Runoff coefficient characteristics and its dominant influence factors of the riparian Myricaria squamosa Desv. shrubs over Qinghai Lake basin, NE Qinghai-Tibet Plateau

Abstract

The runoff coefficient, defined as the portion of rainfall that becomes direct runoff during an event, is a key concept in engineering hydrology and is widely used for design. Also, it is useful for understanding the flood frequency controls in a particular hydrologic or climatic regime. In this paper, the runoff coefficient characteristics and the dominant influence factors of riparian Myricaria squamosa Desv. shrubs were researched based on the data of runoff coefficient, rainfall depth, rainfall intensity, the 10-min maximum rainfall intensity, and antecedent soil moisture measured in Qinghai Lake basin, which will help us to recognize the runoff coefficient and the influence factors of riparian shrubs in highly cold and semiarid districts. The runoff coefficient of riparian M. squamosa Desv. shrubs in the study area is very small (the mean value is 0.39 %). Rainfall depth, rainfall intensity, and the 10-min maximum rainfall intensity are the dominant controls on runoff coefficient of riparian M. squamosa Desv. shrubs over Qinghai Lake basin. Runoff coefficient and rainfall depth have a logarithmic function relationship, and runoff coefficient increases with the increasing of rainfall depth significantly. The relationships between runoff coefficient and rainfall intensity/the 10-min maximum rainfall intensity are both logarithmic, both rainfall intensity and the 10-min maximum rainfall intensity significantly influence runoff coefficient in the study area, and the 10-min maximum rainfall intensity influences runoff coefficient more significantly. Relationships between runoff coefficient and antecedent soil moisture of 10 and 30 cm underground are not significant. This is because of the low soil moisture of 10 and 30 cm underground due to the bad soil water retention in the study area. Significant linear relationships were found between runoff coefficient and antecedent soil moisture of 60 and 80 cm underground, where runoff coefficient decreases with the increasing of antecedent soil moisture of 60 and 80 cm underground.