Background There are many factors affecting the hydrological response at watershed scale. In recent years, more and more studies have been conducted on the effects of spatio-temporal patterns of storm on hydrological response. Most of these studies are based on mathematical models because of the scarcity of high-resolution data. Many research indicated that spatio-temporal patterns of storm events play an important role in runoff discharge and sediment yield at watershed scale. Due to the good data integrity and high resolution, the Fort Cobb watershed in Oklahoma state, USA, was selected as the research site.

Methods Based on high-resolution meteorological and hydrological data, this study quantified and traced the storm path and spatial distribution of 43 storms in Fort Cobb watershed by using K-means clustering method and Kriging interpolation method. And the effects of storm pattern, rainfall intensity and spatio-temporal characteristics on runoff discharge and sediment yield of Fort Cobb watershed were studied.

Results 1) The 43 storm events were classified into 4 patterns. Type A, with small rainfall, variable rainfall duration and medium maximum 30-min rainfall intensity. Type B, with small rainfall, variable rainfall duration and small maximum 30-min rainfall intensity. Type C, with medium rainfall, short rainfall duration and medium maximum 30-min rainfall intensity. Type D, with large rainfall, short rainfall duration, and medium maximum 30-min rainfall intensity. Storms with small rainfall and low maximum 30-min rainfall intensity were the commonest pattern. Type C was the main pattern that caused soil erosion in the research area. 2) The runoff discharge and sediment yield were significantly and positively correlated with rainfall and rainfall erosivity (P < 0.05) even if under different storm patterns (P < 0.05). When the rainfall was the same, different types of storms leads to runoff as C>A>D>B. When the value of rainfall erosivity was equal, different types of storms caused different sediment yield in this area, and the amount from the highest to the lowest was D>B>A>C. 3) The spatial difference of storms was relatively huge. The rainfall was much more in the east and the south than that in the west and the north. The rainfall in the northeast and the southeast accounted for 38.96% of the total. 4) The storms moving downstream and clockwise accounted for the most amount of rainfall of 57.94% and 81.61% runoff discharge and 84.84% sediment yield. Most of storms started from the northwest of the basin and moved downstream. When the process of rainfall was similar, the storm moving upstream had a fast hydrological response and a low peak flow and sediment yield. On the contrary, the storm moving downstream had a slow hydrological response and a high runoff and sediment yield.

Conclusions The spatial and temporal distribution characteristics of storms have impact on the hydrological response of watershed, which is significantly reflected in the hydrological process and sediment yield. This result may provide a basis for understanding the complex interactions between rainfall variability and catchment heterogeneity.