Investigating streamflow variability and hydroclimatic teleconnections: a comparison of regulated and unregulated streamflow stations

This study evaluates the relationship between flow variability of unregulated and regulated streamflow stations and global climate indicators. Mann-Kendall and change-point analysis is applied to investigate the gradual and abrupt changes in streamflow data, followed by the investigation of multi-scale fluctuations in streamflow data using Continuous Wavelet Analysis. Linkages between streamflow and global climate indicators are examined using Cross-Wavelet and Wavelet Coherence Analysis. Results showed contrasting trend values for unregulated and regulated streamflow stations. Surprisingly, all unregulated stations experienced a significant abrupt shift in change point contrary to the regulated streamflow. Further, for unregulated stations, streamflow variability and hydroclimatic teleconnections were observed at a lower scale, indicating that variations in streamflow are more frequent and generally occur on an intra-annual to inter-annual scale. Contrary, regulated stations observed the streamflow variability and hydroclimatic teleconnections at a larger scale (8-10 years), indicating that all the fluctuations are smoothened out. Thus, unregulated stations cannot be used as a proxy for regulated stations in any given basin. Indeed, for better water resource planning and management, both regulated and unregulated streamflow should be investigated.