Spatiotemporal Variations in Climatic Factors,Catchment Characteristic Induced Runoff Changes with Multi-Time Scales across the Contiguous United States

Previous works were mainly concentrated on long-term average runoff alterations, and extreme temperatures and watershed conditions are little analyzed. In this study, we collected gauged river flow and meteorological data time series from 1916 to 2015 and 1941 to 2015 across the contiguous United States(CONUS) for 188 catchments to investigate the temporal trends and spatial features of runoff changes at multi-time scales. We also analyzed the relationships between runoff changes and climatic factors. Median descriptive statistics and Budyko coupled climate elasticity methods were used to calculate runoff elasticity in each time scale. The original Mann-Kendall trend test was used to test their trend significance in four time-scale(11, 20, 40, and 60 a), respectively. The results show that the trend of runoff changes is more significant in high time scales; total changes are heterogeneous over CONUS. After the 1970s, increases of up to 27% decade-1 were mainly concentrated in the mid-northern regions. Maximum temperature and catchment characteristics are vital factors for runoff alteration; runoff changes are independent of rainfall, and wet regions tend to have lower changes. These findings could help develop better regional water resource planning and management.