Characteristics of precipitation intensity regimes in the Rouyuanchuan and Heshuichuan watersheds of the Jing River

Understanding the changes in the regime of precipitation intensity plays an important role in flood risk mitigation and water resources management. Based on the field data of daily and hourly precipitation from 9 rainfall gauge stations in the Rouyuanchuan watershed from 1980 to 2017 and 10 rainfall gauge stations in the Heshuichuan watershed from 1981 to 2017, the changes in the regimes of annual maximum precipitation intensity of 1 h (I_h) and 1 d (I_d) and graded precipitation intensity are analyzed using the MK trend test method. Results indicate that:(1) Spatial distributions of I_h and I_d are found quite different, with the spatial variation coefficient (C_V) of I_h greater than that of I_d, and C_V of I_h and I_d in the Heshuichuan watershed greater than that in Rouyuanchuan. (2) C_V of I_d in the Rouyuanchuan watershed is found to increase significantly (α=0.05) at a rate of 0.018/10 a while that in the Heshuichuan watershed is found to decrease significantly at a rate of −0.039/10 a. (3) The extreme I_d values in the Rouyuanchuan watershed are found to increase significantly at a rate of 7.68 mm/(d·10 a). (4) It is found that no significant change of graded precipitation intensity happens in the Rouyuanchuan watershed while the precipitation intensity of moderate-grade rains and heavy-grade rains in the Heshuichuan watershed show significant increases at rates of 0.61 and 1.29 mm/(d·10 a), respectively.