Runoff variations in small and medium-sized rivers and their response to precipitation: A case study of Qian River

Abstract

[Objective] To further explore the relationship between extreme runoff and river basin precipitation variations in small and medium-sized rivers, and to improve the accuracy of flood disaster warning. [Methods] Taking the Qian River, a representative small and medium-sized river in the semi-arid regions of the Weihe River system in the Yellow River Basin, as an example, the flow and hourly precipitation data from 2010 to 2021 in the Qian River Basin were utilized. Based on the mean standard deviation classification method and the Topsis entropy weight method, the spatiotemporal variations in the river flow were analyzed. Focusing on four extreme runoff events, the sensitivity and lag in the runoff's response to river basin precipitation were investigated. [Results] The result were as follows:(1) the flow in the Qian River Basin exhibited significant interannual variability, showing a trend of first decreasing and then increasing. Seasonal distribution was extremely uneven, with peak flow typically occurring in July, and the flow was mainly in dry or slightly dry states.(2) Based on four extreme runoff events, it was found that the flow was high, with a rapid onset and long flood peak duration. The runoff predominantly exhibited a unimodal pattern, although bimodal occurrences were also observed.(3) The distribution of river basin precipitation affecting extreme runoff in the Qian River was uneven, with strong precipitation concentrated in the upstream area at the junction of Longxian and Qianyang. This was characterized by sudden heavy rainfall, with 14 out of 22 stations reaching the short-duration heavy rainfall level, including two stations with precipitation exceeding 50 mm/h. In addition, continuous rainfall, even at low intensity, could lead to extreme runoff events due to cumulative precipitation.(4) The sensitivity and time lag of runoff responses to precipitation varied across stations. At 14 key stations, significant contributions to runoff were observed, with precipitation at Dongnan, Duyang, Longxian, and Wenshui stations stabilizing the flow variations after 3, 9, 15, and 19 hours, respectively. [Conclusion] The response relationship between runoff and river basin precipitation during extreme runoff events is revealed, which can provide decision-making support for the scientific and rational development and utilization of water resources, as well as flood and waterlogging disaster management.

Keywords

flow / small and medium-sized rivers / wet and dry states / precipitation / response lag / influencing factors