff reached a maximum at 15° and then decreased with slope angles. The inconsistent and complex relationship between runoff and slope angles might be ascribed to the effects of several factors on soil infiltrability.