Background For last 30 years, the global temperature rose with the influence of the precipitation spatial distribution pattern. Economic and social development, the spatial and temporal of the runoff varied significantly, and its evolution also showed a strong randomness at the same time. The Bailianya river basin is located in Dabie mountain, which is the watershed between Yangtze River basin and Huaihe River basin. The study on the characteristics of runoff change in the Bailianya river basin and its relationship with environmental factors may provide decision-making basis for regional flood control and disaster reduction, industrial and agricultural production and rational utilization of soil and water resources.

Methods The variation characteristics of the runoff of Bailianya basin and its correlation with major environmental factors from 1970 to 2009 was detected through the Mann-Kendall test, Yamamoto method of signal-to-noise ratio and the cross wavelet transform analysis. The relationship between time series of environmental factors and runoff in different frequency domain was revealed using cross wavelet analysis. The response of runoff to the change of underlying surface elements was also clarified based on the analysis of remote sensing images in 3 stages. The coupled oscillations of runoff time series, precipitation and air temperature in Bailianya river basin were investigated from the frequency domain, which reflected the correlation between runoff and climatic factors on different time scales.

Results 1) The distribution of runoff was uneven during the year and mainly concentrated in June and July. The 2 abrupt changes of runoff occurred in 1983 and 2004-2005. Runoff demonstrated a small cycle of 0.5-3 year(s). 2) There was strong correlation between runoff and precipitation at a cycle of 1-2 year(s) in 1986-1996 and at a cycle of 2.5-4 year(s) in 1998-2002. Runoff responded to precipitation fast with most high energy time-frequency domain characterized by phase relationship. 3) Interactions between the runoff and the temperature were mainly concentrated in a cycle of 1-3.8 year(s) in 1988-2000. The phase of temperature was prior to that of the runoff. Runoff responded to temperature with a time lag. The change of underlying surface elements strongly changed the nature of the surface of the basin, and had certain influence on the hydrological cycle at different time and space scales, causing the change of runoff and confluence conditions in the basin, and thus changing the hydrological process of the basin. Forest and farmland were the main underlying factors that caused runoff change in Bailianya basin, and had obvious influence on runoff change. With the increase of forest area and the decrease of farmland area, runoff showed a decreasing trend.

Conclusions With the change of climate variation and underlying surface condition, the runoff of Bailianya river basin varies significantly in the interannual period and within a year, showing different correlation characteristics with different environmental factors. Precipitation in Bailianya river basin is the direct factor of the runoff change. The response of the runoff to air temperature is of time delay. Compared with forest, farmland is weak in rainfall interception and infiltration, and the conversion of farmland to forest will lead to the relative reduction of runoff.